HHI

   

N]
‘M

   

HIIHH

I

   

‘H
{n

   

WWWW

r
i

   

IIWI

 
    

O
00-D-

    
 

'—I_‘
Io:
_cn

 

ENTERSPECtFEC F‘M'TERN IN AN OLD-FIELD
COMMUNITY [N SGUTHWESTERN MICHIGAN

Thesis for the Degrae of M. 5..
MECHIGAN STATE UNIVERSITY
John Louis Caruso
W63

f! ‘0 ‘
i'-1‘A ’

f .w . 3.
‘ WU
szflgg .83"???

2am

fa“,
,..

I ("s-1 1) (1,. W73."

// v.

. an. a
1?“? a: (1 a"; 1'.
L! i *' -' «J

092611

 

 

ABSTRACT

INTERSPECIFIC PATTERN IN AN OLD—FIELD
COMMUNITY IN SOUTHWESTERN MICHIGAN

by John Louis Caruso

This study deals with the detection of
interspecific pattern in an old-field com-
munity in Kalamazoo County, Michigan, and is
an attempt to ascertain the role of the dom-
inant Species in producing part of this pattern.
The field was procured by the Federal Government
in 1942 and has not been subsequently plowed.
The dominant Species occupying the community on
well—drained Boyer sandy loam is 293 compressa,
which is distributed in varying abundance and l
vigor throughout the upland. There are several
less abundant species which form conspicuous clumps
within the matrix of 2. compressa.

A plot 40 x 80 meters was marked off in a
relatively homogeneous area of vegetation in the
summer of 1961. Five hundred of the 3200
possible 1 m2 quadrats were chosen at random,
arranged systematically, and sampled in geo—

graphical sequence. Presence of species was

UV¢ua H. v“- V..-

recorded for these quadrats, and the resulting
data were examined for positive and negative
associations using a 2 X 2 contingency table
and a Chi Square (X2) analysis of significance.
Within each of the l m? quadrats, a nested
quadrat measuring 25 X 25 cm was randomly
placed. Presence was recorded and cover es-
timated for each species in the l/lb‘m2

quadrat. The presence data were examined by

the analysis of association as above, and the
cover data for the 18 more frequent Species
were subjected to correlation analysis.

Many more negative than positive correla-
tions were found to exist, irrespective of sig-
nificance, and this is assumed to be due, at
least in part, to the spatial limitations of
the quadrat itself. The majority of the sig-
nificantly positive correlations (5% level)
are between the less abundant species, while the
significantly negative correlations are either
between the two most dominant species, 295.
compressa and Aster pilosus, or between one of
these and one of the less abundant species. The
only exception to this is one significant nega-
tive correlation between Rumex Acetosella and
Dianthus Armeria, and.both of these are above
the mean cover and frequency of the 18 species

dealt with.

Jehn L. Caruso

A hypothesis of spatial exclusion of the
less abundant species by the dominant species
was made. In an attempt to test this hypothesis,
seeds of species significantly correlated with
Poa compressa at the 5% level, both positively
and negatively, and seeds of species too infre-
quent for tests of significance were sown in
successively largggfgggfigngs (0.5 cm, 1 cm,

2 cm and 3 cm) in pots of g, compressa sod
brought from the study area to the greenhouse.
Germination and seedling survival were recorded
for each species tested. To date, Melilotus
spp., which is significantly positively corre-
lated.with.§, compressa, was found to have its
seedling survival related to size of opening

in sod (1% level, analysis of variance). The
larger openings yield a greater number of viable
seedlings. Germination of seeds of Melilotus
spp., however, was not significantly related to
size of Opening in 2, compressa sod, although a
trend does develop. The experiments with.§§tgg
pilosus and Solidagp canadensis var. scabra
(both negatively correlated with 2, compressa)
and Monarda fistulosa and Verbascum ghapsns
(both too infrequent for significance tests)
did not produce clear relationships to sod open-

ings. Solidago, although giving 70% germination

on moist blotter paper, failed to germinate in

thn L. Caruso

the openings. Aster pilosus and Menarda

 

fistulosa germinated slowly in the Openings
and never gave values approaching those achieved

on wet blotter paper. Verbascum ThapsdsJ while

 

giving better germination than the two preceding,
did not approach the values for Melilotus spp..
There was no significant difference between the
opening sizes although more total seeds ger-
minated in large openings.

Because Of technique problems, only the
Melilotus experiments are convincing. They in-
dicate/thfiitth adequate moisture seeds shallowly
buried in Openings as small as 2 cm:?/%;%@Zigg
‘germination and survival rates almost as high as
laboratory germdnation percentages. The data
for the others, though inconclusive, suggest
that further study Of their relationships with
z, compressa is warranted.

The hypothesis that spatial exclusion by
the dominants is a factor in the patterns de-
tected, although not confirmed, is still

tenable in the light Of these experiments.

INTERSPECIFIC PATTERN IN AN OLD-FIELD
COMMUNITY IN SOUTHWESTERN MICHIGAN

By

thn Louis Caruso

A THESIS

submitted to
Michigan State University
in partial fulfillment Of the requirements
for the degree Of

MASTER OF SCIENCE

Department of Botany and Plant Pathology

1963

TABLE OF CONTENTS
page

List or Pimes 0.0.0.0000...OOOOOOOOOOOO 111'

Iii-St Of Tables 00....OOOOOOOOOOOOOOOOO... iv

I. Acknowledgments...................... V
II. Introduction

A. Scope Of problem................. 1

B. Description Of study area........ 6

C. History Of study area............ 8
III.MethOds

A. Sampling......................... 10

B. Experimental..................... 13
IV. Results

A. Pattern.......................... 18

B. Germination and survival studies. 23
V. Discussion........................... 28
VI. Summary and conclusions.............. uh
v11. Literature cited..................... h?
Appendices............................... 50-52

Append1X’A 00.00.00.000. page 50, 51
Appendix-B 0000000000000 page 52

1.
2.

LIST 9;; FIGURES

page
A photograph Of a patch of Rubus flagellaris.. 9

 

Photograph Of a clone Of Solidago canadensis
var. scabra. . . . . . . . . . . . . . . . . . 9

 

Photograph Of study area . . . . . . . . . . . 17

Photograph Of a pure stand Of Poa compressa. . l7

 

Constellation diagram showing species'
groups where N-SOO (Chi Square), and Where
N=h8h (correlation Of cover). . . . . . . . . 33

Constellation diagram showing species'
groups where N=228 (Chi Square) and where
N=228 (correlation Of cover). . . . . . . . . 3h

Survival curves Of seedlings of Melilotus Spp.
resulting from seeds sown 23 June, 1963. . . . 38

 

Survival curves Of seedlings Of Melilotus spp.
resulting from seeds sown 18 FebFuary, 1963. . 39

 

iii

I.

II.

III.

IV.

VI.

VII .

LIST 9;: TABLES

Correlation and Chi Square matrix for greater
number Of quadrats. . . . . . . . . . . . . .

Correlation and Chi Square matrix for fewer
number Of quadrats. . . . . . . . . . . . . .

Chi Square levels Of significance of associa—
tion between Species in bluegrass Old-field
vegetation. O O O O O O O O O O O O O O O O 0

Mean seedling survival Of Melilotus spp.
resulting from seeds sown 18 February, 1963 .

 

Mean seedling survival Of Melilotus spp.
resulting from seeds sown 23 June, 1963 . . .

 

Total seedling survival for Aster pilosus
and Monarda fistulosa resulting from seeds
sown 18 February, 1963. . . . . . . . . . . .

Total seedling survival for VSrbascum

Thapsus resulting from.seeds sown 30 April . .

iv

20

21

22

26

26

27

27

ACKNOWLEDGMENTS

I am very much indebted to my major
professor Dr. thn E. Cantlon, for his con-
tinual aid and surveillance both in my re-
search and scholastic program. I wiSh to
thank the other members Of the graduate come
mittee, namely, Dr. Philip J. Clark and Dr.
William.B. Drew, for their critical review Of
this manuscript; special thanks to Dr. Clark
for his many suggestions concerning the biomp
etry in my work, and also to Dr. Drew for his
critique on the taxonomy Of the species collec-
ted in the study area.

I am.grateful to the Ft. Custer Military
Reservation personnel who were instrumental in
Obtaining the initial permission for me to work
in the area, and my gratitude is here expressed
to Dr. Thane S. Robinson, Director of 0.0. Adams
Center at Western Michigan University, for per-
mitting me tO complete the study after he was
given management responsibilities for the area.

