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Subnivean Access in Forests of Varying Density

Subnivean Access in Forests of Varying Density. Patrick Ellsworth Winter Ecology, Spring 2013 Mountain Research Station. Outline. Intro Methods Results Discussion Conclusion. Introduction. Does forest density affect the density of subnivean access holes?

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Subnivean Access in Forests of Varying Density

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  1. Subnivean Access in Forests of Varying Density Patrick Ellsworth Winter Ecology, Spring 2013 Mountain Research Station

  2. Outline • Intro • Methods • Results • Discussion • Conclusion

  3. 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.

  4. 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

  5. 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

  6. 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

  7. 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

  8. Results • Average tree density • 0.658/m2 • Average hole density • 0.0767/m2 • P-value: 0.91 • R squared: 0.02 • Used regression

  9. Results • Most access holes near debris or trees • Fallen logs common • Only animal signs were squirrel • Lodgepole pines • Densest forests were mostly Aspen forests

  10. 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

  11. Discussion • Data not significant • P-value > 0.05 • R squared well below 1 • Accept null hypothesis • More data needed • Ran only three transects

  12. 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?

  13. 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

  14. 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

  15. 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

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