PARENT SESSION
Poster Session #61: Soil Ecology II.
Thursday, August 8. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC

Tree species effects on soil microbial communities and soil properties.

Chatterjee, Keya^*,1, Lawrence, Deborah¹, Mills, Aaron¹, ¹ University of Virginia, Charlottesville, Virginia

ABSTRACT- We tested the hypothesis that tree species are associated with different soil microbial communities and soil properties due to variation in leaf litter. Monospecific litterbags from three tropical tree species (Pentaclethra macroloba, Casearia arboreal, and Socratea exorrhiza) were incubated underneath conspecific trees for thirty days. Soil samples were taken at the litter-soil interface, directly underneath litterbags. Soil nitrate, ammonium, phosphorous, moisture and bacterial abundance were measured. We also measured soil respiration and leaf litter decomposition as microbially-mediated ecosystem functions that might respond to intraspecific differences in leaf litter. Decomposition, respiration and soil phosphorous were significantly different among the three tree species (two-way repeated measures ANOVAs, P <0.05). However, soil nitrate, ammonium, moisture, and bacterial abundance did not differ by species. Community level physiological profiling (CLPP) and randomly amplified polymorphic DNA (RAPD) analyses on soil samples were used to investigate variation in the soil microbial communities. CLPP analysis, which analyzes the fast-growing, culturable bacterial community, yielded significant differences among tree species (CVA, canonical variate analysis, p<0.05). Amplification of DNA with RAPD primers yielded DNA fingerprints, which contain genetic information about the full microbial communities, including slower growing microbes and fungi. The molecular data showed that the entire soil microbial communities could not be grouped by the tree species under which they were sampled. Either the entire soil microbial community does not differ with respect to litter inputs, or it was not able to respond to litter differences within the 30-day incubation period. In contrast, the culturable subsets of the communities analyzed by the CLPP were different under each tree species. Microbial community structure, as measured by CLPP, was correlated with soil phosphorous, using Mantel analysis. These results suggest that litter input is a direct or indirect influence on both soil phosphorous levels and the structure of the culturable, fast-growing soil microbial community.

KEY WORDS: Tree species, RAPD, CLPP, Soil Microbial Community