I wish to acknowledge the kindness Of Mr.
Frank Austin, Soil Scientist, for his special
trip to the study area to confirm the soil type,
and also to express my appreciation for the
separate, but concerted tasks Of Hrs. NOrma Ray,

Supervisor Of Data Processing Research, and

V0

Miss Margie Williams, Computer Operator, both
at Michigan State University.

This study was supported in part by funds
made available by the National Science Fbunda-
tion (Grant - G1399l).

Additional thanks are due to Dr. thn
Beaman for his helpful discussions earlier in

this study, and to Dr. Irving Khobloch for

reviewing the manuscript.

vi.

INTRODUCTION
A. Scope of Problem.

Pattern in vegetation is a manifestation Of
non-randomness in the plant community. Pattern
is, moreover, an external feature of the comp
munity by which one may perceive intengfifikgégcal
ganization. According to Hutchinson (1953)
pattern is the "structure which.results from
the distribution Of organisms in, or from,
their interactions with their environment...."

That individuals in the plant community
form patches, and these patches collectively
produce the mosaic nature Of much vegetation,
was eloquently defended by Watt (l9h7). Ashby
(l9h8) referred to such aggregates as plants in
a state Of overdispersion, and stated that
underdispersion, or the departure from.randomr
ness in the direction Of uniform spacing, was
much less common in nature. Goodall (1952)
and Skellam (1952) have also pointed to the
general tendency Of plants to form aggregates
or clumps.

Rather elaborate and precise methods have
since been develOped to detect the orders Of
clumping or grouping among plants. The meas-

urements Of distance between nearest neighbours

in reflexive pairs is a method developed by

1.

2.

Clark and Evans (195h) to determine orders of
grouping in one-Species populations. Pielou
(1961) transformed the approach of Clark and
Evans to one in which symmetry between members
of two-species pOpulations could be studied.
Groupings Of more than one species are
seemingly more difficult to elicit from.spatial
relationships Of plants. Grieg-Smith (1957) has
reviewed much Of the important literature on
association and pattern prior to 1956. In
addition, Fager (1957), Bray (1956a), McIntosh
(1962) and Kershaw (1960, 1963) have made use-
ful contributions to the subject. Byer (1960)
studied shifts in interspecific associations
along an environmental gradient. McIntosh.(l962),
in an effort to construct units Of vegetation from
tests Of association, reviewed the methods Of
Goodall (1952) and Hopkins (1957), but con-
cluded a) that the groups one gets depend upon
the significance levels he chooses in selecting
associated pairs, and b) there is no non-arbi-
trary way to decide on prObability level.
Kershaw (1960, 1963), although not com-
pletely resolving the difficulties associated

with interspecific groupings, has nevertheless

proposed a method whereby the scale of pattern
in association can be defined. His method is

one of Obtaining the mean Square or variance in

the joint number Of individuals of two Species

3.

in a given.block size. when the variance is
plotted against the block (sample unit) size,
the peaks Of the graph represent the mean area
Of pattern in the vegetation analyzed. This
contribution is Of great importance when one
considers the many statements concerning pat-
tern, which, in the past, have been.based on
results Obtained from sampling with one fixed
size Of quadrat.

Regarding the causes Of patterning in vege-
tation, Kershaw (1963) has classified them.into
pattern types that are encountered in the field.
They are: (1) morphological pattern, which in
general produces a smaller scale patterning
relative to the size Of the area sampled, such
as that found in plants reproducing by rhizomes,
(2)environmental pattern as resulting from.the
plant's response to its surrounding, which.may
be on a larger scale than the preceding but not
necessarily so, and (3) sociological pattern,
which, although traceable to an interaction.be-
tween organisms, is sometimes impossible to dis-
tinguish from environmental pattern. This is a
somewhat simplified classification Of causes
over that proposed by EMtchinson (1953) who
used: vectorial (environmental), reproductive,

interactive, stochastic and signalling as the

1L.

categories. Kershaw's substitution Of morphological
for reproductive is not entirely satisfactory
and perhaps both have a place.

If one took a cursory glance at a large hump
ber Of the papers written on the subject Of pat-
tern, he would conclude that distribution pat-
terns Of individual species have been Of greatest
concern (intraspecific pattern), while a much
smaller number pertain tO interspecific pattern
(as inferred from interspecific association).

The patterns referred to in this paper are almost
exclusively interspecific associations.

The purpose Of this study is twofold: (1) to
detect Spatial pattern.among vascular plants in
an Old-field community, and (2) to determine to
what extent the abundant vascular Species influ—
ence the less abundant Species in the manner Of
spatial exclusion. The bryophytes and lichens,
although undoubtedly a part Of Old-field pattern-
ing, were excluded from.analysis because Of unre-
liable field identification and cover estimates.

This study can.be considered as an initial
phase of investigation into patterning in Old-
field vegetation, and may have particular imr
portance in eliciting questions pertaining to

competition and chemo-sociology in such an Old-

field ecosystem. As Grieg-Smith (1957) points

5.

out, the detection and analysis Of non-randomness

is not an end in itself, rather it is a starting
point for further investigation into the factors
responsible for the existing spatial character-
istics.

The vegetation selected for the study Of pat-
tern is in a grass-dominated Old-field community.
It is relatively simple in composition, and if

the conjectures Of Grieg-Smith and Kershaw (1958)

are correct, the area studied should have a
greater intensity and concomitant smaller scale
Of pattern than the climax type that will event-
ually arise through succession.

Succession, a dimension Of great significance
in Old-field vegetation, will be given at most a

very brief consideration in this paper. Watt (19h?)
gives a careful analysis Of the relation between

temporal and Spatial patterns in seven communities;
Bray (1956b) and Whitford (l9h9) elucidate temporal
and spatial changes in woodlots; Egler (195k)
confines himself primarily to temporal pattern in
Old-field vegetation, preferring the term ”devel-
opment" to "succession” because Of the latter term‘S
implication Of discontinuity between seres in the
progression. Pertinent general references on Old—
field vegetation include, among others, Clements
(1916), Oosting (19h2), Keever (1950), Bard
(1952)end Odum (1960).

B. Description of the Area

The field chosen for investigation is
located in the Ft. Custer Military Reservation
in the northeast corner Of Kalamazoo County
(sw 1/1. of NE l/h of Sec. 9, £9.23, R.9W). The
longest axis of the field is oriented east and
west, with the Ft. Custer Road and the Kalama-
zoo River forming the main eastern and western
boundaries, respectively.

The study area is in the eastern portion
Of the field. It is somewhat elevated with
gently sloping tOpography, while the unsampled
western portion Of the field is lower on a
terrace nearer the river.

The soil in the study area is mapped on the
county soil survey as Oshtemo sandy loam
(Perkins and Tyson, 1926). Revision Of soil
classification since that survey was made re-
quires a separation of Boyer from.Oshtemo sandy
loam if carbonate material is present less than
h2 inches beneath the soil surface. Field de-
termination has shown that the soil is actually
Boyer sandy loam under the present soil classi-
fication (Frank Austin, Soil Scientist, in voce).
The soil on the terrace below is mapped as Osh-

temo sandy loam but is believed to be an alluvium

of some type.

7.

The floristic differences between the dry
study area and the more moist, unsampled river
terrace are remarkably similar to the differ-
ences for an Old-field in southeastern Michigan
noted.by Evans and Dahl (1955). Poa compressa
(nomenclature following Gleason and Cronquist,
1963) is the dominant in the dry area, while
Poa pratensis characterizes the moist area.

2, compressa is virtually everywhere in
the upland, and this species forms a more-or-
1ess continuous phase in the community, varying
throughout only in number and size Of culms.
Situated in this varying matrix Of bluegrass
are several contagiously dispersed lesser abun-
dant species, which collectively produce a
pattern Of patchiness very much like the complex
mosaic encountered.by Evans and Cain (1952).

The major patch-forming species are: ggggg
flaggllaris (Fig. 1), Solidago canadensis var.
scabra (Fig. 2), Solidago juncea, Solidago
nemoralis, Hieracium longipilum, Hieracium

aurantiacum and Saponaria officinalis. These

 

patches, within which bluegrass is less promi-
nant, belong to a discontinuous phase.

