Subnivean Access in Forests of Varying DensityPatrick EllsworthWinter Ecology, Spring 2013Mountain Research Station

Outline

•Intro•Methods•Results •Discussion•Conclusion

Introduction

•Does forest density affect the density of subnivean access holes?

•H1: There will be a greater density of subnivean access holes in a denser forest.

•H0: Forest density has no affect on the density of subnivean access holes or there is a negative correlation.

Introduction cont.

•Small mammals rely on subnivean zone to survive winter▫Snow insulates ground (0°C)

Marchand, 1996

•Trees radiate longwave radiation▫Warms ground, melts snow▫Creates natural crevasses

Hargis and McCullough, 1984

Introduction cont.

•Purpose: to explore how forests affect the distribution of the subnivean▫And the animals that rely on it

•Subnivean not well understood▫Offer more insight

•Discover which animals use which parts of the subnivean

Methods• Point quarter method

▫ Better for measuring higher densities

• Forests near MRS

• Three 50m transects▫ Different forest densities▫ Four random points

At least 10m apart

• Measure trees and holes

Methods cont.• D=1m/mean tree-to-point

distance2

▫ For trees and holes

• Can’t totally randomize▫ Need some data▫ Danger of bias

• Analyze with regression

Results • Average tree density

▫ 0.658/m2

• Average hole density▫ 0.0767/m2

• P-value: 0.91

• R squared: 0.02▫ Used regression

Results • Most access holes near

debris or trees▫ Fallen logs common

• Only animal signs were squirrel ▫ Lodgepole pines

• Densest forests were mostly Aspen forests

Sources of Error

•Most quadrants had no access holes▫Used a correction factor

Provide more accurate densities •Data not totally random

▫Needed some holes for data•Point quarter method time dependent

▫Snowfall between days could affect access holes

Discussion

•Data not significant ▫P-value > 0.05▫R squared well below 1▫Accept null hypothesis

•More data needed▫Ran only three transects

Discussion cont.

•Distribution of holes likely affected by distribution of animals▫Many species require certain types of forest

Hargis and McCullough, 1984

•Other factors likely▫Food preference ▫Water availability ▫Proximity to humans

•Is the distribution of small mammals affected by forest densities and types?

Conclusion

•Trees provide excellent spaces for subnivean access

•Signs of animals prominent in Lodgepole pine forests

•Amount of subnivean access holes more dependent on local animals than on forests

•More studies needed ▫Examine correlation between forests and

animals that use the subnivean

Acknowledgments

•Tim Kittel for lending me the necessary equipment

•CU Mountain Research Station for allowing me to research on their property

•MRS staff for their hospitality and help

Works Cited• Hargis, Christina D., and McCullough, Dale R. “Winter Diet

and Habitat Selection of Marten in Yosemite National Park.” The Journal of Wildlife Management 48.1 (1984): 140-146.

• Marchand, Peter J. Life in the Cold: An Introduction to Winter Ecology. 3rd ed. Hanover: University Press of New England, 1996.

• Warde, William, and Petranka, James W. “A Correction Factor Table for Mission Point-Center Quarter Data.” Ecology 62.2 (1981): 491-494.

• http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/BIO%20206/206%20Laboratory/Point-Quarter%20Method/point-quarter%20instructions.htm