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This is to certify that the

thesis entitled

THE NUTRITIONAL QUALITY OF ASPEN
AS A WINTER AND SPRING FOOD
FOR RUFFED GROUSE IN NORTHERN MICHIGAN

presented by

Bobbi Lee Webber

has been accepted towards fulﬁllment
of the requirements for

Master of Science degree in Fisheries and Wildlife

 

 

Major professor

Date August 4, 1987

 

0-7639 MS U i: an Aﬁmmu've Action/Equal Opportunity Institution

{11(7(/:%é_6/T

/THE NUTRITIONAL QUALITY OF ASPEN AS A WINTER AND SPRING FOOD
FOR RUFFED GROUSE IN NORTHERN MICHIGAN;

BY

BOBBI LEE WEBBER
H

A THESIS
Submitted to
Michigan State University
in partial fulfillment of the requirement
for the degree of

MASTER OF SCIENCE

Department of Fisheries and Wildlife

1987

ABSTRACT

THE NUTRITIONAL QUALITY OF ASPEN AS A WINTER AND SPRING FOOD
FOR RUFFED GROUSE IN NORTHERN MICHIGAN

BY

Bobbi Lee Webber

Ruffed grouse heavily utilize trembling and bigtooth
aspen as a food resource during winter and early spring.
Abundance and nutritional quality of aspen may be crucial to
overwinter survival and reproductive success.

Bud production and nutritional quality of aspen in the
Pigeon River Country State Forest of Michigan was
investigated in 1985 and 1986. Aspen clones of both
species, sexes, and a diversity of ages and stem densities
were sampled.

Bud production varied between years for both species.
Crude fat content of buds and catkins also varied yearly.
Trembling aspen buds were higher in nutritional quality than
bigtooth aspen buds. Male flower buds were higher in
apparent digestibility than female buds. Flowering male
aspen provided the most bird use days/tree.

Habitat managers should perpetuate aspen clones of both
species and sexes that are consistant and/or abundant flower

bud producers.

ii

ACKNOWLEDGEMENTS

This project was funded in part by the Michigan
Department of Natural Resources and the Michigan State
University Agriculture Experiment Station.

I want to give special thanks to my major professor,
Dr. Jonathan B. Haufler for his patient guidance and
friendship. I will always be greatful to Dr. Haufler for
allowing me the opportunity to continue my education at
Michigan State University. I would also like to give thanks
to my committee members, Dr. K.P. Pregitzer and Dr. H.H.
Prince, both of whom have given me invaluable advice
throughout this project.

I would like to give special thanks to the interns,
fellow graduate students, and friends who participated in
the field work. Most importantly, I want to give my sincere
thanks and acknowledgement to Laura Grantham, whose
sympathetic ear and sound advice I will never forget and
whose friendship I will always cherish.

I would also like to give special thanks to Carl
Bennett, whose confidence in me gave me the faith in myself

that was needed to work hard and be successful.

iii

Lastly, to my husband, Tom, whose enduring love,
friendship, and encourgement gave me the inspiration and

support that made this thesis possible.

iv

man-r
.51”.de

LIST OF TABLES ..........
:UJ. CF FIGUFES 0.0000000
IITTL.D:Y‘¢VCTIOTT o o o o o o o o o c 0 0
STUDY AREA DESCRIPTION ..
HATE? ALS AND METHODS....
Vegetative Sampling
Cherical Analysis ..

Data Analysis ......
FhESTJI-JTS O O O C O O O O O O O I O O O O 0
Flower Bu- Weights .

Bud Produ ..

Nutrient Composit
Bird Use D

DISCUSSION ............

MANAGRVRVT T”? ICATIONS

LAAAbA'AI J-LA-‘A

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TTDIX O O O U C O C U C O O O O Q

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REFERENCES ....

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CONTENTS

vi

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23

(D (“T (i'

r bud production for trembling and
oth aspen in the Pigeon River Country
Forest of Michigan during 1985 and

O (“u

H m U‘ *11
u.) n H- I—4
ii.»

C0 9) -Q

Sumrary of significant differences between
years in the nutrient composition of male
trembling and male bigtooth aspen flower
buds collected in the Pigeon River Country
State Forest of Michigan in 1985 and 1986 ..

Surnary cf significant differences between
years in the nutrient composition of
trenbling and bigtooth aspen vegetative

buds collected in the Pigeon River Country
State Forest of Michigan in 1985 and 1986 ..

Summary of significant differences between
years in the nutrient composition of male
and female trembling aspen catkins collected
in the Pigeon River Country State Forest of
Michigan in 1985 and 1986 ..................

Summary of significant differences in the
nutrient composition of male bigtooth aspen
catkins collected in the Pigeon River Country
State Forest of Michigan in 1985 and 1986 ..

Summary of significant differences in
nutrient composition between male and female
trembling aspen flower buds and catkins
collected in the Pigeon River Country State
Forest of Michigan in 1985 and 1986 ........

vi

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10

11

12

13

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P ’ A: r:
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__....._.

Summary of significant differences in
nutrient composition between trembling and
bigtooth aspen flower buds, vegetative buds
nd leaves collected in the Pigeon River
Country State Forest of Michigan in 1985
and 1986 .................. ....... .... ...... 27

Summary of significant differences in

nutrient composition between trembling and
bigtooth aspen catkins collected in the

Pigeon River Country State Forest of

Michigan in 1985 and 1985 ...... ..... ....... 29

Characteristics for field identification of
aspen clones by season ..................... 46

Means, standard errors, and ranges by year
for nutritional components, bud weights, and
ges of male and female trembling aspen
flower buds collected in the Pigeon River
Country State Forest of Michigan ........... 47

Means, standard errors, and ranges by year

for nutritional components, and ages of male
and fenale trembling aspen catkins collected

in the Pigeon River Country State Forest of
Michigan ............................. ...... 4

C0

Means, standard errors, and ranges by year

for nutritional components, bud weights, and
ages of trembling aspen vegetative buds and
leaves collected in the Pigeon River Country
State Forest of Michigan ........ .......... . 49

Means, stand.rd errors and ranges by year

for nutritional components, bud weights and

ages of bigtooth aspen flower buds and

catkins collected in the Pigeon River Country
State Forest of Michigan ..... ...... ........ 50

vii

18:10.12 Page
14 Means, standard errors, and ranges by year for

nutritional components , bud weights , and ages of

bigtooth vegetative buds and leaves collected in

the Pigeon River Country State Forest of Michigan . . 51

LIST OF FIGURES

Figure Page
1 Location of the Pigeon River Country State
Forest study area in Cheboygan, Montmorency
and Otsego counties of Michigan ............ 8

ix

INTRODUCTION

The ruffed grouse (Bonasa umbellus) is the most widely
distributed game bird in North America, occurring in 38
states and 13 Canadian provinces. It is considered an
important small game resource in 30 of these states and
provinces (Gullion 1977). Therefore, it is desirable to
maintain quality habitat to provide for recreational hunting
opportunities.

The most abundant ruffed grouse populations in North
American occur where snow lies on the ground for a
substantial portion of the winter and temperatures remain
below freezing for weeks or months at a time. Conditions
approaching the optimum for ruffed grouse are found mainly
across southern Canada, northern Minnesota, Wisconsin, and
Michigan, and south through New England, New York, northern
Pennsylvania, and portions of the Alleghenies (Bump et a1.
1947).

Ruffed grouse are considered to be an omnivorous
species, although as an adult, only 1.1% animal material is
taken in comparison to 98.9% vegetable material (Bump et a1.
1947). In New York, 414 plant items have been identified in

stomach contents, consisting of representatives of 65

2
families and over 334 species (Bump et a1. 1947). Ruffed
grouse are therefore primarily vegetarians, browsing on the
buds, twigs, leaves, and fruits of various forest plants,
shrubs, and trees. When the ground is bare of snow, ruffed
grouse feed on a wide variety of green leaves, fruits, and
some insects. When snow covers the ground these birds are
almost exclusively dependent on dormant buds, particularly
the flower and vegetative buds of trembling (Populus

tremuloideg) and bigtooth (E; grandidentata) aspen, and to a

 

lesser extent, the vegetative buds and catkins from species
such as birch (Betula spp.), cherry (Prunus spp.), ironwood
(Ostrya spp.), and beaked hazel (Corylus cornuta) (Bump et
al. 1947; Gullion 1967).