A list Of species arranged in order Of dev
creasing frequency is presented for the study
area (Appendix-A). Species existing in the area
at the time Of sampling that did not occur in

8.

quadrats are contained in the list, but they are
not given a frequency status.

VOucher specimens from the study area are
on file in the Beal-Darlington Herbarium at

thhigan State University.
C. History Of Area

The study area is part Of a kl acre tract
procured by the Federal Government 28 September,
19h2. The tract was leased 1 March, 195k, to an
individual for the purpose of grazing cattle.

The lease terminated 31 August, 1958, however,
the only grazing recorded was during the period
April to October, 1955.

White-tailed deer have been seen on the lower
terrace in the field, and there is some evidence
Of their browsing in the upland. The only other A
Sign Of major disturbance in the area is the
remnant Of an old trail, now existing as a slight
depression grown over by vegetation. The trail
presumably is an outcome Of the maneuvers of the
U.S. Army shortly after the land's procurement

by the government.

gaég‘f“
J ’ .'

 

Fig. l. A 21-year Old field showing a patch
of Rubus flagellaris in the left foreground.
The continuous phase (ng_compressa) on the

right and in the background.

 

 

Fig. 2. A clone of Solids o canadensis Var.
scabra in the foregroun an another of the
same species at mid—distance.

 

METHODS

A. Sampling

The vegetation in the upland was sampled
during the period 20 August to 12 September,
1961. A plot 80 x no meters was marked Off in
a relatively homogeneous area Of vegetation.

The longest axis Of the plot runs north to south
(Fig. 3). Five hundred Of the 3200 possible

1 x 1 meter quadrats were chosen at random, then
they were arranged systematically and sampled in
geographical sequence. PreSence of species was
recorded in each quadrat. Since the degree Of
association Of species depends on the size of
quadrat used (Grieg-Smith, 1957), within each

1 m2 quadrat a nested plot measuring 25 x 25 cm
was placed at random. Presence was recorded and
cover estimated for each Species in the 1/16 m2
quadrat.

Unfortunately, the cover Of 2 g compressa
was underestimated in the first 269 small quad-
rats. The author changed techniques in estimat-
ing the cover of 2, compressa at this point, re-
sulting in 269 uniformly underestimated cover
values. The cover error in the first quadrats
was rectified by a later calculation Of the mean
Of the underestimated values. This mean was then
divided into the mean cover for the remaining 231
more nearly correct values. The resultant

10.

ll.

quotient was used as a correction factor for each
cover value of P. compressa throughout the first
269 quadrats. The possibility of a less reliable
cover value for this one Species should be kept
in mind whenever the greater number of quadrats
is used in a cover relationship involving 2.
compressa.

The presence data Obtained from the large
and small quadrats were examined for positive
and negative associations using a 2 x 2 contingency
table and a Chi Square (x2) analysis Of signif-
icance. The formula incorporating the correct-
ion factor Of Yates was used (Walker and Lev, 1953).
Species whose SXpected values of occurrence
were less than five were excluded from the Chi
Square analysis.

The above analysis for association cannot
be used for species having very high frequencies
Of occurrence (Grieg-Smith, 1957), for example,
22; compressa, which occurs in all 1 m2 quadrats.

Correlation analysis of per cent cover was
Selected as a sensitive measure Of association
for 2. compressa. In order to handle the large
number Of calculations necessary for cover cor-

relations with the many different combinations

12.

of species, two programs were established for
the Integral Computer at Michigan State Univer-
sity. One program was based on cover data Ob-
tained from.h8h quadrats. For reasons Of miss-
ing cover values or Obvious errors, 16 Of the
500 quadrats were discarded from.the cover
study. This program incorporates the correc-
tion factor for 2, compressa cover.

The second program is based on the last
228 quadrats sampled in which the cover values
of P, compressa were more accurately estimated
in the field (three Of the 231 quadrats were
discarded for reasons mentioned above).

Because of limitations on card Space in the
programming, 18 species were used in.both cor—
relations. The basis Of choice of species for
the correlations was frequency of occurrence.
The 18 species chosen were those which occurred
most frequently and for which there was no
problem Of field identification. Appendix—B
contains a list Of Species used in both corre-
lations, the Species Of which are arranged in
order Of decreasing average per cent cover.

The lists are not identical. Poa pratensis is
more abundant in the southern portion of the
study area and was arbitrarily chosen for the

correlation involving the greater number Of

l3.

quadrats. Leptoloma cognatum.appears to be
more abundant in the northern portion of the
area, on the other hand, and its relationships
were studied only in the correlation involving
the northerly 228 quadrats. Similarly,
Ambrosia artemisiifolia takes the place Of
Daucus Carota in the analysis Of data from the

fewer quadrats. Erigeron is represented in the

 

northerly 228 quadrats as one homogeneous taxon

(E. strigosus) as Opposed to the heterogeneous

 

Erigeron spp. referred to in the greater number

 

Of quadrats. The later taxon includes a small
but unknown amount of g, annuus. Finally, be-
cause Of vegetative and floral senescence,
Melilotus 2.1-2.9. and M. Officinalis could not
always be separated in the field, and henceforth
will be referred to collectively as Melilotus

are.

E. Experimental

In an attempt to determine whether, and to
What extent, the dominant species, ng_compressa.
limits the numbers Of the less abundant Species,
a model was conceived to study the influence of
2, compressa on the germination Of seeds and
survival of seedlings Of several Of these species.
Fbr this purpose, sod from.a relatively pure
stand of g. compressa was collected in the study

area in October, 1962 (Fig. h).

1h.

Blocks of bluegrass sod were cut by means
of a sharpened hand trowel to a depth Of about
5 1/2 inches, including most of the tight,
netlike fibrous roots and some mineral soil.
These blocks were then trimmed in diameter so
they would fit snugly into five-inch pots.

The sod samples were transported in the pots

to the greenhouse at Michigan State University.
A few weeks were allowed for the grass to ac-
climate itself tO the greenhouse environment.
Seedlings of any species which appeared were
removed during this time. From.the date Of col-
lection to the termination of the study, the
grass was watered regularly and trimmed occa-
sionally to maintain a uniform height Of between
four and five inches.

Circular Openings of foum: Sizes (.5 cm,

1 cm, 2 cm.and 3 cm) were cut into the sod by
means of cork borers having these reapective
diameters. The borers were inserted to a depth
below the grass rhizosphere so that, upon re-
moval, the plug inside the borerwould contain
all Of the grass roots within a given diameter.
The holes were then filled with soil trimmed
from.the sod blocks and from which all roots

were removed. A large fraction Of this soil was

15.

from below the densest root mat. The soil was
tamped lightly and smoothed to correSpond with the
soil level in the pot.

A wooden disc five inches in diameter
placed over the sod in the pot served as a
template for locating four Openings per pot.
Four templates were used, one for each of the
four different sized Openings. ‘Within each
disc, the four holes were Of equal Size and were
uniformly Spaced with their centers forming a
square measuring 2 l/h inches on a Side. The
wooden disc was placed over the pot and the
borer was inserted through each Of the four
holes having a corresponding diameter. Eight
pots were used for each Of the four different
Sized Openings, thus giving a total Of 32 re-
plicates for each size class for each Species.
The pots were randomly arranged on the green-
house bench.

Seeds Of various species were collected
during the summer and fall Of 1961, and during
the same period in 1962 with the expectation
that certain Of these would later be used in
germination studies. It was desired to use
seeds Of Species that were found to be signif-

icantly positively correlated with bluegrass,

16.

some that were significantly negatively corre-
lated with bluegrass, and seeds Of some species
which.were relatively infrequent. Only one
Species was planted in each pot with three
seeds in the center of each Opening giving a
total Of 96 seeds sown for each Species in

each of the different size classes.

17.

 

Fig. 3. A view diagonally from southwest to
northeast across the sampled universe. The
stake in the foreground marks the southwest
corner; the northeast corner is just to the
right of the tall tree in the center.

 

Fig. h. A relatively pure stand of Poa
compressa from which the sod samples were
taken.

RESULTS
A. Pattern

Correlation coefficients Obtained from.the anal-
ysis Of cover data from.h8h quadrats are presented
in matrix form (Table I). Fbr the purpose of com-
parison, symbols indicating the significance and
Sign of Chi Square analysis of association in the
h99 1/16 m2 quadrats are found within the complemen-
tary portion Of the same matrix. The Species are
arranged along the margin Of the matrix from.1eft1x>
right and from.top to bottom in order Of decreasing
average cover values. A similar matrix based on the
northerly 228 quadrats only is given in Table II.

