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thesis entitled

SPATIAL AND TEMPORAL PATTERNS OF PINUS NIGRA
(AUSTRIAN PINE) SPREAD IN FOUR LAKE MICHIGAN
SAND DUNE HABITATS

presented by
Khara D. Grieger

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6/01 cJCIRC/DateDuepGS-sz

SPATIAL AND TEMPORAL PATTERNS OF PINUS NIGRA
(AUSTRIAN PINE) SPREAD IN FOUR LAKE MICHIGAN
SAND DUNE HABITATS
By

Khara D. Grieger

A THESIS

Submitted to
Michigan State University
in partial fulﬁllment of the requirements
for the degree of

MASTER OF SCIENCE
Department of Plant Biology

2003

ABSTRACT

SPATIAL AND TEMPORAL PATTERNS OF PIN US NIGRA (AUSTRIAN PINE)
SPREAD IN FOUR LAKE MICHIGAN SAND DUNE HABITATS

By

Khara D. Grieger

Planted Pinus nigra is reproducing and spreading in Saugatuck Dunes State Park
Natural Area, significantly altering natural dune conditions and impacting native species.
Ten randomly located sites were selected in each of the four main dune habitats for
estimating the rates and patterns of P. nigra spread and for comparing the selected
parameters of the regeneration niches of P. nigra and native P. banksiana. The spatial
occurrence of threatened C irsium pitcheri and populations most threatened by the spread
of P. nigra were also documented using GPS and GIS techniques. Currently stands of
P. nigra are spreading to the north in the foredunes and northeast in the inland blowouts,
attributed to prevailing southwesterly winds. Foredune stands have increased on average
by 37% in area since original plantings in 1963, while inland blowout stands have
increased 25% since 1966. The average rates of spread per plant ranged from 0.04 m yr'l
to 0.20 m yr", but were as high as 15 m yr'l. The wetpannes were considered the most
threatened dune habitat, due to high densities of P. nigra progeny and the presence of a
unique dune ﬂora and fauna. The measured parameters of regeneration niches of P. nigra
and P. banksiana co-occurring in the vicinity of planted P. nigra were similar, and no
habitat partitioning was apparent. Eleven populations and 29 individuals of C. pitcheri
were documented in the foredunes and inland blowouts, including five critical areas that

contained both P. nigra progeny and C. pitcheri.

ACKNOWLEDGEMENTS

I would like to thank my advisor, Dr. Peter Murphy, for his advise, support,
and guidance throughout this project. I would also like to thank my committee
members, Dr. Kelly Millenbah and Dr. Frank Ewers for their additional help. The
Michigan DNR provided funding for part of this project through the Natural Heritage
Program Nongame Wildlife Fund. Funding also came from The Garden Club of
America, Paul Taylor Fund of the Plant Biology Department, and the Ecology,
Evolutionary Biology, and Behavior program at Michigan State University.

Ethel Burns provided housing for me during the summer of 2001, and even
welcomed four strange Danish men to camp in her beautiful garden. That summer
was monumental for a number of reasons, and Ethel provided me with timeless
wisdom. Also during that summer, Joe Veldman and Laura Olney helped with field
data collection, as we all battled biting ﬂies, annoying mosquitoes and ticks, and
crunchy chewing gum. Back in East Lansing, Teresa Salveta, Jody Reynolds, and
Ben Munn were all extremely helpful as undergraduate researchers.

Special thanks to Joseph Harsh, who provided tree core samples to obtain age
estimations of Austrian pine trees, which were essential to this project. En'ca
McConnel, Skip Van Bloem, Charlotte Murray, Scott Butterfield, and Dr. Lissa
Leege were all of incredible help during all stages of this project.

Of course, I deﬁnitely would not have been able to complete this project
without the unceasing love and support of my mother, father, and step-parents. They
were always there to encourage me, whether it was on the sidelines of plant biology

or lacrosse.

iii

TABLE OF CONTENTS

LIST OF TABLES .............................................................................. vii
LIST OF FIGURES .............................................................................. x
CHAPTER 1
GENERAL INTRODUCTION ................................................................. 1
CHAPTER 2

RATES AND SPATIAL PATTERNS OF INTRODUCED PIN US
NIGRA (AUSTRIAN PINE) SPREAD ON THE SAND DUNES

OF LAKE MICHIGAN .......................................................................... 8
Introduction ............................................................................... 8
Invasion theory .................................................................. 8

Lake Michigan sand dunes ................................................... l 1
Research questions ............................................................ 12
Methods .................................................................................. 13
Study site ....................................................................... 13
Sampling Sites ................................................................. 14

Rates and spatial patterns of Austrian pine spread ........................ 16

Tree age determination .............................................. 16
Rate estimation ........................................................ 17

Spatial pattern ........................................................ 20

Results ................................................................................... 21
Rates and spatial patterns of Austrian pine spread ........................ 21

Rates of spread ........................................................ 2]

Spatial pattern ........................................................ 22

Primary directions of spread ................................................. 27
Discussion ............................................................................... 28
Overview ....................................................................... 28

Rates and spatial patterns of Austrian pine spread ........................ 29
Habitats most invaded by Austrian pine ................................... 32
Conclusions .................................................................... 33

CHAPTER 3

REGENERATION NICHES OF INTRODUCED, INVASIVE
PIN US NIGRA AND NATIVE PIN US BANKSIANA IN FOUR

LAKE MICHIGAN SAND DUNE HABITATS ............................................ 53
Introduction ............................................................................. 53
Austrian pine invasion of Saugatuck Dunes State Park .................. 54

Jack pine: distribution and ecology ......................................... 54

Jack pine in the study site ..................................................... 56

Research objectives ............................................................ 57

Methods ................................................................................... 59

Study site ....................................................................... 59

iv

Patterns of occurrence of Austrian pine and Jack pine
regeneration underneath and surrounding planted

Austrian pine stands ............................................................. 59

Dune features correlated with Austrian pine and Jack pine

regeneration .................................................................... 60
Results ................................................................................... 61

Patterns of occurrence of Austrian pine and Jack pine
regeneration underneath and surrounding planted

Austrian pine stands ........................................................... 61

Dune features correlated with Austrian pine and Jack pine

regeneration ..................................................................... 63
Discussion ............................................................................... 65

Patterns of occurrence of Austrian pine and Jack pine
regeneration underneath and surrounding planted

Austrian pine stands ........................................................... 65
Dune features correlated with Austrian pine and Jack pine
regeneration .................................................................... 66
Conclusions .................................................................... 68
CHAPTER 4
SPATIAL OCCURRENC E OF THREATENED CIRSI UM
PITCHERI AND POTENTIAL EFFECTS OF INVASIVE
PIN US NIGRA .................................................................................... 75
Introduction ............................................................................. 75
Distribution and ecology of Cirsium pitcheri ............................. 76
Research objectives ........................................................... 77
Methods .................................................................................. 78
Study site ....................................................................... 78
Spatial occurrence of Cirsium pitcheri ..................................... 78
Austrian pine effects on Cirsium pitcheri’s density ...................... 79
Results .................................................................................... 80
Discussion ............................................................................... 80
Summary and Conclusions .................................................. 81
CHAPTER 5
GENERAL CONCLUSIONS .................................................................. 84
APPENDICES ................................................................................... 87
APPENDIX A1: AGE DETERMINATION OF PINUS
NIGRA IN SAUGATUCK DUNES STATE PARK ............................... 88
APPENDIX A2: SUPPLEMENTAL DATA ON PIN US
NIGRA AND PIN US BANKS/ANA PROGENY UNDERNEATH
AND EXTENDING FROM PLANTED AUSTRIAN PINE
STANDS ................................................................................. 93

LITERATURE CITED .......................................................................... 98

vi

LIST OF TABLES

Table 2-1. Mean Austrian pine rates of spread (m yr") per plant across

10 foredune sites, based upon randomly selected 1 m2 plots extending

from the edge of parental stands to 5 m or until regeneration was no

longer observed .................................................................................. 35

Table 2-2. Mean Austrian pine rates of spread (m yr") per plant across
10 foredune sites, based upon non-random 1m plots extending from the
edge of parental stands to varying distances .................................................. 35

Table 2-3. Mean Austrian pine rates of spread (m yr") per plant across

10 inland blowout sites based upon randomly selected 1m2 plots

extending from the edge of parental stands to 5 m or until regeneration

was no longer observed ......................................................................... 36

Table 2-4. Mean Austrian pine rates of spread (m yr") per plant across
10 inland blowout sites based upon non-random 1m plots extending from
the edge of parental stands to varying distances. ............................................. 36

Table 2-5. Mean Austrian pine rates of spread (m yr") per plant across
10 forest edge sites based upon randomly selected lm‘ plots at the forest
edge, 5 m, 10 m, and 15 m into the forest .................................................... 37

Table 2-6. Mean Austrian pine rates of spread (m yr") per plant across

10 forest edge sites based upon non-randomly selected 1m2 plots at

varying distances into the forest. This table shows only sites that had

non-random plots included .................................................................... 37

Table 2-7. Mean Austrian pine regeneration densities (#ind/mz)

underneath and at the edge of Austrian pine stand in each dune habitat.

Densities were taken from ﬁve randomly placed 1m2 plots both

underneath and at the edge of Austrian pine canopy in each habitat site.

Ten sites were randomly selected in each dune habitat .................................... 38

Table 2-8. Statistical comparison of mean Austrian pine regeneration
densities underneath and at the edge of Austrian pine canopy within

each dune habitat (SAS Inst. 2001 . one-way ANOVA a=0.05). Densities
were taken from ﬁve randomly placed 1m2 plots both underneath and at
the edge of Austrian pine canopy in each habitat Site. Ten sites were
randomly selected in each dune habitat ...................................................... 3 8

vii

Table 2-9. Directions of Austrian pine spread in the foredunes and

inland blowouts, based on pooled random and non-random sampling.

Random sampling included transects extending in all four cardinal

directions from edge of parental stand to 5 m or to farthest extent of

Austrian pine regeneration, while non-random sampling included

regeneration observed not previously in random samples ................................. 39

Table 2-10. Austrian pine regeneration occurring away from edge

of parental stands in all four cardinal directions in each dune habitat.

The following is a list of the distances and corresponding directions

most statistically signiﬁcant in locating Austrian pine progeny away

from the parental stands (SAS Inst. 2001, ANOVA and Tukey-Kramer

tests, a=0.05). Random and non-random data were pooled for this

analysis in each dune habitat ................................................................... 39

Table 3-1a. Forward stepwise correlation between the presence of
Austrian pine and Jack pine progeny and selected abiotic and biotic
dune features (SAS Inst. 2001. (1:005). In each m2 plot sampled, the
presence of Austrian pine and Jack pine progeny was recorded and

dune features measured in each habitat. A “1” indicates seedlings,

and “2” indicates saplings. A signiﬁcant correlation (PS 0.005) is
indicated by a “*” for Austrian pine and “o” for Jack pine. while a
highly signiﬁcant correlation (P<0.0001) is indicated by “**” for
Austrian pine and “00” for Jack pine. Positive correlations are indicated
by a “+”, while a negative correlation is indicated by a ‘-.“ The total
number of seedlings and saplings observed and analyzed are shown

in Table 3-1b . . . . . ............70

Table 3-1b. The total number of seedlings and saplings observed in

each dune habitat and correlated with selected dune features. The dune

features and their correlationts) with Austrian pine seedlings and saplings

are shown in Table 3-la. AP=Austrian pine. JP=Jack pine. A “1" indicates

seedlings and “2” indicates saplings .......................................................... 70

Table A2-1. Mean number of Pinus nigra (Austrian pine) seedlings

and saplings across 10 foredune, inland blowout. and forest edge sites.

based upon randomly and non-randomly selected 1m2 plots underneath

and extending from canopy edge or into forest (for the forest edge).

Locations underneath the canopy is designated as “- 1 " ..................................... 94

viii

Table A2-2. Mean number of Pinus nigra (Austrian pine) and Pinus

banksiana (Jack pine) progeny extending from the edge of mature

Austrian pine stands across the ten foredune sites, based on random

and non-random sampling. Locations underneath the canopy are

designated as “-1.” Random sampling was performed using randomly

located 1m2 plots underneath and at edge of canopy and along transects

running N, S, E, W from the edge of the stand to 5 m or the furthest

extent of Austrian pine regeneration. Non-random sampling occurred

wherever regeneration was observed not previously captured 1n the

random samples .................................................................................. 95

Table A2-3. Mean number of Austrian pine and Jack pine progeny

extending from the edge of mature Austrian pine stands across the

ten inland blowout sites, based on random and non-random sampling.

Locations underneath the canopy are designated as “-1.” Random

sampling was performed using randomly located lm2 plots underneath

and at edge of canopy and along transects running N, S, E, W from the

edge of the stand to 5 m or the furthest extent of Austrian pine regeneration.
Non-random sampling occurred wherever regeneration was observed

not previously captured in the random samples ............................................ 96

Table A2-4. Mean number of Austrian pine and Jack pine progeny

extending from the edge of mature Austrian pine stands across the

ten forest edge sites. based on random and non-random sampling.

Locations underneath the canopy are designated as “-1.” Random

sampling was performed using randomly located 1m2 plots underneath

and at edge of canopy and along transects running N, S, E, W from the

edge of the stand to 5 m or the furthest extent of Austrian pine

regeneration. Non-random sampling occurred wherever regeneration

was observed not previously captured in the random samples ............................ 97

ix

LIST OF FIGURES

Figure 2-1. Various dune habitats in the Lake Michigan sand
dune ecosystem ................................................................................... 40

Figure 2-2. Location of the study site (Saugatuck Dunes State
Park), in Allegan County, MI (from Cowles I899). The Natural
Area lies within the park ........................................................................ 41

Figure 2-3. Study site: Saugatuck Dunes State Park Natural Area

(SDSPNA). Austrian pine plantations can be seen as dark lines

(see arrow for example) in the foredunes and inland blowout

habitats. 1cm=120m .............................................................................. 42

Figure 2-4. Sampling model for foredune and inland blowout sites,
including randomly placed 1m2 plots underneath and at the edge of
an Austrian pine stand and transects extending in all four cardinal
directions (targeted 1m2 plots are not shown here).* In all Im2
plots, both Austrian pine regeneration densities and abiotic and
biotic dune factors were measured.* Note: in three inland blowout
sites, transects were placed in NE. NW, SE, and SW directions to

avoid interference with other Austrian pine stands ....... . ................................... 43

Figure 2-5. Mean Austrian pine regeneration densities (#ind/mz)

underneath and at the edge of Austrian pine canopy in each dune

habitat. See Table 2-7 for exact values. Five randomly placed lm2

plots were sampled both underneath and at the edge of Austrian pine

stands in each habitat site ........................................................................ 44

Figure 2-6. Mean number of Austrian pine progeny extending from

the edge of mature Austrian pine stands across the ten foredune sites,

based on random and non-random sampling. Locations underneath the

canopy are designated as “-1.” Random sampling was performed using

randomly located lm2 plots underneath and at edge of canopy and along

transects running N, S, E. W from the edge of the stand to 5 m or the

furthest extent of Austrian pine regeneration. Non-random sampling

occurred wherever regeneration was observed not previously captured

in the random samples .......................................................................... 44

Figure 2-7. Mean number of Austrian pine progeny extending from

the edge of mature Austrian pine stands across the ten inland blowout

sites, based on random and non-random sampling. Locations underneath

the canopy are designated as “-1.” Random sampling was performed

using randomly located 1m2 plots underneath and at edge of canopy and

along transects running N, S, E, W from the edge of the stand to 5 m or

the furthest extent of Austrian pine regeneration. Non-random

sampling occurred wherever regeneration was observed not previously

captured in the random samples45

Figure 2-8. Mean number of Austrian pine progeny extending from

the edge of mature Austrian pine stands into the native forest across

ten forest edge sites, based on random and non-random sampling.

Random sampling was performed using ﬁve random 1m2 plots at forest

edge, 5 m, 10 m, and 15 m into the forest at each of ten forest edge sites.
Non-random sampling occurred wherever regeneration was observed

not previously captured in the random samples of the ten forest edge sites.

Note: there were no statistically signiﬁcant differences between densities

found at each location into the forest (SAS Inst. 2001, one-way ANOVA,

a=0.05, P=0.2751) ............................................................................... 45

Figure 2-9. Mean Austrian pine regeneration densities (#ind/mz) at

edge and interior of the wetpannes. In nine wetpannes, densities

were calculated by inventorying the wetpanne for regeneration and

dividing by total area. One wetpanne was sampled for regeneration

using 10 random 1m2 plots at the edge and interior of the wetpanne.

Note: there were no statistically signiﬁcant differences between

densities occurring at the edge and interior of wetpannes (SAS Inst.

2001, one-way ANOVA, a=0.05, P=0.1689) ................................................ 46

Figure 2-10. Austrian pine spread from edge of planted stands in the

foredunes. Sampling was based on randomly and non—randomly located

1m2 transect belts running N, S. E. W from the edge of the stand to 5 m

or the furthest extent of Austrian pine regeneration in 10 sites. Non-random
sampling occurred wherever regeneration was observed not previously

captured in the random samples. Note: original Austrian pine foredune

stands were planted in 1963, based on average tree age estimates and stand

size is not drawn to scale ....................................................................... 47

Figure 2-11. Maximum frontier of Austrian pine spread in the foredunes

as of 2001. This ﬁgure shows the outermost distances that Austrian pine

progeny were found from the stand edge in each direction and indicates

the maximum area of spread across ten foredune sites. According to

this analysis, foredunes stands increased in area by a maximum of 153%

since original plantings in 1963. Stand age was based on average tree age

estimates .......................................................................................... 48

xi

 

Figure 2-12. Average frontier of Austrian pine spread across 10 foredune

sites as of 2001. This ﬁgure shows the average outermost distances

that Austrian pine progeny were found from the stand edge in each

direction. According to this analysis. the average Austrian pine foredune

stand increased in area by 37% Since original plantings in 1963. Stand age

was based on average tree age estimates .................................................... 48

Figure 2-13. Austrian pine spread from edge of planted stands in the

inland blowout habitats. Sampling was based on randomly and non-

randomly located 1m2 transect belts running N, S, E, W in most sites

and NE, NW, SE, SW in three sites from the edge of the stand to 5 m

or the furthest extent of Austrian pine regeneration. Non-random

sampling occurred wherever regeneration was observed not previously

captured in the random samples. Note: original stands were planted in

1966, based on average tree age estimates and stand size is not drawn to

scale ............................................................................................... 49

Figure 2-14. Maximum frontier of Austrian pine spread in the inland

blowouts as of 2001. This ﬁgure shows the outermost distances that

Austrian pine progeny were found from the stand edge in each direction

and indicates the maximum area of spread across ten inland blowout

sites. According to this analysis. inland blowout stands increased in area

by a maximum of 132% since original plantings in 1966. Stand age was

based on average tree age estimates ............................................................ 50

Figure 2-15. Average frontier of Austrian pine spread across 10 inland

blowout sites as of 2001. This ﬁgure shows the average outermost

distances that Austrian pine progeny were found from the stand edge

in each direction. According to this analysis, the average Austrian pine

inland blowout stand increased in area by 25% Since original plantings

in 1968. Stand age was based on average tree age estimates ............................. 50

Figure 2-16. Austrian pine spread from edge of planted stands into

the native forest, based on randomly and non-randomly 1m2 plots at

distances into the forest. Non-random sampling was used wherever

regeneration was observed not previously captured in the random

samples. Note: original stands were planted in 1963, based on average

tree age estimates and stand size is not drawn to scale ..................................... 51

xii

Figure 2-17. Mean number of Austrian pine seedlings and saplings

found at wetpanne interior and edge. Nine wetpannes were surveyed

for Austrian pine regeneration, and one wetpanne, too large to survey.

was sampled using 10 l-m2 plots at the wetpanne edge and interior.

