农牧交错带草地土壤剖面微生物总量、多样性和互作网络的垂直分布特征

【背景】草地土壤微生物是维持草地生态系统功能和稳定的关键要素之一,探寻微生物在土壤剖面的垂直分布特征和构建规律对于理解其在草地生态系统的作用至关重要。【目的】在80cm深的土壤剖面内,全面分析微生物的总量、多样性和物种间的相互作用网络表现出的垂直分布特征。【方法】基于内蒙古农牧交错带上典型草原土壤中原核微生物的定量和高通量测序数据,比较微生物的总量和多样性,使用分子生态网络方法(molecular ecological network approach,MENA)探究微生物相互作用网络的垂直变化。【结果】原核生物的总量和多样性随深度增加而逐渐降低,且群落结构变异沿土壤剖面逐渐增大。网络结构在表层最为复杂,微生物物种间联系紧密;随着深度的增加,微生物间紧密的关联会逐渐变稀疏,网络结构变得简单。此外,酸杆菌是当地土壤生态系统中的优势种群以及网络核心微生物物种,可能对土壤生态服务功能的稳定发挥具有重要的作用。【结论】原核微生物的总量、多样性和物种间的互作网络都表现出高度一致的垂直变化规律,即总量、多样性与深度成负相关,且其群落结构变异会逐渐扩大,同时微生物网络相关性会减弱。这些结果为我们提供了微生物动态变化的重要见解,对典型农牧交错带草地的生态保护具有一定的参考价值。

Vertical distribution features of microbial quantity, diversity and interactions along soil profiles in an agropasture grassland

Background] Microorganisms in grassland soils are important for ecosystem functioning and stability maintaining. To discover the profile of microbes along the soil vertical depths is essential for our understanding about microbial contributions in grassland ecosystems. Objective] To comprehensively investigate the vertical patterns of total prokaryotic quantity, diversity and interaction networks in 0?80 cm soil profiles. Methods] Based on the quantitative PCR and high-throughput sequencing on 16S rRNA gene in a typical agropasture grassland, Inner Mongolia, the total microbial quantity and diversity were cautiously measured. Besides, the molecular ecological network approach (MENA) was used to explore the changes of microbial species interactions. Results] The quantity and diversity of prokaryotes decreased with depths, as well as the variations of community. Along the soil vertical depths, the close association among microbes would gradually become sparse and the network structures become simpler. In addition, Acidobacteria was one of top abundant phyla, and network analysis revealed that some species in Acidobacteria were the keystone taxa in this grassland ecosystem. These species might play an important role in maintaining the stability of soil ecological functions. Conclusion] The quantity, diversity and interactions of prokaryotes showed highly consistent with vertical patterns. The quantity and diversity of prokaryotes is negatively correlated with the soil depth, and the variation of community structure will gradually expand at deep soils. Meanwhile the interactions among species in molecular network are decreasingly weakened. These results provide important insights into the dynamic change of microbial community, and are valuable for the ecological protection of grasslands in typical agropasture area.