PARENT SESSION
Poster Session 30: Soil Ecology.

Wednesday, August 4 Presentations from 5:00 PM to 6:30 PM, Exhibit Hall A 1.

Root influences on microbial community composition in forest soils.

Brant, Justin^*,1, Myrold, David ¹, Sulzman, Elizabeth¹, ¹ Oregon State University, Corvallis

ABSTRACT- We assessed microbial community composition as a function of altered above- and below-ground carbon inputs to soil in forest ecosystems of Oregon, Pennsylvania, and Hungary as part of a larger Detritus Input and Removal Treatment (DIRT) experiment. DIRT plots, which include root trenching, aboveground litter exclusion, and doubling of litter inputs, have been established in four forested ecosystems in the US and Europe that vary with respect to dominant tree species, C background, and N deposition rate. These treatments provide a unique opportunity to study the feedbacks and processes controlling soil organic matter (SOM) transformations in soil. This study used phospholipid fatty-acid (PLFA) analysis to examine changes in the soil microbial community composition in the mineral soil (0-10cm) as a result of the DIRT treatments. At all sites the PLFA profiles from the plots without roots were significantly different than all other treatments, even after accounting for the loss of mycorrhizal fungi after root trenching. PLFA analysis showed that the rootless plots generally had larger quantities of actinomycete biomarkers and lower amounts of fungal biomarkers. In addition, the ratio of cyclopropyl/monoenoic precursors was larger in the rootless plots, suggesting that the microbial community is more carbon limited without root inputs to soil. These data provide direct evidence that root C inputs control microbial community composition in forest soils.

Key words: root trenching, forest soils, PLFAs, soil microbes