The wetpanne edge was deﬁned as the outermost 2 m of the wetpanne.

Although there was greater regeneration at the interior of the wetpannes,

there were no signiﬁcant differences between regeneration found in the

interior and at the wetpanne edges (P=0.1689) .............................................. 52

Figure 3-1. Mean number of Austrian pine and Jack pine progeny

extending from the edge of mature Austrian pine stands across the

ten foredune sites, based on random and non-random sampling.

Locations underneath the canopy are designated as “-1.” Random

sampling was performed using randomly located 1m2 plots underneath

and at edge of canopy and along transects running N, S, E. W from the

edge of the stand to 5 m or the furthest extent of Austrian pine regeneration.
Non-random sampling occurred wherever regeneration was observed not

previously captured in the random samples. These data are consistent with

Table A2-2. .. ............................................................................................................ .71

Figure 3-2. Relative distribution of Austrian pine and Jack pine progeny

underneath and extending from Austrian pine canopy in the foredunes.

based on the total number of progeny found in this habitat. These data

are consistent with Figure 3-l . but are shown in percentages of total

number of pine progeny ........................................................................ 71

Figure 3-3. Mean number of Austrian pine and Jack pine progeny

extending from the edge of mature Austrian pine stands across the

ten inland blowout sites, based on random and non-random sampling.

Locations underneath the canopy are designated as “-1.” Random

sampling was performed using randomly located lm2 plots underneath

and at edge of canopy and along transects running N, S, E, W from the

edge of the stand, or NE, NW, SE. SW in three sites, to 5 m or the

furthest extent of Austrian pine regeneration. Non-random sampling

occurred wherever regeneration was observed not previously captured

in the random samples. These data are consistent with Table A2-3 ..................... 72

Figure 3-4. Relative distribution of Austrian pine and Jack pine progeny

underneath and extending from Austrian pine canopy in the inland

blowouts, based on the total number of progeny found in this habitat.

These data are consistent with Figure 3-3, but are shown in percentages

of total number of pine progeny ............................................................... 72

xiii

Figure 3-5. Mean number of Austrian pine and Jack pine progeny
extending from the edge of mature Austrian pine stands across the
ten forest edge sites, based on random and non-random sampling.
Locations underneath the canopy are designated as “-1 Random
sampling was performed using randomly located 1m2 plots underneath
and at edge of canopy and along transects running N, S, E, W from the

edge of the stand to 5 m or the furthest extent of Austrian pine regeneration.

Non-random sampling occurred wherever regeneration was observed not
previously captured in the random samples. These data are consistent with

Table A2-4 ........................................................................................ 7

Figure 3-6. Relative distribution of Austrian pine and Jack pine progeny
underneath and extending from Austrian pine canopy into the native forest,
based on the total number of progeny found in this habitat. These data are
consistent with Figure 3—5, but are shown in percentages of total number

of pine progeny .................................................................................. 7

Figure 3-7. Mean number of Austrian pine and Jack pine progeny in
wetpanne interior and edge. across ten wetpannes. Nine wetpannes
were surveyed for regeneration. and one wetpanne, too large to survey.
was sampled using 10 l-m2 plots at the wetpanne edge and interior.

a

.3

q

.3

Seedlings and saplings were pooled for both species ....................................... 74

Figure 3-8. Relative distribution of Austrian pine and Jack pine
progeny found in wetpanne interior and edge, based on the total

number of progeny found in ten wetpanne sites ............................................. 74

Figure 4-1. Spatial occurrence of Pitcher’s thistle in SDSPNA and
locations of critical areas. Critical areas were areas containing

Austrian pine regeneration populations within 10 m of Pitcher’s thistle ................. 82

Figure 4—2. Pitcher’s thistle population densities in the absence and
presence of Austrian pine regeneration. There were no statistical
differences between the densities of Pitcher’s thistle populations in
the presence and absence of Austrian pine regeneration (SAS 2001,
one-way ANOVA, (1:0.05, P=O.8209). The mean density in the
absence and presence of Austrian pine progeny are shown numerically

above .............................................................................................. 83

Figure Al-l. Relationship of Austrian pine tree age to stem diameter at
breast height in the foredune habitat. Breast height measured at 1.25 m.

Each point represents an individual ........................................................... 91

Figure A1-2. Relationship of Austrian pine tree age to stem diameter at
breast height in the forest edge habitat. Breast height measured at 1.25 m.

Each point represents an individual ........................................................... 91

xiv

Figure A1-3. Relationship of Austrian pine tree age to stem diameter at
breast height in the inland blowout habitat. Breast height measured at
1.25 m. Each point represents an individual ................................................. 92

Figure Al-4. Relationship of Austrian pine tree age to stem diameter at

breast height in the wetpanne habitat. Breast height measured at 1.25 m.
Each point represents an individual ........................................................... 92

XV

CHAPTER 1

GENERAL INTRODUCTION

Pinus nigra (European black pine or Austrian pine) has been documented as an
invasive species on the dunes of Lake Michigan, reproducing and spreading in Saugatuck
Dunes State Park (SDSP), Michigan and ultimately impacting the native vegetation and
various dune habitats (Leege 1997, Leege and Murphy 2000, 2001). It has been shown
previously to accelerate dune succession, reduce biodiversity, and potentially change
ground water levels (Leege 1997, Leege and Murphy 2000, Sherﬁnski 2000).
Furthermore, it can shade out native plant species and ultimately jeopardize the welfare
of threatened and/or endangered species such as C irsium pitcheri (Pitcher’s thistle)
(Leege and Murphy 2001). The presence, reproduction, and spread of Austrian pine in
SDSP is just one example of the increasing problem of biological invaders drastically
altering native ecosystems.

Biological invaders are species that spread beyond their native range, thriving,
dispersing, and reproducing in their new environment, often causing irreversible damage
to native communities and ecosystems (Mack et al. 2000). Due to increased global trade,
an unprecedented number of organisms are exposed to new habitat areas as human
transportation improves, and Species are thereby introduced both deliberately and
accidentally to new environments (Lodge 1993). Both economically and ecologically,
the negative consequences of invasive species can be seen throughout the world. It was

estimated in 2000 that the US. Department of Agriculture spent $122 billion annually on

the control of invasive species in agrarian systems, including associated property damage
and resource losses (Delfosse 2000).

Ecologically, biological invasions have not only caused an unprecedented rate of
species extinction, but are the second major cause of extinctions after habitat destruction
(D’Antonio and Vitousek 1992). Labeled as ‘biological pollutants,’ and sometimes
regarded as a greater threat to native communities than conventional pollution (Drake
1989, Cronk and Fuller 1995), invasive species can have long-term effects on ecosystems
by altering fundamental processes such as trophic structure and disturbance regime of an
invaded area (Vitousek 1990, Colton and Alpert 1998). In fact. many of these biological
invasions are considered irreversible (C oblentz 1990). Native populations and
communities are especially impacted when invasives outcompete native species by
consuming precious resources or by changing pre-existing environmental conditions
(Crawley 1986, D’Antonio and Vitousek 1992, Williamson 1996). Furthermore, it is
estimated that approximately 10% of all introduced species will become established and
10% of those established will become invasive (Williamson and Fitter 1996). Plant
invaders can alter ﬁre patterns, nutrient cycling, hydrology, and energy budgets of native
ecosystems (Mack et al. 2000). Many exotic trees, for example, have been planted in
place of native species due to greater resistance to pests and disease, tree hardiness,
adaptability to unfavorable conditions. and higher growth rates (Zobel et al. 1987).

Invasions by the genus Pinus have been documented worldwide, and at least 16
species have been listed as invasive in the Southern Hemisphere alone (Richardson et al.
1994). The widespread planting of this genus has led to the increased invasions

(Richardson 1998a), and in many cases introduced pines have become a vigorous and

dominant part of the local ﬂora (Richardson and Bond 1991 ). A wide variety of
problems attributed to pine introductions exists. especially for watersheds, protected
areas, and managers of grazing lands (Richardson et al. 1994). Because they tend to
grow in large, dense stands that may dominate natural ecosystems, invasive pines can
alter ecosystem functions and processes, decrease native biodiversity, alter ﬁre regimes,
reduce water yields, change nutrient cycling processes. and alter biomass accumulation
processes (Richardson and Bond 1991, Richardson et al. 1994, Richardson 1994).
Commonly found on stressed sites, such as nutrient-deﬁcient soils and sand dunes,
invasive pines can also provide microhabitat space for native species not usually present
under natural conditions (Richardson et al. 1994).

The presence of Austrian pine on the Lake Michigan sand dunes is just one
example of an introduced pine dominating and altering a fragile native ecosystem.
Originally planted as a sand stabilizer between 1956 and 1972 in the area now known as
Saugatuck Dunes State Park Natural Area (SDSPNA), Austrian pine is changing the
natural dune ecosystem (Leege 1997, Leege and Murphy 2000, 2001, Sherﬁnski 2000).
Although Austrian pine is native to southern Europe, northern Africa, and Asia Minor, it
has been planted worldwide due to its broad environmental tolerance (Dalimore and
Jackson 1966, Burns and Honkala 1990). For example, it was one of the earliest tree
introductions in the United States, and was planted in the Sandhills of Nebraska in 1891
as well as on the Great Plains in the early 1900’s as a windbreak. In the northeast areas
of the US, Austrian pine has been especially successful on acidic soils, and in the Great
Lakes it has been successful on a broad range of soils including sandy loam, silty clay.

and calcareous soils (Parﬁtt and Wade 2000). It has been widely planted as an

L»

ornamental and along roadsides throughout Michigan and surrounding regions (Barnes
and Wagner 1981). Austrian pine also has been widely planted in the Southern
hemisphere and has been documented as a naturalized invasive in Australia and New
Zealand, invading large tracts of land (Richardson et al. 1994). The invasion of Austrian
pine has affected Eucalypt forests. grasslands, scrublands, and montane shrublands in
these areas. In New Zealand. Austrian pine established most frequently beneath tussock
canopy and in sparse, low-growing vegetation between tussocks. It was documented to
be the most inﬂuential, widespread invasive pine on the island and less affected by pests
and disease than other pine species. Austrian pine seedlings are also considered less
palatable to herbivores than other pine species at these sites in New Zealand (Crozier
1990). Although Austrian pine is found in smaller populations and is more limited in
distribution in Australia than in New Zealand, it is still regarded as one of the most
inﬂuential invasive pines. In North America. it is reported to have become naturalized in
areas of New England and parts of the Great Lakes region of the US. where it is
successfully reproducing and surviving without human intervention (Burns and Honkala
1990, Parﬁtt and Wade 2000).

Mature Austrian pine individuals produce a dense, pyramidal crown with two
leaves per fascicle (Ouden and Boom 1965). Under favorable conditions, Austrian pine
can grow to 30 m in height and reach 300 years of age (Van Haverbeke 1986). Its
reproductive maturity usually occurs at 15-20 years of age. similar to most other pines.
and maximum cone production occurs between 60-90 years. The window of time for
successful pollination. similar to most pines. is short, around three days (Barnes and

Wagner 1981). Under most conditions trees produce cones every year. but every 3-4

years the cone production is abundant. One pinecone will usually produce about 30-40
seeds, approximately 50% of which are viable (Leege 1997). Austrian pine seeds are
wind-dispersed, although some animal dispersal is also thought to occur (Burns and
Honkala 1990).

Leege and Murphy (2000, 2001) showed the extent to which introduced Austrian
pine has become dominant on the dunes, and documented certain aspects of its
reproduction, germination, seedling establishment, and invasive potential. They
demonstrated that Austrian pine survivorship varied across dune habitats, being greatest
in the wetpannes and lowest in the foredunes (for a description of the dune habitats see
Chapter 2). Foredune seedlings had the lowest survivorship because of greater canopy
cover, lower light intensity, and a deeper needle-litter layer (Leege and Murphy 2000,
2001). Leege (1997) and Leege and Murphy (2000, 2001) also documented that the
wetpannes contained the highest growth rates of Austrian pine populations, compared to
other dune habitats.

Leege and Murphy (2000, 2001) examined some microsite conditions that could
inﬂuence seedling establishment and success. They investigated the role of soil moisture,
light levels, litter layer depth, canopy openness, and soil pH on Austrian pine seedling
establishment. Soil moisture was found to be the most important abiotic factor affecting
germination and survivorship of Austrian pine, while light intensity and litter layer were
found to be important in establishment and growth.

Some aspects of Austrian pine dispersal were also studied by Leege and Murphy
(2000). Seed cones and seeds were collected and counted. and mean seed production per

reproductive tree was calculated. They found average seed production per tree in the

foredunes to be 10 times higher than in the wetpanne and inland blowouts, and 20-40
times higher than along the surrounding deciduous forest.

Sherﬁnski (2000) and Beneﬁel (unpublished report) examined the effects of
Austrian pine on wetpanne ecology by comparing wetpanne characteristics in the
presence and absence of Austrian pine. They studied the transpiration rates of Austrian
pine and the native Pinus banksiana (Jack pine), and the potential long-term effects of
their transpiration rates on wetpanne hydrology. Sherﬁnski (2000) concluded that
Austrian pine has the potential to transpire more than Jack pine, due to a greater total leaf
surface area, ultimately affecting ground water levels for wetpannes and thus, changing
surrounding wetpanne ﬂora and fauna.

Currently, the presence of invasive Austrian pine on the Lake Michigan sand
dunes is of great concern. Austrian pine has the potential to rapidly alter native sand
dune conditions and ultimately threaten endemic species. such as Pitcher’s thistle. This
study focuses primarily on the rates and Spatial patterns of Austrian pine spread
immediately surrounding planted Austrian pine stands on the dunes of Lake Michigan.
and compares the regeneration niches of Austrian pine and Jack pine in the dune habitats.
Chapter 2 documents the rates and spatial patterns of Austrian pine spread in the study
site. The rate of spread is of particular interest because it suggests how quickly the dune
environment may be altered by further Austrian pine establishment. The spatial patterns
of spread in four habitats were examined to identify the speciﬁc habitats most impacted
by the spread of Austrian pine and to pinpoint the areas most likely to be affected by
Austrian pine. Chapter 3 compares some aspects of the regeneration niches of Austrian

pine and Jack pine near Austrian pine stands in each dune habitat. The pattern of

occurrence of both species in and around planted Austrian pine stands were compared.
and microsite conditions favorable for the establishment, of seedlings and saplings of both
species were determined. Finally, Chapter 4 documents the spatial occurrence of
Pitcher’s thistle, an endemic plant on the Federal list of threatened species, and identiﬁes
areas where Pitcher’s thistle populations are in close proximity to areas of Austrian pine

spread in the study site.

CHAPTER 2
RATES AND SPATIAL PATTERNS OF INTRODUCED PINUS NIGRA
(AUSTRIAN PINE) SPREAD ON THE DUNES OF LAKE MICHIGAN

INTRODUCTION

Invasion theory

Successful invasions are usually dependent upon characteristics of both the
invader and the recipient environment. Habitats characterized by low levels of vegetation
cover can easily be invaded by exotic plants, where competition with native species is
limited (Crawley 1987). Areas with low levels of vegetation cover are often found on
unstable substrates, nutrient-poor soils, or where there is high competition for ground
water. In fact, most invasive pine trees are found in marginal habitats (Richardson and
Bond 1991). It has also been well-documented that sites subject to some form of
alteration in level of disturbance are especially vulnerable to invasive plants (Baker
1974). For example, changes in grazing and browsing, ﬁre frequency, deforestation. and
shifting cultivation have been cited to precede pine invasions (Richardson and Bond
1991). In addition, Richardson et al. (1994) listed four vegetation types most vulnerable
to pine invasion: sparse vegetation on coastal dunes (most vulnerable). grassland.
shrubland, and forest (least vulnerable).

It has been documented that invasive plants usually have a short juvenile period,

small seed mass, and rapid population growth (Rejmanek and Richardson 1996). Also,

longer ﬂowering periods and vegetative reproduction are characteristics commonly
associated with invasive plants. There are also some characteristics of pine trees that
make them excellent invaders, such as small seed mass, short juvenile periods, and short
intervals between large seed crops (Strauss and Ledig 1985, Richardson and et al. 1994).
Richardson and Bond (1991) claimed that pines are successful colonizers, and in some
cases invaders, due to drought—tolerance, subsistence in nutrient—poor sites, well-
dispersed seeds and pollen, lack of required co-adapted agent, and ability of new colonies
to form from isolated pioneers.

Pine spread is a dynamic process that is inﬂuenced by climatic factors, grazing
pressure, species ecophysiology, seed source size and location, duration of delayed
germination, seed dissemination duration, and site requirements (Ledgard 1988, Belton
and Ledgard 1991, Richardson and Bond 1991, Richardson et al. 1994). Initial pine
dispersal and spread occur in a negative exponential curve from the edge of the parental
stands (Yocum, 1968, McCaughley et al. 1986, Richardson 1998a). Dispersal distances
of pine seeds usually range up to 100 m from the parental source, but distances up to 8
km are common and 25 km was observed in one study (Richardson et al. 1994). At one
location in New Zealand, Austrian pine seedlings were found up to 250 m from the
parental source and most were found downwind (Ledgard 1988). Dispersal distances of
pine seeds, and consequently tree spread, are also inﬂuenced by seed mass: larger seeds,
such as those of Austrian pine (mean seed weight 0.0175 grams) (Burns and Honkala
1990), tend to land closer to the parental tree than smaller pine seeds. Most long distance
seed dispersal originates from “take-oft” sites, such as a ridge, hilltop, slopes exposed to

prevailing winds, or via animal transport (Ledgard 1988).

P0pulations of spreading pine generally occur as masses of even-aged seedlings
(Ledgard 1988). It also has been documented that pine seedlings sometime do not appear
until several years after the parents ﬁrst produce cones. In one study, Pinus mugo (Dwarf
mountain pine) seedlings were not found until the parents were age 15, although cones
are usually produced before age 8. Pine trees have also been documented to produce
cones earlier in harsher environments (i.e., water-stressed sites) (Ledgard 1988).

Directions of spread seem to be primarily controlled by the location and timing of
the ﬁrst arrival, topography, and climate, including prevailing wind speed and direction.
Rates of pine spread, on a per tree basis, typically range from 81-400 m yr'l in North
America to as much as 1500 m yr"l in Europe on favorable sites (Richardson et al. 1994).
At least one study examined pine spread around plantations in Australia and deﬁned
“light tree spread” as 1 individual/ 200 m2 and “very low density spread” as ranging from
1 individual/ 10,000 m2 to 1 individual/100,000 m2 (Belton and Ledgard 1991).

