The Effects of Slope on Tree Well Shape and Sub-Nivean Access Points

Paige PruisnerEBIO 4100 Winter Ecology, Spring 2013

Mountain Research StationUniversity of Colorado Boulder

How Does Slope Angle Effect Tree Well Shape and Sub-Nivean Burrowing?

Snow

Trees Mammals

Chan

ge Sn

ow

Pack

InsulationBurrow

Ups

lope

Ra

dius

Left Radius Right Radius

Dow

nslo

pe

Radi

us

Tree Well

Upslope Quadrant

Right QuadrantLeft Quadrant

Downslope Quadrant

Upslope HalfDownslope Half

Field Methods

Tree

Data Analysis•

X

X

Y

Y

where a, b, c, d, are any number

8 10 12 14 16 18 20 22 24 261.0

1.2

1.4

1.6

1.8

2.0

2.2

f(x) = 0.00590075088506565 x + 1.27292028644723R² = 0.012967705688527

Circularity Index vs. Slope Angle

Circularity Index

Linear (Circularity Index)

Downslope

Side

Upslope

Slope Angle (degrees)

Circ

ular

ity In

dex

1.321.41

1.33

Average Circularity Index

Downslope Side Upslope

Circ

ular

ity In

dex

P = 0.907

19.4015.75 14

Average Slope Angle

Downslope Side Upslope

Slop

e An

gle

(Deg

rees

)

P=0.365

Discussion

• Circularity vs. Slope Angle– Continuity– Steeper slopes– Wind

• Burrowing preference– No advantage

Other Observations

Conclusions

• Insignificant relationship between slope angle and tree well circularity

• Insignificant relationship between tree well circularity and access point location

• Insignificant relationship between slope angle and access point location

• Further research into steeper slopes, wind and forest density effects, hole shape, pathways between trees

Acknowledgements: Dr. Tim Kittel and Derek Sweeney for equipment and advising

BibliographyDecker, K. L. M., D. Wang, C. Waite, T. Scherbatskoy (2003), Snow Removal and

Ambient Air Temperature Effects on Forest Soil Temperatures in Northern Vermont, Soil Sci. Soc. Am. J., 2003 67: 1234–1242, doiL 10.2136/sssaj2003.1234.

Hardy, J. P., R. E. Davis, R. Jordan, X. Li, C. Woodcock, W. Ni, and J. C. McKenzie (1997), Snow ablation modeling at the stand scale in a boreal jack pine forest, J. Geophys. Res., 102(D24),29397–29405, doi:10.1029/96JD03096.

Merritt, J. F., Lima, M. and Bozinovic, F. (2001), Seasonal regulation in fluctuating small mammal populations: feedback structure and climate. Oikos, 94: 505–514. doi: 10.1034/j.1600-0706.2001.940312.x

Sturm, M., "Snow distribution and heat flow in the taiga" (1992). Aspen Bibliography. Paper 2488.http://digitalcommons.usu.edu/aspen_bib/2488

Appendix

6 6

5

Frequency

Downslope Side Upslope

Freq

uenc

y of

Occ

uren

ce

Bibliography

How Does Slope Angle Effect Tree Well Shape and Sub-Nivean Burrowing?

• Snow– Insulates (Decker et al., 2003)

– Non-uniform distribution (Sturm, 1992)

• Trees– Modify snow pack (Hardy et al., 1997)

• Mammals– Shelter (Merritt, 2001)

How Does Slope Angle Effect Tree Well Shape and Sub-Nivean Burrowing?

Snow

Trees Mammals

Chan

ge Sn

ow

Pack Co

vers

InsulationBurrow

Shelter, Food

Reproduction/Distribution