Friday, August 10, 2007

PS 72-127: Effects of gaps on soil moisture and microbial biomass

Jenna Halsey, Indiana University

Microbial communities are affected by several factors including vegetation, nutrient content, and soil moisture. Soil moisture may be one of the more important factors that determine the microbial community.  This study was conducted to further investigate the relationship between soil moisture and microbial biomass. Furthermore, this study examines the complexity of soil moisture in a recently logged forest gap and how the microbial community response to the variable soil moisture. Forest gaps typically have increased solar radiation and increased wind, therefore typically lower soil moisture. In this study two transects reaching a total of 100 meters into the forest were evaluated soil moisture and microbial biomass in a total of 16 plots.  Preliminary results show that there was a consistent pattern in soil moisture in each transect as the distance from the gap into the forest increases.  Results also show a significant correlation between microbial biomass and soil moisture.  Generally, as soil moisture increases, microbial biomass also increases. Due to compaction of clay soil in the gap, soil moisture was higher in plots in gap than plots located 100 meters deep into the forest.  However, the compaction and the lack of vegetation in the gap limited the microbial community more than the higher soil moisture, and thus resulted in the lowest level of microbial biomass. Therefore, in general, soil moisture determines the activity of microbes; however, it is not the only factor. Other factors such as vegetation and compaction also play important factors of microbe activity. These factors are especially important in gaps and along forest edges. Studying underground environments in gaps and edges is becoming increasingly important as human pressure on forests, such as logging and building roads increases.

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