It Should be noted that there are many more neg-
ative than positive correlations in.both matrices,
irrespective Of significance. When the mean number
Of negative correlations and positive correlations
for all species are compared, it is found that the
negatives are more numerous (the significance of the
difference at the 1% level, T-test).

Looking at only those correlations which.are
significant at the 5% level the negative cover cor-

relations are almost exclusively found between the

two most dominant species Poa compressa and Aster

pilosus, and between one of these two dominants and

18.

19.

less dominant species. The majority Of the Signifi-
cant positive correlations, however, are between the
less abundant species.

The significance Of the tests Of association as
determined.by Chi Square analysis for the 500 m2
quadrats are presented in Table III. The most fre-
quent species that could be tested was A. pilosus
(91.h%) and the least frequent that could be used was

Vitis Sp. (1.2%) whose SXpected joint occurrence with

A. pilosus reaches five.

 

 

Table I. Obi Square levels of significance of association in lower left of table apply to 499 1/16 m2 quadrats.
Cover correlations in upper right of table apply to 481» 1/16 m2 quadrats.

°5éadeééésé
Egg: O+positive.10 ~negative.01 fig g 3%?) a; g 4; 3 '3 £3 'é‘ E a 8 Z .3 5° 8E
+positive .05 ’“positive .05 g H H E ,3 3 :2: g .H 3 3 3 a) a. a '3 .3“ ,5}
++ positive .01 *poeltlve .01 o '8. H <1 3 «a o o . . . It . . . . .
O-negative .10 :negative.05 p: ‘3 a; F; g m- p; v; ,,; m m a m o p, m n a,
- negative .05 2 negative .01
**
Poacompressa..............o .zngAQmaoequqlgEgéo 02112921042033_3_OLP79830__O_6021

*Il *Ik

Asterpiloeus..................ugLaiossousfiflLJgLOOSOWlLozl0309;
Ru‘busflagellaris..................OBSMOllmmmm016m167mmmmm
mantmasmerla .................+...lgzsaawémmmgagofionoyzmumoos921
Helilotusspp......................+...u000m1héflz_gflmmm2055mm133
Rumeeretoeena..... .+.'".‘. . .. mquamggmomoosmmmom
Potentillarecta.................'......... wmmmlfimémmoamm
Solidagocanadensisv.ecabra......................L113_QIS_Q11221915.93.8Q28921911Q2A
saponarlaerficlnaue............i...............ooémgz9_gazgz§mmmgzz
Solanumcaronnenae.............=:.................0u6mgzy_173235mm100

SOIIGagonemoralis..o...............-:............... 063mmmmmm

** ,
Euphorbiacorollata..............o°'.................. 055mm105wm

Erigeronspp. ....................................... glamoszggzom
axemmnem..............."'.'........+.................019m.5_qopom
Poapratensis................'I".......'."'...................Q_l_§_QQLOZl
Hieraciumlongipilum..........................................mm

Damusoamtaeoeoooecoo-0000......beeeoooooooooeee0.000.000.0002

eqlisetumlaevigatum....e........................... o

'02

 

 

Table II. Chi Square levels of significance of association in lower left of table apply to 228 1/16 1112 quadrats.

Cover correlations in upper right of table apply to 228 1/16 2112 quadrats. 5
In
0 e e e e .4 5:! g e .p
1531: 0+ positive .10 -- negative .01 . . .2 a g g g «3 .3. g 5' .3 w P m g)
+ positive .05 “ positive .05 g a g g +; 'd g 3 go 3 «3 r3 '8!) 3 '3) a E E
++ positive .01 '"' positive .01 H g E ,9, g; § § 33 g g g '53 g :1 p o 1.. a
0- negative .10 " negative .05 '5' " ‘4 3;; 4 0 0 (H a o o .-u n m o m ,_.
.. negative . 5 finegative .01 .3 g: n. 2" ,3; u5 n: m. m. V; M. v; In. 0- m. .5 4; a.
an a: an e s _
16291229521001 129.926.912.152000 075221054 079 SLLQ 132 93119.51

Asterpilosus................

roaeompreesa..................mimizzfimozzfizimmmmmmmmsm
DianthusAmeria.................. o3lg§im101ggzoa3gfiq§2m1gqégm5mmfi
QLQflfiifilLQkaQfiQZZQléommuQfllQfl
MmeXAcetosella............ ..... .... . mmmzozolzmonmowlm016092081
Solidagocanadensls.......................Qéémmmmozsmmonmmm
Potentillarecta.....................0-.... mflmmmoszmmmmm
Saponarlaofficlnalle..........................083mmmmmgzammlm
Rubusflag0113rie..............................QZ&QMQ§LMQZ{LO5OQ£QZS_QZ§
Solidagonemoralie............................... g5gIlgLiQ3iQHQLZQLiQ9i
Inphorbiacorollata.................................103Qg_10’+0_0320220€_)ggg§_
Solanumcarolinenee...................................gamQQéOZBfiLl-IIIB
mmmaam

“Blilotussypo.o...........-.-.......

metaciumlongipiluInoonoIOOOOOOOOOOOOCOOQOOOno...COO-ee0

Omlis nil-191.11 O .— 0 0 I . O O O O I O .0”: O O O I 0 O O I O O O O O O O O O O I O O O C O O O 0 9-3-2. _& 1714‘ m
911 5212 9.13.

*I‘
0.15. 156

Erigeron strigosus e e e e e e e e e e e e e e e e e e e e u e e e e e e e e e e e e e e e e e e e e
“$010133 ngatum e e' e e e e e e e e e e e e e .0. e e e e e e e e e e e e e o e e e e e e e e e e e e o
Alibi-.0818. artamisiifolia e e e o e e e e e e e e e e e e e e e e s e e e e e e e e e e e e e e e e e e e e e e 015

Eq‘flsetmnlaevigatum..o..o.........................o..............

'IZ

22.

Table III. Chi Square levels of significance of association
between species in bluegrass old-field vegetation. The 22
missing cells on right hand side of table contain no signifi-

cant associations, and g. compressa which was ubiquitous
could not be tested. N=SOO 1m quadrats except for the *

where N=447 due to identification problems in field.

Key:

0+

4.
++
0..

positive
positive
positive
negative
negative
negative

.10
.05
.01
.10
.05
.01

artemisiifolia

recta
Dillenii
Melilotus app.
corollata
cognatum
carolinense
Officinalis

Ameria

R.‘Acetosella

P.
R. flagellaris

E.
Erigeron Spp.

A. pilosus
D.

0.

L.
1s. nemoralis
5.

A.

3.

 

Aster pilosus
Dianthus Armeria
Rumex Acetosella +
Potentilla recta +
Oxalis Dillenii
Melilotus spp.
Rubus flagellaris
Euphorbia corollata +
Leptoloma cognatum*
Solidago nemoralis
Solanum carolinense
Ambrosia artemisiifolia
Erigeron Spp.
Saponaria Officinalis +
Hieracium longipilum
Daucus Carota
Solidago canadensis v.
scabra
Equisetum laevigatum
Agropyron repens*
Achillea Millefolium - +
Poa pratensis
Physalis heterOphylla
Lactuca canadensis + -
Trag0pogan pratensis
Chrysanthemum leucanthemum
Verbascum thapsis
Panicum sp.
Prunus serotina
Solidago juncea
Taraxacum officinale
Hypericum perforatum
Plantago lanceolata
Ulmus americana , -
Setaria glauca -

Trifolium pretense
Vitis sp.

 

 

 

 

++

 

 

 

 

 

B. Germination and Survival Studies

In choosing which of the many possible eXperi-
ments to make relative to the effect of bluegrass
sod on germination and seedling survival, two cri—
teria were considered important. These were a)
whether the seeds of a particular species gave depen-
dable and high germination, and b) whether the species
was interesting from the standpoint of pattern. Ger-
mination trials resulted in the selection of Eelilotus
spp., §§£§§_ ilosus, Solidagp canadensis var. scabra,
Monarda fistulosa and Verbascum.Thgpsg§. The first
is significantly positively associated with 222.

compressa; the next two are significantly negatively

 

associated.with E, compressa, and the last two are

 

species present but too infrequent to be used in a
significance test.

