Litter diversity effects on microbial decomposer communities and C, N and P dynamics in an Amazonian rainforest.
Hättenschwiler, Stephan*,1, Bracht Jorgensen, Helene1, 1 CEFE-CNRS, Montpellier, France
ABSTRACT- Recent evidence suggests that plant litter diversity can have an important functional role for the process of decomposition, but the mechanisms behind this diversity-function relationship are essentially not understood. In an ongoing experiment we address the question whether changing tree litter diversity influences the composition and activity of microbial decomposer communities and how these changes feedback on carbon and nutrient dynamics during decomposition in an Amazonian rainforest. Litter species diversity and composition is experimentally manipulated in field microcosms using four litter types of abundant tree species, ranging in P concentrations, and C/N ratios between 0.015 to 0.036, and 58 to 37, respectively. Microcosms are inserted 0.15 m deep into the intact forest soil and either allows complete access of all soil organisms up to 10 mm in diameter, or excluding litter-feeding macrofauna larger than 1 mm in diameter. We expect that microbial community composition evaluated by phospholipid fatty acids analysis (PLFA) and DNA characterization using T-RFLP, to be affected by litter diversity. Likewise, preliminary data indicate that rates of litter mass loss, CO2 release, N and P losses, and DOC leaching differ among litter diversity treatments. It seems that litter species composition is more important than species numbers, indicating the possibility to link some of the responses to changing litter diversity to litter species-specific quality traits. We hypothesize that litter species composition of the litter layer influences microbial community composition and the fluxes of C and nutrients during decomposition. Accordingly, losses of particular tree species producing leaf litter of specific traits may change carbon and nutrient cycling in tropical forests. Data collection and analyses are not yet completed, but newest results will be presented at the meeting.
Key words: decomposition, microbial diversity, nutrient cycling, tropical rainforest
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