Undergraduate Honors Theses

Thesis Defended

Spring 2017

Document Type

Thesis

Type of Thesis

Departmental Honors

Department

Ecology and Evolutionary Biology

First Advisor

Timothy Seastedt

Second Advisor

Pieter Johnson

Third Advisor

Daniel Doak

Abstract

Considering their sensitivity to change, alpine plant communities are useful systems in studying the indirect effects of anthropogenic activities on the environment. Climate change is increasing variability of temperature and precipitation, shifting wind patterns, and altering nutrient composition and cycling (especially deposition of nitrogen (N) and phosphorus (P)). Therefore, it is becoming increasingly important to understand how climate change impacts vegetation. This study continues efforts of a Long Term Ecological Research program in the Colorado Rocky Mountains by surveying plant community composition in response to nutrient additions (N and P) and changing moisture regimes mimicking potential climate shifts. In addition to updating such surveys, species-specific responses to nutrients and functional differences between treatments were considered in order to expand our understanding of how alpine ecosystems function. Over time, there has been a shift towards species that capitalize on added N and P rather than deposition of one or the other. This indicates that P deposition may neutralize the effects of N deposition, favoring generalist species. Additionally, alpine vegetation appears to be relatively resistant to changes in moisture caused by snowmelt. A longer growing season, as evidenced by cover increases in areas with earlier snowmelt, may increase primary productivity in the alpine tundra. Neither N nor P additions alone related to any single functional trait, but both leaf area (typically smaller in stressful environments) and chlorophyll content (indicating photosynthetic rates) appear to increase in the presence of N and P. Overall, these vegetative communities remain resistant to certain climatic alterations and may even mitigate the impacts of shifts such as N deposition and changing precipitation patterns.

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