Flory and Cynthia Huebner Causes of High Deer Populations improved - - PowerPoint PPT Presentation

Effects of overabundant deer in the lower Midwest on native biodiversity and interactions with invasive species Keith Clay, Daniel Johnson, Angie Shelton, Luke Flory and Cynthia Huebner

Causes of High Deer Populations

– improved forage from agriculture – elimination of natural predators – increase in edge habitat – supplemental feeding – warm winters – hunting biased towards bucks

Images from Fairfield County, Conn. Deer Management Alliance. www.deeralliance.com

History of Deer Population in Indiana

• early 1900s: Deer eliminated from Indiana by hunting and

habitat destruction

• 1930s: Deer reintroduced to state
• 1950s: Populations re-established and modern hunting

programs begun

• 1990s - present: Historically high deer populations
• Today: Forest vegetation in Bloomington area more visibly

affected by deer than nearby areas

Johnson, D. J., S. L. Flory, A. Shelton, C. Huebner and K. Clay. 2015. Interactive effects of a non‐native invasive grass Microstegium vimineum and herbivore exclusion on experimental tree regeneration under differing forest management. Journal of Applied Ecology 52: 210-219. Shelton, A.L., J.A. Henning, P. Schultz and K. Clay. 2014. Effects of abundant white-tailed deer on vegetation, animal communities, mycorrhizal fungi, and

• soils. Forest Ecology and Management 320: 39-49.

Deer Exclosure Study at IU’s Griffy Woods

Area of Deer Exclosure Study

Griffy Lake Region

• 15 fenced exclosures

and 15 unfenced controls

• Constructed 2005–2010
• 15 x 15 m each

Fences exclude deer (and probably turkeys) but allow access by most other animals.

• Counted pellet piles in

early spring 2011

• Standard method for

estimating deer densities

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

13 times more pellet piles at Griffy Woods

Questions:

• What are effects of exclosures on

native vegetation?

• On invasive plant species?
• On animals?
• On soil properties?

Vegetative Structure

• Run tape at 3 heights

above ground level

• Count number of times

vegetation contacts tape

20 cm 60 cm 140 cm

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

Plots invaded by Stiltgrass

Effects on Woody Plants

• pen forest plot

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

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

Growth Rate:

• Tree seedlings grow faster

inside exclosures

• All types of woody plants

grow faster in exclosures, especially invasive shrubs

Time Density Facilitation Inhibition ?

Species Richness of Spring Ephemerals

5 10 15 20 25 30 35 40 2009 2010 2011 2012 Mean Species / Plot Control Exclosure

P = 0.046 P = 0.017 P = 0.005 P = 0.2922

Effects on Forest Animals

• Live trapped mice and released in

same location

• More mice inside deer fences.
• Juveniles found much more often in

exclosures (none in controls 2011)

image: http://www.cedarcreek.umn.edu/mammals/cricetidae.html

5 10 15 20 25 30 35 40 45 50 ADULT JUVENILE

Total Mice Captured Control Exclosure

P = 0.0012 with help from Evie Rynkiewicz

Ticks

• Sample ticks with CO2 traps
• Sampling period was very hot

and after peak questing time.

• May be more indicative of

environmental conditions than host availability

0.5 1 1.5 2 2.5 Control Exclosure Mean Ticks / Plot P = 0.018 with help from Evie Rynkiewicz

Dermacentor variabilis

Soil Compaction

• Soil inside exclosures is

significantly less compacted than soil in control plots after only 2 years of fencing!

Treatment effect P < 0.0001 Habitat effect P < 0.0001

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 lowland ridge slope soil compaction (kg/cm2) habitat controls exclosures with Jeremiah Henning & Peggy Schultz

Mycorrhizal Diversity

No significant effect of treatment. Some effect of plot and depth.

With Jeremiah Henning and Peggy Schultz

0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0-5 5-15 AMF Species Richness Soil Depth (cm) control exclosure 5 10 15 20 25 30 35 40 0-5 cm 5 - 15 cm Total Spore Abundance Soil Depth control exclosure

Conclusions:

• Exclosures resulted in increases in spring ephemerals,

native tree seedlings and invasive shrubs

• Increased growth rate of woody plants
• Increased abundance of mice and ticks but no effects on

salamanders or earthworms

• Decreased soil compaction and trend for increased

mycorrhizal diversity and abundance

Microstegium vimineum, an invasive annual grass How do abundant deer and invasive species interact to affect forest regeneration?

1m 1m 1-2m

Herbicide sprayed to remove Microstegium (pre-emergent sprayed year 2)

with Microstegium without Microstegium

Blocks with two paired plots (x10 per site) Six sites – three with no timber harvest for > 20 yrs, three with timber harvest w/i 3 yrs

1m 1m 1-2m

with Microstegium without Microstegium

Half of each plot fenced to exclude deer and other vertebrate herbivores

1m 1m 1-2m

with Microstegium without Microstegium

20 tree seedlings of five species planted per plot

Followed growth and survival (Acer saccharum, Prunus serotina, Quercus alba, Q. rubra and Q. shumardii) for two years

Potential Outcomes:

Associational Resistance Predator Refuge Interspecific Competition

Fence No fence Mv no Mv

Factor P Removal <0.0001 Exclosure <0.0013 Species <0.027

Tree Seedling Survival

Factor P Removal <0.0001 Management <0.0013 Species <0.0001 R x M <0.032

Seedling Biomass

Conclusions:

• Removal of Microstegium improved seedling performance
• Excluding herbivores also improved seedling performance

but less than removal

• No removal x exclosure interactions
• Management history affected biomass, and interacted

with removal

• Variation among species. Removal especially good for oaks

Acknowledgements

Collaborators

• Peggy Schultz
• Jeremiah Henning
• Rich Phillips
• Burney Fischer (SPEA)

Assistance

• Michael Chitwood and IURTP staff
• Evie Rynkiewicz and Clay Lab Group
• ISCC: Thomas Jackson & Xuefu Wang
• Curtis Conrad, Katherine Zaiger,

Nathan Wells, Julia Ferguson, Rachel Maranto, Elizabeth Ridens, Barrett Goodale, Sean Fox, Eric Menigat, Piotr Madej, Hannah Milano, Alicia Cooley, Environmental Biology students

Funding

• USDA Forest Service,

Northern Research Station

• Indiana Hardwood

Ecosystem Experiment

• Indiana Academy of Science