Influences of plant litter diversity on decomposition, nutrient mineralization and soil microbial community structure

Although plant litter identity has long been recognized as one of the important drivers of terrestrial ecosystem processes, our understanding on this issue is limited. We incubated leaf litter of four grassland species showing different functional types (C3, C4, legumes and forbs) with identical soil singly as well as in mixture of multiple species litter (two-species, three-species and all four-species litter) for 60 days under laboratory conditions to address the following questions: (i) how litter mixing (composition and richness) affects ecosystem functions including nitrogen (N) mineralization and mass loss rate; and (ii) how litter mixing impacts soil microbial community structure. Soil microbial community structure was evaluated by phospholipid fatty acid (PLFA) profiling and polymerase chain reaction (PCR)-based denaturing gradient gel electrophoresis (DGGE) analysis following amplification of 16S rDNA and 18S rDNA fragments for bacteria and fungi, respectively. The results revealed an additive effect of litter mixing on N mineralization rate. However, the results also showed that litter mixing had a synergistic effect on mass loss rate, albeit the effect tended to depend on the species identity present in the mixture. Microbial community structure measured by PLFA analysis and PCR-DGGE method showed non-additive effects of litter mixing. Bacterial community composition showed a significant positive correlation with the mass loss rate indicating a feedback between plant and soil microbial communities. Overall, the results of this study indicated the importance of litter identity rather than litter species diversity per se in driving decomposition processes.