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The Affects of Elevation on Tree Growth along Niwot Ridge

The Affects of Elevation on Tree Growth along Niwot Ridge. Steven Griffin Winter Ecology, Spring 2013 Mountain Research Station , University of Colorado, Boulder . Question:. How does elevation affect the age structure of subalpine forests along Niwot Ridge? . Hypotheses .

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The Affects of Elevation on Tree Growth along Niwot Ridge

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  1. The Affects of Elevation on Tree Growth along Niwot Ridge Steven Griffin Winter Ecology, Spring 2013 Mountain Research Station, University of Colorado, Boulder

  2. Question: • How does elevation affect the age structure of subalpine forests along Niwot Ridge?

  3. Hypotheses • H1: The subalpine forest of Niwot Ridge vary in age structure along an elevation gradient due to biotic and abiotic environmental conditions. • H0: The age structure of the subalpine forest on Niwot Ridge shows no variation along an elevation gradient.

  4. Experiment Design • Sample 50m transects of subalpine forest at three sites between Niwot Ridge tree line and the CU MRS to determine approximate age structure • Data Collection: • Intended Method: Incremental Tree Bores • Performed Method: Diameter at Breast Height

  5. Key Assumptions • By Changing my research method from tree cores to DBH, I am unable to make claims about the age structure of the subalpine forests. • DBH is a poor proxy for tree age, especially near timberline where growth is stunted by exposure • The DBH data collected provides an estimate of the size structure of Niwot Ridge’s subalpine forest

  6. Statistical Analysis • Tree data was classified into three diameter ranges for statistical testing • The Chi Square test was used to compare the normalized distribution of trees against the size structure observed at each site • No statistical difference was found in the tree sizes

  7. Results • Treeline X-squared = 1.2915, df = 2, p-value = 0.5243 • Ribbon X-squared = 1.7249, df = 2, p-value = 0.4221 •  Mountain Research Lab X-squared = 4.7538, df = 2, p-value = 0.09284

  8. Conclusion • Fail to Reject Null Hypothesis • Given the small sample size and limited scope of the sampling method, significant results are unlikely. • Although the numbers don’t support my hypothesis, I suspect that there is are significant differences between tree age, distribution and size by elevation

  9. Discussion • Much more research is required • GIS & Satellite imagery can help map forest geography • Tree size is not an acceptable age proxy at elevation

  10. Take-Home Points • Field work is HARD-Pick sites WISELY • Its important to scrutinize data collection methods and results to ensure appropriate claims are made and supported • Have a contingency plan • Bring hand warmers

  11. References: "The Subalpine Ecosystem". National Park Service. Archived from the original on 2007-08-09. Retrieved 2013-2-10. Jørgensen, S.E. (2009). Ecosystem Ecology. Academic Press. ISBN978-0-444-53466-8. "Alpine Tundra Ecosystem". Rocky Mountain National Park. National Park Service. Retrieved 2011-05-13 Peet, R.K. (2000). "Forests and Meadows of the Rocky Mountains". In Barbour, M.G.; Billings, M.D. (2nd ed.). Cambridge University Press. ISBN978-0-521-55986-7. http://en.wikipedia.org/wiki/Pearson's_chi-squared_test

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