Ruffed grouse are dependent upon aspen as a winter and
early spring food resource. Stollberg and Hine (1952) found
that trembling aspen leaves and buds constituted the most
common species in terms of percent total volume and percent
occurrence in a fall collection of grouse crops in Wiscon-
sin. In Minnesota, studies of winter and spring feeding
activities have shown an almost exclusive dependence upon
the flower buds of male aspen (Gullion 1967). McGowen
(1973) has reported that buds and twigs of trembling aspen
and various species of willows (Selig spp.) were the most
heavily utilized foods during the winter season in Alaska.
Phillips (1967) has also reported aspen as an important fall

and winter food of ruffed grouse in northern Utah.

3
Korschgen (1966), in summarizing ruffed grouse food habits
studies, emphasized the importance of aspen as a winter food
resource to ruffed grouse throughout its range north of 40
degrees latitude and east of 66 degrees longitude.

It has also been shown that ruffed grouse use aspen
buds and catkins as a primary food source 2 to 6 weeks after
snow melt in spring (Bump et al. 1947; Godfrey 1967; Svoboda
and Gullion 1972). Crop content analysis in Maine (Brown
1946) has shown that buds of trembling and bigtooth aspen
are utilized in spring in even greater amounts (71.4%) than
during winter. Therefore, the utilization of aspen buds
extends into the period when hens begin egg laying. The use
of aspen leaves during incubation has also been documented
in Minnesota (Maxon 1974).

The importance of this tree species as a habitat
component is further suggested by the fact that the
distribution of ruffed grouse in the United States and
Canada closely parallels that of aspen. Only in warmer
climates, where grouse encounter less severe winter
conditions, do they persist in the absence of aspen, and
there they seldom approach the widespread abundance found in
more northern regions where aspen is a prevalent component
of the forest composition (Gulllion and Svoboda 1972).
Consequently, although ruffed grouse are known to utilize a
diversity of food items, throughout their primary range,
aspen appears to be the most important plant contributing to

their yearlong welfare.

Several factors may contribute to the advantages
availed to grouse in utilizing aspen buds as a winter and
spring food resource. The physical characteristics of the
aspen twigs and the arrangement of the flower buds seem to
be important. The twig is rigid, providing the feeding bird
with a firm hold, eliminating much fluttering and balancing.
The twigs usually enter the fall season with 6 to 8 easily
detached flower buds near the tip. This bud arrangement is
such that from a single position a bird can take its meals
quickly and quietly. Ruffed grouse have been observed
taking flower buds at a rate exceeding 45/minute, and birds
feeding in aspen seldom spend more than 15 to 20 minutes
collecting 90 to 100 g of buds (Gullion and Svoboda 1977).
It is of great survival advantage to these birds to feed
rapidly and with a miminum amount of commotion as morning
and evening feeding activities coincide with the early
foraging flights of avian predators.

The nutritional quality of aspen flower buds may also
influence survival through physiological mechanisms.
Examinations of ruffed grouse carcasses collected during the
fall and winter months indicate very little visible fat,
with no marked seasonal increase in lipids being observed
(Thomas, Lumsden, and Price 1975). Therefore, stored lipids
do not appear to be of great metabolic importance to ruffed
grouse, supporting an hypothesis that energy supplied by
aspen may be a limiting factor to these birds during the

winter. Previous research (Doerr 1973) suggested that ruffed

grouse select aspen buds with the highest protein levels
implicating protein as also being an important nutritional
requirement during winter.

The ruffed grouse has long been considered a "cyclic"
species, although the factors affecting the often dramatic
changes in ruffed grouse population densities and mechanisms
by which these factors operate have proven somewhat elusive
to biologists (Gullion 1970). Several hypotheses for the
cyclic declines in grouse numbers have been proposed,
including predation, disease, sunspot activity, and weather
(Criddle 1930: DeLury 1930; Ritcey and Edwards 1963),
although none of these postulations have been conclusive.
Most recently, it has been suggested that annual variations
in ruffed grouse food resources may in some way be
responsible for changes in grouse densities between years.
Gullion (1969) has suggested that the availability of flower
buds of trembling and bigtooth aspen largely determines the
distribution of breeding grouse. Periodic fluctuation in the
nutrient content of aspen buds, tree age, density, thrift,
sex, levels of secondary compounds, as well as periodicity
of bud production may all influence population cycles, or at
least the magnitude of the peaks and troughs of these
cycles.

Current habitat management techniques for ruffed grouse
are designed primarily to enhance the cover requirements
throughout the life cycle. As aspen appears to be a

critical food resource during winter and spring seasons

6
throughout the northern range of ruffed grouse, specific
management for food resources would appear to be beneficial.
An important first step in deveIOping specific management
recommendations for aspen as a food resource is the
quantitative evaluation of nutritional quality. The
objectives of this study were to 1) Determine if sex of
dormant aspen flower buds can be differentiated based on bud
size, 2) Evaluate the nutritional quality of male and female
flower buds, catkins, vegetative buds, and leaves of
trembling and bigtooth aspen, 3) Determine if yearly
fluctuations in nutritional quality occur, and 4) Determine

if yearly fluctuations in abundance of flower buds occurs.

STUDY AREA DESCRIPTION

The study area was the Pigeon River Country State
Forest which is located in parts of Cheboygan, Montmorency,
and Otsego counties in northern lower Michigan (Figure 1).
The 37652 ha forest has a topography consisting of moranic
uplands, steep moranic slopes, sandy outwash plains, and
river bottoms. The podzol soils of the area range from
highly fertile organic soils in the swampy areas to dry
sandy soils on the outwash plains. Medium fertility soils
are found on the till plains and moraines (Moran 1973).

The forest is composed of a variety of cover types.
Coniferous swamps are dispersed throughout the forest and

contain tree species such as spruce (Picea spp.), northern

 

 

 

 

white cedar (Thgi_ occidentalig), balsam fir (Abigg
balsamea), and tamarack (Larix laricina). Upland cover types
include mixed and pure stands of aspen (P. tremuloides and
g; grandidentata), maple (Age; spp.), beech (Eggug
grandifolia), basswood (Tilia americana), cherry (Prunus

 

 

spp.), birch (Betula spp.), jackpine (Pinus banksiana), red
pine (P; resinosa), and white pine (g; strobus) (Ficher
1939).

The typical climate of the area is characterized by

long cold winters, short cool summers, mild autumns, and

8
\ Cheboygan
///

 

 

Montmorency

 

 

Otsego

 

 

Pigeon River Country State Forest

Figure 1. Location of the Pigeon River Country State study
area in Cheboygan, Montmorency and Otsego counties of
Michigan.

9
late cold springs. The growing season over the study area
is approximately 77 days. Temperatures average -8.0()C in
January and 190C in July. Average annual precipitation is

approximately 71 cm. Total average snowfall is 290 cm.

MATERIALS AND METHODS

VEGETATIVE SAMPLING

Within the study area clones of both trembling and
bigtooth aspen were selected for vegetative sampling. Aspen
clones vary considerably in genetic traits such as leaf
morphology, seasonal coloring, stem form, branching habit,
growth rates, bark characteristics, sex, and phenology
(Barnes 1964). The characteristics useful for clone
delineation by seasons have been outlined by Barnes (1969)
(Appendix, Table 9). The techniques and suggestions of
Barnes (1969) were used to delineate aspen clones on the
study area. Clones were identified and marked in the fall of
1984 and spring and fall of 1985.

Delineation between the sexes was accomplished during
the winter by the use of a disecting microscope. The
presence of pollen sacks indicated that flower buds were
male, and conversely the absence of pollen sacks indicated
that the flower buds were female. Sex was subsequently
confirmed in the field during spring at time of flowering.

All trees within an aspen clone are genetically and

chemically the same (Blake 1963), therefore, 1 tree was

10

11
selected within each clone for sampling, and was considered
to be representative of the entire clone. Both vegetative
and flower buds were collected during winter sampling.
Catkins were taken during spring sampling. In addition,
leaves were collected in the spring of 1985, during the time
when ruffed grouse were involved in incubation activities.

