Griffy Lake Nature Preserve Vegetation Monitoring Update - Summer 2017
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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 Populations
Primary causes of deer increase
– improved forage from agriculture & towns 12
•
•
– elimination of natural predators 10
•
••
•
••
•
•
Deer per square km
• • •
– increase in edge habitat preferred by deer 8
••• •
• ••• •
• •
•
6 ••
• •
– supplemental feeding 4
••
••• ••
•
– warmer winters 2
– hunters (and regulations) often favor bucks 0
1960 1965 1970 1975 1980 1985 1990 1995 2000
– Reduction in number of hunters Deer populations in
Wisconsin from 1960
to 2000
Images from Fairfield County, Conn. Deer Management Alliance. www.deeralliance.com
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
Large-flowered Trillium, Trillium grandiflorum
Fraction in Each Life Stage
Population Growth Rate
increasing
population
Reproductive Value
declining
population
Average % Herbivory
% Herbivory
Knight, Caswell, and Kalisz. 2009. Forest Ecology and Management 257: 1095.
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
Subset of species have fewer
on previous graph flowering
plants at GLNP.
Graph shows only the
less common species
from previous slide.
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
Height of these species is a good
indicator of deer browsing
intensity in Indiana (Webster and
Parker 1996)
Average Height
(cm)
control fenced
jack-in-the-pulpit 10.6 14.0
sweet cicely - 14.7
white baneberry 10.3 20.5Effect 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
Hwy 37 Locations of Pellet
Count Surveys
350
9 – 95
per plot
300 Nashville
average pellet piles/ha
250 45/46
200 Hwy 46
3rd
St
150
Hwy 446
100
2–5 0–6
50 per plot per plot
0
Griffy Woods
Griffy Moores
Lilly
Creek
Moores Dickey
Lilly Woods
Woods Creek Dickey Approximately 11 times more
Woods
pellet piles at Griffy Woods than
* Plot Area = 1664 m2. 1 ha = 10,000 m2.
at two other nearby Preserves.Effects on Woody Plants
open forest plot fenced forest plot
28 woody plants 204 woody plants
7 species 21 speciesVegetative Structure
20
P < 0.0001 Unfenced
Japanese stiltgrass is more
# Touches by Vegetation
16 Fenced abundant in controls than
exclosures.
12
P = 0.0003 Suggests interaction between
8 deer and invasive species.
P = 0.0211
4
Plot invaded by Stiltgrass
300
Control
# Touches by Vegetation
0 250
20 60 140 Exclosure
Height (cm) 200
150
Vegetation is significantly more abundant 100
inside exclosures at all heights within 50
browse range. Data collected after 2-3 0
years of fencing. 20 60 140
Height Above Ground (cm)Tree and Shrub Seedlings
40
P = 0.0047 Outside exclosures: Control
35
- No native trees are
Exclosure
30 regenerating
25 - Dominated by invasives
# new seedlings
unpalatable
and unpalatable species
20 invasive
15
native trees
10
5
0
pawpaw
viburnum
multiflora rose
honeysuckle
spicebush
beech
barberry
musclewood
sassafras
privet
grape
sugar maple
ash
hickory
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