Pines are usually wind-dispersed, but birds and mammals are also known to
inﬂuence the rates and spatial patterns of population spread (Ledgard 1988, Richardson
1998a). Especially Sciurus carulinem'is (Grey squirrel). species of Calyptorhynchus
(Cockatoos), Peromyscus leucopus (white-footed mouse), and various species of rabbits
have been known to disperse pine seeds (Buchanan 1989, Belton and Ledgard 1991,
Richardson 1998a). In fact. stands of invasive Pinus pinea (Italian stone pine) increased
in size in at least one site due to seed dispersers that were attracted to the pine stands
(Richardson and Cowling 1995). In fact, Richardson (1998b) cited rodents as an integral
part of pine dispersal and establishment. Conversely, rabbits, hares, and grazing

livestock have been known to control populations of Austrian pine and other pines in

10

New Zealand by browsing seedlings (Richardson and Bond 1991, Richardson et al.
1994), and Didelphis virginiana (opossums) have been cited to severely browse
developing Austrian pine seedlings (Wills and Begg 1986). However, Richardson et al.

(1994) found no evidence that seed predation has prevented spread in any region.

Lake Michigan sand dunes

Due to the shifting sand, the Lake Michigan sand dune ecosystem is an
environment subject to disturbance, characterized by dry conditions caused by porous
sand and minimal shading (Peterson and Dersch 1982). A strong prevailing
southwesterly wind from Lake Michigan is inﬂuential in creating distinct habitats,
including foredunes, inland blowouts, wetpannes, and forested dunes (Olson 1958)
(Figure 2-1). Although it is recognized that there are more than four main dune habitats
in this system, these are the primary habitats recognized and used in previous studies
(Leege 1997, Leege and Murphy 2000. 2001. Sherﬁnski 2000) and throughout this paper.
The foredunes are the youngest dunes near the beach and run parallel to adjacent Lake
Michigan. Dune formation is initiated when foredune vegetation, such as stands of
Ammophila breviligulala (Marram grass). establish and anchor the sand with their roots
and rhizomes. These open areas are characterized by especially high light and dry
surface conditions, and are subjected to high levels of sand burial or removal. The
wetpannes (also known as interdunal ponds) are low-lying areas that can become
saturated and contain standing water when the water table is high, but may be completely

dry at other times. Wetpannes have a unique dune ﬂora and fauna that exploit the

II

moister conditions. The oldest and most stable dunes, known as the backdunes or

forested dunes, are found furthest from the beach. The forested dunes are characterized
by deciduous forest vegetation growing on dune sand. Occasionally disturbance events
will create blowout regions, characterized by open areas of shifting sand, referred to as

inland blowouts.

Research questions

This chapter addresses the following questions:
1. What is the rate and spatial pattern of Austrian pine spread in the study site?
2. What are the primary directions of spread?
3. Which habitats are most invaded by Austrian pine and which areas contain the

most Austrian pine regeneration?

To answer these questions, data were collected during the summers of 2001 and
2002 in each of the four dune habitats in the study site: foredunes, forest edge. inland

blowouts, and wetpannes.

12

METHODS

Study site

This study was conducted in SDSPNA near the city of Saugatuck and located in
Allegan County, MI (42° 41 ’N, 86° 12’W) (Figure 2-2). The Natural Area lies north of

the Kalamazoo River and is in the southern portion of the park.

The average annual rainfall for the study site is between 76 and 81 cm (Seeley
1917). The mean annual temperature is approximately 83°C, while the mean January
and July temperatures are -3.8°C and 21 . 1°C, respectively. The lowest temperature can
reach -23°C, while the highest temperatures range from 34°C to 36°C (Seeley 1917).
The winds primarily prevail from the southwest (Eichmeier 1971), and average wind
speed is 16.4 km hr", average gust speed is 36.8 km hr". and high wind speed is 28.8 km
hrl (Andresen 2003). During storm events, high winds range from 40.3 km hr" to 53.1

km hr" (Andresen 2003).

Approximately 26,000 Austrian pine trees were planted as small seedlings in the
study site between 1956 and 1972 by private landowners as part of a sand stabilization
measure. The seedlings were planted in each of the four previously deﬁned dune habitats
throughout the study site (foredune, forest edge, inland blowout. and wetpanne). In the
last decade, many of the original trees became reproductively mature and Leege (1997)
was the ﬁrst to fully document the successful establishment and growth of Austrian pine

on the Lake Michigan sand dune.

Sampling sites

To sample Austn'an pine rates of spread (m yr"), spatial patterns of spread, and
seedling and sapling densities (# individuals/m2), 10 sites were randomly selected in each
of the four habitats using a stratified random sample design. The sample size of 10 sites
per habitat was considered to be adequate, based on a power statistical analysis for each
habitat (Z-test). A stratified random sample was used in each habitat to ensure
representative sampling of the entire study site (Figure 2-3). In the foredune, inland
blowout, and wetpanne habitats, study sites were comprised of stands of mature (planted)
Austrian pine trees. In the forest edge, a habitat site was deﬁned as a 50 m x 15 m area
along the edge of the forest, adjacent to the planted Austrian pine trees (Figure 2-3).
Fifteen meters was chosen as the greatest distance to randomly sample Austrian pine
spread into the forest due to poor visibility for seedlings and saplings in the dense forest
vegetation (Figure 2-3).

The study site contains two large inland blowouts, formed by strong
southwesterly winds eroding the dune surface following post-logging disturbances. In
the study site, wetpannes are usually found on the eastern (i.e., inland) side of the
foredunes. Austrian pine was originally planted in the foredunes, inland blowouts, and
areas surrounding the wetpannes of the Natural Area. It was not planted within the
deciduous forest, but sampling was performed in this habitat to document any Austrian
pine intrusion. The forested dunes comprise the oldest, most stable dunes, and are found

on the eastern edge of the study site.

14

Sample sites in the foredunes, inland blowouts, forest edge, and wetpannes
contained planted Austrian pine stands that varied in size, density, and individual tree
characteristics. In the foredunes, the average stand size ranged from 9 m2 (consisting of 2
trees) to 7,500 m2 and averaged 1,853 m2. Density of foredune stands varied from 1.6
trees 100m'2 to 21 trees 100m’2 and averaged 9.1 trees 100m’2. Stand age ranged from
32-39 years and averaged 38 years. Average tree height was estimated as 6.9 m and
average stem diameter at breast height (DBH) (1.25 m above ground level) was 20.3 cm
(Leege 1997). Stands in the inland blowouts ranged in size from 576 m2 to 7,740 m2, and
averaged 2,276 m2. Stand density ranged from 1 tree mom2 to 28 trees 100m‘2, and
averaged 9.3 trees 100m", while stand age ranged from 33 years to 39 years and
averaged 35 years. Average tree height was estimated as 7.1 m and DBH as 15.6 cm
(Leege 1997).

Austrian pine stands adjacent to the native forest ranged in age from 34 to 41
years and averaged 38 years. Although forest-edge stand size was not estimated, since
sample sites were along a 50 m transect and 15 m into the native forest, Leege (1997)
documented that forest edge stands averaged 11.8 trees 100m'2. Average tree height was
estimated as 8.9 m and DBH as 14.8 cm (Leege 1997). Wetpannes ranged in size from
37.4 m2 to 1680 m2 and averaged 307.5 m2. Adjacent Austrian pine trees ranged in age
from 31-41 years and averaged 36 years, and average stand density was 11.7 trees 100m"2

(Leege 1997). Tree height was estimated as 9.6 m and DBH as 17.2 cm (Leege 1997).

15

Rates and spatial patterns of Austrian pine spread

To determine the rates and spatial patterns of Austrian pine spread, sampling
occurred in each of the 40 previously described habitat sites. Seedlings were deﬁned as
individuals less than 20 cm in height (Wenny and Dumroese 1991). Saplings were
individuals greater than 20 em but less than 30 years of age, thereby including all
Austrian pine regeneration. Seedlings and saplings that have established through natural
reproductive processes are termed regeneration, and collectively referred to as progeny.
Because this study was designed to determine the rates and spatial patterns of Austrian
pine spread from the original plantations, all individuals that had established through
natural processes (i.e., were not planted) were included. Since Austrian pine plantations
in the park were ﬁrst established in 1956, and the species typically starts reproduction
after 15 years of age (Burns and Honkala 1990), all Austrian pine progeny in the study
site were assumed to be less than 30 years of age. For comparative purposes, Jack pine
seedling and sapling densities were also estimated in each habitat and will be discussed in

Chapter 3.

Tree gge determination

Austrian pine age determination was based on DBH measurements and whorl
counts. Relationships between age and DBH were determined for each dune habitat with
the assistance of Mr. Joseph Harsh. See Appendix A1 for methodology and relationships

of age and DBH for all four dune habitats.

l6

Rate estimation

Estimates of the rates at which Austrian pine trees are spreading from planted
trees were based on analysis of the ages of seedlings and saplings and their distances
from presumed seed-source trees, which were assumed to be the closest mature

individual. The following equation was used:

Rate (m yr") = distance from seed source (m)

 

(age of seed source trees in years -15) - age of seedling and sapling (yrs)

The rate of spread (m yr") reﬂects the rate at which an individual Austrian pine tree has
become established in the dune habitat, based on its distance from the assumed parental
source and the ages of both the progeny and parental tree stand, and it is acknowledged
that some seeds may have been dispersed to greater distances than recognized in this
work. A factor of 15 years was subtracted from the age of seed source trees to account
for the fact that Austrian pine does not generally reproduce before age 15 (Burns and
Honkala 1990). Age of parental trees and larger sapling trees was estimated from DBH,
as described in Appendix A1. Age of seedlings and smaller saplings were based on the
number of branch whorls (Wenny and Dumroese 1991), and since most non-serotinous
pine seeds do not persist long in the soil bank (i.e., due to high predation rates), it was
assumed that seedlings established in the same year as seeds were dispersed (Richardson

1998a)

17

At each habitat site, random and targeted (i.e., non-random) lm2 plots were
sampled for Austrian pine regeneration. Targeted 1m2 plots were used to record the
occurrence of above-average densities of seedlings and saplings not included within the
random samples for the purpose of documenting all regeneration. but these data were not
included in any of the estimates of average values unless speciﬁed. It was acknowledged
that targeted plots were indeed selected non-randomly, and they were therefore data
additional to the random samples. Targeted plots included 1 in2 plots that contained ﬁve
or more seedlings (based upon average seedling densities estimated using random
samples) or any saplings (since saplings represent established individuals). In each 1m2
plot, seedling height, sapling stem diameters (cm), and whorl counts were measured for
age estimations. Distance (m) and direction of progeny relative to the parental source
were also recorded. Parental stand age was estimated from average tree DBH (see
Appendix A1).

In the foredune and inland blowout sites, randomly placed belt transects
containing 1m2 plots were run from the parental stands to 5 m or to the furthest extent of
regeneration in each cardinal direction (N , S, E. W). Transects extended to 5 m because
most regeneration occurred at the stand edge or in the immediate areas surrounding the
parental stands (see Results). Transects that were closer than 5 m to another stand in
foredune and inland blowout sites were omitted. Consequently, in three inland blowout
sites in close proximity to the other sites. transects were run in NE, NW, SE, and SW
directions.

Sampling along the forest edge was designed to document any Austrian pine

spread into the native deciduous forest at each of the 10 random sites. Along a 50 m

18

tape placed at the edge of the deciduous forest, five random lm2 plots were located at
the edge of the forest, 5 m, 10 m, and 15 m into the forest. Fifteen meters, rather than
5 m as in the other habitats, was chosen as the farthest distance to sample into the
native forest because of the poor visibility of Austrian pine progeny among the dense
deciduous forest trees.

Because the sampled wetpannes were typically surrounded by Austrian pine trees,
it was the spread of Austrian pine into the interior of the wetpanne that was measured.
Austrian pine seedling and sapling densities in the wetpannes were determined by
inventoryin g the entire wetpanne for regeneration and recording whether regeneration
was found in the wetpanne interior or at the edge (deﬁned as the outermost 2 m of the
wetpanne). The total number of seedlings and saplings was divided by the total
wetpanne area (m2) to estimate density. Nine wetpannes were completely inventoried
for regeneration. One wetpanne site, too large to be completely inventoried, was
sampled using 10 x 1m2 plots in both the edge and interior. Seedling and sapling
densities found at the edge and interior of the wetpannes were then compared.

Statistical tests were run on the regeneration densities at given distances (and
directions, used in determining spatial pattern) from the parental source. Using the SAS
statistical program, two-way analysis of variance (ANOVA) tests were performed to
detect differences between different distances and directions of Austrian pine
regeneration both between and within each habitat. Tukey-Kramer multiple comparison
tests were also performed, with direction and distance as two factors, to indicate at what
distances and directions from the Austrian pine stands most regeneration occurred. A

Significance criterion of 0t=0.05 was used for all statistical tests.

19

Spatial pattern

Austrian pine, seedling and sapling densities were estimated both underneath and
at the edge of planted Austrian pine stands. Sampling under and around the stands was
designed to determine if Austrian pine is reproducing underneath its canopy, and
therefore replacing itself, and/or if it is successfully reproducing at or beyond the edge of
its canopy, and therefore spreading. Within each habitat site in the foredunes, inland
blowouts, and wetpannes, ﬁve 1an plots were randomly placed underneath the Austrian
pine canopy and ﬁve 1m2 plots at the edge. Refer to Figure 2-4 for more detail on the
sampling procedure used in the 10 foredune and inland blowout sites.

In the forest edge sites, the previously described 1m2 plots extending from the
forest edge to 15 m into the forest were used to estimate rate and spatial pattern of
Austrian pine spread. Directions and distances from the parental source were measured
and recorded for all regeneration found in these sites.

Using SAS as the statistical program and (F005, one-way ANOVA‘S were
performed with location (underneath or at the edge of the canopy) as the factor to
determine differences between regeneration densities found in each location both
between and within each habitat. Tukey-Kramer multiple comparison tests were run to
indicate which location had the highest regeneration. To detect directional aspects of
spread, densities extending away from the parental stands were pooled for their direction
(N, S, E, W). Tukey-Kramer multiple comparison tests were used to identify the

direction(s) most correlated with regeneration for each habitat.

20

RESULTS

Rates and spatial patterns ofAustrian pine spread

Rates of spread

The mean rate of spread for Austrian pine, on a per-tree basis, across all foredune
sites was 0.06 m yr", while the mean rate across inland blowout sites was 0.20 m yr"
(Table 2-1, Table 2-3). These values were based upon random sampling of seedlings and
saplings. However, rates of spread obtained through targeted plots were higher because
of the inclusion of all regenerating seedlings and saplings: 0.18 m yr" in the foredunes
and 0.67 m yr" in the inland blowouts (Table 2-2, Table 2-4). Based on random
sampling across the foredune and inland blowout sites, mean rates of spread ranged from
0.00 in two sites to 0.28 m yr" in the foredunes, and 0.00 in ﬁve sites to 1.61 m yr" in the
inland blowouts. The maximum rate of spread observed for an individual. based on
random sampling, was 0.54 m yr" in the foredunes. and 0.73 m yr" in the inland
blowouts (Table 2-1, Table 2-3).

For the above stated reasons, targeted plots showed higher rates than randomly
selected plots in the foredune and inland blowout habitats (Table 2-2, Table 2-4). Rates
of spread obtained through targeted plots ranged from 0.01 to 1.88 m yr" in the foredunes
and 0.06 to 15 m yr'l in the inland blowouts. The maximum rate of spread for an
individual found in the entire study site. located in the inland blowout, was 15 m yr"

(inland blowout site #4), compared to 1.88 m yr" in the foredunes (foredune site #10).

Although the forest edge sites had very little regeneration compared to the other
dune habitats (Table A2-1, Figure 2-5). the mean rate of spread in the forest edge was
0.04 m yr" (Table 2-5). Based on random sampling, rates of spread ranged from 0.00 m
yr'l in two Sites to 0.12 m yr". However, rates as high as 2.1 l m yr" were seen in one

forest edge site (forest edge site #1) (Table 2-6).

In the wetpannes, although Austrian pine regeneration was found both underneath
and at the edge of planted Austrian pine stands, seedling densities were highest at the
canopy edge. Sapling densities were the highest in the wetpannes compared to the other
habitats, averaging 0.42 saplings m"2 underneath the canopy and 0.33 m"2 at the edge
(Table 2-7, Figure 2-5). However. there were no differences between the amount of
regeneration at the edge or underneath Austrian pine canopy (P=0.1707). There was site-
to-site variation of seedling and sapling densities in the interiors and edges of the
wetpannes, and there were no differences between densities found at the edge and interior

of the wetpannes (P=0.1689) (Figure 2-9).

Spatial pattern

Mean seedling densities found at the edge of Austrian pine stands were greater
than those found underneath the canopy in all habitats except the forest edge (Table 2-7.
Figure 2-5). In the foredunes. mean seedling density at the edge of Austrian pine canopy
was 2.19 m’2 compared to 1.34 m'2 underneath the canopy. In the inland blowout habitat,
mean seedling density was 1.48 m'2 at the edge of the canopy and 0.42 m‘2 underneath.

In the wetpannes. mean seedling density was 1.10 m'2 at the edge of the canopy and 0.36

m'2 underneath. However, in the forest edge habitat, the mean seedling density was 0.06
m'2 at the canopy’s edge compared to 0.12 m'2 underneath the canopy.

Mean sapling densities found at the edge of Austrian pine canopy were also
higher than underneath the canopy in the foredunes, 0.04 m‘2 and 0.00 m'2 respectively
(Table 2-7, Figure 2-5) In the inland blowout and forest edge, mean sapling densities
were the same at both locations (0.12 m"2 and 0.08 m'2 respectively). However, in the
wetpannes, the mean sapling density was higher underneath Austrian pine canopy than at
the edge of the canopy (0.42 m’2 and 0.33 m"2 respectively).

Only in the inland blowout habitat were there differences between regeneration
densities underneath and at the edge of the canopy (P=0.0004) (Table 2-8). However,
when comparing habitats, the foredunes had the greatest amount of regeneration
underneath the canopy (Lsmcans=0.8083), followed by the wetpannes (Lsmeans=0.2760)
and inland blowouts (Lsmeans=0.2013) (SAS. Inst. 2001, Tukey-Kramer Tests, (1:005).
The forest edge had the least amount of regeneration underneath the canopy
(Lsmeans=0.1665). Similarly, the foredunes had the greatest amount of regeneration at
the edge of the canopy (Lsmeans=0.6265), followed by the wetpannes (Lsmeans=0.61 19)
and inland blowouts (Lsmeans=0.4200) when compared to the other dune habitats. The
forest edge also had the least amount of regeneration at the edge of Austrian pine canopy
(Lsmeans=0.0400).

Based on random and non-random sampling, the average number of progeny was
greatest at the edge of the Austrian pine canopy and decreased as distance increased from
the stand edge in the foredune, inland blowout, and forest edge habitat (Figures 2-6 to 2-

8, Table A2-1). There was a trend in all three habitats, although there were no strong

23

correlations between the average number of progeny and distance from parental stand.
The strongest relationship between the average number of progeny as a function of the
distance from the parental stand was found in the inland blowout (R2=0.557). In the
foredunes, there was a weaker relationship between the average number of progeny and
distance from the parental stand (R2=0.4526). The forest edge had the weakest
correlation (R2=0.3488).

