The Influence of Forest Substrate on Young
Seedling Dynamics
John L. Willis, Forestry, Michigan State University, East Lansing, Michigan
Michael B. Walters, Forestry, Michigan State University, East Lansing, Michigan
Kurt W. Gottschalk, USDA Forest Service Research Station, Morgantown, West Virginia
Outline
Current seedling
demographics
Management strategies and
assumptions
Substrate case study 1:
soil availability influence
seedling establishment
within harvest gaps
Substrate case study 2:
mechanisms of seedling
survival and development
on different types of
forest substrate
(preliminary)
Questions
Species Depauperate Seedling Layer
(Matonis et al. 2011)
Varying Harvest Gap Size
(Shields and Webster 2007; Bolton
and D’Amato 2011; Kern et al. 2013)
Assumption #1
Desired species
already are/will
become established
in harvest gaps
Germination
Substrate
Easily penetrated by roots
High moisture holding
capacity (clays>silt>sand)
Majority of plant available nutrients
Harvesting Legacy #1
reduced bare mineral
soil/humus
-Removing mature, suppressed, diseased
trees
-Harvesting in the winter
Assumption #2
Desired species will
have access to light
within harvest gaps
Access to Light
Competing non-tree vegetation
Density and height correlate
positively with gap size
Herbivory
Loss of aboveground biomass
40 acre rich mesic northern hardwood stand
Emmet County, Michigan
Continuous range of gap sizes from single-tree gap to 1.58 acres and
four unharvested understory plots
.
% Light Availability
Substrate Coverage
(modified by overstory and
(% cover)
forest floor vegetation)
Non-Tree Vegetation
(% cover and height)
Hemlock Germination
Hemlock First Year Survival
Hemlock Seedlings/2m2
Hemlock Seedlings/2m2
70
60
50
40
30
20
10
70
60
50
40
30
20
10
0
0
0
10
20
30
40
50
60
70
80
0
10
20
30
40
50
60
70
80
% Light Availability
% Light Availability
Hemlock Seedlings/2m2
Hemlock Second Year Survival
ST(<.1ac)
70
GS (.1-.5)
PS (.5-2)
60
50
40
30
20
10
0
0
10
20
30
40
50
60
% Light Availability
70
80
Eastern Hemlock (Tsuga canadensis)
60
R2=0.56
p<.0001
50
40
Effect of Light Availability on Survival (Year 1)
100
Proportion Surviving
Hemlock Seedlings/ 2m2
Effect of Scarification on Germination
S
30
20
10
0
80
60
40
R2=0.28
p<.0001
20
0
0
10
20
30
40
50
60
70
80
10
20
30
40
50
60
70
80
% Light Availability
% Light Availability
Effect of Light Availability on Survival Year (2)
Proportion Surviving
100
ST(<.1ac)
R2=0.20
p<.0001
80
GS (.1-.5)
PS (.5-2)
60
40
20
0
0
10
20
30
40
50
60
% Light Availability
70
80
Eastern Hemlock (Tsuga canadensis)
Paper Birch First Year Survival
140
Paper Birch Seedlings/2m2
Paper Birch Seedlings/2m2
Paper Birch Germination
120
100
80
60
40
20
0
0
10
20
30
40
50
60
70
80
140
120
100
80
60
40
20
0
0
10
% Light Availability
20
30
40
50
60
70
80
% Light Availability
Paper Birch Seedlings/2m2
Paper Birch Second Year Survival
140
ST(<.1ac)
120
100
GS (.1-.5)
80
PS (.5-2)
60
40
20
0
0
10
20
30
40
50
60
% Light Availability
70
80
Paper birch (Betula papyrifera)
140
Effect of Light Availability on Survival (Year 1)
100
R2= .41
120
Proportion Surviving
Paper Birch Seedlings/2m2
Effect of Scarification on Germination
p <.0001
100
80
60
40
S
20
0
10
20
30
40
50
60
70
80
60
40
20
R2=.06
p=.0289
0
80
10 20 30 40 50 60 70 80
% Light Availability
% Light Availability
The Effect of Light Availability on Survival (Year 2)
Proportion Surviving
100
ST(<.1ac)
R2= .15
p=.0237
80
GS (.1-.5)
60
PS (.5-2)
40
20
0
0
10
20
30
40
50
60
% Light Availability
70
80
Paper birch (Betula papyrifera)
Yellow Birch First Year Survival
2
120
100
80
60
40
20
0
0
10
20
30
40
50
60
70
80
Yellow Birch Seedlings/2m
Yellow Birch Seedlings/2m2
Yellow Birch Germination
120
100
80
60
40
20
0
0
10
% Light Availability
30
40
50
60
70
80
% Light Availability