Mixed seeds of Melilotus alba and E, Officinalis
germinated at between 70—80% when moistened on blotter
paper in petri dishes in the greenhouse. A.mixture
of seeds from.the same collection sample was planted
18 February, 1963, according to the design described
earlier. At each reading, viable seedlings were
totalled for each pot. The first reading 13 days
after planting discloses a distinctly greater propor-
tion of the seedlings surviving in the larger open-

ings (Table IV). An analysis of variance of the data

23.

2h.

showed that the survival of Melilotus spp. seedlings

 

is related to the size of opening in bluegrass sod,
significance at the 1% level. Later readings were
taken, and the initial significant difference in
seedling survival was found to persist through time.

The above experiment was duplicated by planting
seeds in freshly dug openings 23 June, 1963. To
study the effect of size Opening on germination of
seeds in addition to survival of seedlings, the first
readings were taken six days after planting (29 June).
This was seven days sooner than in the first experi-
ment and only a slight increase in viable seedlings
was found in the successively larger openings (Table
V). An analysis of variance in data revealed no
significant difference in germination between size
classes. The readings of u July, (11 days after
planting) disclosed a greater difference in numbers
of viable seedlings, and this difference, through
the same analysis, proved to be significant at the
1% level which is very similar to the results of the
13 day readings in the previous experiment.

Seeds of égggg.pilosus and Solidago canadensis
var. scabra, both negatively correlated withwz.

compressa, and seeds of the two species that are

relatively infrequent in the community (menarda
fistulosa and Verbascumlkhapsfls) have been sown in

the different sized openings in bluegrass sod. At

25.

the time of writing, Verbascum.Thapsas is the only
other species tested that shows some indication that
its seedling survival may depend on the degree of
Openness in bluegrass sod. It is possible that
faulty watering techniques caused the seeds of these
very light-seeded species to be displaced into the
sod. This may explain the poor germination results
which did not give enough data to permit statistical
analyses. The results of these plantings, with the
exception of §, canadensis var. scabra, are presented
in Tables VI and VII. Although §, canadensis var.
scabra gave 70% germination on wet blotter paper,

no germination was recorded for this species in

bluegrass sod.

26.

Table IV. Mean seedling survival out Of 12 W
seeds per pot for each Of four sizes Of opening in 2.-
cO ressa sod at 13, 340 and 65 days after sowing.
firmee seeds were planted 18 February, 1963, in each Of
four Openings Of same diameter per pot. Eight pots
were used for each size class, giving 96 seeds sown
per size class Of Opening. Germination percentage on
wet blotter paper was 75%. A standard error is given
with each mean, and the significance Of the differences
between size classes as determined by analysis Of var-
iance is given below for each reading.

 

 

Qpening in sOd Days after planting
a a .622
0.5 cm 2.5003598 .750i .278 .875: .295
1.0 cm 3.3753821; 1.375; .1720 1.500: .1463
2.0 cm 145001.628 1.875;; .639 1.625: .571
3.0 cm 6.6253861; n.87511.1i1 h.375~_+,l.ll7
P:.Ol P=.01 =.Ol

Table V. Mean seedling survival out Of 12W
seeds per pot for each Of our sizes Of openings in 3°
cogpressa sOd at 6, ll, 17 and 27 days after sowing.
Three seeds were planted 23 June, 1963, in each Of four
Openings Of same diameter per pot. Eight pots were
used for each size class, giving 96 seeds sown per size
class Of Opening. Germination on wet blotter paper was
undetermined, but an earlier test in this room gave
values approaching 100%. A standard error is given
with mean, and the significance Of the differences be-
tween size classes as determined by analysis Of vari-
ance is given below for each reading.

ni
3:830:38 Days after planting

Q. .1}. 1.7. 2.7.
0.5 cm 6.625il.068 3.6253680 3.7503773 3.8753789
1.00m 7.125: .611 5.5003821; 5.3753882 5.250;.881
2.0 cm 7.375;: .625 6.750;.590 6.8753667 7.0003732

3.0 cm 7.625;. 565 7.1253515 7.2503559 7.2503559

P = not P=. 01 P=.01 1==.05
significant

27.

Table VI. Total seedling survival for Aster pilosus and
Monarda fistulosa out Of 96 seeds planted in- each Of
four sizes Of opening in 2. compressa sod at 13, 13,0, 55
and 65 days after sowing. Three seeds were planted 18
February, 1963, in each Of four Openings Of same diameter
per pot. Eight pots were used for each size class,
giving 96 seeds sown per size class Of Opening. Ger-
mination for A. pilosus and M. fistulosa on wet blotter
paper was no and 30.6, respectively.

I

Species and daysg after p ntin
Opening size 13 1L0 65

Aster pilosus

 

 

 

0.5 cm 2 2 5 6
1.0 cm 0 2 2 2
2.0 cm 2 3 3 l;
3.0 cm 1 Li 6 7
Monarda . fistulosa
0.5 cm 0 3 5 6
1.0 cm 1 2 5 6
2.0 cm 0 3 1L 5
3.0 cm 0 1 1 3

 

Table VII. Total seedling survival for Verbascum ME.
out Of 96: seeds planted in each of four silzee of ‘opening
in P. compressa sod at 18, 28, 50 and 55 days after sow-
ing? Three seeds were planted 30 April, 1963, in each Of
four Openings of same diameter per pot. Eight pots were
used for each size class, giving 96 seeds sown per size
class Of Opening. Germination on wet blotter paper

was 75%.

 

 

 

0pening days after fianting

in sod A 28: 50 55
0.5 cm 25 28 13 9
1.0 cm 15 18 6 6
2.0 cm 29 35 9 12

3 . 0 cm 31 3h 23 22

DISCUSSION

 

It is hard to conceive Of a vegetation that
does not have at least some of its component parts
in a non-random spatial arrangement. The pattern or
departure from randomness may be subtle, but it is
probably extant in all forms Of vegetation. It is
possible that one stage in the develOpment Of vege-
tation may display more Obvious pattern than other
stages. According to Scurfield (1956) competition
is the main directional force in community pattern
and is manifested particularly in succession. Thus,
the and state or climax vegetation is seen to be
more ordered and/display more pattern. Grieg-Smith
and Kershaw (1958) are diametrically Opposed to the
suggestion made by Scurfield, and moreover, state
with some good evidence that spatial arrangement Of
plants proceeds from randomness in colonizers to non-
randomness in the intermediate phases, and finally to
a more-or—less random distribution in the end state.
Kershaw (1963) refers to earlier work Of Grieg-Smith
which demonstrates little non-randomness and associa-
tion in an undisturbed rain forest in Trinidad. Ker-
shaw cites other cases to support the hypothesis.
Grieg-Smith and Kershaw do admit that although pattern
decreases in intensity in a stable state, the scale

Of pattern generally increases here. There appears

28.

29.

to be a great need for sampling and analysis Of vari-
ous changing communities before one can, with certi-
tude, point to the direction in which.pattern increases.
One thing is abundantly clear, the Old-field
under investigation has Obvious morphological pat-
tern (following Kershaw's classification) as exempli-
field.by Solidagg canadensis var. scabra; the field
has environmental pattern which is somewhat less
discernible, fer example the change in dominance Of
Poa compressa to 駧§3.pilosus in the northern portion
Of the study area (Appendix-B). There is an indica-
tion of a sociological pattern in the preponderance
Of negative correlations Of plant cover.
The greater number Of negative correlations
among the 18 species tested is probably a result of
one Of the simplest Spatial relationships. Within
any given quadrat, as one species tends to increase
in cover another species will generally tend to de-
crease in cover. This is due primarily to restriction
in area Of the quadrat itself (Grieg-Smith, 1957).
The negative correlation is magnified when the two
species also require slightly different microenviron-
ments or actually prove to be inhibitory to each other.
If a factor is Operative which produces an effect
that is contrary to the above, then within a given

area two species will tend to cancel out the negative

30.

tendency. If the factor is strong enough in its
action the species will increase together. For ex-
ample, both species may have similar micro-environ-
mental requirements, Or one or both respond favour-
ably tO the presence Of the other.

It is axiomatic that less abundant species are
less capable Of occupying ground in the community
than.the dominant ones. In some cases this may be
due to differences in speed Of vegetative reproduc-
tion, in other cases it may be related tO the rela-
tive competitive abilities Of the dominant and non-
dominant Species.- In either case, in micro-sites in
which.the dominant does poorly, non-dominant species,
provided they can grow well there, are apt to have
higher probabilities Of occurrence. Many positive
associations between non-dominants in the Old-field
could.be due to such breaks in.the less-hospitable
£93 cover.