All trees used for vegetative sampling were felled.
Samples were collected randomly from throughout the entire
tree. For small trees (d.b.h. < 5") all buds, catkins, or
leaves were removed. For large trees (d.b.h. > 5"), a
composite sample was taken from throughout the entire tree.

For each tree sampled, d.b.h. and tree height were
measured. Stem density was measured for each clone by
counting all stems greater than 2.54 cm d.b.h. in a 10 x 10
m area centered in the clone. A cross section of each tree
was collected for determination of age. These were sanded
smooth, and a phenoglucinol dye was added to illuminate the
rings. The presence of heart rot in many of the trees
impeded highly accurate age determination, although it is
felt that tree ages were accurate to within 5 years.

Bud production was estimated during the winter of each
sampling year. Production estimates were made both in terms
of the number of identified clones flowering, as well as the
number of buds produced per sampled tree. During the

winters of 1985, 1986, and 1987 each identified clone was

12

checked to determine if flowers were produced, thereby
determining the percentage of clones flowering. During the
winters of 1985 and 1986, the number of flower buds produced
per tree was estimated from trees used for nutritional
sampling. For small trees (d.b.h. < 5"), all buds on the
tree were collected, and bud production was estimated by
total bud counts. On larger trees (d.b.h. > 5"), total
sample collection was not possible due to large losses of
buds when the tree was felled, therefore an estimation
technique was developed. This technique involved first
counting the total number of main branches extending from
the bole of the tree. Once the tree was felled, the total
number of short shoots was counted on every third main
branch, thereby giving an estimate of the average short
shoots per main branch. A random subsample of 10 of these
short shoots was then taken to determine the average number
of buds per short shoot. Total bud production was
calculated by multiplying:

total branches X average number of short

shoots/branch X average buds/short shoot
Checks were made on several d.b.h sizes, and the accuracy of
the technique was found to be within 10%.

Average bud weight of flower and vegetative buds was
determined as a means of comparing the quantity of food

available between the 2 types of buds. Average weights of

13

vegetative buds were determined from a subsample of 100
buds, and a subsample of 200 buds was used for flower buds.

At the time of collection samples were placed in large
plastic bags. Once in the laboratory, samples were kept
frozen until subsequent analysis. Samples were then dried
in a gravitational oven at 50.4C)C until they reached
constant weight. Dried samples were ground in a Wiley Mill
to pass a l m sieve and stored in whirl paks until time of

analysis.

CHEMICAL ANALYS I S

All vegetative samples were analyzed for the following
nutritional components: $dry matter (*DM), *ash, $crude fat,
torude protein , neutral detergent fiber ($NDF), acid
detergent fiber (tADF), acid detergent lignin (*ADL), and
caloric value (kcal/g). When there was insufficient vegeta-
tive material for all analyses priority was assigned in the
following order: $DM, torude protein, *crude fat, caloric
value, %ADF, *ADL, %NDF.

Ash content and *crude fat were determined by methods
described in AOAC (1975). Crude fat methods were modified
by weighing ground samples into tared filter paper ‘packets'
instead of thimbles. This allowed for a larger number of

samples to be analyzed per extraction.

14

To determine %DM of a sample, 1.0 - 1.1 g of dried
ground sample was weighed into pretared porcelain crucibles
and oven dried at 1000C for 24 hours. After drying, samples
were cooled in a desicator and reweighed. The original
sample weights used in all analyses were multiplied by this
percentage in order to determine the actual amount of
vegetation used.

Total nitrogen was determined by Kjeldahl digestion
(AOAC 1975). Samples were digested on a Tecator Block
Digestor, model DS-4O (Tecator, Inc. Boulder, Co), in
concentrated sulphuric acid at 3800C. Values were obtained
using a Technicon Autoanalyzer II (Technicon Industrial
Systems, Tarrytown, N. Y. ). Crude protein values were
determined by multiplying total Kjeldahl N values times 6.25
(AOAC 1975).

Fiber analysis (%NDF, tADF, tADL) were conducted
according to the procedures of Goering and Van Soest (1970).
Hemicellulose, cellulose, and lignin are the cell wall
constituents (CWC) determined through NDF analyses. Cell
soluble material (CSM) consisting of soluble carbohydrates,
starches, organic acids, proteins, and pectin were
determined by subtracting CWC values from 100 (Goering and
VanSoest 1970). Hemicellulose values were calculated by
subtracting ADF from NDF values. Cellulose content was

calculated by subtracting ADL from ADF values.

15

Caloric value of samples was determined by the use of a
Parr adiabatic calorimeter (Parr Instrument Co., Moline
111.). This instrument measures the amount of heat released
when a 1.0 g sample of plant tissue is completely oxidized.
The plant sample is placed in a combustion chamber which
contains excess oxygen. The combustion chamber is immersed
in an insulated water jacket and ignited. The temperature
rise in the surrounding water is proportional to the samples
chemical energy content.

Quality control of the nutritional analysis were
checked by running duplicates for 10% of the samples. Any
duplicate samples that were not within 10% of the first
sample were retested. In addition, any sample yielding what

appeared to be spurious results were retested.

ATA ANALYSIS
To test for nutritional differences between years,
sexes, and species, the Mann-Whitney U nonparametric test
was used (Siegel 1956). The Mann-Whitney U was also used to
test for bud size differences between male and female

dormant flower buds and vegetative buds.

RESULTS

FLOWER BUD WEIGHTS

Average flower bud weight calculated for male trembling
aspen trees was 0.099 g and for female trembling aspen trees
was 0.050 g. Analysis of the data indicate that there was a
statistically significant difference (p10.01) in bud weight
between male and female dormant flower buds. However, the
range of bud weights was found to overlap. Males ranged in
weight from 0.034 g to 0.172 g, and females ranged in weight

from 0.028 g to 0.077 g.

BUD PRODUCTION

In 1985, 65 trembling and 46 bigtooth aspen clones were
identified and marked. Of the trembling aspen clones
identified, 18 or 27.7% contained flower buds, and of the
bigtooth aspen clones identified 18 or 39.1% flowered. The
sex ratio for the trembling clones was 1.2 males to 1.0
females, for bigtooth clones the sex ratio was 5.0 males to
1.0 females.

In 1986, 76 trembling and 56 bigtooth aspen clones were
identified. Of the trembling aspen clones identified, 44.7%

contained flower buds. In contrast, 28.8% of the bigtooth

16

17
aspen clones reduced flower buds in 1986. Sex ratios were
4.0 to 1.0 for trembling and 4.5 to 1.0 for bigtooth.

In 1987, 95 -rembling and 61 bigtooth aspen clones were
identified. Only 6.3% of the trembling aspen clones
flowered, and 15.0% of the bigtooth aspen clones flowered.
Sex ratios in 1987 were 0.66 to 1.0 for trembling aspen and
1.33 to 1.0 for bigtooth aspen.

In addition to the number of clones flowering the
number of flower buds on the sampled trees within each clone
was also estimated. Data indicate that bud production per
tree was higher in 1986 than 1985 for both species (Table
1).

Correlations between bud production and site quality,
stem density, age, and d.b.h. were examined to determine the
factors which may influence yearly variations in bud
production. In all cases, however, no strong relationships

were observed between these variables.

NUTRIENT COMPOSITION

The nutrient composition of both species of aspen were
compared in several ways. Yearly comparisions of nutri-
tional quality were made for aspen vegetative buds, and both
sexes of aspen flower buds and catkins. Comparisons of
nutritional quality were also made between sexes and between
species. When making comparisons of nutritional quality

between years, comparisons were made between samples

18

 

 

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19

collected from the same clones each year. Aspen catkin
samples were the only exception to this. For aspen catkins
we were unable to sample the same clones each year,
therefore a random sample of different clones was used to
test for differences between years.

YEARLY FLUCTUATIONS

Differences between years in the nutrient composition
of trembling and bigtooth aspen flower buds are shown in
Table 2. For trembling aspen male flower buds, the only
significant differences found between years were in %crude
fat. Percent crude fat was significantly higher in 1985
than 1986. For bigtooth aspen male flower buds %crude
protein and %cellulose were the nutrients that varied
between years. Percent crude protein was significantly
higher in 1986 than 1985, and % cellulose was significantly
higher in 1985 than 1986. Sample size of trembling and
bigtooth aspen female flower buds were not sufficient to
make statistical comparisons.