In the foredunes and inland blowouts, the highest mean number of Austrian pine
progeny was found at the edge of the stands and decreased with distance from the stand
edge (Figure 2-6, Figure 2-7, Table A2-1). The mean number of progeny was based on
the total number of progeny found at a given distance from the stand edge or underneath
the stand divided across all 10 sites per habitat. In the foredunes, the mean number of
Austrian pine progeny found at the stand edge was 29.6 individuals which decreased by
68% at 1 m from the stand to 9.5 individuals. The mean number of progeny continued to
decrease with distance from the stand. The mean number of progeny found underneath
the stand was also 51% less than the mean number found at the edge of foredune stands
(14.5 individuals), and at least one individual was 22 m from the parental stand in this
habitat (Figure 2-6, Figure 2-10). In the inland blowouts, the mean number of Austrian
pine progeny found at the edge, 13.6, decreased by 52% to 6.5 at Im from the stand edge,
and continued to decrease with distance from the stand. The mean number of progeny
found underneath the stand was also 55% less than the mean number found at the edge of
inland blowout stands, and progeny were found out to 19 m from the parental stand in

this habitat (Figure 2-7, Figure 2-13).

24

In the forest edge habitat, similar to the foredunes and inland blowouts, the
highest mean number of Austrian pine progeny was found at the edge of the forest (1.3
individuals) (Figure 2-8). Progeny decreased by 54% to 0.6 individuals at 1 m into the
forest, and increased to 1.2 individuals at 5 m into the forest and decreased again with
distance into the forest. However. one Austrian pine tree, located through non-random
sampling, was found 28 m into the forest under dense forest canopy (Table A2-l , Figure
2-8, Figure 2-16). This suggests that although the forest edge generally is not conducive
to Austrian pine regeneration, there are cases of substantial penetration (e.g., 28 m) into
the forest.

The patterns of Austrian pine spread in the foredunes showed high variability
across years of progeny establishment (Figure 2-10). Most spread occurred within a few
meters from the planted stands in the north and west directions. However, progeny that
were established in 1993, 1994, 1996, and 1997 all showed a southwesterly direction of
spread. The 10 year sapling found 22 m from the stand edge may be an outlier in these
data.

The average size of the original planted Austrian pine stands located in the
foredunes was estimated as 1,853 m2. Based on age analysis using tree DBH, the average
age of foredune stands was 38 years (Table 2-1). As of 2001 , the maximum percent
increase in area of Austrian pine spread in the foredunes was 153% estimated by the
maximum frontier of Austrian pine spread. deﬁned as the greatest distances that Austrian
pine progeny were found from a stand edge in each direction in the foredunes (Figure 2-
1 1). However, the average percent increase in area of Austrian pine spread in the

foredunes was found to be 37%. estimated by the average frontier of spread across all ten

I-J
UI

foredune sites (Figure 2-12). Therefore, 38 years after the foredune trees were originally
planted in 1963, the average stand size increased in area by 37% to 2.529 mg.

Although Austrian pine spread in the inland blowouts varied annually, spread was
mainly to the northeast (Figure 2-13). Spread was also seen more frequent to the north
and east, but visible in all cardinal directions from the planted stands. In the early years
of pine spread (i.e., 1983-1989). most regeneration was found within 5 m from the
parental stands. In years 1983, 1987, 1991, 1993, and 1994, there was only 1 remaining
individual from the frontier of spread of those years and could potentially be an outlier.
Using established DBH to tree age relationships in the inland blowout. the average
Austrian pine stand in the inland blowouts was estimated as 35 years (planted in 1966)
with a size of 2,276 m2. As of 2001, the maximum percent increase in area of Austrian
pine spread in the inland blowouts was 132%. estimated by the maximum frontier of
Austrian pine spread (Figure 2-14). However. the average percent increase in area of
Austrian pine spread in the inland blowouts was found to be 25% (Figure 2-15).
Therefore, 35 years after the original Austrian pine plantings in the inland blowouts,
these stands have increased in area on average by 25% to 2855 m2 (Figure 2-15).

Although spread into the native forest was limited, there was a general pattern of
northern spread into the forest edge (Figure 2-16). Similar to the foredunes and inland
blowouts, the pattern of Austrian pine spread was variable across years. In many cases.
there is only one individual from certain age classes (i.e., individuals established in 1981,
1983, 1984, 1988, 1989, 1990, 1997, and 1999) and could potentially be outliers.
exhibiting rare spread events into the native forest. As previously mentioned, there was

one individual found 28 m (northeast) from the presumed parental source, as well as an

26

individual of age 4 years found 20 m north from the parental trees. These indicate that
long distance seedling establishment events are possible, even within the dense native
forest or via animal transport. Average stand increases in the forest edge and wetpannes
were not estimated since spread was measured into the native forest (with little
regeneration found) and into the wetpannes from planted adjacent stands.

Although the average number of Austrian pine seedlings and saplings were higher
in the wetpanne interior than at the wetpanne edge (25.2 and 13.7, respectively), there
were no differences between the number of seedlings and saplings found at either

wetpanne location (P=0.1689) (Figure 2-17).

Primary directions ofspread

In the foredunes. the majority of Austrian pine spread is within two meters from
the parental stands in the northern and western directions, shown statistically and also
through observation (Table 2-9, Table 2-10, Table A2-1, Figure 2-10). Although the
majority of spread was to the north and west of the planted stands, spread in the eastern
and southwestern directions was also observed (Figure 2-10). The pattern of spread in
the inland blowouts is primarily in the northern and eastern directions. with the majority
of progeny in the northeastern direction (Table A2-1, Figure 2-13). Statistically, the
primary directions of spread were between 1 and 3 m from the parental stand to the north
(Table 2-9, Table 2-10).

Austrian pine spread into the forest edge is mainly between the edge and 5 m into

the forest, but there were no statistical differences among regeneration densities found at

27

different locations in this habitat (P=0.2751) (Figure 2-8). Although spread in the forest
edge habitat is limited and Austrian pine does not appear to be signiﬁcantly spreading

into the forest, patterns of spread display a northern direction (Figure 2-16).

DISCUSSION

Overview

Rates of Austrian pine spread across the study site were highest in the inland
blowouts, averaging 0.20 m yr", and lowest in the forest edge, averaging 0.04 m yr"
(Table 2-3, Table 2-5). The foredunes exhibited intermediate rates of spread, averaging
0.06 m yr"(Table 2-1). Furthermore. rates as high as 15 m yr" were seen in the study site
and at least some penetration (i.e.. up to 28 m) into the native deciduous forest was
observed (Table 2-4, Figure 2-16). Austrian pine spread is primarily in the northern
directions, due to the prevailing southwesterly winds of Lake Michigan. On average,
foredune stands have increased in area by 37% since original plantings in 1963, while
inland blowout stands have increased 25% since 1966. While regeneration was found in
all dune habitats, most regeneration occurred at the edge of the Austrian pine stands in
the foredune and inland blowout habitats and in the wetpannes. In the foredunes. forest
edge, and inland blowouts. average number of progeny was related to distance from the
parental source, although the square of correlation values were not signiﬁcant (ranged
from R2=0.3488 to R2=0.557). The wetpannes contained the highest sapling densities

(0.42 m'2 underneath Austrian pine canopy and 0.33 m'2 at canopy edge). due to greater

28

densities of seed source trees and favorable soil moisture conditions compared to the
other dune habitats. Although the wetpannes contained high levels of Austrian pine
regeneration, there were no differences between regeneration found at the wetpanne

interior and edge, suggesting no differential spread into the wetpannes (P=0.1689).

Rates and spatial patterns ofA ustrian pine spread

Mean rates of Austrian pine spread in the inland blowouts ranged from 0.00 m
yr" in some Sample stands to 1.61 m yr" in others, with an average of 0.20 m yr" across
the ten sites (Table 2-3, Table 2-4). However, maximum rates of spread in this habitat
and for the study site were as high as 15 m yr", and progeny were found up to 19 m from
the parental source (Table 2-4, Figure 2-13). Rates of spread in the foredunes ranged
between 0.00 and 0.28 m yr", with an average of 0.06 m yr" across the ten sites (Table
2-1, 2-2). Rates inthe foredunes were as high as 1.88 m yr", and progeny were found up
to 22 m from the parental stand (Table 2-2, Figure 2-10). Consistent with Leege (1997)
and Leege and Murphy (2001), the forest edge had the least amount of Austrian pine
regeneration. Although regeneration densities in this habitat were relatively low, it is
notable that at least one Austrian pine individual was found 28 m into the forest under
dense forest canopy. This also suggests that similar relatively long-distance dispersal
events may have occurred in the other habitats as well, and perhaps the wrong parental
source may have been assumed. It is also recognized that pine dispersal via animal
' transport may be possible and account for long-distance dispersal events, such as

individuals found deep into the native forest. Rates of spread ranged from 0.00 to 0.12 m

yr", averaging 0.04 m yr", and reached as high as 2.1 1 m yr" in one site (Tables 2-5.
Table 2-6).

Although the foredune and inland blowout habitats had the highest seedling
densities, the highest sapling densities were found in the wetpannes (Figure 2-9). This
may be a result of greater seed production but lower survivorship in the foredunes and
inland blowouts, as well as greater soil moisture levels in the wetpannes, consistent with
Leege (1997) and Leege and Murphy (2000). In the foredune, forest edge. and inland
blowout habitats, regeneration occurred both underneath and at the edge of the Austrian
pine canopy, but the greatest densities and average numbers of progeny occurred at the
stand edge, consistent with previous studies on pine seed fall (Yocum 1968, Richardson
1998a) (Figure 2-6 to 2-8). This suggests that the planted stands are both replacing
themselves and expanding in area of coverage. All three habitats had a similar trend of
decreasing average numbers of progeny as distance increased from stand edge, consistent
with McCaughey et a1. (1986) who documented that the pattern of pine seed dispersal
was exhibited by a negative exponential curve with a peak frequency at the edge of the
parental tree stands. However, the foredunes and inland blowouts had a stronger
correlation between the average number of progeny and distance from the parental stand
than the forest edge. The most signiﬁcant correlation was in the inland blowouts
(R2=0.557) (Figure 2-7).

Austrian pine spread is mainly towards the north in the foredunes and northeast in
the inland blowouts, resulting from the prevailing southwesterly winds (Figures 2-10 to
2-15). Pine spread was also observed to the west of the foredune stands (Figure 2-10),

unexpected from the direction of the prevailing winds. However, this may be caused by

the more open dune areas to the west of the foredunes stands or due to complicated
eddies not found in other habitats. Although spread was limited in the native forest, a
general pattern of spread to the north was shown in the forest edge habitat. Austrian pine
stands in the foredunes have increased, in area, on average by 37%, while the stands in
the inland blowouts have increased on average by 25% (Figure 2-12, Figure 2-15).
However, based on the maximum distances Austrian pine progeny were found from a
stand edge across all foredune and inland blowout sites, foredune stands increased up to
153% and inland blowout stands increased up to 132% (Figure 2-11, Figure 2-14). This
shows the potential for Austrian pine spread in these habitats. Inland blowout sites had
the greatest amount of local dispersal events around Austrian pine stands in the study site,
consistent with the literature on the spread of pines, due to ‘take off sites’ where seeds
may be dispersed at farther directions from the original Austrian pine stands (Richardson
and Bond 1991). Although the wetpannes contained high regeneration densities
(especially sapling densities), there were no statistically signiﬁcant differences between
densities found at the edge and interior of the wetpannes (P=0.1689) (Figure 2-17). This
indicates that seedlings and saplings established equally as well in both locations.
Because most wetpannes were surrounded by mature Austrian pine trees, it was spread
into the wetpannes that was documented whereas possible spread away from the
wetpannes was not determined.

Although there are few documented examples of the spatial patterns of pine
spread over a large area extending from planted pine stands, the spatial pattern and
densities of Austrian pine spread in the study site were higher than those found by Belton

and Ledgard (1991). Belton and Ledgard (1991) documented pine spread in Australia

31

that ranged from 1 individual/ 200 m2 to as low as 1 individual/ 100,000 m2. In the study
area, the spread of Austrian pine is remarkably greater in density than those found by
Belton and Ledgard (1991), which may suggest that Austrian pine spread is quite
vigorous and aggressive compared to other examples of the spread of invasive pines.
However, rates of Austrian pine spread in the study site are lower than average rates of
native pine spread in North America and Europe (Richardson et al.1994), which range
from 81-400 m yr". Richardson et al. (1994) cited rates of pine spread based on pines
spreading in their native habitats. and not those for exotic or invasive pines in novel
(especially harsh) conditions. Finally, more examples of local patterns of pine spread in
and around planted stands in non-native regions is needed to fully characterize and

compare Austrian pine spread on the dunes of Lake Michigan.

Habitats most invaded by Austrian pine

The wetpannes are considered the most invaded and thus the most endangered
dune habitat in the study site, due to high Austrian pine seedling and sapling densities and
the high concentration of seed—source trees, consistent with previous dune research
(Leege 1997, Leege and Murphy 2000, 2001, Sherﬁnski 2000). Stands in the wetpannes
contained high densities of seed-source trees relative to the other dune habitats and have
contributed to the successful regeneration of Austrian pine (Leege 1997). Austrian pine
may also reduce ground water levels in these areas. as supported by Sherﬁnski (2000),
and also may affect other dune areas by producing large numbers of progeny due to the

high concentrations of parental trees. The wetpannes possess unique dune ﬂora and

L.)
to

fauna, resulting from higher soil moisture, and therefore are at an even greater risk from
Austrian pine alteration than the other dune habitats. Although stand densities in the
inland blowout were signiﬁcantly lower than in the wetpanne, the inland blowouts
contained the highest rates of spread and may harbor take-off sites to aid in further
Austrian pine spread. The inland blowouts, therefore, should also be closely monitored

for future impacts of Austrian pine.

Conclusions

All dune habitats within the study site contained Austrian pine regeneration.
Regeneration occurred both underneath and at the edge of the Austrian pine canopy, but
the greatest densities occurred at the edge. This suggests that the planted stands are both
replacing themselves and expanding in area of coverage. On average. the foredune
stands have increased 37% since 1963, while the inland blowout stands have increased
25% since 1966.

Austrian pine spread is mainly towards the north in the foredunes and forest edge
and northeast in the inland blowouts. resulting from the prevailing southwesterly winds.
Mean rates of Austrian pine spread in the inland blowouts ranged from 0.00 m yr" in
some sample stands to 1.61 m yr" in others, with an average of 0.20 m yr" across the 10
inland blowout sites. However, maximum rates in this habitat were as high as 15 m yr".
Rates of spread in the foredunes ranged between 0.00 and 0.28 m yr". with an average of
0.06 m yr" across the 10 foredune sites. Maximum rates in the foredunes were as high as

1.88 m yr". The forest edge had the least amount of Austrian pine regeneration.

b)
b)

However, at least some penetration into the native forest was observed (i.e., up to 28 m).
Rates of spread ranged from 0.00 to 0.12 m yr", averaging 0.04 m yr", and reached as
high as 2.11 m yr" in one site. The wetpannes contained high regeneration densities
relative to the other dune habitats (0.42 and 0.33 saplings m'z. underneath and at the edge
of Austrian pine canopy, respectively). most likely attributed to high soil moisture levels
and proximity to seed-source trees. However. there were no clear differences between
regeneration found at the edge and interior of the wetpannes (P=0.1689). suggesting that

regeneration occurs equally as well at both locations.

Table 2-1. Mean Austrian pine rates of spread (m yr") per plant across 10 foredune sites.
based upon randomly selected 1 m2 plots extending from the edge of parental stands to 5

m or until regeneration was no longer observed.

Table 2-2. Mean Austrian pine rates of spread (m yr") per plant across 10 foredune sites,
based upon non-random 1m2 plots extending from the edge of parental stands to varying

distances.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Site# Mean SE Min Max N Parental

Rate Rate Rate (# m2 age (yrs)
plots)

1 0.000 0.000 O 0 20 32.1

2 0.002 0.002 0 0.04 20 38.9

3 0.002 0.002 0 0.05 32 37.9

4 0.283 0.017 0 0.51 20 37.4

5 0.045 0.015 0 0.20 20 37.4

6 0.008 0.005 0 0.06 20 37.2

7 0.048 0.012 0 0.18 20 38.4

8 0.043 0.013 0 0.13 20 38.4

9 0.000 0.000 0 0.00 20 38.9

10 0.118 0.033 0 0.54 28 39.1

Mean 0.06 37.6

SE 0.03 0.61

Total N 10 220 10

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Site# Mean SE Min Max N (# Parental

rate Rate Rate m2 age (yrs)
plots)

1 0 32.1

2 0.117 0.001 0.11 0.12 5 38.9

3 0 37.9

4 0.078 0.006 0.03 0.17 60 37.4

5 0 37.4

6 0.056 0.043 0.01 0.12 6 37.2

7 0.081 0.008 0.05 0.14 28 38.4

8 0.159 0.069 0.05 0.56 7 38.4

9 0.318 0.130 0.04 0.45 3 38.9

10 0.437 0.077 0.05 1.88 23 39.1

Mean 0.18 37.6

SE 0.01 0.61

Total N 7 132 10

 

35

 

 

Table 2-3. Mean Austrian pine rates of spread (p1 yr") per plant across 10 inland
blowout sites based upon randomly selected lm‘ plots extending from the edge of
parental stands to 5 m or until regeneration was no longer observed.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Site# Mean SE Min Max N (# Parental

Rate Rate Rate m2 age (yrs)
plots)

1 1.612 0.032 0 0.40 20 33.5

2 0.003 0.003 0 0.006 20 33.6

3 0.000 0.000 0 0.00 20 34.7

4 0.000 0.000 0 0.00 20 33.2

5 0.000 0.000 0 0.00 20 33.4

6 0.000 0.000 0 0.00 20 36.8

7 0.109 0.014 0 0.27 20 34.9

8 0.169 0.032 0 0.48 20 37.6

9 0.055 0.034 0 0.73 20 36.5

10 0.000 0.000 0 0.00 20 38.7

Mean 0.20 35.3

SE 0.16 1.1

Total N 10 200 10

 

 

 

 

 

 

 

 

Table 2-4. Mean Austrian pine rates of spread (m yr") per plant across 10 inland
blowout sites based upon non-random lm2 plots extending from the edge of parental
stands to varying distances.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Site# Mean rate SE Min Max N (# Parental

Rate Rate at2 age (yrs)
- plots)

1 0.298 0.149 0.15 0.46 4 33.5

2 0 33.6

3 0.874 0.357 0.08 2.08 6 34.7

4 1.866 1.265 0.06 15.00 1 1 33.2

5 0.143 0.338 0.06 0.35 14 33.4

6 . 0 36.8

7 0.067 0.001 0.07 0.070 3 34.9

8 0.559 0.121 0.09 1.38 12 37.6

9 0.727 0.000 0.73 0.73 I 36.5

10 0.865 0.045 0.82 0.91 2 38.7

Mean 0.67 35.3

SE 0.20 1.1

Total N 8 53 10

 

 

 

 

 

 

 

 

Table 2-5. Mean Austrian pine rates of spread (m yr") per plant across 10 forest edge
sites based upon randomly selected lm‘ plots at the forest edge, 5 m. 10 m, and 15 m into

the forest.