Yellow Birch Second Year Survival
Yellow Birch Seedlings/2m2
20
ST(<.1ac)
GS (.1-.5)
PS (.5-2)
120
100
80
60
40
20
0
0
10
20
30
40
50
60
70
80
% Light Availability
Yellow Birch (Betula alleghaniensis)
100
120
R2= .31
100
Proportion Surviving
Yellow Birch Seedlings /2m2
Effect of Scarification on Germination Effect of Light Availability on Survival (Year 1)
p<.0001
80
60
40
20
80
60
40
20
R2=.17
p=.0012
0
0
10
20
30
40
50
60
% Light Availability
70
80
10
20
30
40
50
60
70
80
% Light Availability
ST(<.1ac)
GS (.1-.5)
PS (.5-2)
Yellow birch (Betula alleghaniensis)
White Pine First Year Survival
White Pine Seedlings/2m2
14
12
10
8
6
4
2
0
0
10
20
30
40
50
60
70
80
14
12
10
8
6
4
2
0
0
% Light Availability
10
20
30
40
50
60
70
% Light Availability
White Pine Second Year Survival
White Pine Seedlings/2m2
White Pine Seedlings/2m2
White Pine Germination
ST(<.1ac)
14
12
GS (.1-.5)
10
8
PS (.5-2)
6
4
2
0
0
10
20
30
40
50
60
% Light Availability
70
80
White Pine (Pinus strobus)
80
White Pine 1st Growing Season Survival
14
12
10
8
6
4
2
0
100
R2<.01
p=.9054
Proportion Surviving
White Pine Seedlings/2m2
Effect of Scarification on Germination
80
60
40
R2=.11
R2=.11
P =009
P =009
20
0
10
20
30
40
50
60
% Light Availability
70
80
10
20
30
40
50
60
70
80
% Light Availability
ST(<.1ac)
GS (.1-.5)
PS (.5-2)
White pine (Pinus strobus)
Hemlock
Paper Birch
Effect of Clipping on Survival
Effect of Fencing on Survival (Year 3)
F
R2=0.19
p=0007
80
60
40
ST(<.1ac)
20
R2=.36
p=<.0001
80
C
60
40
20
0
0
GS (.1-.5)
0
0
10
20
30
40
50
60
% Light Availability
10
20
30
40
50
60
70
80
% Light Availability
70
Effect of Fencing on Survival
PS (.5-2)
100
Proportion Surviving
Proportion Surviving
100
Proportion Surviving
100
R2=.19
p=<.0001
80
F
60
40
20
0
0
10
20
30
40
50
60
% Light Availability
70
80
Conclusions
-Bare mineral soil/humus is CRITICAL for light seeded species
germination, but not white pine.
-Low light availability is NOT a significant barrier to
germination
-Increasing harvest gap size IMPROVES seedling survival for
all species initially, but deer and non-tree vegetation are
beginning to influence seedlings access to light(hemlock
and paper birch)
-Group selection harvest gaps (.1-.5ac) may present the
best opportunity to recruit this group of species….stay
tuned
Case Study# 2:
Seedling development
across substrates
Harvesting/thinning reduces
interrupts the cycle of nurse log
creation by:
-Removing mature/diseased/suppressed trees
Decaying Coarse Woody Debris (Nurse Logs)
Hardwood litter avoidance
Species specific
pests/pathogens escape
Competition from nontree vegetation
Drought stress
(Harmon and Franklin 1989)
Nurse Log Seedling Demographics
1.Sugar Maple provides
poor substrate for all
species of seedlings
2. Hemlock most capable
of surviving on nurse logs
3. Sugar maple least
capable of surviving
on nurse logs
4. Yellow Birch is
better adapted for
surviving on hemlock
nurse logs
(Marx and Walters 2008)
Nutrient Limitation
Substrate
[N], µg/ml
Hemlock wood
1.5
Yellow birch wood
2.45
Sugar maple wood
3.18
Soil
3.62
Nmin µg.ml1.day-1
0.115
0.018
0.019
0.19
pH
3.7
3.9
6.4
3.4
(Marx and Walters 2006)
Nutrient Extraction
Carbohydrates
-Increased volume of soil
explored
Nutrients
- Breaking down previously
insoluble compounds
All samples transported back
to MSU Tree Research Center
Potted plant experiment:
12tree species X 7
substrates X 2 treatments
Tree species: PB,YB,WP,RP,SM,
RM,RO,HEM,WS,BF,WA,NWC
Substrates: CWD of
PB,SM,YB,HEM,BF,NWC and Soil
Sterilization Treatments:
Gamma irradiated or not
Yellow Birch Development
Paper Birch Development
30
40
Unsterilized
Sterilized
Unsterilized
Sterilized
25
Height Growth (cm)
Height Growth (cm)
30
20
20
15
10
5
10
0
0
BF
HEM
PB
SOIL
YB
NWC
SM
BF
HEM
PB
SOIL
YB
NWC
SM
Acknowledgements