Trembling and bigtooth aspen vegetative buds also

showed yearly variations in %crude fat and %crude protein

L»)

(Table ). No significant differences were found between
years in the fiber components, %ash, or caloric value of
trembling vegetative buds, however a highly significant
difference was found for %crude protein. Protein levels

were higher in 1986 than 1985. For bigtooth aspen vegetative

buds, significant differences were found in both %crude fat

20

 

 

 

 

 

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nuoougwn mama paw ocﬁHQEmuu mHmE

pcmoﬂuwgmﬁm mo mnmeesm .N mHQmB

 

 

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9.
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memo» comaumm mwma mmma mummy cwwzumm wwma mmmﬁ mbnmﬂwpsz
mocwwmwuﬂo moCmuwwuﬂD
pcmoﬁuﬂcoﬁm gmmz uQMUﬂuﬁanm nmmz

 

Comma ngOuOﬁm

 

comma gcﬂanﬁmuB

 

wo goﬁuwmoaeoo pamﬁuuss on» Ca mumwm swmzuwn mmoswuwuwﬂp unmoﬂwﬁnoﬂm mo hnmﬁESm

.mmma ppm mwma Ge cmoﬁnoﬂz mo ammuom
wumum muonsou Hm>ﬁm nomgﬁm mnu cw pmuomaaoo mesh m>ﬂumumgw> smumm nuoougﬁn paw ogﬁHnEmuu

.m magma

22
and %crude protein. Percent crude fat was significantly
higher in 1985 than 1986, and %crude protein was higher in
1986 than 1985.

For both male and female trembling aspen catkins, the
only statistical differences observed between years was in
*crude fat (Table 4). For both sexes %crude fat was
significantly higher in 1985 than 1986. For male bigtooth
aspen catkins, highly significant difference were found
between years in %crude fat, and all fiber components except
%hemicellulose (Table 5). Percent NDF, %ADF, %ADL, %cellu-
lose, and %crude fat were all significantly higher than

1986.

DIFFERENCES BETWEEN SEXES

Data from 1985 and 1986 were combined to make
comparisons between sexes. Flower buds from male trembling
aspen were significantly higher in %crude fat and caloric
value (Table 6). Female flower buds were significantly
higher in all fiber components except %hemicellulose. No
significant differences were found to exist for %crude
protein between sexes. Several differences were found
between male and female trembling aspen catkins (Table 6).
Females were found to be significantly higher in %crude
protein and all fiber components except %hemicellulose. No
significant differences were found in %crude fat, %ash, %

hemicellulose, or caloric value. Sample size of bigtooth

Aao.wmv uchﬂuﬁcoﬁm magmas «a
Amo.Wmv ucmuwuﬁcmam «
pcmoauaamam you .m.z

 

23

 

 

 

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meEwm mam:

 

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cowoﬁm map a“ Umuomaaoo mcﬁxumo swamm UGanEmuu mamamu paw mama mo cowpﬂmoaeoo
ucmﬁuusc mg» C“ mummh awmzumn mmucwnmumwp unmoﬂuwGme mo hnmEESm .v mHQMB

24

Table 5. Summary of significant differences in the nutrient
composition of male bigtooth aspen catkins collected in the
Pigeon River Country State Forest of Michigan in 1985 and
1986.

 

Male
Bigtooth aspen

 

Significant Differences

 

 

Nutrients Between Years
% Ash N.S.
% NDF **
% ADF **
% ADL **
% Hemicellulose N.S.
% Cellulose **
% Crude Fat **
% Crude Protein N.S.
Caloric Value N.S.
(Kcal/g)
N.S. not significant

** highly significant (Pg.01)

25

Table 6. Summary of significant differences in nutrient
composition between male and emale trembling aspen flower
buds and catkins collected in the Pigeon River Country State
Forest of Michigan in 1985 and 1986. (Sex under which
nutrient is listed has the greater value.)

 

 

 

 

Female Male
Trembling Aspen Trembling Aspen
Significant Significant
Nutritional Differences Nutritional Differences
Component Between Sexes Component Between Sexes
Flower % NDF ** % Crude Fat *
Buds
% ADF ** Caloric Value **
(Kcal/g)
% ADL **
% Celulose **
Catkins % NDF **
% ADF **
% ADL **

% Crude Protein **

% Celulose *

 

significant (Pg.OS)
** highly significant (Pg.Ol)

26
aspen female flower buds and catkins were not sufficient to

make comparisons between sexes of that species.

DIFFERENCES BET'EEN SPECIES

When making comparisons between species, data from 1985
and 1986 were again combined. Several differences were found
between species in flower buds, vegetative buds, and leaves
(Table 7). Trembling aspen flower buds were significantly

higher in caloric value and all fiber components except

%henicellose. Bigtooth aspen flower buds were significant
higher in %hemicellulose, %crude protein and %ash. No
significan differences were found between species for
%cellulose. For trembling and bigtooth aspen vegetative

buds, highly significant differences were found between
species for all nutritional components. Bigtooth aspen

vegetative buds were higher in all of the fiber components
except %ADL. Trembling aspen vegetative buds were higher in
%ADL, %crude fat, %crude protein, and caloric value. Leaves
collected from both species showed no siginificant
differences in %NDF and %crude fat. However, bigtooth aspen
leaves were found to be significantly higher in %ash, %crude
protein, %hemicellulose, and %cellulose. Trembling aspen
leaves were significantly higher in %ADF, %lignin, and
caloric value.

The greatest overall variation in nutrient content of

all materials assayed was found between male trembling aspen

27

Table 7. Summary of significant differences in nutrient
composition between trembling and bigtooth aspen flower

buds, vegetative buds and leaves collected in the Pigeon
River Country State Forest of Michigan in 1985 and 1986.
(Species under which nutrient is listed has the greater

value.)

 

 

 

Trembling Aspen Bigtooth Aspen
Significant Significant
Nutrient Differences Nutrient Differences

Composition Between Species Composition Between Species

Flower % NDF ** % Ash **
Buds
% ADF ** % Hemicellulose *
% ADL ** % Crude Protein *
Caloric Value **
(Kcal/g)
Vegetative
Buds % ADL ** % NDF **
% Crude Fat ** % ADF **
% Crude Protein ** % Ash **
Caloric Value ** % Hemicelulose **
(Kcal/g)
% Cellulose **
Leaves % ADF ** % Ash **
% ADL ** % Crude Protein *
Caloric Value ** % Hemicellulose **
(Kcal/g)
% Cellulose *

 

* Significant (Pg.05)
** Highly Significant (Pg.01)

and male bigtooth a pen catkins. Because of these var-

m

iations, data from 1985 and 1986 were not combined for

(.0

comparisions, and were analyzed separately. Table
summarizes tne differences between species for trembling and
bigtooth aspen catkins. In 1985, the only significant

differenc s found between the species were in %crude fat and

(1)

%crude protein. Trembling aspen catkins Were significantly
higher in %crude fat, and bigtooth catkins were signifi-
cantly higher in % crude protein. In 1986, significant
differences were found in all of the fiber components accept
%hemicellulose. Trembling catkins were significantly higher
in %MDF, %ADF, %ADL, and %cellulose. Bigtooth catkins were
significantly nigher in %ash, and %crude protein. No
significant differences were found between species for
%crude fat, %hemicellulose, or caloric value.

The neans, standard errors and ranges by year for
nutritional components, bud weights, and ages of the
trembling aspen and bigtooth aspen trees sampled are listed

in Tables 10-13 in the Appendix.

BIRD USE DAYS

One value of Standard Metabolic Rate (SMn) has been
reported in the literature for ruffed grouse. Brander and
Rasmussen (1973) determined that the SMR for a 644g ruffed
grouse was 46.1 kcal per day, assuming a respiratory

quotient (RQ) of 0.30. It was felt that the size of a

29

Table 8. Summary of significant differences in nutrient
composition between trembling and bigtooth aspen catkins
collected in the Pigeon River Country State Forest of
Michigan in 1985 and 1986. (Species under which nutrient is
listed has the greater value.)

