Griffy Lake Nature Preserve Vegetation Monitoring Update Summer - - PowerPoint PPT Presentation

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 – 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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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. Fraction in Each Life Stage Reproductive Value

% Herbivory Large-flowered Trillium, Trillium grandiflorum

Average % Herbivory

Population Growth Rate

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

• n previous graph

Largest plants

• f all six

species were shorter at GLNP than

• ther 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

• f 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
• wnership
• ERAC chair
• Advisor for Deer Task Force

Griffy Woods Deer Density

50 100 150 200 250 300 350 Griffy Woods Moores Creek Lilly Dickey Woods

average pellet piles/ha

Griffy Woods Moores Creek 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 plot 0 – 6 per plot

* Plot Area = 1664 m2. 1 ha = 10,000 m2.

Effects on Woody Plants

• pen forest plot

fenced forest plot 204 woody plants 21 species 28 woody plants 7 species

Vegetative Structure

4 8 12 16 20 20 60 140 # Touches by Vegetation 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.

50 100 150 200 250 300 20 60 140 # Touches by Vegetation Height Above Ground (cm) Control Exclosure

Plot invaded by Stiltgrass

5 10 15 20 25 30 35 40

ash pawpaw multiflora rose spicebush privet hickory honeysuckle sassafras beech grape musclewood sugar maple viburnum barberry

# new seedlings Control Exclosure

Tree and Shrub Seedlings

tree or shrub species

Outside exclosures:

• No native trees are

regenerating

• Dominated by invasives

and unpalatable species

unpalatable invasive native trees P = 0.0047