摘要
河流泛滥平原是受到人为压力因素严重威胁的具有生态和经济价值的生态系统。泛滥平原土壤中的微生物群落介导关键的生物地球化学过程，但我们对这些群落之间的关系以及与土地管理或地形有关的水文连通性变化的了解很少。在这里，我们提出了宏基因组证据，即三个漫滩土壤中微生物群落之间的差异与水文连通性的长期梯度相对应。具体而言，所有严格的厌氧分类和代谢途径都与增加的水文连通性和洪水频率正相关。相反，大多数有氧类群和所有严格有氧途径与水文连通性和洪水频率呈负相关。此外，随着水文连通性的增加，代谢有机化合物的遗传潜力趋于下降，这可能反映了观察到的土壤有机质同时减少或厌氧分类群和途径同时增加。土壤N的下降伴随着营养缺乏型氮获得子系统的遗传潜力的增加，这表明土壤养分也在这些土壤中形成微生物群落。我们得出结论，泛洪平原土壤微生物群落之间的差异可以通过水文连通性的梯度概念化。此外，我们表明，这些差异可能是由于连接相关的淹水频率，土壤有机质和土壤N的变化。我们的研究结果尤其与河流泛滥平原湿地微生物介导的生物地球化学过程的恢复和管理有关。
Riverine floodplains are ecologically and economically valuable ecosystems that are heavily threatened by anthropogenic stressors. Microbial communities in floodplain soils mediate critical biogeochemical processes, yet we understand little about the relationship between these communities and variation in hydrologic connectivity related to land management or topography. Here, we present metagenomic evidence that differences among microbial communities in three floodplain soils correspond to a long-term gradient of hydrologic connectivity. Specifically, all strictly anaerobic taxa and metabolic pathways were positively associated with increased hydrologic connectivity and flooding frequency. In contrast, most aerobic taxa and all strictly aerobic pathways were negatively related to hydrologic connectivity and flooding frequency. Furthermore, the genetic potential to metabolize organic compounds tended to decrease as hydrologic connectivity increased, which may reflect either the observed concomitant decline of soil organic matter or the parallel increase in both anaerobic taxa and pathways. A decline in soil N, accompanied by an increased genetic potential for oligotrophic N acquisition subsystems, suggests that soil nutrients also shape microbial communities in these soils. We conclude that differences among floodplain soil microbial communities can be conceptualized along a gradient of hydrologic connectivity. Additionally, we show that these differences are likely due to connectivity-related variation in flooding frequency, soil organic matter, and soil N. Our findings are particularly relevant to the restoration and management of microbially mediated biogeochemical processes in riverine floodplain wetlands.
https://link.springer.com/article/10.1007/s00248-016-0883-9
