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The effects of temperature and moisture on alpine microbial processes across a gradient of soil development




Osborne, Brooke Bossert, author
Baron, Jill, advisor
Cotrufo, Francesca, committee member
von Fischer, Joseph, committee member
Wallenstein, Matthew, committee member

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Alpine ecosystems are being transformed by global change. Climate change and atmospheric nitrogen deposition are exposing soils to novel temperature regimes, melting alpine glaciers, altering precipitation patterns, and directly introducing bioavailable nutrients. Because microbial communities are important drivers of nutrient cycling and ecosystem function in the alpine, and because temperature, moisture and nutrient availability are primary controls of microbial abundance and activity, it is likely that microbial linkages exist between global change and ecosystem-level consequences of global change in alpine regions. Deglaciation in high-elevation regions incrementally exposes soils to primary succession, which creates a wide range of soil environments. Yet, little is understood about these unusual environments' respective microbial communities or how they respond to the influence of global change. This research studied the effects of changing temperature and moisture controls on microbial carbon and nitrate (NO3-) processing in a range of alpine soils. The soils were collected from a watershed that exhibits characteristics of nitrogen saturation as a result of atmospheric nitrogen deposition. Glacial outwash, talus, and meadow soils were characterized by physical, chemical and biological properties. Soil temperature regimes were highly variable in the field, with some soils experiencing great diurnal fluctuations, while others remained consistently cold. The response of microbial community size, structure, activity and behavior to warming and changing soil moisture was addressed with laboratory incubations. Microbial community size and nutrient availability increased with increasing soil organic carbon. Microbial activity in all soils increased with temperature and moisture, as evidenced by total and microbial biomass-specific rates of respiration. However changes in microbial biomass carbon and parameters of community structure and behavior differed among the soils. This indicated that the soils responded using individual mechanisms to changing microclimate conditions during the incubations. The net production of NO3- occurred in all soils under all experimental conditions, however the rate at which NO3- was produced responded differently to temperature and moisture treatments. This suggests that global change may affect biological controls of NO3- availability in the alpine.


2012 Summer.
Includes bibliographical references.

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alpine soils
microbial communities
global change
atmospheric deposition


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