Hsu Shi-Fang, Buckley Daniel H
Department of Crop and Soil Sciences, Cornell University, Ithaca, NY 14853, USA.
ISME J. 2009 Jan;3(1):124-36. doi: 10.1038/ismej.2008.82. Epub 2008 Sep 4.
Microbial ecologists continue to seek a greater understanding of the factors that govern the ecological significance of microbial community structure. Changes in community structure have been shown to have functional significance for processes that are mediated by a narrow spectrum of organisms, such as nitrification and denitrification, but in some cases, functional redundancy in the community seems to buffer microbial ecosystem processes. The functional significance of microbial community structure is frequently obscured by environmental variation and is hard to detect in short-term experiments. We examine the functional significance of free-living diazotrophs in a replicated long-term tillage experiment in which extraneous variation is minimized and N-fixation rates can be related to soil characteristics and diazotroph community structure. Soil characteristics were found to be primarily impacted by tillage management, whereas N-fixation rates and diazotroph community structure were impacted by both biomass management practices and interactions between tillage and biomass management. The data suggest that the variation in diazotroph community structure has a greater impact on N-fixation rates than do soil characteristics at the site. N-fixation rates displayed a saturating response to increases in diazotroph community diversity. These results show that the changes in the community structure of free-living diazotrophs in soils can have ecological significance and suggest that this response is related to a change in community diversity.
微生物生态学家一直在努力更深入地了解那些决定微生物群落结构生态意义的因素。群落结构的变化已被证明对于由少数几种生物介导的过程具有功能意义，例如硝化作用和反硝化作用，但在某些情况下，群落中的功能冗余似乎可以缓冲微生物生态系统过程。微生物群落结构的功能意义常常被环境变化所掩盖，并且在短期实验中很难检测到。我们在一项重复的长期耕作实验中研究了自由生活的固氮微生物的功能意义，在该实验中，外部变化被最小化，固氮率可以与土壤特性和固氮微生物群落结构相关联。研究发现，土壤特性主要受耕作管理的影响，而固氮率和固氮微生物群落结构则受到生物量管理实践以及耕作与生物量管理之间相互作用的影响。数据表明，在该地点，固氮微生物群落结构的变化对固氮率的影响比土壤特性更大。固氮率对固氮微生物群落多样性的增加呈现出饱和响应。这些结果表明，土壤中自由生活的固氮微生物群落结构的变化可能具有生态意义，并表明这种响应与群落多样性的变化有关。
