Undergraduate Honors Theses

Thesis Defended

Spring 2012

Document Type

Thesis

Department

Ecology and Evolutionary Biology

First Advisor

Diana Nemergut

Abstract

Environmental change in the form of increased nitrogen (N) deposition is occurring at high elevation sites across the Rockies at sites such as Niwot Ridge. It is unknown if, or how, this N input affects soil microbes, specifically those in talus sites where microbes are ecologically significant. Microbes are abundant and ubiquitous across the planet, especially in soils. Understanding whether nutrient inputs are affecting the growth strategies of talus microbes is important, as demonstrated by (i) the influence of microbes on biogeochemical cycling of nutrients, (ii) the impact of microbes on plant production through symbioses and nutrient pulses caused by microbial turnover and (iii) the role of microbes as “filters” of groundwater to downhill systems, such as watersheds with economic relevance. Our results indicate that nutrient inputs can cause shifts in the growth strategies of microbes, and this could influence the kinetics of microbial growth and the subsequent downhill transport of nutrients and materials from these sites. An environment dominated by copiotrophs (microbes dependent on high nutrient levels in soil) as was found in N amendments, could lead to a rapid depletion of resources, which could negatively influence the growth and development (succession) of other microbes at talus sites as well as potentially influencing the transport to downhill systems highlighted in the Landscape Continuum Model (Seastedt et al., 2004 BioSci, 54(2):111). Future experiments focusing on how various types of N (NH4+ vs. NO3-) impact microbial communities, studies measuring the growth and development of other ecologically significant talus soil microbes, as well as incubation experiments with more replicates will all be valuable to better understand how talus soil microbial communities will respond to ongoing environmental changes such as N input from various sources.

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