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

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

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???

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.

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

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

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

Density Trees within 5 meter reach from primary tree 5m Flagging

The Data: obvious and curious

Relating to Height.. Exposed Semi-Exposed Protected

A Bit of a Curveball… Exposed Semi-Exposed Protected

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

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

Example of lower exposure, lower density Example of high exposure, high density

Implications/Conclusions Does exposure affect treeline mechanics? YES In what ways? 1.Height limitation 2.Circumference limitation 3.Density 4.Grouping strategy

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

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 Published by: Opulus Press Stable URL: Accessed: 01/03/ :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 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 Published by: Ecological Society of America Stable URL: Accessed: 01/03/ :35 Special thanks to Phil McDonald for field assistance

Protected zone

Semi exposed zone

Tracks from the exposed zone

Research Assistant