Griffy Lake Nature Preserve Vegetation Monitoring Update Summer 2017
Griffy Lake Nature Preserve
Vegetation Monitoring Update
Summer 2017
History of Deer Population in Indiana
• early 1900s: Essentially all deer in Indiana killed by hunting and habitat destruction
• 1930s: Deer reintroduced to state
• 1950s: Populations re-established and modern hunting programs begun
• 1990s - present: Historic high deer populations
• Forest vegetation in Bloomington area more affected by deer than other nearby areas
Causes of High Deer PopulationsPrimary causes of deer increase
– improved forage from agriculture & towns
– elimination of natural predators
– increase in edge habitat preferred by deer
– supplemental feeding
– warmer winters
– hunters (and regulations) often favor bucks
– Reduction in number of hunters
Images from Fairfield County, Conn. Deer Management Alliance. www.deeralliance.com
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0
2
4
6
8
10
12
1960 1965 1970 1975 1980 1985 1990 1995 2000
Deer
per
square
km
Deer populations in
Wisconsin from 1960
to 2000
Effects of Deer on Ecological Communities
Study of Effects of Deer on Indiana State Parks by George
Parker and Chris Webster in 1996
• Unhunted state parks had
– fewer tree seedlings and shrubs
– lower % cover of herbaceous species
– higher cover of unpalatable species
• Since state park hunts began, there has been a dramatic
increase in understory forest diversity and plant coverage
• In Wisconsin, several state parks without hunting lost over
50% of plant species
Effects of Deer Browsing on a Forest Herb
Knight, Caswell, and Kalisz. 2009. Forest Ecology and Management 257: 1095.
Fra
ctio
n
in E
ach
Lif
e S
tag
eR
ep
rod
uct
ive
Va
lue
% Herbivory
Large-flowered Trillium, Trillium grandiflorum
Average % Herbivory
Po
pu
lati
on
Gro
wth
Ra
te
increasing
population
declining
population
Griffy Lake Nature Preserve
Comparative Vegetation Data
2017
Data collected by Peter Slothower 28 April – 12 May 2017
Data summarized by Angie Shelton, 18 May 2017
All six species
have fewer
flowering
plants at GLNP.
See detailed view of
less common
species on next
slide.
All six species
have fewer
flowering
plants at GLNP.
Graph shows only the
less common species
from previous slide.
Subset of species
on previous graph
Largest plants
of all six
species were
shorter at
GLNP than
other sites.
Why Survey Spring Ephemerals?
• Very susceptible to deer browsing: first fresh green food after winter
• Most species are long-lived perennials that have to get several years old before they have energy to make flowers
• If plants are browsed, they may grow back smaller next year and delay flowering.
• This can lead to extinction of local populations.
Indicator Species for Deer in Indiana
Average Height
(cm)
control fenced
jack-in-the-pulpit 10.6 14.0
sweet cicely - 14.7
white baneberry 10.3 20.5
Height of these species is a good
indicator of deer browsing
intensity in Indiana (Webster and
Parker 1996)
Effect of Deer on Plant Height
After protection
from deer, plants
grow taller.
Taller plants have
greater chance
of reproduction.
Ecological Effects of Deer Overpopulation
• increases plant invasions (Vavra et al 2007, Baiser et al 2008)
• reduces size of eaten and uneaten plants (Heckel et al 2010)
• increases soil compaction (Heckel et al 2010)
• inhibits natural succession and tree regeneration (Côté et al 2004, Rooney & Waller 2003)
• causes shift to alternative community types (Webster et al 2008, Augustine et al 1998, Waller & Alverson 1997)
• reduces habitat for birds, small mammals, other animals(McShea & Rappole 2000)
• reduces food resources for other herbivores (Côté et al 2004)
• reduces litter depth (Heckel et al 2010)
• increases bare soil � erosion and sediment runoff
• increases disease in deer populations (Côté et al 2004)
• makes humans cranky (countless citizens)
• Researcher in IU Biology Department
• Work for IU Research and Teaching Preserve
• Map of Preserve Sites/ Map of Griffy
ownership
• ERAC chair
• Advisor for Deer Task Force
Griffy Woods Deer Density
0
50
100
150
200
250
300
350
Griffy WoodsMoores CreekLilly Dickey Woods
ave
rag
e p
elle
t p
ile
s/h
a
Griffy Woods
MooresCreek
Lilly Dickey
Woods
Approximately 11 times more
pellet piles at Griffy Woods than
at two other nearby Preserves.
Hwy 37
Hwy 46
Hwy 446
45/46
Nashville
3rd
St
Locations of Pellet
Count Surveys
9 – 95
per plot
2 – 5
per plot0 – 6
per plot
* Plot Area = 1664 m2. 1 ha = 10,000 m2.
Effects on Woody Plants
open forest plot fenced forest plot
204 woody plants
21 species
28 woody plants
7 species
Vegetative Structure
0
4
8
12
16
20
20 60 140
# T
ou
che
s b
y V
eg
eta
tio
n
Height (cm)
Unfenced
Fenced
P < 0.0001
P = 0.0003
P = 0.0211
Vegetation is significantly more abundant
inside exclosures at all heights within
browse range. Data collected after 2-3
years of fencing.
Japanese stiltgrass is more
abundant in controls than
exclosures.
Suggests interaction between
deer and invasive species.
0
50
100
150
200
250
300
20 60 140
# T
ou
che
s b
y V
eg
eta
tio
n
Height Above Ground (cm)
Control
Exclosure
Plot invaded by Stiltgrass
0
5
10
15
20
25
30
35
40
ash
paw
paw
mu
ltif
lora
ro
se
spic
ebu
sh
pri
vet
hic
ko
ry
ho
ney
suck
le
sass
afra
s
bee
ch
gra
pe
mu
scle
wo
od
sug
ar m
aple
vib
urn
um
bar
ber
ry
# n
ew
seed
lin
gs
Control
Exclosure
Tree and Shrub Seedlings
tree or shrub species
Outside exclosures:- No native trees are
regenerating
- Dominated by invasives
and unpalatable speciesunpalatable
invasive
native trees
P = 0.0047