Characterization of different compacted wheel tracks by means of microbial properties in a forested site

Forest operations can have severe impacts on the soil structure and the soil microbial communities. Foto: Beat Frey (WSL).

Soil compaction caused by passage of logging machinery reduces the soil air capacity. Changed abiotic factors might induce a change in the soil microbial community and favour organisms capable of tolerating anoxic conditions. Aerated soils that are shifted to anoxia can produce the greenhouse gases methane and N2O. For example, methanogenesis is the dominating electron-accepting process during the anaerobic oxidation of organic matter. Thus, the prolonged compaction of forest soils might enhance greenhouse gas-producing microbial activities and lead to a gradual, quantitative shift in the occurrence and activities of associated prokaryotes. This shift might be of general importance, because heavy machinery is increasingly used for logging activities.

Aims

The goals of this study were to resolve differences between soil microbial communities obtained from wheel-tracks (i.e. compacted) and their adjacent undisturbed sites, and to evaluate differences in potential anaerobic microbial activities of these contrasting soils. Special emphasis will be given to organisms which are responsible for the production of greenhouse gases (nitrous oxide, methane) after soil compaction.

Methods

• Characterization of microbial communities with molecular tools (T-RFLP fingerprinting, DGGE, cloning and sequencing)
• Quantification of functional genes (quantitative PCR)
• Soil Microbial Measurements (C-mineralization, respiration, microbial biomass C)

Projectpartners

Peter Lüscher and Stephane Sciacca (both WSL)