Controls on nitrogen rentention and loss in tropical forest soils: Part II. Linking microbial community structure to nitrogen cycling.
Pett-Ridge, Jennifer*,1, Templar, Pamela 1, Silver, Whendee1, Firestone, Mary1, 1 U.C. Berkeley --Ecosystem Sciences, Berkeley, CA, USA
ABSTRACT- Microbial communities are the hidden translators that link the soil environment to soil ecosystem functions. In conjunction with a week-long 15N addition experiment, we measured redox-indicative traces gases and examined microbial molecular fingerprints in a wet tropical soil where soil redox patterns are particularly crucial regulators of microbial populations and nutrient cycling. This work was carried out in the Luquillo Experimental Forest LTER of Puerto Rico across a range of sites with similar aboveground plant communities. In a principal components analysis with 84% of data variance explained, sites with trace gas fluxes indicative of lower pE had significantly different T-RFLP profiles compared to higher and more variable redox sites. As expected, these microbial communities were not influenced by isotope label addition, yet a canonical correspondence analysis shows that amongst all measured ecosystem N transformations, dissimilatory nitrate reduction to ammonium (DNRA) and nitrification had the strongest correlation with soil microbial community patterns. These results clearly demonstrate that microbial communities are highly structured by soil redox regimes, and correlate more closely with soil moisture and belowground CH4, N2O, H2 and O2 than with aboveground plant patterns. Our work illustrates how microbial population characteristics define biogeochemically-important ecosystem processes.
Key words: microbial, soil, nitrogen, tropical
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