Table 2-6. Mean Austrian pine rates of spread (m yr") per plant across 10 forest edge
sites based upon non-randomly selected lm‘ plots at varying distances into the forest.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Site# Mean rate SE Min Max N (# Parental

Rate Rate at2 age (yrs)
plots)

1 0.116 0.092 0 1.82 20 38.5

2 0.069 0.022 0 0.27 20 39

3 0.061 0.045 0 0.66 20 38.7

4 0.039 0.034 0 0.67 20 33.9

5 0.002 0.002 0 0.04 20 39.8

6 0.000 0.000 0 0 20 41.3

7 0.025 0.025 0 0.50 20 39.1

8 0.009 0.009 0 0.176 20 38.7

9 0.000 0.000 0 0 20 36.5

10 0.092 0.072 0 1.43 20 38.9

Mean 0.04 0.013 38.5

SE 0.14 1.0

Total N 10 200 10

 

 

 

 

 

 

This table shows only sites that had non-random plots included.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Site# Mean rate SE Min Max N (# Parental

Rate Rate m2 age (yrs)
plots)

1 1.118 0.054 0.05 2.11 5 38.5

2 0.134 0.062 0.04 0.44 6 39

3 0 38.7

4 0.908 0.573 0.34 1.48 2 33.9

5 0.042 0.000 0.04 0.04 1 39.8

6 0.106 0.026 0.08 0.16 3 41.3

7 0 39.1

8 0.416 0.086 0.16 0.417 9 38.7

9 0 36.5

10 0.98 0.289 0.05 1.82 5 38.9

Mean 0.53 31 38.5

SE 0.19 1.0

Total N 7 200 10 I

 

 

 

 

37

Table 2-7. Mean Austrian pine regeneration densities (#ind/mz) underneath and at the
edge of Austrian pine stand in each dune habitat. Densities were taken from ﬁve
randomly placed 1m2 plots both underneath and at the edge of Austrian pine canopy in
each habitat site. Ten sites were randomly selected in each dune habitat.

 

 

 

 

 

 

 

 

 

 

Underneath cano At edge of canopy
Habitat Seedling SE Sapling SE Seedling SE Sapling SE
Foredune 1.34 0.17 0.00 0.00 2.19 0.41 0.04 0.01
Forest edge 0.12 0.04 0.08 0.01 0.06 0.0 | 0.08 0.01
Inland blowout 0.42 0.07 0.12 0.02 1.48 0.23 0.12 0.03
Wetpanne 0.36 0.08 0.42 0.13 1.10 0.14 0.33 0.06

 

 

 

 

 

 

Table 2-8. Statistical comparison of mean Austrian pine regeneration densities
underneath and at the edge of Austrian pine canopy within each dune habitat (SAS Inst.
2001, one-way ANOVA (1:0.05). Densities were taken from ﬁve randomly placed 1m2
plots both underneath and at the edge of Austrian pine canopy in each habitat site. Ten
sites were randomly selected in each dune habitat.

 

 

 

 

 

 

 

 

 

Habitat Differences between Austrian pine Signiﬁcance
regeneration densities underneath value (P)
and at the edge of Austrian pine
canopy?

Foredune No 0.2014

Forest edge No 0.2052

Inland blowout Yes 0.0004

Wetpanne No 0.1707

 

 

Table 2-9. Directions of Austrian pine spread in the foredunes and inland blowouts.
based on pooled random and non-random sampling. Random sampling included
transects extending in all four cardinal directions from edge of parental stand to 5 m or to
farthest extent of Austrian pine regeneration, while non-random sampling included
regeneration observed not previously in random samples

 

 

 

 

 

 

 

 

 

 

Habitat Direction Signiﬁcance value
(LSMEANS)

Foredune North* 0.1543

West 0.1212

East 0.0396

South 0.0050
Inland blowout North“ 0.093

East 0.035

South 0.0106

West 0.0050

 

 

 

 

* indicates the cardinal direction most statistically signiﬁcant in locating Austrian pine
regeneration in each dune habitat

Table 2-10. Austrian pine regeneration occurring away from edge of parental stands in
all four cardinal directions in each dune habitat. The following is a list of the distances
and corresponding directions most statistically signiﬁcant in locating Austrian pine
progeny away from the parental stands (SAS Inst. 2001, ANOVA and Tukey-Kramer
tests, a=0.05). Random and non—random data were pooled for this analysis in each
dune habitat.

 

 

 

 

 

 

 

 

 

 

 

 

 

Habitat Distance Direction Signiﬁcance value

(m) (Lsmeans)
Foredune I W 0.650

1 N 0.639

2 N 0.444

2 W 0.300

10 E 0.250

1 1 E 0.250
Inland Blowout l N 0.325

2 N 0.200

3 N 0.125
Forest Edge ** ** **
Wetpanne ** ** **

 

 

 

 

 

** indicates no statistically signiﬁcant directions in locating Austrian pine progeny

 

Foredune Wetpanne Inland Blowout Forested dunes

Figure 2-1. Various dune habitats in the Lake Michigan sand
dune ecosystem.

4O

    

$Saugatuck Dunes State Park

...... :-.---S; :? v\\ ‘ NorthT

Scale: 1:2,8 50,000

 

I
‘v

Figure 2-2. Location of study site (Saugatuck Dunes State Park), in Allegan
County, MI (from Cowles 1899). The Natural Area lies within the park.

41

 

Figure 2-3. Study site: Saugatuck Dunes State Park Natural Area (SDSPNA). Austrian
pine plantations can be seen as dark lines (see arrow for example) in the foredunes and
inland blowout habitats. 1cm=120m.

Key:

I = foredune site 0 = inland blowout site

A = wetpanne site * = forest edge site

42

 

5m

Ni

II... 1.4% v *2 I'll.

/%A Agar

Austrian pine stand

 

A = Austrian pine mature tree

ﬁ, =1m2 plot that is randomly sampled underneath Austrian pine
cano

* =1 m plot that 15 randomly sampled at edge of Austrian pine
canopy

 

 

 

Figure 2-4. Sampling model for foredune and inland blowout sites, including randomly
placed 1m2 plots underneath and at the edge of an Austrian pine stand and transects
extending 1n all four cardinal directions (targeted 1m2 plots are not shown here). * In all
Im2 plots, both Austrian pine regeneration densities and abiotic and biotic dune factors
were measured.

*Note: in three inland blowout sites. transects were placed in NE, NW. SE, and
SW directions to avoid interference with other Austrian pine stands

43

Mean Austrian pine regeneration densities undemeaﬂi and at
the edge of Austrian pine canopy (#indlmZ)

 

 

 

 

 

3 22 2 2 2 222 2 222-222-222--. 2
. 2: 2_5 .22- _ 2 2 2 2 2 - - - 2 - 2 - 2 c1 seedlings
'5 under
‘ 5 2 _ _g_ g 2.2 g g g _ _ _~_ _ - p canopy
‘ 0 ﬁ‘ Iseedlings
i S E t d f
..‘U1.5r- .—— - 2 2 aegeo
E 5 l2: canopy
'1 o E .
r: 1 * 2:5; -* 22 - ~ -— Dsaplangs
. g a, under
1% 0'5 .2- 51:22 2222 22 _2 canopy
. n saplings at
0 edge of
Foredune Forest edge Inland blow out Wetpanne canopy

‘ Dune habitat
Figure 2-5. Mean Austrian pine regeneration densities (#ind/mz) underneath and at the
edge of Austrian pine canopy in each dune habitat. See Table 2-7 for exact values. Five
randomly placed 1m2 plots were sampled both underneath and at the edge of Austrian
pine stands in each habitat site.

Mean number of Austrian pine progeny extending from foredune
Austrian pine stands

40 .2... 2.22.2. __ . . ._ _...__._-2 . __ 2

1 E 35 .__._22.__-._22._2 222- .. 2.-. - . . . -2_-_.. 2.. .-22.__2.2 2222.2-.2...2.-2 . .-_2_ 22-2
‘5 g, y= 4.6828Ln(x) + 14.029
.9 30 -— 2 ~ 2 22221-22----2____22__2. -
. a R -0.4526
.uo- 25 .22 2.--222- .2 - -2 2-_ .. 22. .-_..-,.222---2_.-.- ....---_.-2. -
1 3

a
l E
. 3
‘ C
1 6:

>

<

 

 

-10.7122.63468101214161820
meters away from Austrian pine stand

Figure 2-6. Mean number of Austrian pine progeny extending from the edge of mature
Austrian pine stands across the ten foredune sites, based on random and non-random
sampling. Locations underneath the canopy are designated as “-1." Random sampling
was performed using randomly located 1m plots underneath and at edge of canopy and
along transects running N, S. E. W fromthe edge of the stand to 5 m or the furthest extent
of Austrian pine regeneration. Non-random sampling occurred wherever regeneration
Was observed not previously captured in the random samples.

44

Mean number of Austrian pine progeny extending from inland
blowout Austrian pine stands

45 2..-222222222. .- 2222- 22. . .- .22. _ -22 -_2--- _

 

 

 

- 2221152219121-11(82‘2725-269 22-}
1 5 R2: 0.557 %

 

 

 

 

 

 

Avg. num

 

 

 

-1 1 2 4 6 7 9 11 12.2 14 16 18 19
meters away from Austrian pine stand

Figure 2-7. Mean number of Austrian pine progeny extending from the edge of mature
Austrian pine stands across the ten inland blowout sites, based on random and non-
random sampling. Locations underneath the canopy are designated as “-1.” Random
sampling was performed using randomly located 1m2 plots underneath and at edge of
canopy and along transects running N, S, E, W from the edge of the stand to 5 m or the
furthest extent of Austrian pine regeneration. Non-random sampling occurred wherever
regeneration was observed not previously captured in the random samples.

A
(.11
l
l

—-..~2«-_-._.2.2 -..‘~._.~22 “.4“- .-.._-.......a.-—...... 2,.__.._,2__-_.. 2.2-2... ....--_.2.t-~.

8
l
l
l
l
I
1
l
1
l
l
l
l
1
l
l

(J!
l
i
l
l
l
1
l
1
l

 

y= -0.2248Ln(x) + 0.7581
R2: 0.3488 " '

o
I
l
l
1
1

1
1
1
1
1
1
1

NNMU

o
l
l
l
1
l
l
l
l
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l
l
l
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Avg.tnumber of progeny 4
a
1
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l
|
1
i
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l
1
I
1
1
I

 

 

 

O U!
l
1
1
1

012 4 6 81012141618202224262830
meters away from Austrian pine stand

Figure 2-8. Mean number of Austrian pine progeny extending from the edge of mature
Austrian pine stands into the native forest across ten forest edge sites. based on random
and non-random sampling. Random sampling was performed using ﬁve random 1m2
plots at forest edge, 5 m, 10 m, and 15 m into the forest at each of ten forest edge sites.
Non-random sampling occurred wherever regeneration was observed not previously
captured in the random samples of the ten forest edge sites. Note: there were no
statistically signiﬁcant differences between densities found at each location into the forest
(SAS Inst. 2001, one-way ANOVA, (1:0.05, P=0.2751).

45

Austrian pine regeneration densities in

 

 

 

 

 

 

1 wetpannes
0.9 .——‘———-— 2 ﬂ 2 T _ 2 2

8 0.8

‘5
+3 0.7

c A

N08

8 g
.3 c

g 30.4
1 2 T
. 8, 0.3
‘ e» 0.2

1:

.0
u—I

 

 

 

 

 

 

 

 

O

 

1 2 3 4 5 6 7 8 9 10
Wetpanne Sites

Figure 2-9. Mean Austrian pine regeneration densities (#ind/mz) at edge and interior of
the wetpannes. In nine wetpannes, densities were calculated by inventorying the
wetpanne for regeneration and dividing by total area. One wetpanne site was sampled for
regeneration using 10 random 1m2 plots at the edge and interior of the wetpanne. Note:
there were no statistically signiﬁcant differences between densities occurring at the edge
and interior of the wetpannes (SAS Inst. 2001, one-way ANOVA, 01:0.05, P=0.1689).

46

1995 10 m
2000 North

1991

 

 

10m 22m

 

l

 

 

£393 . , I 10 m I
Austrian pine spread from edge of planted stands in the foredunes
Ke : C —— Frontier of Austrian ine 5 read
y .3 3:85 E yr. old p p
A 3 yr. old 7 yr. 0:3
82.4 yr. old 3118 I£13181
.5ytom

Figure 2-10. Austrian pine spread from edge of planted stands in the foredunes.
Sampling was based on randomly and non-randomly located 1m2 transect belts running
N, S, E, W from the edge of the stand to 5 m or the furthest extent of Austrian pine
regeneration in 10 sites. Non-random sampling occurred wherever regeneration was
observed not previously captured in the random samples. Note: original Austrian pine
foredune stands were planted in 1963, based on average tree age estimates and stand size

is not drawn to scale.

47

9m

  

12

   

' L
Original Austrianpie
stand 1963 22 m

2m
1 50m

 

9m

Figure 2-11. Maximum frontier of Austrian pine spread in the foredunes as of 2001.

This ﬁgure shows the outermost distances that Austrian pine progeny were found from
the stand edge in each direction and indicates the maximum area of spread across the ten
foredune sites. According to this analysis, foredune stands have increased in area by a
maximum of 153% since original plantings in 1963. Stand age was based on average tree
age estimates.

 

Figure 2-12. Average frontier of Austrian pine spread across 10 foredune sites as of
2001. This ﬁgure shows the average outermost distances that Austrian pine progeny
were found from the stand edge in each direction. According to this analysis, the average
Austrian pine foredune stand increased in area by 37% sine original plantings in 1963.
Stand age was based on average tree age estimates.

48

1993

16m

   

1987, 1991

i; ' 17m

Austrian pine spread from edge of planted stands in the inland blowouts

o 1 yr. old - 6 yr. old . 12 yr. Old V 18 yr. old

. 2 yr. old : 7 yr. old 6' 13 yr. old
A 3 yr. old 3 Y'- Old 63 14 yr. old
A 4 yr, old W 10 yr. old a 15 yr. old

5yr. old *11yr.o|d C>16yr.old

——Frontier of Austrian pine spread

Figure 2-13. Austrian pine spread from edge of planted stands in the inland blowout
habitats. Sampling was based on randomly and non-randomly located lmz transect belts
running N, S, E, W in most sites and NE, NW, SE, SW in three sites from the edge of the
stand to 5 m or the furthest extent of Austrian pine regeneration. Non-random sampling
occurred wherever regeneration was observed not previously captured in the random
samples. Note: original stands were planted in 1966, based on average tree age estimates

and stand size is not drawn to scale.

49

iOriginaIAustrian pine

31.3.1968)

 

 

17m

Figure 2-14. Maximum frontier of Austrian pine spread in the inland blowouts as of
2001. This ﬁgure shows the outermost distances that Austrian pine progeny were found
from the stand edge in each direction and indicates the maximum area of spread across
the ten inland blowout sites. According to this analysis, inland blowout stands have
increased in area by a maximum of 132% since original plantings in 1966. Stand age was
based on average tree age estimates.

     
 

Original Austrian pine

stand 1966 x 2.5m

50m

2.5 m

Figure 2—15. Average frontier of Austrian pine spread across 10 inland blowout sites as of
2001. This ﬁgure shows the average outermost distances that Austrian pine progeny
were found from the stand edge in each direction. According to this analysis, the average
Austrian pine inland blowout stand increased in area by 25% since original plantings in
1966. Stand age was based on average tree age estimates.

1999—}.
28m

1997——) AZOm A

1990\ North
‘1-

 

1933 I 8.x {—1984, 1981

l
1989—} g 5 m r 10 m
Austrian pine spread from edge of planted stands into the native forest

O1r.old I51" Old O12yr old :1 rolId
.2yr old I61yr old O13y rold~ 110071

J
I

A4 yr. old yr. old 014 yr old i 18 yr ol|d
—Frontier of Austrian pine spread 20 yr. Old

Figure 2-16. Austrian pine spread from edge of planted stands into the native forest,
based on randomly and non- -randomly 1m2 plots at distances into the forest. Non- random
sampling was used wherever regeneration was observed not previously captured in the
random samples. Note: original stand were planted in 1963, based on average tree age
estimates and stand size is not drawn to scale.

Planted Austrian pine tree
(1965)

   
     

Wetpanne edge

  

A

13.7

 

Figure 2-17. Mean number of Austrian pine seedlings and saplings found at wetpanne
interior and edge. Nine wetpannes were surveyed for Austrian pine regeneration, and one
wetpanne, too large to survey, was sampled using 10 l-m2 plots at the wetpanne edge and
interior. The wetpanne edge was deﬁned as the outermost 2 m of the wetpanne.
Although there was greater regeneration at the interior of the wetpannes, there were no
signiﬁcant differences between regeneration found in the interior and at the wetpanne
edges (P=0.1689).

CHAPTER 3
REGENERATION NICHES OF INTRODUCED, INVASIVE
PINUS NIGRA AND NATIVE PINUS BANKSIANA IN FOUR LAKE MICHIGAN
SAND DUNE HABITATS

INTRODUCTION

Previous studies have documented the successful establishment and spread of
introduced, exotic Pinus nigra (Austrian pine) on the dunes of Lake Michigan, near
Saugatuck MI, and have shown its capacity to alter the native dune conditions (Leege
1997, Leege and Murphy 2000. 2001. Sherﬁnski 2000). These studies have shown that
Austrian pine, originally planted as 26.000 seedlings between 1956 and 1972 in
Saugatuck Dunes State Park Natural Area (SDSPNA), is impacting native vegetation and
signiﬁcantly changing the dune environment by accelerating succession. reducing
biodiversity, and potentially changing ground water levels (Leege 1997. Leege and
Murphy 2000, 2001, Sherﬁnski 2000). Austrian pine was originally planted throughout
the dune system, and is now reproducing, replacing itself and increasing stand size (see
Chapter 2). However, the patterns of occurrence of Austrian pine and the native Pinus
banksiana (Jack pine) and microsite conditions favorable for the establishment of both
pines, have not been determined in this dune area. The patterns of occurrence of Austrian
pine and Jack pine regeneration (i.e.. seedlings and saplings that established through
natural reproductive processes) in and around stands of Austrian pine are important to
study if fundamental similarities and/or differences between the regeneration
characteristics of both species in the study site are to be determined. Additionally,
information on microsite conditions favorable for Austrian pine and Jack pine

regeneration will aid in making predictions of the dune sites and/or habitats most likely to

be invaded in the future. Therefore. this study identiﬁes the patterns of occurrence of
Austrian pine and Jack pine regeneration in and around planted stands of Austrian pine in
SDSPNA, and also documents the microsite conditions correlated with the distribution of

both species.

Austrian pine invasion ofSaugatuck Dunes State Park

Between 1956 and 1972, private landowners planted approximately 26,000
Austrian pine trees in the area now known as Saugatuck Dunes State Park (SDSP). To
stabilize the shifting dunes, seedlings were planted in stands along the foredunes, in large
erosional areas (inland blowouts), around the wetpannes, and adjacent to the native
deciduous forest. For Austrian pine stand characteristics, see Chapter 2. Jack pine is
found naturally in SDSP and although it can be found scattered throughout the dune

habitats, the highest densities are found in and surrounding the wetpannes.