The above statements might explain, at least in
part, the fact that the significantly positive corre-
lations are more numerous among the less abundant
species in both matrices (Tables I and II), while the
significant negative correlations are found between
2, compressa and Ag§g§_ ilosus, and between either

Of these species and less abundant species. The only

31.

exception is in the case Of Rumex Acetosella and

 

Dianthus Armeria which.are significantly negatively
correlated in cover (P=.05) in.the Sample NILLBLL.~
'These two species are also abOve the mean cover and
frequency values Of the 18 species studies (Appendix-
A, -B).

Spatial exclusion as postulated here is not a
new concept. It has been.considered as an important
element in pattern in vegetation for some time
(Ashby, 19h8, Cooper, 1961, Pielou, 1960; Kershaw,
1963, among others). Since the dominants occupy more
area than the other species, they would be expected
to exert a rather major influence on determining the
location, abundance and cover Of the less dominant
and rarer species.

If one does not focus exclusively on spatial ex-
clusion and strong negative correlations, and instead
brings into perspective-the positive relationships,
the concept Of groups Of plants appears unavoidable
in the description Of pattern. Fager (1957) has pro-
posed a rather involved method for the determination
and analysis Of recurrent groups. McIntosh (1962),
in.his review Of methods Of group identification,
does not mention Fager's prOposal, but he does give
convincing evidence that no Objective method exists

at present by which one may group plant species. It

32.

seems reasonable to assume that tendencies to occur
together rather than strong bonds between individuals
form the basis Of groups. The levels Of these ten-
dencies are functions Of many things including the
scales Of microenvironmental patterns, the sizes
and tolerances Of the organisms concerned, and not
tO be forgotten, the size of sampling units for which
tendency toward co-occurrences is being tested. These
groups are more akin to the patterns presented by
the coocurrences Of, say, human occupations in a
large city than to the organography Of a plant. An
attempt to portray vegetation in terms Of "basic
units" such as Hopkins (19h7) has described will
not be rewarding except possibly in highly patterned
vegetation such as occurs in polar or alpine regions.
Nevertheless, it seemed worthwhile in this study
to compare groups Of positively associated Species
at the 5% level that were Obtained in both correla-
tion and Chi Square analyses. The groups recognized
from.the samples over the entire field, and from
those in the last half only are illustrated in
Figures 5 and 6, respectively. The groups are,
arranged subjectively according tO their relative

positions with regard to degree Of develOpment Of

bluegrass sod.

 

33.

  

 

  
  

 

Hi racium
EuEhorbia
ieraci L
PO entilla
ume
ter igeron
Olidag Dianthus/E
nemoralis
O 3113 R bus
uphorbia D ucus
0 alis
otentilla \elilotus
lianthus p aponaria
s:
.6111 tus g E uisetum
quisetum E)
«\l 8 P08
SO ,3 compressa
'3 Solanwn._.~‘§~__‘-~‘¥o
0a pratensis ”3 1 a
pratensis
t

Fig. 5. Constellation diagram showing species grouped according
to positifie associations (Chi Square significance at 5% level,
N=500 l m quadrats) on left, and correlations Of cover signifi-
cant at 5% level (N=h8h 1/16 m2 quadrats) on the right. Between
the upper and lower clusters there are some significant negative
associations and correlations (see Tables I and III).

31L.

  
  

 

   
 

 

 

Hieracifi
Solidago
ne oralis
Solidago
nemoralis
Lme Euph rbia
xali Ambrosi
orbia b//Egm3:\\£
Ru us rigeron
Rubus
Leptolom +3 Solanum
s L Oxali
g
g E uisetum
H
0
e
Dianthus .3
\ .3
Saponaria——.elilotus ”3 Saponari&——jMelilotus
\V Poa compressa
F180 60

Constellation diagrams showing species grouped accord-
ing tO positive associations (Chi Square significance at 5%
level, N=228 l m2 quadrats) on left, and correlations Of cover
significant at 5% level (N=228 1/16 m2 quadrats) on the right.

Between the upper and lower clusters there are some significant
negative correlations (see Table II).

35.

The constellation diagrams, although.subjec-
tively constructed, do have a basis in reality.

warner (19h5) discovered in Iowa that E. compressa

 

in abundance was indicative Of low available soil
moisture. It was able to withstand drought better
than 2, pratensis but was less Of a sod former than
the later and could not compete with 2, pratensis
under more favourable moisture conditions. An
analagous relationship seems to Occur between 2.
compressa and some Of the less abundant species in
the Old—field in this study. 2, compressa is the
primary sod former in the upland phase Of the Old-
field, and Just as 2, pratensis can be considered a

later stage Of succession in Warner's study, so too

 

.3. compressa is here considered to be a more ad-
vanced and relatively more mesic stage than the
Hieracium—Solidagg nemoralis group in Figure 6.
Although soil moisture was not studied, the higher
organic matter in the soils supporting sod are like-
ly to be more retentive of moisture than the more erod-
ed.1eee productive bald Spots found within the field.
These less productive looking sites are occupied by
the Hieracium-Solidagg complex which includes 32fl2§_
and Oxalis (Fig. 5) or by the same group with the
addition Of Leptoloma (Fig. 6).

36.

In these same constellation diagrams, Melilotus
and Saponaria tend to occur as a unit. Both species
do well on dense sod, and both species are most Of-
ten conspicuously absent from eroded sites occupied
by the complexes referred to previously. 0n the
other hand, the relationships Of Mblilotus spp. and

Saponaria Officinalis with 2, compressa are quite

 

different.

Ԥ. Officinalis appears to grow well in areas Of
2, compressa sod, but is not positively correlated
with bluegrass. The dense clones,frequently with
10-20 tightly spaced individuals Of S. Officinalis,
may spatially exclude E, compressa since its cover
is clearly less within the clones.

Ielilotus spp., on the other hand, is positively
correlated with 2, compressa (10% level, Table I;
5% level, Table II). ' Melilotus alba and g. Offici-
gg1;§_are leguminous plants containing nitrogen fix-
ing bacteria in their root nodules (Allaway, 1957).
Perhaps when these roots decay nitrates are re-
leased in sufficient amounts to cause an increase
in the number and vigour Of bluegrass culms in their
proximity. Or it may be that bluegrass sod, having
more organic material, retains moisture that is
utilized by the legumes. warner (l9h5) found that

2, pratensis sod accumulated greater amounts Of

 

organic material in the area he studied.

37.

The results of germination studies on a mixture
or Seeds of Melilotus Egg and g. Offjipinalis show
that seed germination in these species is not sig-
nificantly related to the size Of Openings in sod,
although a trend does exist (Fig. 7). The important
point is that germination counts are almost as high
as on.moist blotters in.petri dishes. There appears
to be little likelihood Of a germination suppressing
effect by the sod.

Early seedling survival is correlated with the
size Of Opening in bluegrass, the larger Openings
yielding the greatest number Of viable seedlings
(significance at the 1% level, as determined by
analysis Of variance). After the initial high rate
Of mortality among seedlings in the small Openings,
the remaining viable seedlings appear to have a
good chance for survival, under conditions Of little
moisture stress as portrayed by their greenhouse
survival curves (Figs. 7, 8). This indicates that
self-thinning in Melilotus spp. seedlings is much
more pronounced in smaller sized Openings in blue-
grass. Judging from.the slightly etiolated and
stringy appearance Of many seedlings in these smaller
Openings, it is possible that this self-thinning is
due to competition for light. An underlying prin-

ciple might be density-dependent mortality which has

NUMBER OF SEEDLINGS _

38.

 

Q
C)
00
on
o
3

.p
2’

«b «h
{D «D
if
a
3

O

l0 (a
o N
on
O
3

-

N
L
V

 

 

.1 s .L t i
l2 IO 24 so 36
DAYS AFTER PLANTING

 

C)
1n..

‘ Fig. 7. Survival curves of seedlings Of

Melilotus spp. in Openings in bluegrass sod
ranging in diameter size 0.5 tO’3 cm.
Seeds were sown 23 June, 1963.

39.

 

524.

43‘
447
340‘

Ease

- -
N o
1 A
V I

V
’-

V

0

j

0

V

V

 

l I l
I

db
1.

