What are the effects of Exposure on the treeline ecosystem?

1. What are the effects of Exposure on the treeline ecosystem? Brian Schleckser Winter Ecology spring ’09 Mountain Research Station, University of Colorado, Boulder

2. Established Literature and How it Guided me • “Facilitation and Competition on Gradients in Alpine Plant Communities” Choler, Michalet and Callaway -shed light on gradients, and competition • “Influences of Wind and Snow on Northern Tree-Line at Manitoba, Canada” SCOTT, HANSELL and ERICKSON - discussed how wind and snowdrifts effect an ecosystem • “Predicting Vegetation Types at Treeline Using Topography and Biophysical Disturbance Variables” Brown - was a highly advanced study, but in detail explained the variables of choice, possible pitfalls, as well as vegetation types along the gradient

3. Thought Progression How does the treeline ecotone behave with regard to exposure? What variables can I study in a timely manner; but will be properly representative? Can my predicted results possibly occur based on past casual observation? Can I even make it to treeline with daylight when I start at noon???

4. Experimental Design • Study 3 zones: Exposed Semi-Exposed Protected • Gauge the sample’s: overall growth grouping strategy observable characteristics • Set sample goals large enough to be statistically robust, but appropriate for time.

5. Methods Sample five trees in three zones: -Full exposure -Partial exposure -Full protection Variables of Interest: -Height -DBH -Density -Flagging -Grouping shape Each variable measured or characterized the tree groupings in an important way. Exposed Protected

6. Height Circumference (DBH) Circumference of primary tree in grouping. Measured at Chest level Measuring height (meters) of primary tree in grouping. Important for assessing max growth.

7. Density (Grouping) • Bunch Cluster Krumholz • Group w/ neighbors Consolidated Forest

8. Flagging Density • Trees within 5 meter reach from primary tree 5m

9. The Data: obvious and curious

10. Relating to Height.. Exposed Semi-Exposed Protected

11. A Bit of a Curveball… Exposed Semi-Exposed Protected

12. Distribution of Tree Sizes, by Zone Exposed Semi- Exposed Protected

13. Newly Understood Relationship • Increased Specimen Density goes hand in hand with Increased Exposure.

14. Example of lower exposure, lower density Example of high exposure, high density

15. Implications/Conclusions • Does exposure affect treeline mechanics? YES • In what ways? • Height limitation • Circumference limitation • Density • Grouping strategy

16. Future research? • Presence and impact of scrub willow in semi-exposed zone -what allows it to grow? • Summer repetition of study -include wind scouring, re-tally density counts, lingering snowpack

17. Works Cited • Predicting Vegetation Types at Treeline Using Topography and Biophysical Disturbance Variables Author(s): Daniel G. Brown Source: Journal of Vegetation Science, Vol. 5, No. 5, Applications of Remote Sensing and Geographic Information Systems in Vegetation Science (Nov., 1994), pp. 641-656 Published by: Opulus Press Stable URL: http://www.jstor.org/stable/3235880 Accessed: 01/03/2009 12:25 • Influences of Wind and Snow on Northern Tree-Line Environments at Churchill, Manitoba, Canada, PETER A. SCOTT,’ ROGER I.C. HANSELL’ and WILLIAM R. ERICKSON*I (Received 26 August 1992; accepted in revised form 19 January 1993 http://pubs.aina.ucalgary.ca/arctic/Arctic46-4-316.pdf • Facilitation and Competition on Gradients in Alpine Plant Communities Author(s): Philippe Choler, Richard Michalet, Ragan M. Callaway Source: Ecology, Vol. 82, No. 12 (Dec., 2001), pp. 3295-3308 Published by: Ecological Society of America Stable URL: http://www.jstor.org/stable/2680153 Accessed: 01/03/2009 12:35 • Special thanks to Phil McDonald for field assistance

18. Protected zone

19. Semi exposed zone

20. Tracks from the exposed zone

21. Research Assistant