Jack pine: distribution and ecology

Jack pine is a small to medium-sized coniferous tree found throughout the North
American boreal forests (Rudolph and Laidly 1990). It is one of the most widely
distributed conifers in North America. and its native range extends from northern Canada
to the northeastern and midwest states of the US. (Riemenschneider 1982). Mature trees
reach 15-20 m in height and 20-30 cm in diameter (Kenkel 1988). While it is a relatively

short-lived species (mature trees start to deteriorate after 80 years 011 the best sites and

54

after 60 years on poor sites), some individuals have been known to survive to 230 years
(Rudolph and Laidly 1990). Especially during the ﬁrst 50 years of growth, Jack pine has
a high growth rate, and growth usually stops after 80 years (Reimenschneider 1982).
Under most conditions. the age of ﬁrst reproduction is between 5 and 10 years. and
reproduction is fairly regular and increases annually until crown competition becomes a
limiting factor (Rudolph and Laidly 1990).

Jack pine is well adapted to pyric and semipyric (such as SDSP) ecosystems, and
the spatial and temporal distribution (i.e.. age classes) of this species is controlled mainly
by ﬁre (Gauthier et al. 1996). It primarily produces serotinous cones, however,
especially in the southern portion of its range, nonserotinous cones are also produced.
The cones open immediately after a ﬁre or following high surface soil temperatures,
releasing a large number of seeds (15-72 seeds/cone). While seed dispersal distances are
usually up to two tree heights (30 m) from the parental tree, the majority of established
seedlings are found within one tree height (15 m) (Xie and Knowles 1991). Seedling
establishment is most successful when there is a high water table, some shade, and
reduced competition from other vegetation (Kenkel 1986, Rudolph and Laidly 1990).

The natural distribution of Jack pine populations has been described as both
random and non-random. According to Ohmann (1968), Jack pine found in ltsaca Park,
Minnesota exhibited a random distribution. However. Kenkel (1988) concluded that only
the combination of living and dead trees gave a random distribution. Kenkel stated
further that live trees showed a regular distribution, while the dead trees showed a
clumped distribution. Kenkel et al. (1989) concluded that local competition in naturally

occurring Jack pine populations resulted in self-thinning and more even-sized stands.

55

Although Jack pine usually grows on sandy spodosols and entisols, it can also be found
on loamy and rocky soils and performs best on well-drained loamy sands (Rudolph and

Laidly 1990, Riemenschneider 1982).

Jack pine in the study site

Jack pine is a native species on the dunes of Lake Michigan and is distributed
throughout the four dune habitats. It can be found in small stands or as individual trees
scattered throughout the foredunes and occasionally in the deciduous forest. Larger
stands are found in the inland blowouts, and especially high densities of Jack pine are
commonly found in and around the wetpannes. This distribution pattern also occurs in
other Great Lake dune ecosystems. For example, one Indiana dune ecosystem contained
Jack pine within and surrounding wetpannes. on open slopes, in woodlands, on dune-
complexes, or in mixed-hardwood stands (Menges and Armentano 1985). Jack pine
reproduction was shown to be especially dense in and around the wetpannes, which is
consistent with its reproduction in the study site. but it also occurred in more open areas
with cottonwood, sand cherry, and red cedar (Menges and Armentano 1985).

Although Austrian pine has been documented as an invasive species in the study
site, it is unclear how Jack pine compares to Austrian pine with respect to its site
preferences, ability to spread on the dunes, and competitiveness with Austrian pine. Jack
pine, similar to other pine species, has been cited as invasive in Australia and New
Zealand. For example, it has invaded extensively managed grasslands, shrublands, and

tussock grasslands in South Island, New Zealand (Sykes 1981, Richardson et al. 1994).

56

Furthermore, Grotkopp et al. (2002) described Jack pine as more invasive than Austrian
pine, at least in certain habitats. They used the Z scores established by Rejmanek and
Richardson (1996) that ranged from 11.41 for the most invasive to -1 3.58 for least
invasive, to categorize 29 pine species based on their invasiveness. Their results show
that Jack pine has a Z score of 8.85, while Austrian pine is rated as 1.33. The Z scores
were based upon the species mean seed mass. minimum juvenile period, and mean

interval between large seed crops and did not take into account speciﬁc site conditions.

Research objectives

This study compares some aspects of the regeneration niches of Austrian pine and
Jack pine in SDSPNA. examining the spatial occurrence and distribution and microsite
conditions favorable for successful germination and establishment of progeny. More
speciﬁcally, the patterns of occurrence of Austrian pine and Jack pine seedlings and
saplings are compared underneath and around Austrian pine stands in the study site. If
the patterns of occurrence are similar for Austrian pine and Jack pine, then the two
species may be able to regenerate under similar conditions and thus, little or no niche
partitioning may occur in this system. Alternatively, if Austrian pine and Jack pine
regenerate under different microsite conditions, there would be less reason to expect a
severe impact from Austrian pine on Jack pine, such as competition for resources and/or
space, and perhaps habitat or niche partitioning may occur.

This study also compares the microsite conditions favorable for the regeneration

of the two pines. More speciﬁcally. abiotic and biotic dune features such as % coverage

57

and depth of litter, slope, % coverage of overstory vegetation, % coverage of understory
vegetation, associated dominant plant species, and height of understory vegetation were
correlated with the occurrence of Austrian pine and Jack pine regeneration to determine
site and/or habitat preferences for both species. A comparison of the distribution patterns
of Austrian pine and Jack pine in and around Austrian pine stands will document
fundamental similarities or differences in the regeneration niches of both species.
Therefore, the objectives of this study were to determine some aspects of the
regeneration niches of Austrian pine and Jack pine in and around planted Austrian pine
stands in SDSPNA. This includes determining the patterns of occurrence of seedlings
and saplings of both species where they coexist as well as the dune microsite conditions
for successful establishment of the two species in those areas.
The following research questions formed the basis for this study:
1) Are there fundamental similarities between the regeneration niches of Austrian
pine and Jack pine regeneration in and around planted Austrian pine stands?
a. Does the regeneration of both species occur in similar patterns in and
around Austrian pine stands?
b. Are both species found in similar microsites?
c. 15 there habitat partitioning between Austrian pine and Jack pine?
2) Does the spread of Austrian pine influence, either positively or negatively. where
Jack pine may be able to occur in the dune system? If yes, where on the dunes

does Jack pine face competition from Austrian pine?

58

METHODS

Study site

This investigation took place in the Natural Area of Saugatuck Dunes State Park
(SDSPNA), as described in Chapter 2. Sampling occurred in each of the four dune
habitats (foredunes, forest edge, inland blowouts. and wetpannes) during the summers of

2001 and 2002.

Patterns ofoccurrence ofA ustrian pine and Jack pine regeneration

underneath and surrounding planted Austrian pine stands

Randomly and non-randomly located 1m2 plots were sampled for Austrian pine
and Jack pine regeneration underneath and surrounding Austrian pine stands. as described
in Chapter 2. The same 1m2 plots used to document the rates and spatial patterns of
Austrian pine spread (Chapter 2), were used to document Jack pine regeneration. In each
1m2 plot sampled, the presence of both Austrian pine and Jack pine seedlings and
saplings were recorded and abiotic and biotic dune features were measured. Seedlings
and saplings will be referred to collectively as progeny. Jack pine seedlings were deﬁned
as individuals less than 20 cm tall, while saplings were individuals greater than 20 em but
not yet reproductively mature (i.e.. no cones visible) (Rudolph and Laidly 1990).
Austrian pine seedlings were deﬁned as individuals less than 20 cm in height (Wenny and

Dumroese 1991). Austrian pine saplings were individuals greater than 20 cm in height

59

and less than 30 years in age, thereby encompassing all trees that had established through
natural processes (i.e., were not planted). Because Austrian pine plantations in the park
were ﬁrst established in 1956, and the species typically starts reproduction after 15 years
of age (Burns and Honkala 1990), all Austrian pine progeny in the study site were
assumed to be less than 30 years of age. Age determination was based on stem diameter
measurements and whorl counts (see Appendix A l ). For the purposes of displaying
patterns of occurrence of Austrian pine and lack pine regeneration, progeny were pooled,

by species, in the analysis.

Dune features correlated with Austrian pine and Jack pine regeneration

Several abiotic and biotic dune features were sampled along with the presence of
pine regeneration to identify habitat and/or site characteristics conducive for successful
pine establishment and survival. Similarities and differences of the habitat and/or site
characteristics were compared between Austrian pine and Jack pine progeny. In each
1m2 plot sampled for pine regeneration, the following measurements were also taken: %
coverage and depth (cm) of litter, slope (%), % coverage of overstory vegetation. %
coverage of understory vegetation, dominant plant species, and height of understory
vegetation (cm). Slope was measured with a clinometer. Percent coverage of overstory
vegetation, understory vegetation, and litter were measured once per site to calibrate the
researcher’s eye and were estimated in subsequent 1m2 plots. The % coverage of
understory vegetation and litter was measured using a 1m2 frame divided into 100 100-

cm2 sections, while % coverage of overstory vegetation was measured with a

60

densiometer. Individual plant species were recorded and later categorized as tree, shrub,
grass, or forb for statistical analysis.

Using SAS (2001) as the statistical program (01:0.05), the correlations between
the occurrence of seedlings and saplings and the previously described dune features were
determined. These correlations help determine if Austrian pine progeny and Jack pine
progeny are found in similar habitats and/or sites. A binary system was used for density,
where “0” indicated absence and “1” indicated presence of seedlings or saplings. Because
of the non-normal distribution of the data, a forward stepwise regression was used as the
regression model. This model chose the dune feature(s) most correlated with the
presence of seedlings and/or saplings and produced corresponding signiﬁcance values.
Any dune feature with a P-value less than 0.05 was considered signiﬁcant, and less than

0.01 highly signiﬁcant, in contributing to Austrian pine or Jack pine regeneration success.

RESULTS

Patterns of occurrence of Austrian pine and Jack pine regeneration underneath

and surrounding planted Austrian pine stands

Although the mean number of Jack pine progeny found underneath and extending
from an Austrian pine stand in the foredunes were lower than those of Austrian pine, as
expected, the relative distribution of both species were nearly identical (Figure 3-1,
Figure 3-2). Compared to the total number of progeny found in the foredunes, the

relative distributions of both species were extremely similar. Thirty percent of both

61

Austrian pine and Jack pine progeny were found underneath the canopy, and doubled at
the edge of the canopy to 62.3% for Austrian pine and 63.2% for Jack pine. Both species
decreased in abundance extending away from the canopy edge and thereafter.

In the inland blowouts, similar to the pattern observed in the foredunes, the mean
number of Jack pine progeny was lower than those of Austrian pine underneath and
extending away from the canopy edge (Figure 3-3). However, the relative distribution of
Austrian pine and Jack pine progeny underneath and extending from the edge of the
Austrian pine stand were extremely similar (Figure 3-4). Underneath the canopy, 26.6%
of the total Austrian pine progeny and 18.2% for Jack pine progeny were found, and
increased to 59.3% for Austrian pine and 72.7% for Jack pine at the canopy edge. At a
distance of 0.1 m to 3 m away from the canopy edge, the percent of Austrian pine and
Jack pine progeny decreased to 11.1% for Austrian pine and 9.1% for Jack pine and
continued to decrease in abundance extending away from the canopy edge.

In the forest edge. similar to the foredunes and inland blowouts. the pattern of the
relative distribution of Austrian pine and Jack pine progeny underneath and around
Austrian pine stands was similar (Figure 3-5, Figure 3-6). Both species showed a similar
pattern of the greatest abundance at the edge of the native forest (Figure 3-5). Based on
the total number of progeny found in this habitat, 53.7% of Austrian pine progeny and
64.5% of Jack pine progeny were found at the edge of the forest. Extending into the
native forest, both Austrian pine and Jack pine progeny decreased in abundance.

Due to the greater concentration of Jack pine parental trees and favorable
conditions found in the wetpannes (i.e., higher soil moisture levels), lack pine progeny

were more abundant in the wetpannes than in the other dune habitats. The pattern of

62

occurrence of Austrian pine and Jack pine progeny found at the wetpanne edges and
interior were similar (Figure 3-7 and Figure 3-8). Both Austrian pine and Jack pine
progeny were found in greater abundance in the interior of the wetpanne than at the edge,
although the differences were not statistically different. Based on total number of
progeny found at the wetpanne interior and edge, 55% of Austrian pine progeny were
found at the wetpanne interior (an average of 38.9 individuals), compared to 67.9% for
Jack pine progeny (an average of 32.8 individuals). Forty-ﬁve percent of Austrian pine
progeny were found at the wetpanne edge (an average of 31.6 individuals), compared to
32.1% for Jack pine (an average of 15.5 individuals). The average size of the 10

wetpanne sites was 307 m2 (see Chapter 2).

Dune~ features correlated with Austrian pine and Jack pine regeneration

In the foredunes, the percent of litter cover was negatively correlated with Jack
pine seedlings and Austrian pine saplings and highly negatively correlated with Austrian
pine seedlings (Table 3-la, Table 3-1b). Jack pine seedlings were highly positively
correlated with the percent of understory vegetation and positively correlated with the
percent of overstory vegetation. Austrian pine saplings were negatively correlated with
the percent of understory vegetation, and positively correlated with the percent of
overstory vegetation. Austrian pine and Jack pine seedlings were positively correlated
with the depth of litter layer. Austrian pine seedlings and saplings and Jack pine saplings

were highly negatively correlated with the presence of dominant grasses and forbs.

In the forest edge, Austrian pine seedlings and Jack pine seedlings and saplings
were positively correlated with the percent of litter cover. while Austrian pine saplings
were negatively correlated with the percent of litter coverage (Table 3-1 a). Austrian pine
seedlings and Jack pine saplings were positively correlated with the percent of overstory
cover, while Jack pine seedlings were negatively correlated with the percent of overstory
cover. The depth of litter layer was correlated only with Austrian pine saplings
(negatively). Austrian pine and Jack pine seedlings were negatively correlated with the
presence of dominant grasses. while Austrian pine saplings were highly positively
correlated. .1 ack pine seedlings were negatively correlated with the dominant shrubs.
Both Austrian pine and Jack pine seedlings were positively correlated with the dominant
trees, while Austrian pine saplings were highly negatively correlated.

In the inland blowout habitat, Austrian pine seedlings were highly positively
correlated with the percent of understory and overstory vegetation, and highly negatively
correlated with the percent of litter cover (Table 3-la). Austrian pine saplings were
positively correlated with the percent of overstory vegetation, the height of understory
vegetation, and the slope. Jack pine seedlings were negatively correlated with the percent
of understory and overstory vegetation. and positively correlated with the slope and the
height of understory vegetation. Austrian pine seedlings were negatively correlated with
the dominant shrubs and trees. while Austrian pine saplings were highly negatively
correlated with the dominant shrubs and trees.

Finally, in the wetpannes. Austrian pine seedlings were positively correlated with
the percent of overstory vegetation. the height of understory vegetation, and highly

positively correlated with the depth of the litter layer (Table 3-1 a). Jack pine seedlings

64

were negatively correlated with the percent of understory vegetation. Austrian pine and
Jack pine saplings were also positively correlated with the height of the understory
vegetation, and Jack pine saplings were positively correlated with the depth of the litter
layer. Austrian pine seedlings were positively correlated with the presence of the
dominant forbs and grasses, while Jack pine seedlings were highly positively correlated.
Austrian pine and Jack pine saplings were highly positively correlated with the presence
of the dominant forbs. Austrian pine saplings were highly positively correlated with the
presence of the dominant grasses, while Jack pine saplings were highly negatively

correlated.

DISCUSSION

Patterns of occurrence o/‘A ustrian pine and Jack pine regeneration underneath

and surrounding Austrian pine stands

Because sampling occurred in and around stands ofAustrian pine in each dune
habitat, the low numbers of Jack pine progeny compared to Austrian pine were expected.
and are not indicative of fundamental differences in population characteristics of the two
species. Of signiﬁcance is the fact that despite the lower abundance of Jack pine progeny
in the foredunes, forest edge, and inland blowouts, both species have similar patterns of
occurrence underneath and extending from the Austrian pine stands (Figures 3-1 through
3-6). The wetpannes showed similar patterns of occurrence of both Austrian pine and

Jack pine on a percentage basis and on a total number of progeny basis (Figure 3-7,

Figure 3-8). Therefore, the patterns ofoccurrence of both Austrian pine and Jack pine
progeny were extremely similar underneath and extending from the edge of Austrian pine
stands and in the wetpannes, and habitat partitioning is not apparent under these

conditions.

Dunefeatures correlated with Austrian pine and Jack pine regeneration

Based on the literature, pine seedlings. including Austrian pine and Jack pine.
require high light and low-litter conditions for successful establishment (Steven and
Carlisle 1959, Fowles 1965, Huntley and Birks 1983, Delcourt and Delcourt 1987,
Rudolph and Laidly 1990, and Richardson 1998a). Furthermore, most pine seeds will
readily germinate given adequate soil moisture and temperatures (Richardson 1998a).
These results are consistent with those found in the study site. Lower percent litter cover,
greater overstOry vegetation, taller understory vegetation with fewer forbs, grasses. and
shrubs are the most important dune features correlated with successful establishment of
Austrian pine and Jack pine establishment.

In all dune habitats but the forest edge, there was a negative correlation between
the percent litter cover and pine regeneration, indicating more regeneration in sites with
low percent litter cover. The forest edge innately had more percent litter cover, due to
dense forest vegetation in this habitat. Percent of litter cover is usually related to the
amount of overstory and understory vegetation (i.e., fallen leaves and twigs, senescent
grass blades, dead/decaying plant tissue), and a low percent litter cover would indicate

less shading for the developing seedlings. Leege (1997) veriﬁed the importance of

66

sufﬁcient light for Austrian pine regeneration in the study site, and it is well-documented
that Jack pine, similar to most pines. also requires sufﬁcient light for developing
seedlings (Harrington and Kelsey 1979, Rudolph and Laidly 1990).

The height of understory vegetation and percent overstory cover of vegetation are
both positively correlated with Austrian pine and Jack pine regeneration. Progeny of
Austrian pine and .1 ack pine were positively correlated with the height of understory
vegetation, which implies more regeneration in sites with taller understory vegetation
(i.e., less direct shading), consistent with results of Wills and Begg (1986). Although the
percent of overstory vegetation was negatively correlated with Jack pine seedlings in the
forest edge and inland blowouts, the majority of correlations were positive. A greater
percent of overstory vegetation would indicate greater canopy cover, consistent with the
general pattern of greater regeneration at the edge of the canopy of either Austrian pine
stands or the native forest.

The presence of dominant shrubs was negatively correlated with both Austrian
pine and Jack pine regeneration. except for Austrian pine saplings. This negative
correlation is most likely attributed to the dense, shorter structure of most dune shrubs,
blocking light needed for developing seedlings. Austrian pine saplings were highly
positively correlated with the presence of the dominant shrubs. however. attributed to
their greater height and less susceptibility to light blocked from shrubs. While the
majority of correlations between grasses and pine regeneration were negative. except in
the wetpannes with naturally greater densities of wetpanne ﬂora, the majority of
correlations between trees and pine regeneration were positive. Grasses have been known

to outcompete pine seedlings. especially for soil moisture (Richardson and Bond 1991),

67

while trees may provide a deeper litter depth, and consequently higher soil moisture,
although they may also partially shade pine progeny. The correlations between forbs and
pine progeny were negative in the foredunes and positive in the wetpannes. Forbs.
similar to grass species, may outcompete pine seedlings for light, soil moisture, and/or
soil nutrients. However, in the wetpannes with greater soil moisture and soil nutrients,
pine progeny were able to survive and co-exist with other wetpanne ﬂora.

