Abstract

Although biogeochemical processes are often studied at the watershed scale, watershed scale microbial distributions are poorly understood. Global scale studies have shown that edaphic
factors, such as pH and carbon to nitrogen ratios (C:N), can drive microbial community diversity, composition, and structure, but it is not clear if these edaphic factors are also influential at smaller
scales. In this thesis, we examined the distributions of Bacteria and Archaea and how they related to slope aspect, vegetation type, and edaphic factors within two regions of the Gordon Gulch
watershed of the Boulder Creek Critical Zone observatory near Boulder, CO. We found that bacterial diversity across the landscape was positively correlated with pH and negatively correlated with soil C:N. Microbial distributions varied depending on slope aspect, vegetation type, and between the upper and lower regions of the watershed. These differences in community composition were driven by edaphic factors, namely pH and C:N. Though rare, the relative abundance of Archaea was inversely correlated with C:N, and tended to be absent from communities at C:N ratios higher than 30. Similar to what has been observed globally, microbial distributions at the watershed scale are predictable by edaphic factors, thereby providing clues to the ecology of uncultivated organisms. Where organisms’ ecology is known, this study also demonstrated the potential of using microbial distributions to identify biogeochemical hotspots.

Citation

Eilers, Kathryn. (2011): Landscape-Scale Variation in Soil Microbial Communities Across a Forested Watershed. Thesis, University of Colorado, Master of Arts, Department of Ecology and Evolutionary Biology.

This Paper/Book acknowledges NSF CZO grant support.