模拟增雨对荒漠土壤古菌多样性的影响

为探讨生长季增雨对荒漠土壤中古菌群落结构的影响，根据内蒙古磴口多年平均降水量，设计了模拟增雨试验，包括对照、2个增雨时段（生长季前期与后期）、每个时段2个增雨梯度（50%与100%）共计5种处理。增雨后提取荒漠土壤总DNA，对古菌群落编码16S rRNA基因的V4区进行Hiseq测序，分析古菌群落丰度、多样性及结构组成等。结果表明：该地区荒漠土壤中古菌群落均以奇古菌门（Thaumarchaeota）和广古菌门（Euryarchaeota）为优势菌群。NMDS和3种非相似性分析（MRPP、ANOSIM和Adonis）表明，生长季前期增雨未显著改变古菌的群落结构，生长季后期增雨显著改变了古菌的群落结构，当生长季后期增雨量达到100%时，古菌丰富度和多样性显著降低。与氨氧化过程密切相关的奇古菌门（Thaumarchaeota）相对丰度在生长季后期100%增雨条件下显著增加，将促进荒漠土壤的硝化过程。Mantel检验发现荒漠土壤古菌群落结构受土壤湿度、土壤温度、土壤硝态氮含量的影响。未来全球变化背景下降水格局变化将会对荒漠土壤古菌群落结构产生影响，并可能影响氮循环过程。

Effects of rainfall additions on the archaeal communities in the desert ecosystem

Our study was conducted to reveal responses of archaeal communities' composition and diversities to rainfall addition in different periods of growing seasons, and analyze main environmental factors affecting the archaeal community structure. We conducted a field manipulative experiment with five simulated rain addition treatments, including control, rainfall addition (50%, 100%) in early growing season and rainfall addition (50%, 100%) in late growing season. We extracted total DNA from soil samples, and sequenced the V4 region of the 16S rRNA gene on Hiseq platform. Results showed that archaeal communities in this desert was dominated by the phylum of Thaumarchaeota and Euryarchaeota. NMDS and three non-similarity analyses (MRPP, ANOSIM, and Adonis) showed that the archaeal communities composition significantly changed in rainfall addition in late growing season treatments whereas archaeal communities composition remain stable in rainfall addition in early growing season treatments, indicating that archaeal communities had different responses to rainfall in different periods. The relative abundance of the Thaumarchaeota, which associated with the ammoxidation process, significantly increased under 100% rainfall addition in the late growing season condition, suggesting that the nitrification process in desert soil would be stimulated by the rainfall addition. Mantel test results showed that the archaea community structure in desert soil was affected by the soil moisture, soil temperature and soil nitrate nitrogen contents. Above results suggest that the global precipitation change will have significant impacts on archaeal community structures in desert soils, which may affect the nitrogen cycling in desert ecosystems in the future.