 

 

 

Trembling Aspen Bigtooth Aspen
Significant Significant
Nutrient Differences Nutrient Differences

Composition Between Species Composition Between Species

1985 % Crude Fat ** % Crude Protein **

1986 % NDF ** % Ash *
% ADF ** % Crude Protein **
% ADL **

% Cellulose **

 

* significant (Pg.05)
** highly significant (Pg.01)

number of indiVidual
kcal of gross energy was
used to calculate th'
types of both speci
calculations were

appeared to vary between years for

size appe
In 1985, approx.
buds than

flower

needed to supply the

day. Approximately
vegetative buds would
aspen male flower buds.

female aspen flower

vegetative buds than male flower buds were needed

46.1 kcal of energy per

In 1985,

aspen flower buds could not be

flowering female

vegetative buds than bigtooth

to produce 46.1 cal

times

approximately 5.0

times more vegetative

made for

trembli

buds,

comparisi

trees.

g influence the nutritional

for ruffed grouse. Therefore, tne
food ICEVS required to produce 46.1
calculated This value was then

bird use days/tree for bud

es. flower buds, separate

1985 and 1986 as flower bud size
bud

both species. Veg.

red to remain constant between years.

2.5 times more trembling aspen female

flower buds would have been

7‘ ?“ .-\
ng iale

energy required to maintain SMR for 1

.3 times more trembling aspen

have been needed compared to trembling

In 1986, 3.5 times more trembling

and 9.5 times more trembling aspen
to supply
day.

ons between male and female bigtooth

made due to the lack of
However, 1.70 more bigtooth aspen
male flower buds were needed

gross energy in 1985. In 1986,

more bigtooth female flower and 5.0

flower buds were

required to supply the energy needed to support 1 ruffed
grouse at SMR.

Bird use days/tree was calculated by dividing average
bud production for sampled trees by the average number of
buds required to produce 46.1 kcal energy/day. For
vegetative buds, bird use days per tree did not vary between
years. For trembling aspen vegetative buds an average of
2.15 days per tree in 1985 was calculated. This was only
slightly lower than 2.69 days per tree calculated for 1986.
For bigtooth aspen vegetative buds 2.07 bird use days in
1985 and 1.93 bird use days in 1986 were calculated. Male
trembling aspen trees had the highest average bird use days

at 5.10 days per tree in 1985 and 25.53 days per tree in

1986. These figures are almost twice those of female tremb—
ling aspen trees in 1985, and triple those of female
trembling aspen trees in 1986. A similar trend was also

seen for bigtooth aspen. Males had an average value of 14.20
bird use days/tree, twice that of 7.74 for female bigtooth

aspen in 1986.

DISCUSSION

Previously, sex in dormant aspen flower buds has been
determined based on visual bud size, with the larger flower

buds being sexed as males and the smaller flower buds as

females. Our work indicates that male and female buds
overlap in size, although males on the average will be
larger. It is therefore felt that sex determination based

on bud size is not an entirely accurate technique, and
alternate techniques should be used. Lester (1963),
determined that by mid August floral differentiation and
development in aspen has reached a condition where only the
physiological requirement of cold treatment must be met
before floral maturity can occur. Under natural conditions
flower buds are physiologically ready for development by mid
December or January. Therefore, for a period of
approximately 8 months, from mid August to mid April, sex
can be determined by microscopically examining floral
structures. At these times the pollen sacks and stamen
primordia of male buds are easily seen when the bud is
sliced in half and placed under a microscope. A light
microscope is required to see these structures from August
to .id December or January. From January until floral
elongation in April only a dissecting microscope or hand

lens is required.

33

Aspen trees begin flowering at 10 to 20 years of age,
and flower production varies from light to heavy crops on
cycles of 3 to 5 years (Brinkman and Roe 1975). Data from
this study indicate that the number of clones flowering, as
well as the number of flower buds produced per tree varies
between years. The factors influencing bud production, both
in terms of the number of clones producing flower buds, as

well as the number of flower buds produced per tree have not

“'3

yet been determined. Relationships between age, stocking
density, site quality, and bud production were evaluated,
but no strong relationships were observed.

Yearly weather conditions and variations as well as
genetic inheritance may be the factors influencing bud
production. Weather has been shown to have an important

influence on carbohydrate production and subsequent

'V‘
uh

(f

produc i' primordia development in douglas fir

(I)
Q
(U

1

(

'U

5 do. m-n iesii) (Ebell 1971). Morris (1947) has

(I)
(1’
(I)
m
,‘u
«o
N

V
.a

 

stated that weather conditions during the growing season
influence the carbon-mineral nutrient ratio of balsam fir,
and thus affects bud production. Apparently there is a
correlation between hot, dry years, which favor
photosynthesis rather than uptake of minerals, and heavy
seed years immediatley following for balsam fir. This
process may also be true for aspen as the nutritional status
of many plants is an important aspect of floral production.

Flowering parts of plants are particularly dependent on

34
availability and translocation of nutrients. The
carbonznitrogen ratio has been shown to be extremely
influential in flower production in many dioecious species
(Copeland 1976).

The genetic make up of aspen clones may also be an
important component influencing flower production as well as
flowering periodicity. In controlled experiments with
aspen, Valentine (1975) found strong genetic control of sex
ratio and earliness of flowering. His studies have indicated
that genetics may influence flowering frequency as well.
His study also showed that male trees flower more frequently

and at a younger age than do female trees. Further studies

such as Valentine's ar needed to more fully evaluate the
genetic control of flowering frequency. Based on
information collected from other species, it can e
speculated that yearly weather conditions and genetic

differences between clones may be the factors ultimately in-
fluencing yearly bud production in aspen as well.

The nutritional data from this study indicate that
%crude protein and %crude fat vary between years for flower
buds, vegetative buds, and catkins. Huff (1973) in Minnesota
also foun wide year to year variations in the levels of
%crude fat for male trembling and bigtooth aspen flower
buds. Both protein and energy may play an important role in
over-winter survival and/or subsequent body condition in the

spring. Th~ level of protein in the diet may have an

r)
F

35
important influence on body condition, and protein has been

shown to affect many aspects of reproductive success in

captive ruffed grouse (Beckerton amd Middleton 1982). For
female red grouse (La 0 us lagopus scoticus) dietary

nitrogen has been shown to be particularly important in
establishing the ”nutritive condition" and subsequent
breeding success (Moss, Watson, and Parr 1975). Thomas et
al. (1975) determined that ruffed grouse have low body
reserves of lipids and glycogen, and large reserves of
protein during winter months. Under adverse winter
conditions grouse may deplete these limited energy reserves

and thus have to utilize body protein as an energy source

(Beckerton and Middleton 1983). As a consequence of winter
protein catabolism, birds could potentially enter the

breeding season with suboptimal protein reserves. Field
observations (Maxon 1974) have indicated that aspen is a
preferred food source at least during the pre-incubation and
incubation periods. The continued use of aspen buds and
catkins in the spring may be related to a need to increase
nitrogen retention as ovarian recrudescence occurs. In
evaluating the effects of 5 levels of dietary protein on
body weight, food consumption, and nitrogen balance of
ruffed grouse throughout the breeding cycle, Beckerton and
Middleton (1983) have shown that females consuming foods
with high protein levels maintained better physiological

condition than those with low dietary protein levels.

 

.4
i

d grouse population cycles since 1958 at

)

Studies of ruff-

(1

Cloquet, Minnesota conclude that the periodic fluctuations
in grouse populations are not entirely the result of any
"die-off", as they are the failure to recruit young birds
each season to replace those lost through "normal" attrition
(Gullion 1970). Therefore, in addition to the role aspen
buds may play in the overwinter survival of ruffed grouse,
the nutritional plane in which these birds enter the
breeding season and their subsequent breeding and brood
rearing success may be equally influenced.

