Date of Award

2019

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Natural Resources

First Advisor

Aimee T. Classen

Abstract

Living (biotic) and non-living (abiotic) factors drive the function of ecosystems across a variety of scales from the root-soil interface to the watershed. Biotic and abiotic global change pressures such as increasing temperature and invasive species are shifting how ecosystems function. Thus, exploring and understanding how these factors shape function across the landscape is an important research area. For example, climate change both directly and indirectly affects soil microbial functions – such as carbon mineralization and nitrogen transformations – through increasing activity under warming and altering inputs to the soil through species composition changes. Mountains provide a useful tool for studying relationships among biotic and abiotic factors because climate and species diversity shift along gradients. Here, I measured carbon and nitrogen soil processes as well as microbial extracellular enzyme activity along an elevational gradient to explore how changes in climate, edaphic properties, and biotic composition affects ecosystem function. As expected, climate and species composition varied in predictable ways along the gradient – actual evapotranspiration declined, and conifer dominance increased. Soil functions also shifted along the gradient. Potential carbon mineralization increased with elevation and with conifer dominance. Potential nitrogen mineralization rates increased with elevation and with conifer dominance. Surprisingly, there were few predictors for potential soil nitrification, which increased only with soil functional diversity. While temperature and moisture availability drive ecosystem function at broad scales and biotic factors typically drive function at the regional scale, we saw that function of soils at the mountain watershed scale was best explained by a combination of both abiotic and biotic factors.

Language

en

Number of Pages

57 p.

Available for download on Saturday, June 12, 2021

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