Overall, Austrian pine and Jack pine seedlings and saplings seem to regenerate
under similar conditions in each dune habitat in the study site. The relative distribution
of both Austrian pine and Jack pine progeny underneath and around Austrian pine stands
were extremely similar in all dune habitats. Microsite conditions favorable for the
regeneration of the two species were also similar, indicating that habitat partitioning does
not seem to occur between the two species. F inally, it is acknowledged and recognized
that while all Austrian pine individuals that arose through natural processes (i.e., were not
planted) were included, to fully document the invasive potential of exotic Austrian pine
in the study site, only reproductively immature Jack pine individuals were included. This
project was designed to document some aspects of Jack pine regeneration in the study
site, and therefore immature individuals were only included. which may present at least

some inequalities in sampling Austrian pine and Jack pine progeny.

Conclusions

Austrian pine and Jack pine appear to have similar regeneration niches in and

around the planted Austrian pine stands in each dune habitat throughout SDSPNA. The

68

relative distribution of both species seems to occur in similar spatial patterns. where most
regeneration occurs at the edge of the Austrian pine stands or at the edge of the native
forest. Both species were found in similar microsites and were favored by similar
environmental factors. Austrian pine and Jack pine progeny were correlated with a low
percent of litter cover, greater overstory vegetation, taller understory vegetation with few
forbs, grasses, and shrubs. Therefore, habitat partitioning is not apparent between
Austrian pine and Jack pine regeneration in the vicinity of Austrian pine stands. since
both species seem to occur in similar patterns and microsite conditions. The spread of
Austrian pine may affect the present and perhaps future distribution of Jack pine. Sites
that are currently occupied by Austrian pine may be conducive to Jack pine regeneration,
since both species require similar habitat and/or environmental conditions. For future
management purposes, Jack pine may potentially be planted in areas currently occupied
by Austrian pine with the intent of eventually replacing Austrian pine and converting the
Lake Michigan sand dunes into a more natural state. However, continued research is
needed to determine the speciﬁc interactions of Austrian pine and Jack pine seedlings and

saplings and the role of interspeciﬁc competition between the two species.

69

Table 3-1a. Forward stepwise correlation between the presence of Austrian pine and Jack
pine progeny and selected abiotic and biotic dune features (SAS Inst. 2001, 01=0.05). In
each m2 plot sampled, the presence of Austrian pine and Jack pine progeny was recorded
and dune features measured in each habitat. A “1” indicates seedlings, and “2” indicates
saplings. A signiﬁcant correlation (P_<_ 0.005) is indicated by a “*” for Austrian pine and
“O” for Jack pine, while a highly signiﬁcant correlation (P<0.0001) is indicated by “**”
for Austrian pine and “00” for Jack pine. Positive correlations are indicated by a “+”,
while a negative correlation is indicated by a “.“- The total number of seedlings and
saplings observed and analyzed are shown in Table 3-1b.

 

 

 

 

 

 

 

 

 

 

 

 

 

Dune feature Foredune Forest edge Inland Wetpanne
blowout

l 2 l 2 l 2 l 2
% litter cover **, - *,- *,+ *,- **9.

0,- o,+ o,+
% understory vegetation *,- **,+

OO,+ o”- 0‘.
% overstory vegetation *-+ *,+ **,+ *,+ *,+

O,+ 0,- o,+ 0,.
Height of understory *,+ *,+ 13+
vegetation o,+ o,+ o,+
Depth of litter layer *,+ *9- **,+

O,+ 09+
Slope (%) *.+

o,+
Dominant Forbs **,- **,- *.+ ”9+
00,- oo,+ oo,+
Dominant Grasses **,- **,- *,- **,+ *,+ **,+
00,- o,- oo,+ 00,-
Dominant Shrubs *9 - * *9-
0’.
Dominant Trees *,+ * ’1". *9- * *9-
0,-1-

 

 

 

 

 

 

 

 

 

 

Table 3-lb. The total number of seedlings and saplings observed in each dune habitat
and correlated with selected dune features. The dune features and their correlation(s)
with Austrian pine seedlings and saplings are shown in Table 3-la. AP=Austrian pine.
JP=Jack pine. A “1” indicates seedlings and “2” indicates saplings.

 

Habitat APl AP2 JP] .1 P2
FD 694 50 76 13
FE 22 36 15 0
IB 248 97 37 1
WP 490 250 204 275

 

 

 

 

 

 

 

 

 

 

 

70

2 Mean number of Austrian pine and Jack pine progeny
underneath and extending from Austrian pine canopy in the

 

 

 

 

 

45 foredune3”” 22- --
+Austrlan
_ 3‘ 40 “ ‘ ‘ "" " 2-2.222-2 ”" ‘ M“ pine
1 §§ 35 ' r — r “r ”r 2 “r " "“_ “r" +Jack
‘ a W 30 - pine
{3 2 2 2. ...2_..._2
I s .3 25 — --
3 0
1 g g 20 . 22-
. c 5g
1 g 15 1 -22 -
(S 10 - -—-—- - ~— -
. 5 _ 2-
O '__T
-1 O 0.1-3 3.1-6 6.1-12 12.1-18 18.1-22

Distance from Austrian pine stand (111)

Figure 3-1. Mean number of Austrian pine and Jack pine progeny extending from the
edge of mature Austrian pine stands across the ten foredune sites, based on random and
non-random sampling. Locations underneath the canopy are designated as “-1.” Random
sampling was performed using randomly located 1m2 plots underneath and at edge of
canopy and along transects running N, S, E, W from the edge of the stand to 5 m or the
furthest extent of Austrian pine regeneration. Non-random sampling occurred wherever
regeneration was observed not previously captured in the random samples. These data
are consistent with Table A2-2.

Relative distribution of Austrian pine and Jack pine progeny
underneath and extending from Austrian pine canopy in the

 

 

 

 

 

 

 

 

 

100 222...-- .2- - 2. _.-foredunes.-------22. 22--.-- ,
Austrian '1
‘ pine 1 ,
'2 2 2 2— _22 2.2 .2 2 - .. ..L _ l.
g , DJackpnne 1
’u - --—~-- ~- -- 1
‘E 2 2 ._ ____ _ _ 2-2____--i
3
1.5 ~— - - —- -~ - — 2.. — ~
‘5 22222 222
0
e 2 2 2_22 _ 2 2_ .2 .2 22.222.22.22
a»
1L 2 _ _ -
2_-:_2_-— -—
-1 0 0.1-3 3.1-6 6.1-12 12.1-18 18.1-22

Distance from Austrian pine stand (m)

Figure 3-2. Relative distribution of Austrian pine and Jack pine progeny underneath and
extending from Austrian pine canopy in the foredunes, based on the total number of
progeny found in this habitat. These data are consistent with Figure 3-1, but are shown in
percentages of total number of pine progeny.

71

Mean number ofAustrian pine and Jack pine progeny
1 underneath and extending from Austrian pine canopy in the

 

 

 

 

‘* ' "inlandbiowo‘uts 22222 y
16 _ _ 2 _ _ ’ +Austrlani
—— 2--“ pine |
5‘ 14 l
a g r T "' T ' "T ' T” T _ 2- ' i +Jack
? E s12 Eff-.22
'3 £10 - _ 22 22
: E 3
g E 8 2 22—22
i C 5 5 222 2 2 22
c b
g 3 4
i _ ._ -- -- _. 22 223
o 22;,- _22...-§-_..222l m

 

-1 0 0.1-3 3.1-6 6.1-12 12.1-18 18.1-22
Distance from Austrian pine stand (rn)

Figure 3-3. Mean number of Austrian pine and Jack pine progeny extending from the
edge of mature Austrian pine stands across the ten inland blowout sites. Mean values
were based upon random and non-random sampling. Locations underneath the canopy
are designated as “-1.” Random sampling was performed using randomly located 1m
plots underneath and at edge of canopy and along transects running N, S, E, W from the
edge of the stand, or NE, NW, SE, SW in three sites, to 5 m or the furthest extent of
Austrian pine regeneration. Non-random sampling occurred wherever regeneration was

observed not previously captured in the random samples. These data are consistent with
Table A2-3.

Relative distribution of Austrian pine and Jack pine progeny
underneath and extending from Austrian pine canopy in the

 

 

 

 

100 222.222.22-222 "M" "inlandbtowmm "W" “W‘m’mj‘ima‘;
90 .2 i’ " -2-..2 ' 22-22, pine
at 222222222 —— - — , i
' - DJack pine I
3 _ 2-2 2. __._ _ . j
- E
' ,2 .2. . 22.. ._..._.2__. . . . _ ..“"'T—‘2‘.2'21'.""“
u
' .5
h 2 2 2 2 222
. O
#5 2 2 2 2 2 2 2
, o
u 2 22 .2 22 2 2 2
b
. o
0- 22 2 22 2 22 2 2 2 2

 

0.1-3 3.1-6 6.1-12 12.1-18 18.1-22
Distance from Austrian pine stand (m)

Figure 3-4. Relative distribution of Austrian pine and Jack pine progeny underneath and
extending from Austrian pine canopy in the inland blowouts, based on the total number
of progeny found in this habitat. These data are consistent with Figure 3-3, but are shown
in percentages of total number of pine progeny.

72

per

Mean number of progeny

e
.A
A

forest edge sit

—l_l
'm'ooM

_.\
AN

99
000

9.0
Mb
I

7 Mean number of Austrian pine and Jack pine progeny
extending into the native forest
-. +7 V Austrian?
pine ‘

    

 

 

O

15.1-20 20.1-28

0.1-1 1.1-5 5.1-10 10.1-15
Distance into native forest (m)

0

Figure 3-5. Mean number of Austrian pine and Jack pine progeny extending from the
edge of mature Austrian pine stands across the ten forest edge sites. based on random and
non-random sampling. Locations underneath the canopy are designated as “-1." Random
sampling was performed using randomly located 1m2 plots underneath and at edge of
canopy and along transects running N. S. E. W from the edge of the stand to 5 m or the
furthest extent of Austrian pine regeneration. Non-random sampling occurred wherever
regeneration was observed not previously captured in the random samples. These data
are consistent with Table A2-4.

Percent of individuals

 

Relative distribution of Austrian pine and Jack pine progeny
extending into the native forest

 

 

2- 22 __ _ , 22 2 7,; "- Austria?
‘ pine
‘ ~ “7 V W_ WTVM A W 3 DJack pine
E2 22
o 0.1-1 1.1-5 5.1-10 10.1-15 15.1-20 20.1-28

Distance from Austrian pine stand (m)

Figure 3-6. Relative distribution of Austrian pine and Jack pine progeny underneath and
extending from Austrian pine canopy into the native forest. based on the total number of
progeny found in this habitat. These data are consistent with Figure 3-5. but are shown in
percentages of total number of pine progeny.

73

 

Mean number of Austrian pine and Jack pine progeny in wetpanne
50 interior and edge

Vi ’Aisﬁénf
pine l
_ El Jack ‘

  
  

 

 

 

 

 

 

interior edge

 

 

Figure 3-7. Mean number of Austrian pine and Jack pine progeny in wetpanne interior
and edge, across ten wetpannes. Nine wetpannes were surveyed for regeneration, and
one wetpanne, too large to survey, was sampled using 10 l-m2 plots at the wetpanne edge
and interior. Seedlings and saplings were pooled for both species.

Relative distribution of Austrian pine and Jack pine progeny found

  

100 s- in wetnenne-inter-iqranded e - 2.222
p l Wetpanne
. 90 ’ ’ a ’ edge
80 2 El Wetpanne
interior

Percent (%)
l
l

 

 

 

 

 

Austrian pine Jack pine

Figure 3-8. Relative distribution of Austrian pine and Jack pine progeny found in

wetpanne interior and edge, based on the total number of progeny found in ten wetpanne
sites.

74

CHAPTER 4
SPATIAL OCCURRENCE OF THREATENED CIRSI UM PITCHERI
AND POTENTIAL EFFECTS OF INVASIVE PINUS NIGRA

INTRODUCTION

C irsium pitcheri (Pitcher’s thistle) is a species endemic to the Great Lakes sand
dune ecosystem and is listed as threatened in both the US. and Canada (Congress of the
United States 1988). Population numbers have continued to decline due to lakeshore
development, artificial dune stabilization measures, and dune traffic caused by
pedestrians and vehicles, resulting in its federal listing (Harrison 1988, Pavlovic et al.
1992). The most detrimental effects to Pitcher’s thistle populations have occurred in the
southern tip of Lake Michigan, where land use has been most intensive (MacEachem et
al. 1994). Further threats from invasive plant species, such as the invasive Pinus nigra
(Austrian pine), could jeopardize the survival of Pitcher’s thistle on the eastern shores of
Lake Michigan. Originally planted in the area now known as Saugatuck Dunes State
Park (SDSP) by private landowners in a sand-stabilization effort between 1956 and 1972,
Austrian pine has dramatically altered the native dune conditions. It has been
documented to shade out native plant species, reduce sand movement, decrease species
diversity, and possibly alter ground-water levels (Leege 1997, Leege and Murphy 2000,
2001, Sherfmski 2000). Although the speciﬁc effects of Austrian pine reproduction,
dispersal, and local spread on rare dune species such as Pitcher’s thistle are currently
unknown, it is certain that Austrian pine will directly threaten the long-term persistence

of rare species by altering native dune conditions.

75

Distribution and ecology ofCirsium pilchcri

Pitcher’s thistle is a rare dune plant naturally occurring along the shoreline dunes
of Lakes Huron, Michigan, and Superior. Although its range extends from southern Lake
Michigan to northern Lake Superior, most Pitcher’s thistle populations are found on the
eastern shore of Lake Michigan (Beal 1870, Hamze and 10115 2000). The largest
populations in the US. occur only within protected parks of the Great Lakes, including
Indiana Dunes, Sleeping Bear Dunes, and Pictured Rocks National Lakeshores
(McEachern 1992). Pitcher’s thistle usually colonizes open dunes and blowouts, but has
also been found on more stabilized dunes (Loveless and Hamrick 1988).

Although most populations are relatively small, consisting of 20-30 ﬂowering
individuals per year, larger populations containing up to 100 individuals have been
known to occur (Loveless and Hamrick 1988). Metapopulation dynamics play an
important role in the survival of Pitcher‘s thistle, where a metapopulation is defined as a
group of subpopulations inhabiting separate locations and actively exchanging
individuals among subpopulations. It has been documented that the perpetuation of
multiple populations comprised of smaller subpopulations are required to sustain this
species (McEachern et al. 1994). As a monocarpic perennial with no vegetative
reproduction, Pitcher’s thistle usually persists as a rosette for 2-8 years before ﬂowering.
with light cream-colored inﬂorescences suited for bee, moth. and butterfly pollination
(Loveless 1984, McEachem et al. 1994, Hamze and Jolls 2000). While plants are self-

compatible. outcrossing is more common and rates of outcrossing range between 35-

76

88%. After fertilization, the mature fruits (achenes) are wind-dispersed. Pitcher‘s thistle
seeds are the largest of any North American thistle (Gleason 1952), and therefore most
dispersal is within ﬁve meters of the parent plant. Dispersal over longer distances is rare,
attributed mostly to secondary dispersal and ﬂower head detachments (Loveless and
Hamrick 1988). Seedling emergence begins in late May, and the first true leaves are
entire and densely tomentose. In later years, the leaves are pinnatifid and tomentose.
Studies have shown that seeds require burial for successful germination and emergence
(Hamze and Jolls 2000). Hamze and Jolls (2000) also concluded that long-term
protection and propagation of Pitcher’s thistle depends on the conservation of natural

sand erosion and burial patterns necessary for maintaining open dune habitats.

Research objectives

The objectives of this study were to document the spatial occurrence of Pitcher’s
thistle and the populations most threatened by Austrian pine spread in Saugatuck Dunes
State Park Natural Area (SDSPNA). In addition, Pitcher‘s thistle population densities
were compared in the presence and absence of Austrian pine regeneration (i.e., seedlings
and saplings that established through natural reproductive processes). Because Pitcher's
thistle is a rare species, endemic to the Great Lake sand dunes, and also an endemic on
the Federal list of threatened species, documentation of the spatial occurrence of this
species is of the utmost importance to monitor present and future populations in this area.

It is also important to identify populations that are most threatened by the spread of an

77

invasive pine to provide information that may be useful in the overall assessment of the
Austrian pine threat.

The following questions formed the basis for this study:
1) Where is Pitcher’s thistle located in Saugatuck Dunes State Park Natural Area?
2) Where are the populations of Pitcher’s thistle most threatened by the spread of
invasive Austrian pine?
3) Does the presence of Austrian pine regeneration affect Pitcher’s thistle population

densities?

METHODS

Study site

This investigation took place in the Natural Area of Saugatuck Dunes State Park

(SDSPNA), as described in Chapter 2.

Spatial occurrence of C irsium pitcheri

The study site was surveyed for Pitcher’s thistle populations and individuals.
Since this species requires some disturbance and high light levels to complete its life
cycle (Hamze and Jolls 2000). the foredune and inland blowout areas, with relatively low
levels of vegetation cover. were the only areas surveyed for Pitcher’s thistle. These areas

were thoroughly surveyed, using transects spaced approximately 15 meters apart. Other

78

dune areas, such as the wetpannes and forest edge (see Chapter 2 for description of dune
habitats) were also brieﬂy searched to ensure the absence of Pitcher‘s thistle in these
habitats with dense vegetation cover. Locations of Pitcher‘s thistle populations were
documented using a Trimble® GPS unit and were saved as polygon shapeﬁles. Most
Pitcher’s thistle populations were saved as polygon shapeﬁles, but individuals not found
within a larger population were saved as individual (point) shapefiles. Because it is listed
as a federally threatened species, areas that contained Pitcher’s thistle populations within
10 m of a population of Austrian pine regeneration were also documented using a
Trimble® GPS unit and labeled as critical. Ten meters was chosen due to the average
dispersal distance of Pitcher’s thistle (within 5 m of parental plant), and most Austrian
pine regeneration occurred within 10 m of the parental source inthe study site (see

Chapter 2).

Austrian pine eff/eats on Cirsium pitcheri density

To measure densities of Pitcher’s thistle populations and investigate the potential
effect of Austrian pine on these populations, the population densities (# ind/m2) in ﬁve
populations with, and five populations without, Austrian pine regeneration were
compared using a one-way analysis of variance test (ANOVA) (SAS Inst. 2001,

or=0.05).

79

RESULTS

Eleven Pitchers thistle populations and 29 individual plants not found within a
larger population were located in the foredunes and inland blowouts of the study site
(Figure 4-1). Five critical areas were located that contained Pitcher’s thistle populations
within 10 m of Austrian pine regeneration (Figure 4-1). All five critical areas were found
in the inland blowout habitat. The mean density of Pitcher’s thistle populations in the
absence of Austrian pine regeneration was 0.148 ind/ m2. compared to 0.167 ind/ m2 in
the presence of Austrian pine regeneration (Figure 4-2). However, there were no
differences between Pitcher’s thistle population densities in the presence or absence of
Austrian pine regeneration (P=0.8209). It should also be noted that although the
wetpannes and forest edge were not sampled for Pitcher’s thistle, no individuals or

populations were found in these habitats.