Yearly variations in levels of %crude fat may also have
an important role in body condition of ruffed grouse.
Examinations of ruffed grouse carcasses collected during the
fall and winter months indicate very little visable fat,
with no marked seasonal increase in lipids being observed
(Thomas et al. 1975). Therefore, stored lipids do not
appear to be of great metabolic importance to ruffed grouse,
particularly during the winter months, supporting the
hypothesis that energy supplied by aspen may be a limiting
factor to these birds during the winter. Percent crude fat
is a measure of the lipid content of foods, but also
includes waxes and other compounds that may interfere with
digestion or palatibility. It has been hypothesized that
levels of secondary plant compounds in aspen may also vary
between years (Gullion 1977). Therefore, yearly fluctua-

tions in %crude fat could be a reflection of fluctuating

37

levels cf various compounds, and may not accurately
represent digestible energy from fats. Bryant and Kuropat
(1980) have shown that winter forage preferences of Alaskan
ruffed grouse are negatively correlated with the resin
winter browSe. These authors have also shown
this to be true in Canada. Staminate buds collected from
preferred quaking aspen clones in Alberta were less resinous
than those collected from rejected clones. Furthermore,
trembling aspen staminate buds collected from crops of
Alberta ruffed grouse were less resinous than those
collected at random from preferred trembling aspen clones.
Resins of Egpglgs contain several methylated flavonols that
may inhibit protein digestion (Wollenweber 1973).
Antimicrobial resins may be effective defenses against cecal
digestors such as ruffed grouse, as digestion in the cec m
is dependent upon the microbial fermentation of plant
material. Ingestion of antimicrobial resins may reduce
production of microbial protein, vitamins, and volatile
fatty acids. Therefore, variations in levels of %crude fat
content between years could be influencing the nutritional
quality of flower buds as well as vegetative buds for ruffed
grouse.

Aspen catkins show a wide variation in nutrient content
between years. Most of the differences observed are felt to
be due to the rapid progressi'e changes in plant physiology

at the time of flowering, as flower development is highly

38

temperature dependent. Catkin elongation and pollen shed
can occur as rapidly as a few hours if temperatures are
high. Genetic differences in flowering phenology between
clones also influences the physiological stage of catkin
development at a given time (Pregitzer and Barnes 1981).
Therefore, standardization between years and clones was
difficult to achieve, probably accounting for the wide
variations observed.

In evaluating differences between sexes, male trembling
flower buds and catkins had higher %crude fat and caloric
values than female catkins and buds. In terms of total
fiber, males appear to be more digestible than females,
although higher levels of digestion inhibiting compounds in
the %crude fat of males could potentially reduce digesti-
bility. In terms of protein no differences existed between
sexes. It appears that bud size, and therefore the amount
of nutrients consumed per bite, may be the major difference
between male and female flower buds. Huemphner (1981), in a
study of ruffed grouse winter arboreal feeding behavior,
also felt that bud size may be an important factor
determining canopy and perhaps clone preference.

Studies by Huemphner (1981) have shown an approximate
preference of 2:1 for trembling aspen flower buds over those
of bigtooth aspen. Huemphner also found that during high

ruffed grouse population densities, bigtooth aspen was

39

utilized more heavily than during low ruffed grouse
population densities. When comparing the 2 species, bigtooth
flower buds were higher in %crude protein and lower in
apparent digestibility than male trembling flower buds. No
differences were found in %crude fat. When evaluating the
nutritional quality of vegetative buds from both species, it
appears that bigtooth vegetative buds are of lower
nutritional quality than trembling buds, as %total fiber was
higher, and %crude fat, %crude protein, and caloric value
were lower.

Aspen leaves are a highly preferred late spring and
summer food for ruffed grouse. At Cloquet in Minnesota,
leaves ranke first among all identifible materials
(Vanderschagen 1970). In this study, aspen leaves contained
a significant amount of protein, the mean being higher than
that of male flower buds or male catkins. It must be
remembered however, that these samples were collected in
early spring at the time of leaf flush, accounting for the
high protein levels. Results indicate that bigtooth leaves
were higher in protein, but this result is felt to be the
consequence of leaf phenology at the time of sampling, as
trembling aspen were about 2 weeks ahead of bigtooth leaves
in terms of phenological development and therefore would be
expected to have lower levels of protein. Laying and

incubating female ruffed grouse feed for only short periods

40

during the day. Therefore, they need to obtain a highly
nutritious diet in a relatively short period of time. Naxon
(1974), using telemetry to study female ruffed grouse in

Minnesota, found that female ruffed grouse have a marked

(1)
n.

(1

pr ferenC“ for tr mbling aspen leaves as a food source

du

H

g incubation. Our data suggest that aspen leaves

{‘5

1
provide ruffed grouse with a highly nutritious and easily
digestible food resource at this time of the year.

The Standard Metabolic Rate (SMR) for a 644 g ruffed
grouse has been calculated to be 46.1 kcal/day, assuming a
respirtatcry quotient of 0.80 (Rasmussen and Brander 1973).
The energy reserves of ruffed grouse may not last more than
a few days, consecuently regular feeding must be a vital
component in the energy budget of ruffed grouse during
winter. For maintenance of a long term energy balance, the
daily quantity of energy metabolized from the food must at
least equal the daily energy expenditure. Data indicate that
staminate flower buds of both species provide a greater
amount of nutrients per bud than vegetative or pistillate
flower buds. This may account for the observed preference

for staminate buds as the male flower buds would allow the

m
D;

birds to "fill up" quickly, thus reducing the time expOS‘
to predation as well as reducing energy expended to maintain
body temperature. It should also be noted though, that this

study has shown an observed sex ratio that is skewed towards

w ‘\ r- v c ‘ ‘x c
.31. tre-s. Pr-‘ious stu'ies of ruf_ed grouse iced
'\ c :~ I‘ r- v r\ - ' 2 ~ .~. . : 1»- ,A. :\ v- v!- - -: . '
preferences have not ceternihed the sex ratio in the

sampling area. A sex ratio skewed towards males would
automatically show a preference toward Tale trees, as the

availability of male trees would be greater than the

Foods other than aspen may be extremely important to

ruffed grouse when we consider the variability of aspen in

terrs of both bud production and nutritional quality. Gray

(unpub. data), in evaluating the nutritional quality of

 

black cherry (P. serotina), paper bircn (B. papyrifera),
yellow birch (B. lutea), alder (Aldus rugosa), and willow

 

or) buds in the Pigeon River Country State

 

Forest of Michigan, found that many of these species were
similar or often higher in nutritional quality and energetic
value than aspen. Other researchers have also shown paper
birch catkins and buds (Schemnitz 1970), and black cherry
buds (vap et al. 1947), to have higher or similar levels of
%crude protein and %crude fat than aspen flower buds.

Studio in Mi.nesota have shown the winter diet of ruffed

H
C)
(.1.
<
{D
H
H

J
(T
} l
O
:3
U)
r—h
H,
O

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O
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9.)
H
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IT
(D
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>4
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grouse to have ra‘

(Doerr 1973: VanderSCnaegon, 1970). Therefore, it is felt

r - 1 "\ ‘ r'\ vv ‘ 1 ". ' q. , .-, 5 ' A
to ruffed grouse, the availability of other _oods in the

Ruffed grouse have be n shown to preferentially feed on

('1)

certain aspen clones, although no consistent relationship
has been found between the forage preferences of ruffed
grouse and the phosphorous, micronutrient, soluble
carbohydrate, or fiber content of trembling aspen (Doerr et
al. 1974). Currently it is being speculated that yearly
variations in nutritional quality and/or yearly variations
in bud production may be influencing the ability of ruffed
grouse to maintain the nutritional plane required to survive
winter and/or breed and raise broods successfully in the
spring.

Studies (Ficher 1939; Bump et al. 1947) have indicated
that the abundance of ruffed grouse is not uniform through—
out its range. That is, birds have been known to be
increasing in some localities while decreasing in others.
If ruffed grouse population fluctuations are a response to
the quantity and/or quality of food resources during the
time of year when food resources are scarce, yearly
variation in aspen nutrition and production may influence
ruffed grouse population cycles. The fact that ruffed grouse
inhabit relatively limited ranges throughout their lifetime
makes them subject to nutritional stresses brought about by
the variant nutrient composition of materials from
relatively few plant species. Therefore, the combination of

low bud production, varying nutritional quality, digestion

43
inhibiting compounds in crude lat, and the availability of
foods other than aspen could trigger the population levels
to oscillate over time in response to specific environmental

conditions and the quality and availability of food

IESOUI‘CES .