.5 cm ”0

 

 

l . I
U U U

6 :2 us 24 so 36 42 4e 54 60
DAYS AFTER PLANTING

Fig. 8. Survival curves Of seedlings Of Melglgotus spp. in Open-
ings in bluegrass sod ranging in diameter size 0.5 to 3 cm.
Seeds were sown 18 February, 1963.

 

to.

been shown to exist for seedlings Of other species
(Harper, 1961).

The results Of the above experiment concur
with an unsupported statement made by Milthorpe (1961):
"It is reasonably certain that the establishment Of
plants from.seed in vegetation occurs only in 'bare
areas' arising from the death Of previous occupants
or from incomplete coverage". The Melilotus data
give some idea Of how small the size Of Opening can
be, and also help to distinguish between germination
success and seedling survival.

If subsequent experimentation bears out the come
plete failure Of germination Of Solidagg_canadgg§yg
var. scabra and the very low and much retarded germi-
nation Of Agpgg.pilosus and MOnarda fistulosa;
Milthorpe's suggestion will be further supported,
but would indicate that even larger openings are
necessary. Further, the negative correlations be-
tween the first two Of these Species and §g§_gggr
pressa may, in part, reflect this suppression. At
this point, however, caution is necessary pending
confirmation Of these data.

The problems of establishment are not the only
basis Of pattern. Solidago canadensis var. scabra
is a strong clone former (Fig. 2) and once estab-
lished appears to be able to eXpand successfully in

29a compressa sod. It appears tO preclude many Of

1&1.

the other species from.growing within its circular
boundary. Poa compressa, although found within such
clumps, is much diminished in cover here. The per-
centages of cover of the two species are negatively
correlated (S,/es‘i§g%1iofficance) in Tables I and II.

In the sample N-hBh, g, canadensis var. scabra is
seen to be the only species having all of its cor-
relations (17) negative in sign; when N=228 only
two of the correlations are positive in sign, and
these are not significant. The postulate that this
Solidago tends to preclude other species from grow-
ing within its clone could be tested by transplant
_and seed germination experiments in the field.
Specific clumps have been observed for two suc-
cessive years, and from.the size of the clumps and
their probable growth rate, they would appear to
date back nearly to the time of abandonment.

Cover of other plants may serve as a protective
layer for the develOping seedlings or basal rosettes
in others. Dianthus Armeria is a.31ender, erect
plant which overwinters as a green.basa1 rosette.
This Species appears to do better under the covercfl'

a large number of other species. It is significantly

positively correlated with.Poa pratensis, Potentilla

recta, Melilotus spp. and Rubus flagellaris and in

 

 

 

the field appeared to be strongly correlated with

Poa compressa litter.

#2.

The interspecific patterns of §glanumlgarolinense
and Eguisetum,laevigatum.are rather puzzling. When
the entire study area is considered (N=h8h) these
two species are positively correlated in cover,
(significance at the 533 level), and both are identi—
fied with the sod forming group (Fig. 5). Once
detected from.the analysis of the data, this rela-
tionship is locally conspicuous in the field, es-
pecially in the somewhat lower portion of the study
area, which has not suffered erosion. In the slight-
ly elevated section of the study area, where moisture
appears to be more limiting and eroded spots more
frequent, the Equisetum-Solanum correlation is the
strongest of any of the species studied (Table II).
However, here the unit is found with the Solidago
complex (see Fig. 6). In this drier area the

EguisetumrSolanum association appears to reach its

 

peak on the lower portions of convex surfaces in
the soil which.catch small rivulets of runoff, while
the rest of the Solidago nemoralis contingent appears
to thrive on the more eroded crests of such con-
vexities. This shift in pattern affiliation needs
further study.

Obviously the field is not homogeneous in the
strict sense, and the shift in dominance from §_o_a_

compressa to Aster pilosus in the northerly section

 

of the study area bears this out. FUrthermore, the

Lo.

change in the association of the EquisetumrSolanum

 

complex illustrates that a local change in habitat
can exert a profound change in small scale pattern-
ing. The analagous work of Hairston and Byer (l9Sh)
and Kershaw (1963) lends credence to this statement.
According to Grieg-Smith (1957), sample size
has a great effect on the associations that one
obtains. Fortunately, data from nested quadrats
in this study are available for comparison with
results obtained in the larger quadrats (Table III).
Moreover, the Chi Square analysis of significance
of tests of association for the 1 m2 quadrats pre-
sented in Table III, bring to light a certain amount
of interspecific pattern ndtdetectable from the

small quadrats.

SUMMARY AND CONCLUSIONS

Interspecific pattern in the vegetation in an
old-field was investigated. Correlation of cover
of 18 species, whose range in average per cent
cover is .01 to .80, disclosed a much higher num-
ber of negative than positive correlations, irre-
spective of significance. This is presumably a
simple spatial relationship, due at least in part
to the spatial limitations of the quadrat. The
12 significant negative correlations (5% level)
occur with one exception, between the two most

abundant species Poa compressa and Aster pilosus,

 

 

and between these two and less abundant species.
Ten of the 13 significant positive correlations
(5% level) are between the less abundant species.
This polarity between dominant and non-dominant
species in the distribution of significant posi-
tive and negative correlations suggests the possi-
bility that the two dominant Species influence the
non-dominant species, as well as each.other, in
the manner of spatial exclusion.

That the action is not all one way is sug-
gested by the reduction in cover of Poa compressa
in clones of Rubus flagellaris and Solidago cana—

densis var. scabra. The later species is negatively

ML.

LLB.

correlated with nearly all other species tested,
and field examination suggests it tends to preclude
many other Species from.growing within its cir-
cular boundary. The area of these dense clones
appears to have been increasing, apparently into

areas formerly occupied by Poa compreSsa.

 

In order to test whether the results of the
correlation and association studies could be in-
terpreted in terms of seedling establishment, a
series of experiments was performed. .From.the anal-
ysis of the vegetation, species were grouped into
three categories relative to Egg, the primary domi-
nant: negative, positive and infrequent. Germina-
tion and seedling survival of representative species
in each category were tested in various sized Open-
ings (0.50m, 1 cm, 2 cm and 3 cm) in bluegrass sod.
At the time of writing, Melilotus spp. (fl. 333g and
M. Officinalis), which are positively related to

 

2, compressa, produced the only convincing results.

 

The germination of seeds of’Nblilotus spp. proved

to be independent of the Size of opening in blue-
grass sod, although a trend does develop. Further,
germination percentages were nearly as high as on
wet blotter paper. When tested by analysis of vari-
ance, however, early seedling survival is correlated

with.the Size of opening at the 1%:level. The two

1L6.

larger openings gave a significantly greater number
of seedlings. .The survival curves indicate a rapid
early drop but then levelled out suggesting the
chances for the remaining seedlings to survive will
be quite good.

Germination and survival results for the other
species were subject to suspicion because of possi-
ble displacement by irrigation of the very light
seeds, since the seeds were sown at the soil sur-
face. The recorded failure of, or very low and slow
rates of germination, if not an artifact, suggest
that Poa compressa does exert a rather profound in-
fluence on these Species even in openings up to
3 cms. in diameter.

Thus the positive cover correlation of blue-
grass and sweet clover Shown in the sampling for
the mature plants occurs in spite of a significant
effect on seedlings of sweet clover by bluegrass
which appears to be minor at distances between 2
to 3 cms.. It is now desirable to study further
germination and seedling performances of the spe-
cies which are negatively correlated with §g§_
gpmpressa and those infrequent in fields dominated

by its sod.

LITERATURE CITED

Allaway,W.H. 1957. Soil, USDA Yearbook of Agriculture,
no.30. U.S.Govt.Print.0ffice. p.386.

Ashby, E. 19MB. Statistical ecology. A reassess-
mBnto BOto Rev. lu:222’23ho

Bard, G. E. 1952. Secondary succession on the Pied-

mont of New Jersey. Ecol. Monograph

Bray, J; R. 1956. A study of mutual occurrence of
plant Species. Ecology 37:21-28.

1956. Gap phase replacement in a maple-
basswood forest. Ecology 37:598-600.

 

Byer, M. D. 1960. An analysis of pattern and inter-
specific association along a soil
moisture gradient on the jack pine
plains of northern Lower Michigan.

M. S. Thesis. Michigan State
University, East Lansing, Michigan.
257 p.

Clark, P. J. and F. 0. Evans. 195k. Distance to
nearest neighbor as a measure of
spatial relationships in populations.

Ecology 35:uh5-k51.

