Assessing effects of forest management on microbial community structure in a central European beech forest

This study aimed to characterize the effects of forest management on soil microbial community structure and function in a European beech (Fagus sylvatica L.) forest. We used community level physiological profiles, phospholipid fatty acid (PLFA) profiles, microbial biomass, culturing, and respiration approaches to quantify soil microbial community structure and activity at two sites in a naturally regenerated beech forest subjected to intermediate and heavy thinning and control (unthinned) in southern Germany. PLFA showed that the northeast-facing (NE) site contained significantly greater bacterial and fungal biomass than the southwest-facing (SW) site. Heavy thinning (tree basal area reduction from 27 to 10 m(2)center dot ha(-1)) significantly reduced microbial biomass in the NE site, measured using fumigation-extraction, but both bacterial and fungal biomass increased with thinning on the SW site. Soil microbial activity was significantly higher in the control plots of the NE compared with the SW site and was significantly reduced by heavy thinning, again only on the NE site. Our findings are consistent with our initial hypotheses that contrasting N uptake by beech on these two sites after thinning may relate to differences in the soil microbial biomass, population structure and function on the two sites.