Our results include a number of findings pertinent to
ruffed grouse habitat management. Current habitat
management recommendations suggest leaving nature male aspen
clones in large aspen clearcuts to provide winter food. Our
results indicate that because of the clonal growth habit of
aspen, it would be disadvantageous to ruffed grouse for
forest managers to leave aspen clones that are regular
and/or prolific flower bud producers. That is, in terms of
aspen as a ruffed grouse winter food, by leaving flowering
clones standing we are in essence loosing the superior
genetic stock. Ideally, to improve the ge.etic quality of
aspen stands for ruffed grouse, managers should manipulate
the clonal composition of an area to reduce the proportion
of inferior clones, thereby perpetuating and expanding
prolific and/or regular flower bud producers. Furthermore,
the current recommendation of leaving only male aspen may
also be questioned. The nutritional data from this study

suggest that nutritional differences between sexes are not

highly significant, especially in terms of %crude protein
and *crude fat, the nutritional components that may be

physiologically the most important to ruffed grouse during
winter and early spring. Highly productive female clones may

therefore also contribute an important food resource.

(u

Yearly variations in asp-n flower bud production
appears to be a function of environmental factors and/or
genetics. Therefore, yearly fluctuations cannot be managed
for specifically at this time. One management suggestion is
to leave enough nature aspen so that there is adequate food
even during years of low bud production.

Furthermore, and perhaps most importantly, it is feel
that further research on aspen as a winter food resource is
needed. Further evaluation of yearly bud production and the
types and levels of c npounds in crude fat are needed. It is
also felt that yearly production and nutritional inform.tion
for "other” ruffed grouse winter foods is needed. And
finally, to bring the research full circle, a complete
knowledge of the energetic and nutritional requirements of

ruffed grouse must be obtained to begin to understand the

l}

k l
:3
HI
FJ
c

enc that aspen may have on ruffed grouse population

0
LC,
0
}._.l
G)
U)

APPENDICES

 

Table 9. Characteristics for field identification of aspen
clones by season. (from Barnes 1969)

Spring

1. SEX

2 Time of flowering and floral characteristics
3. Tire, color, and progression of leaf flushing
Autumn

1. Leaf coloration

2. Time and progreSSion of leaf fall

Sumner

1. Leaf shape (BW/BL ratio), color, and size

2. Configuration of blade base

3. Leaf margi tooth number, size, and shape
4. Configuration of blade tip

All Seasons

Bark

(f)
(T

(z)

har

C
1

A.
’5

h .

'u
H

‘ .

OW U1 DJ [0 H (’7

acteristics
Bark texture
Bark color

teristics

em form

Branching habit
Suceptibility to injury
Vertical profile
Miscell n ous

5;:

ac
St

a. pruning ability
b. leaf rust
c. aphic galls

 

Table 10. Kea.ns, st a1da1d e rors ard 1a g: s by ye: r for nltr- iynal coapon.* nts, bud
weights and ag as if :Tale and fa e tr e l:ling aspen floisr buds c311ect:d in the Piga
River Country State Fo1est of Lichigan.

 

 

 

 

”ale Faﬁale
Trerbling Tspen Trembling lepen
1985(n=9) 1986(n=31) 1985(n=3) 1986(n=6)
Co non nts V-31 ‘-i“ (S E.)' Fang; rap (S E ) Binge
Bud Veight 1985 0.09(0.01) 0.03-0.13 0.04(0.01) 0.03—0.04
(g) 1986 0.13(0.02) 0.04-0.17 0.06{0.01) 0.04-0.08
% D.X 1385 0. 96(0. 02) 0.94-0.96 0.96(0.03) 0.95-0.96
1986 0. 95(0.01) 0.93-0.97 0.95(0.01) 0 97-0.94
% nSh 1985 2 54(0.12‘ 2.09-3.15 2.65(0.19) 2.26-2.-
1936 2 30(0.07) 1.27-3.35 2. 910.17) 1.90-3.25
% ND? 1935 59 20(0 ° 56.04-63.52 63 00(0.78) 1 67 64 39
19°F 59 45(0 , 53.28-61.49 64 88(1.42) 59.18-69.51
% ADF 1985 46.r 1 O4) 59.88—51.88 49.70(1.96) 45.79-51.76
19c6 47.53(0 43) 42.70-49.85 52.83(1.18) 49.54-57.65
% 101 1983 26.22(1.00) 21.40-30.42 29.99(0.69) 28.67-31.15
198 28.20(0.40) 23.78-33.78 30.14(0.59) 28.21-31.97
% Hemicellulose 1985 12.52(0.99) 8.28-17.37 13.30(1.34) 11.39-15.88
1986 11.91(0.37) 6.56-17.58 12.38(1.43) 9.52-19.31
% Cellulose 1985 15.94(1.70) 17.50-25.08 19.71(2.09) 15.72—22.79
198 19.33(0.38) 16.75-24.29 22.40(1.24) 18.80—26.93
% Crude Fat 1985 20.06(0.74) 16 59-23 80 l6.58(0.44) 16.01-17.44
1986 14 Q4(0.44) 9.10-20.48 12.01(1.10) 9.52-16.36
% Crude Protein 1985 10.05(0.45) 7.56-12.06 10.88(0.26) 10.56-11.41
1986 10.34(0.22) 8.25-13.12 9.56(0.51) 8.37-15.56
Caloric Value 1985 4.68(0.91) 4.18- 5.01 4.53(0.02) 4.51- 4.59
(Kcal/q) 1986 4.79(0.19) 4.61- 5.13 4 71(0.04) 4.52- 4.84
Age (yrs) 1985 38.66 17.00-65.00 31.00 21.00-50.00
1986 33.48 15.00-60.00 27.57 16.00-50.00

 

t3; dard Ehror

133

(1

Table 11. K”ano, standard err
male and female trembling aspen catkins collected in the Pigeon River Country State Forest
of Hichigan.

L)

ors and ranges by year for nutritional conpgnents and ages of

 

 

 

 

Male Female
Trat‘bling Aspen Trerrbling Aspen
1985(n=2) 98 (n=19) 1985(n=3) 1986(n28)

Cogponants Year Kean (S.E.)' Range Kean (S.E.) Range
% D.H. 1985 0.94(0.01) 0.94-0.95 0.96(0.01) 0.94- 0.98
1986 0.95(0.01) 0.9390.97 0.96(0.01) 0.94- 0 97

% Ash 198 4.24{O.13) 4.11- 4.30 5.80(1.30) 4.08- 8.35
1986 4.78(0.14) 3.76- 5.96 5.70(O.45) 3.86- 7.32

% NDF 1985 54.43(3.80) 50.63-58.23 57.57(2.34) 54.18-62. 5
1986 51.01(0.75) 46.30-56.95 56.10(0.94) 53.36-60.97
% ADF 198 42.87(1.04) 41.83-43.92 47.30(2.60) 42.28-51.01
1986 39 86t0 65) 35.97-44.44 45.00(1.37) 39.67-51.65
% ADL 1985 23.59(1.31) 22.28-24.90 26.79(1.25) 24.48-28.78
1986 21.03(0.49) 16.36-24.36 24.37(0.79) 20.24-26.53
% Hemicellulose 1985 11.55(2.75) 8.80-14.31 10.27(1.22) 7.88-11.90
1986 11.15(0.44) 8.67-14.63 11.10(0.81) 8.09-14 2

% Cellulose 1985 19.28(0.25) 18.02-19.55 20.51(1.37) 17.80—22.2
1986 1 .83(0.35) 16.55-21.40 20.63(0.84) 17.24-24 89

% Crude Fat 1985 19.72(1.65) 18.07-21.37 12.94(1 05) 10 99-13.79
1986 10.4l(0.33) 8.38-13.27 9.73(0.66) 7.42-13.55

% Crude Protein 1985 11.56(1.56) 10.00-13.13 14.50(0.57) 13 75-15.63
1986 1 .51(0.54) 9.81-18.94 16.01(0.98) ‘2 37-21.31

Caloric Value 1985 4.41(0.15) 4.26- 4.55 4.60(0.09) 4.46- 4.77
(K cal/g) 1986 4.57(0.04) 4.29- 4.77 4.53(0.11) 4.32- 4.68
Age (yrs) 1985 33.50 17.00-50.00 35.66 18.00-50.00
1986 32.74 15.00-60.00 24.37 20.00-45.00

 

495

r. q -. §- q -, Ava / - AA — - o- 31- — v - ~ A a - \‘N %.-‘.\VH_ - x -----
Tah16 11. ”6ais, stania1i 611015 arii 3.3-5 by y1a1 far nutiit13..l CUHVQUCntS, bud eights
and ac es of trembl an as en Jeqetati e buds ale leares coll;:t d in the Pigeon River Countsy

St~a te Far; st of ”ichi gan.

