Date of Award

Spring 1-1-2014

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Ecology & Evolutionary Biology

First Advisor

William D. Bowman

Second Advisor

Timothy R. Seastedt

Third Advisor

Susan W. Beatty

Fourth Advisor

Brett A. Melbourne

Fifth Advisor

Kendi F. Davies

Abstract

As an environment changes over time, pedogenesis influences the amount of soil nutrients available to plants. The effect of long term soil development on the quantity of plant available nutrients has been well documented. However, what remains poorly understood is how soil development affects fine scale spatial heterogeneity of soil nutrients. The goal of my dissertation research was investigate how spatial heterogeneity of nutrients is affected by long term soil development and to test the effects of nutrient spatial heterogeneity on plant community structure and invasibility by new species. Using a combination of field experiments implemented along a 2 million year old chronosequence located at the Colorado Front Range adjacent to the Rocky Mountains, I addressed these questions in the following data chapters: (1) how does long term soil development influence spatial heterogeneity of soil biogeochemistry, (2) how does nutrient spatial heterogeneity affect plant community structure, and (3) how does nutrient spatial heterogeneity affect plant community invasibility? In the first data chapter, spatially explicit soil samples were obtained at five age sites distributed along the 2 million year old chronosequence to measure biogeochemical properties. These results suggest that long term soil development can increase fine scale spatial heterogeneity of soil nutrients. In the second data chapter, I manipulated the fine scale spatial heterogeneity of soil nutrients and measured its affect on plant community structure by conducting plant surveys throughout the four-year study. I found that increasing nutrient spatial heterogeneity leads to an increase in species richness of natives. In the third data chapter, I conducted a field simulation of plant invasions to investigate community invasibility among differing levels of nutrient spatial heterogeneity treatments. I found that as fine scale spatial heterogeneity of soil nutrients increased, so did the invasibility of the plant community. Overall, the knowledge gained from these studies provided valuable insight into how soil development influences nutrient spatial heterogeneity, and how nutrient spatial heterogeneity can increase plant species richness and community invasibility.

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