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