 

 

 

 

V;g:tatixe BICS Lea.es
1985(n=24) 1986.n=18) 1985(n—15)
C ‘,L-".*1-“S Y-“ " an {3.3.)' 312$“ ".11 (S E ) 9‘7“:

8“? " * ‘t 1985 0 26(0.01) 0.91-0.04 --- ----
(a) 1986 0 03(0.01) 0.02-0.04 --- ----

8 D! 1985 0.9610.15) 0.93- 0.97 0.95(0.56) 0.11 0.97
1986 0.9610.01) 0.94- 0.97 --- ---

8 Ash 1985 2. 57(0. 07) 1.87-3.31 5 61’0 17) 4 6 6’
1986 2. 63(0. 11) 1.77-3.55 --- ---

8 NDF 1985 58.9811.04) 50.10-69.88 53.41(0.66) 48.60-57.38
1986 56.80(1 07‘ 50. 08- 65.62 ---- ---

% ADF 1n85 49.44(0.84) 41.75-58.20 44.64(1.02) 38.72-53.20
1986 4°.50(0.81) 44.79-54.57 --- ---

8 ADL 1 -5 33.42(0.72) 29.11-41.13 30.79(1.03) 24.63-39.11
186 34.42(0.82) 28.02-38.87 --- ----

8 Hanicellnlose 1985 9.54 (0. 41) 6.47-13.09 8.76(0.53) 4.18- 11. 28
1986 7.31(0. 68) 3.38-12.73 --- ----

 

% Cellulose 1985 16.02(0.49) 10 2,12 .63 13 85(0. 56) 10.55-17.92
1986 14.76(O.50) 10.09-17.68 ---—

% Crude Fat 1985 23.34(1.27) 11.23-33.48 10.85(0.78) 6.62-17.75
198. 18.24(1.31) 9.69-27.69 ---

 

) 4.75- 8.19 22.05(1.35) 15.03-32.38

% Crude Protein 19 5
1 . 4) 7.12-10.31 ---

 

Caloric Value 1935 5.15(0.97> 4. 30- 5.52 4.73(0.05> 4.15— 4.86
(Kcal/g) 1986 5.06(0 27) 4. 68- 5. 40 ——- —-——-
16.3 (yrs) 19.55 38.62 17.00—64.00 35.00 16.00-61.00

1986 31 1'7 18.00-50.00 --——— ————

 

Staniard Er‘or

5C3

Table 13. Heans, standard errors and ranges by year for nutritional components, bud weights
and ages of bigtooth aspen flower buds and catkins collected in the Pigeon River Country
State Forest of Kithigan.

 

 

 

 

Kale Kale
Flower Buds Catkins
1985(n=7) 1986(n=7) 1985(n=5) 1986(n=11)
igrporents Year 13.3111 (5 E )' Ranxre Z-Iean (S E ) Pal I;

Bud Weight 1985 0.07(0.01) 0.05- 0.10 --- ---

(g) 1986 0.11(0.01) 0.08- 0.13 --- ---
8 D ’ 1985 0.96(0.36) 0.94- 0.97 0.95(0.01) 0.93- 0.96
1986 0.96(0.01) 0.94- 0.97 0.96(0.01) 0.94- 0.98
8 Ash 1985 2 89(0.08) 2 57 3 21 5 3 (0.59) 3.59- 7.21
1986 2 7C(0.15) 2 47 3.68 5 48(0.24) 4.30- 7.08
8 NDF 1995 55.67(0 10 49.49-61.73 54.49(1.46) 50.73-59.02
1996 55.44(0 53 52 55-57.4 41.94(0.78) 37.47—45.93
8 ADF 1985 40.93(0.96) 37.96-45.28 41.66(1.19) 39.62-46.14
198 2.67(0 92) 39.54-46.81 30.07(0.70) 25.35-33.57
8 ADL 1985 21.65(0.59) 19.88-24.00 22.99C0 89) 20.50-25.98
1986 23.15(0.70) 20.35-26.19 1 .26(0.50) 14.10-20.49
8 Hezicellulase 1985 14.74(1.06) 10.50-16.45 12.83(0. 4) 10.65-14.17
1986 l2.71(0.71) 9.31-16.12 11.81(0.73) 8.64-14.39
8 Cellulose 1985 19.28(0.45) 18. 8-21.76 18.66(0.65) 16.54-19.61
198 19 26 .32) 18.42-2 .67 1 .86(0.41) 11.25-16.38
8 Crude Fat 1985 16.13(0.89) 12.62-19.33 12.44(l.64) 9.61-18.67
1986 13.60(1.32) 9.29-18.57 6.48(0.35) 4.11- 8.53
8 Crude Protein 1985 10.72(0.43) 9.00-12.38 16.64(1 05) 13.36-19.44
1986 1.69(0.14) 11.12-12.37 19.03(0.55) 16.31-22.81
Caloric Value 1985 4.68(0.10) 4.18- 5.00 4.17(0.25) 3.66- 4.54
(Kcal/g) 1986 4.58(0.03) 4.41- 4.72 4.45(0.01) 4.39- 4.52
Age (yrs) 1985 51.71 35.00-64.00 46.20 35.00-50.00
1986 49.30 40.00-60.00 53.27 40.00-64.00

 

' Standard Error

 

 

 

 

Table 14. 1'eans, standard 3rrors and rants by y;ar for nutritianal ccaponents, bud weichts ar.d f.
of bid tm th aspen leaetati e buds and lea es col1ected in the Pigeon River Country State For :t if
Ficbi'ir
V5 g3tativ e Buds Leaves
1985(n=18) 19 86(n=7) 1985(n=15)
C5rgcnents Year Kean (3.3.) Range Kean (S.E.) Range
Bud Weight 198 0.0. 0 ) --—-

CD
5?:- U1
5

3
(g) 1986 0.03

 

8 D.H. 1985 0.96(0.01) 0,96- 0 97 0.96(0 01) 0 93- 0 93
1936 0.96(0.01) 0 95- 0 97

8 Ash 198 3.85(0.09) 3 00 4.4 6.69(0.14) 6 35- 7 86
1986 3.71(0.15) 3 1 - 4.34 --- ---

8 J2? 1-85 66 56(0 6 62.50-70.93 52.30(0.74) 47.77-56.36

. a)
1986 66.02(0.72) 63.37-68.10 —--— —.———

 

 

30.13(0.57) 26.50-35.29 19.75(1.66) 12.60-33.04
, .83) 30.08-34.69 —-- —-—-—

8 Hemicellulose 19 2.09 18.02(1.47) 7.69-27.98

4.94 ---—- -—-—

8 ellulose 1985 22.27( .'1) 18.63-24.90 15.44(0.53) 12.12-19.04
1986 21.63(0.38) 19.98-22.79 --—- ---

8 Crude Fat 1985 12.33(0.51) 9.85-19.33 11.43(0.55) 8.55-15.32
1986 6.38(0.43) 4.88- 7.06 --—- -—-——

8 Crude Protein 1985 5.90(0.21) 5.13- 8.78 25.73(0.87) 20.19-33.25
1986 .67(0.42) 6. 1- 9.75 -—-— -—-—

Calaric Value 1985 4.59(0.04) 4.24- 4.80 4.47(0.05) 4.24- 4.84
(Kcal,’g) 1986 4.65(0.04) 4.51- 4.8 --- --——-

Age (yrs) 198 46.44 14.00-75.00 45.46 19.00-67.00
1986 44.85 19.00-60.00

 

 

' standard error

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235," “3"" WI ]

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