Clements, F. E. 1916. Plant succession: an analysis
of the develOpment of vegetation.
Carn. Inst. Wash. Publ. no. 2&2.
512 p.

Cole, L. C. 19h9. The measurement of interspecific
association. Ecology 30:hll-h2h.

Cooper, 0. F. 1961. Pattern in ponderosa pine forests.
Ecology h2:h93-h99.

Egler, F. E. 195k. Vegetation science concepts I.
Initial floristic composition, a
factor in old-field vegetation
develOpment. Vegetatio h:hl2-hl7.

Evans, F. C. and S. A. Cain. 1952. Preliminary stud-
ies on the vegetation of an old-field
community in southeastern Michigan.
Contr. Lab. Vert. Biol. Univ. of Mich.
51 :1’17 0

1L7.

h8~

Evans, F. C. and E. Dahl. 1955. The vegetational
structure of an abandoned field
in southeastern Michigan and its
relation to environmental factors.
Ecology 36:685-706.

Fager, E. W. 1957. Determination and analysis of
recurrent groups. Ecology 38:586u595.

Gleason, H. A. and A. Cronquist. 1963. Manual of
vascular plants of northeastern
United States and adjacent Canada.
D. VanNostrand Company, Inc.,
Princeton. 810 p.

Goodall, D. W. 1952. Quantitative aspects of plant
distribution. Biol. Rev. 27:19h—2h5.

Grieg-Smith, P. 1957. Quantitative plant ecology.
Butterworths Scientific Publications.
London. 198 p.

and K. A. Kershaw. 1958. The Signifi-
cance of pattern in vegetation.
Vegetatio 8:189-192.

 

Hairston, N. G. and G. W. Byers. 1954. The soil
arthropods of a field in southern
Michigan: a study in community
ecology. Contr. Lab._Vert. Biol.
Univ. of Mich. 6h:l-37.

Harper, J. L. 1961. Mechanisms in biological compe-
tition. Academic Press, Inc., Publ.
New Yerk. p. 1.

Hopkins, B. 1957. Pattern in the plant community.
J. Ecology h5:h51-h63.

Hutchinson, G. E. 1953. The concept of pattern in
ecology. Proc. Adad. Nat. Sci.
Phila. 10531-12.

Keever, Catherine. 1950. Causes of succession on
old-fields of the Piedmont, North
Carolina. Ecol. Monographs 20:231-250.

Kershaw, K. A. 1960. The detection of pattern and
association. J. Ecology u8:233-2h2.

#9.

Kershaw, K. A. 1963. Pattern in vegetation and its
casuality. Ecology hh:377-388.

McIntosh, R. P. 1962. Pattern in a forest community.
Ecology h3:25-33.

Milthorpe, F. L. 1961. Merchanisms in biological
competition. Academic Press, Inc.,
Publ. New Yerk. p.330.

Oosting, H. J. 19u2. An ecological analysis of the
plant communities of Piedmont,
North Carolina. Am. Midland
Naturalist 28:1-126.

Perkins, S. 0. and J. Tyson. 1926. Soil Survey of
Kalamazoo County, Michigan. U. S.
Dept. Agric. wash. Gov. Printing
Office.

Pielou, E. C. 1960. A single mechanism.to account
for regular, random, and aggregated
populations. J. Ecology h8:575—58h.

1961. Segregation and symmetry in two-
species populations as studied by
nearest neighbour relations.

Jo Ecclogy (49:255’2690

 

Scurfield, G. 1956. Note on experimental ecology and
the uses of a biological flora.
Vegetatio 7:3-8.

Skellam, J. G. 1952. Studies in statistical ecology I,
_ * spatial pattern. Biometrika 39:3h6-362.

hhlker, H. M. and J. Lev. 1953. Statistical inference.
Holt, Rinehart and Winston. New
York. 510 p.

warner, R. M. 19h5. Relation of vegetative cover to
- the plant growth conditions of
eroded soils. Iowa State Col. J.

Watt, A. S. 19u7. Pattern and process in the plant
community. J. Ecology 35:1-22.

Whitford, P. B. 19h9. Distribution of woodland plants
in relation to succession and clonal
growth. Ecology 30:199-208.

* Odum, E.P. 1960. Organic production and turnover in
old-field succession. Ecology 41:34-49.

APPENDIX-A

 

Species % Frequency in % Frequency n
A500 1 m2 199 1A6 m

Poa compressa 96. h+

Aster pilosus
Dianthus Armeria
Rumex Acetosella
Potentilla recta
Oxalis Dillenii
Melilotus spp.

Rubus flagellaris
Euphorbia corollata
*Leptoloma cognatum
Solidago nemoralis
Solanum carolinense
Ambrosia artemisiifolia
Erigeron spp.
Saponaria Officinalis
Hieracium longipilum
Daucus Carota

|-‘
WWFF'O‘NGJGS

NN
CDCDl-‘NVIUIOUIOH

O O O O C O I O O O
OOON OCDN GOF'O

26.8

62.
£82
18.0
11.0
12.0

00000000
WWW:

‘19““
an '

Solidago canadensis v. scabra
Ehuisetum.laevigatum
*Agropyron repens
Achillea‘Millefolium
Pea pratensis
Physalis heterOphylla
Lactuca canadensis
Tragepogan pratensis
Chrysanthemum leucanthemum
Verbascum thapsns
Panicum.sp.
Prunus serotina
Solidago juncea
Taraxacum.officinale
Hypericum.perforatum
Plantago lanceolata
Ulmus americana
Setaria glauca
Trifolium.pratense
Vitis Sp.
Fraxinus pennsylvanica
Asclepias syriaca

id
Luhnpru#?hH4~LF”‘\flU1GKR<3

0.0.0.... 0.0.0
FHA
cocoon... Oooooo

O
momFmemooomrmromomomomrm

O
rarrmprmoomk mmmomrmmommmmommor

HHHHHHHNNNNNNwWme©NQmwF

Ooo

* % frequency for these Species is based on AM? quadrats
because of their misidentification in the first 53 quadrats.

50.

f 1'11“".

 

APPENDIX-A

 

 

 

Species % Frequency in % Frequency in
500 1 m2 LL99 1/16 m2

Cornus Amomum .6 0
Pleum.pratense .6 0

Carya ovata .h .2
Hieracium.aurantiacum .h 0
Hieracium.Gronovii .h 0
Monarda fistulosa .h 0
Quercus Mahlenbergii. .h .2

Acer saccharum. .2 0
Asclepias tuberosa .2 O
Cornus stolonifera .2 0
Dactylis glomerata .2 0
Parthenocissus quinquefolia .2 0
Potentilla argentea .2 0
Prunus Mahaleb .2 0
Vernonia altissima .2 O
Cirsium.sp. .2 0

Species occurring in the study area but not sampled:

Anemone virginiana
Anaphalis margaritacea
Apocynum.sibiricum
Celtis occidentalis
Desmodium.spp.
Oenothera biennis

Species sampled in unknown amounts:

Antennaria 8p 0
Erigeron annuus
Erigeron strigosus
Melilotus alba
Melilotus Officinalis

.51".

 

APPENDIX-B

Species List: program in_which N=h8u.

Poa compressa

Aster pilosus

Rubus flagellaris
Dianthus Armeria
Melilotus Spp.

Rumex Acetosella
Potentilla recta
Solidago canadensis var. scabra
Saponaria Officinalis
Solanum.carolinense
Solidago nemoralis
Euphorbia corollata
Erigeron spp.
OxaliS'Dillenii

Poa pratensis
Hieracium longipilum
Daucus Carota
Equisetum,1aevigatum

Species List: program in which N=228.
Aster pilosus

Poa compressa

Dianthus Armeria

Melilotus Spp.

Rumex Acetosella

Solidago canadensis var. scabra
Potentilla recta

Saponaria Officinalis

Rubus flagellaris

Solidago nemoralis

Euphorbia corollata

Solanum carolinense

Hieracium longipilum

Oxalis Dillenii

Erigeron strigosus

Leptoloma cognatum.

Ambrosia artemisiifolia
Equisetum.laevigatum

520

Average %_cove

in 484 1116 m >

.13
.12
.07
.01

Average % cove

_;n 228 1/16 m

12.10
10.83
n.39
2.80
Z-AS
2.
1.9
1.93
.87
.h9
038

.3
.1
.12
.08
.06

.03
.02

‘ ‘ '. 0'1”.” 0.1-,

"I11'?ii‘fliifl'flifl'iifliflfl