DISCUSSION

Eleven populations and 29 individuals of Pitcher’s thistle were located and
documented in the open areas of the foredunes and inland blowouts. Consistent with the
literature, most populations were found in open dune areas usually associated with high
light conditions. Five areas were considered critical because they contained Pitcher‘s
thistle populations in close proximity to Austrian pine regeneration. These critical areas
should be monitored for future changes in Pitcher’s thistle populations, such as changes

in location, size, density, and ﬂowering frequency, especially since it is known that

80

smaller subpopulations are vital to the persistence of this species (McEachern 1992,
McEachem et al. 1994). Although this study did not show any significant Austrian pine
effect on Pitcher’s thistle population densities (P=O.8209), it is believed that there will be
negative long-terrn effects. Since it has already been documented that Austrian pine
reduces sand movement and shades out understory plants (Leege 1997, Leege and
Murphy 2000, 2001), the persistence of Pitcher‘s thistle may be jeopardized, since this
species requires high light and moderate sand burial conditions. Additional threats from
pedestrian traffic and tramping are recognized, as Pitcher’s thistle is found near hiking

trails located throughout the study site.

Summary and Conclusions

Eleven Pitcher’s thistle populations and 29 individual plants were found in the
open areas of the foredunes and inland blowouts of the study site. These populations
should be monitored to ensure protection of this rare and threatened species. Although it
is possible that some Pitcher’s thistle populations have already been displaced by
Austrian pine, our data showed no evidence that Pitcher’s thistle density is presently
affected by Austrian pine regeneration. However, as Austrian pine continues to spread, it
will encroach upon Pitcher’s thistle and other sensitive populations. These data may be
useful for developing future management plans concerning rare, endangered. and

threatened species in the presence of an invasive pine on freshwater dune systems.

8]

mum.” .325
230355 252. page: o
22.238 235 9.225 I H

m__u.=<zm om.

baucsom no.3 .2352

 

Spatial occurrence of Pitcher’s thistle in SDSPNA and locations of critical

Figure 4- 1.

m

Austrian pine regeneration populations with

as were areas containing

areas. Critical are

10 m of Pitcher’s thistle.

82

Pitcher's thistle population densities, in absence and presence of
Austrian pine (AP)

 

05 _-..u-.--.__--a.-,,.,.- h- Wm---” -,.,-a___-...._.s...-_-
0.4 ,
0.35 - -
0.3 -
0.25
0.2 ~
0.15
0.1
0.05 ,
0 .

 

 

J Population idenslty

 

 

 

 

 

 

 

 

(#indlm2)

 

 

 

 

 

 

 

 

AP absent AP present
Pitcher's thistle location

Figure 4-2. Pitcher’s thistle population densities in the absence and presence of Austrian
pine regeneration. There were no statistical differences between the densities of Pitcher’s
thistle populations in the presence and absence of Austrian pine regeneration (SAS 2001,
one-way ANOVA, a=0.05, P=O.8209). The mean density in the absence and presence of
Austrian pine progeny are shown numerically above.

83

CHAPTER 5

GENERAL SUMMARY AND CONCLUSIONS

This study provides information on the rates and spatial patterns of the spread of
the invasive Pinus nigra (Austrian pine) immediately surrounding planted Austrian pine
stands on the dunes of Lake Michigan, and compares regeneration niches of Austrian
pine to the native Pinus banksiana (Jack pine). The spatial occurrence of the endemic
and threatened Cirsium pitcheri (Pitcher’s thistle) was also documented, and the potential
effects of Austrian pine regeneration on Pitcher’s thistle population densities were
analyzed.

Originally planted between 1956 and 1972. Austrian pine is now reproducing in
the four main dune habitats in the study site: foredunes, forest edge, inland blowouts, and
wetpannes. In the foredunes and inland blowouts. although regeneration did occur
underneath the stands, most regeneration occurred at the stand edge and decreased with
increased distance from the stand edge. This suggests Austrian pine stand replacement
and expansion. The wetpannes contained high regeneration densities of both seedlings
and saplings, most likely due to close proximity to seed-source trees and higher soil
moisture levels, and the highest sapling densities across all dune habitats were found in
this habitat. However, the high densities of progeny at the edge and within the wetpannes
were not signiﬁcantly different from each other (P=0.1689), suggesting no spread into the
wetpannes. There was limited regeneration in the forest edge compared to the other

habitats, consistent with previous studies (Leege 1997, Leege and Murphy 2000, 200] ).

84

However, there were some individuals found up to 28 m into the forest, suggesting the
possibility of relatively long-distance dispersal events, perhaps via animal transport.

Rates of Austrian pine spread on a per-plant basis ranged from 0.00 m yr" in
some stands to 15 m yr". Rates in the inland blowouts ranged from 0.00 m yr" to 1.61 m
yr", averaging 0.20 m yr", and were as high as 15 m yr". Rates in the foredunes ranged
from 0.00 to 0.28 m yr", with an average of 0.06 m yr". Maximal rate of spread found in
this habitat was as high as 1.88 m yr". Higher rates in the inland blowouts are most
likely attributed to their open nature, where adjacent Lake Michigan winds can disperse
seeds to greater distances. The forest edge had the least amount of spread, ranging from
0.00 to 0.12 m yr", averaging 0.04 m yr". The highest rate observed was 2.11 m yr'l in
one site, where an individual was found 28 m from the presumptive parental tree. Local
patterns of spread were mainly towards the north in the foredunes and northeast in the
inland blowouts, most likely attributed to the strong prevailing southwesterly winds. On
average, foredune stands have increased in area by 37% since the original plantations
were established in 1963, while inland blowout stands have increased by 25% since 1966.
However based on the greatest distances that Austrian pine progeny were found from a
stand edge in the foredunes and inland blowouts, the maximum increase in area was
153% for foredune stands and 132% for inland blowout stands. This represents the
potential for Austrian pine to disperse in these directions and distances under favorable
conditions in the study site.

Measured parameters of the regeneration niches of Austrian pine and Jack pine in
the vicinity of Austrian pine stands were extremely similar in the study area. The relative

distribution of Austrian pine and Jack pine progeny were strikingly similar in each of the

85

four main dune habitats, where most regeneration occurred at the edge of Austrian pine
stands or at the edge of the native forest. These results are consistent with the literature.
stating that pine seedlings require high light and low-litter conditions and thus most
seedlings successfully establish near the stand edge (Yocum 1968, McCaughey et al.
1986, Richardson 1998a). Austrian pine and Jack pine progeny were found under similar
microsite conditions and were favored by similar environmental factors. A low percent
of litter cover, greater overstory vegetation, and taller understory vegetation characterized
by few forbs, grasses, and shrubs were correlated to pine regeneration. As both species
have similar habitat requirements, habitat partitioning between Austrian pine and Jack
pine is not apparent in or around Austrian pine stands in the study site. The spread of
Austrian pine may inﬂuence the distribution of Jack pine, and sites currently occupied by
Austrian pine may be open for future invasion from Jack pine. However, more research
is needed to determine the specific interactions between Austrian pine and Jack pine
regeneration, especially competition factors between the two species.

The spatial occurrence of Pitcher’s thistle was documented in the study site.
Eleven populations and 29 individuals were located within the foredunes and inland
blowouts. Although our data did not show any significant effect of Austrian pine
regeneration on the density of Pitcher’s thistle populations, it is believed that future
Austrian pine spread will affect Pitcher‘s thistle persistence. Pitcher’s thistle populations
should be routinely monitored for changes in population structure and location, especially
in association with Austrian pine reproduction and local population spread. These data
may be useful for managing federally threatened Pitcher’s thistle or other rare species in

the Lake Michigan sand dune ecosystem.

86

APPENDICES

87

APPENDIX A1: AGE DETERMINATION OF PINUS NIGRA
IN SAUGATUCK DUNES STATE PARK
By

Joseph Harsh and Khara Grieger

INTRODUCTION

The primary objective of this study was to determine a tree age to stem-diameter
relationship for introduced Pinus nigra (Austrian pine) in Saugatuck Dunes State Park
Natural Area (SDSPNA), located near Saugatuck MI. This study expands on a previous
study of Austrian pine tree age and radial growth (Leege 1997, Leege and Murphy 2000,
2001), and was designed to aid in the estimation of rates of Austrian pine spread in the
study site.

Preliminary studies ofAustrian pine in the study site established the viability of ring
counting as an appropriate approach in the estimation of tree age, although cross-dating in
young trees was difﬁcult due to a few drought years (Leege 1997, Leege and Murphy 2000,
2001). Leege (1997) established: (1) the number of rings present corresponded well within
the range of planting dates, and (2) broad annual growth increments were observed for most
years except for narrow rings representative of two drought years (198 7, 1988). These
results led to the assumption that the tree cores exhibited no missing rings and therefore can

be used in age estimation.

88

METHODS

Mature Austrian pine trees were selected for analysis in all four dune habitats:
foredune, forest edge, inland blowout, and wetpanne. Using a stratiﬁed random sample
design, adult trees were chosen from ten sites per habitat, using sites previously selected
in the determination of the rates and spatial patterns of Austrian pine spread (Chapter 2).

Individuals were measured for stem diameter at breast height (DBH) and cored at
1.25 m above ground level, using standard coring, mounting, and analysis techniques of stem
increment cores (Stokes and Smiley 1968) consistent with previous studies (Leege 1997).
Austrian pine was classiﬁed into four stratiﬁed diameter classes for sampling: (1) small (S) 0
to 10.99 cm, (2) midrange-small (MS) 11.0 to 20.99 cm, (3) midrange-large (ML) 21.0 to
30.99 cm and (4) large (L) >31.0 cm. Seven individuals per diameter class were randomly
selected for coring at DBH for each habitat. totaling'112 individuals cumulatively sampled in
the dune system. Four individuals per habitat were cored or cut for disc analysis at ground
level (i.e., root collar) and also at breast height for the determination of an age correction
value for the period required to reach 1.25 m (breast height). In addition, seven woody
juvenile individuals shorter than breast height were measured for diameter and cut for disc
analysis at ground level in only the foredunes, inland blowout, and wetpannes. Forest edge
juveniles below breast height were not collected due to sparse regeneration found in this
habitat (Leege 1997, Leege and Murphy 2000, 2001, and Grieger 2003). All trees were
measured, cored, and/or cut for disc analysis in 2001 and 2002.

Depending on stem diameter, increment cores were either taken entirely through

the individual or from opposite sides to average asymmetric growth and allow analysis of

89

samples exhibiting tree damage. branch growth, or the presence of incomplete rings. Age
correction values, the observed age difference between ground and DBH level samples
within each habitat, were applied to the age of trees sampled at DBH for a more accurate
representation of individual tree age.

From the initial sampling of 128 individuals, only 1 19 individuals were analyzed
due to structural damage or sampling error. The total number of individuals analyzed in
each habitat is as follows: foredune (n=28), forest edge (n=3 1 ), inland blowout (n=29),
and wetpanne (n=31). This deﬁcit of individuals, however, is solely from the small size

class (0-10.99 cm), having a nominal effect on the age to DBH relationship.

RESULTS AND DISCUSSION

Contrary to previous ﬁndings (Leege 1997, Leege and Murphy 2000),
relationships of stem diameter to age exhibited low levels of variation within each
habitat. Therefore these relationships are of value in estimating tree age based on stem
diameter at breast height. Diameter of individuals <1.25 m tall, sampled at ground level,
are not of value in age prediction due to variation levels which may be attributable to low
sample size (n=7) and/or the sensitivity of juvenile individuals to intrinsic environmental

factors. Therefore, ages of individuals <1 .25m tall were estimated by whorl counts.

90

Austrian pine age to DBH relationship in the foredunes

50 _.___- - z , , haPEat.-- - z _
45: #— — . .
4o 4 ----- -

 
  

Y = 6.7553Ln(x) «3 151.8802 0

Age (years)

20 La. _...l. IL! . ' . -_R2_._= 0549.7 ,

15 ~ A A , ,,

10 77 v

5 1, - - -

0 ,.__ 2 , - ., . -- ,, , .
0 5 10 15 20 25 30 35 40 45

DBH (cm)

Figure A1-1. Relationship of Austrian pine tree age to stem diameter at breast height in

the foredune habitat. Breast height measured at 1.25 m. Each point represents an
individual.

Austrian pine age to DBH relationship in the forest edge
50 _- f_ V M if . habitat _

 

 
 

> 25 i— -—-. -1 . . r {YF 6.1909Ln(x) + 20.245,
v 2 .-
c, 20, R _- 0.6155 ,

0 5 10 15 20 25 30 35 40
DBH (cm)

Figure A1-2. Relationship of Austrian pine tree age to stem diameter at breast height in

the forest edge habitat. Breast height measured at 1.25 m. Each point represents an
individual.

91

T'L.

Austrian pine age to DBH relationship in the inland
blowout habitat

   

Y: 9.9163Ln(x) + 4.3575
g R? = 0.33815

0 i 5 10 15 20 25 30 35 40

DBH (cm)

Figure A1-3. Relationship of Austrian pine tree age to stem diameter at breast height in
the inland blowout habitat. Breast height measured at 1.25 m. Each point represents an
individual.

Austrian pine age to DBH relationship in the wetpanne
habitat

  
 

Y= 9.4509Ln(x) + 6.498
R2 = 0.8172

0 5 10 15 20 25 30 35 40 45
DBH (cm)
Figure A1-4. Relationship of Austrian pine tree age to stem diameter at breast height in

the wetpanne habitat. Breast height measured at 1.25 m. Each point represents an
individual.

92

APPENDIX A2: SUPPLEMENTAL DATA ON PINUS NIGRA AND

PINUS BANKSIANA PROGENY UNDERNEATH AND EXTENDING

FROM PLANTED PIN US NIGRA STANDS

Table A2-1. Mean number of Pinus nigra (Austrian pine) seedlings and saplings across
10 foredune, inland blowout. and forest edge sites, based upon randomly and non-
randomly 1m2 plots underneath and extending from canopy edge or into forest (for the
forest edge). Locations underneath the canopy is designated as “-1.”

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Distance from Foredune SE Forest SE Inland SE
Austrian pine stand edge blowout

edge (m)

-1 14.5 3.69 0 0 6.1 2.14
0 29.6 10.4 1.3 0.5 13.6 3.08
0.7 0.3 .3 0 0 0 0
0.5 0 0 0.1 0.1 0 0
0.91 0.2 0.2 0 0 0 0

1 9.5 5.91 0.6 0.27 6.5 4.09
1.1 0 0 0.2 0.2 0 0
1.2 0.4 0.4 0 0 0.3 0.21
2 4.4 3.04 0.3 0.3 2 0.83
2.5 0.5 0.5 0 0 0 0
2.6 0.2 0.2 0 0 0 0
2.7 0.3 0.3 0 0 0 0

3 3.2 1.55 0.3 0.21 1.4 0.45
3.5 0.9 0.9 0 0 0 0

4 1.5 0.79 0 0 0.4 0.27
5 1.2 0.85 1.2 0.51 0.5 0.22
6 0.1 0.1 0.1 0.1 0.3 0.21
6.3 0 0 0 0 0 1 0.1
7 0.3 0.21 0 0 0 3 0.21
8 0.4 0.4 0 0 0.2 0.13
9 0.7 0.6 0.1 0.1 0 0

10 0.7 0.5 0.3 0.21 0.2 0.2
1 1 0.1 0.1 0 0 0 0

12 0.1 0.1 0.1 0.1 0.1 0.1
12.2 0 0 0 0 0 1 0.1
13 0 0 0 0 0 0

14 0 0 0 0 0 0

15 O 0 0.7 0.33 0.1 0.1
16 0 0 0.3 0.21 0.3 0.21
17 0 0 0 0 0.2 0.2
18 0 0 0 0 0 0
18.7 0 0 0 0 0.1 0 1
19 0 O 0 0 0 0
20 0 0 0.2 0.13 0 0

21 0 0 0 0 0 0
22 0.1 0.1 0 0 0 O
23 00 0 0 0 0 0
24 0 0 0 0 0 0
25 0 0 0 0 0 0
26 0 0 0 0 0 0
27 0 0 0 0 0 0
28 0 0 0.1 0.1 0 0
29 0 0 0 0 0 0
30 0 0 0 0 0 0

 

 

 

 

 

 

 

 

 

94

Table A2-2. Mean number of Pinus nigra (Austrian pine) and Pinus banksiana (Jack
pine) progeny extending from the edge of mature Austrian pine stands across the ten
foredune sites, based on random and non-random sampling. Locations underneath the
canopy are designated as “-1.” Random sampling was performed using randomly located
1m2 plots underneath and at edge of canopy and along transects running N, S, E, W from
the edge of the stand to 5 m or the furthest extent of Austrian pine regeneration. Non-
random sampling occurred wherever regeneration was observed not previously captured
in the random samples.

Distance from Mean No. of Austrian SE Mean No. of Jack SE
stand ed m ine ine
-1 14.5 1.3
O 29.6 2.7
0.7 0.3 . 0
0.91 0.2 . 0
1 9.5 0.9
1.21 0.4 . 0
2 4.4 0.5
2.5 0.5 . 0.1
2.6 0.2 . 0
2.7 0.3 . 0
3 3.2 0.3
3.5 0.9
4 1.5

1.2

0.1
0.3
0.4
0.7
0.7
0.1
0.1

 

95

Table A2-3. Mean number of Austrian pine and Jack pine progeny extending from the
edge of mature Austrian pine stands across the ten inland blowout sites. based on random
and non-random sampling. Locations underneath the canopy are designated as “-1.”
Random sampling was performed using randomly located 1m2 plots underneath and at
edge of canopy and along transects running N, S, E, W from the edge of the stand to 5 m
or the furthest extent of Austrian pine regeneration. Non-random sampling occurred
wherever regeneration was observed not previously captured in the random samples.

Distance from Mean No. of Austrian
stand ed m inc

0 1.3

0.5 0.1

0.6

0.2

0.3

0.3

0
j 7

ob

0.1

_
.—

\OOOQONUIAUJNr‘

wrdNNNNNNNNN~—————-—-——o—
OomNGMAth—OOOONO\MAUJN—O

SE

0.5
0.1

0.2
0.3

0

0.1

 

96

Mean No. ofJack
ine

0.4

0

0

0

0
0
0.2
0

Table A2-4. Mean number of Austrian pine and Jack pine progeny extending from the
edge of mature Austrian pine stands across the ten forest edge sites, based on random and
non-random sampling. Locations underneath the canopy are designated as “-1 Random
sampling was performed using randomly located 1m2 plots at the canopy edge, 5 m, 10
m, and 15 m into the native forest. Non-random sampling occurred wherever
regeneration was observed not previously captured in the random samples.

Distance from Mean No. of Austrian SE Mean No. of Jack
stand ed m ine inc

-1 6.1 0.1

O 13.6 0.4

6.5 0.2

0.3 0
7

‘-

1.4
0.4
0.5
0.3
0.1
0.3
0.2

N

Lo)

1.
2
3
4
5
6
6.
7
8

NO

0.2

———
N—O

0.1
0.1

 

97

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98

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