Interactive effects of clipping practice and experimental warming on soil microbial communities involved in nitrogen cycling in a tallgrass prairie

Background/Question/Methods

Biofuels derived from diverse mixtures of native grassland perennials with low external input (LIHD) are believed to have greater greenhouse gas reductions and without direct competition with food. However, the responses of soil microbial community to clipping, a land use practice for producing biofuels on LIHD, is still unclear, especially under the future warming scenarios. The functional gene changes of soil microbial community involved N processes may have important implications for ecosystem nitrogen (N) cycling, which is important in regulating terrestrial carbon (C) sequestration. Here, we present a study utilizing GeoChip to investigate how clipping and warming interactively affected nitrogen (N) functional genes of soil microbial communities at a long-term experimental field in a tall grass prairie ecosystem.

Results/Conclusions

Results showed that warming tended to stimulate N genes without clipping, but such trend was completely dismissed by its interactive effect with clipping. Clipping tended to enhance N cycling under control, while its interactive effect with warming not only dismissed such trend but also changed the direction by decreasing the abundances of some N genes, especially for denitrification. Though litter mass was decreased by clipping at the same level (80%) under control and warming, soil N availability, especially NH₄⁺ , was decreased by clipping under control but did not change under warming. The reduced N loss through lower denitrification activity and unchanged N fixation, indicated by relevant functional genes, may be one mechanism to explain the soil N availability maintenance in clipping plots under warming. Meanwhile, the decreased soil N availability by clipping under control could be explained by the enhanced denitrification activities, which may aggravate N loss and counteract or even overwhelmed the increased N fixation. All these results illustrate the complexity of soil microbial community responses in future scenarios with multiple factors simultaneously and the importance of understanding microbially-mediated mechanisms for ecosystem responses under such scenarios.