水氮互作对设施菜田土壤氮素形态组成以及细菌群落结构的影响

利用室内模拟培养试验，研究了不同水氮互作条件对设施菜田土壤氮素形态组成和细菌群落结构的影响。主因素为2种土壤水分条件:70%田间持水量和100%田间持水量；副因素为5种氮素添加形态:不施氮肥、纯无机氮、纯有机氮、2/3无机氮 + 1/3有机氮和1/3无机氮 + 2/3有机氮。结果表明:水氮互作效应对土壤无机氮含量和土壤细菌群落Shannon和Simpson指数的影响显著（P < 0.05）。高含水量条件下，土壤无机氮含量显著降低（P < 0.05），但土壤细菌群落的Shannon，Ace和Chao1指数极显著升高（P < 0.01），并且随着土壤含水量升高，Aeromonas和Flavobacterium菌属的相对丰度增加；培养30 d后，添加有机氮处理的土壤有机氮含量显著高于添加无机氮处理，添加有机氮使Cellvibrio和Devosia菌属相对丰度上升。可见，设施菜田施用有机氮肥尽管短期内不利于土壤速效氮的积累，但在适宜的水分条件下，土壤优势菌群发生了较大改变，部分固碳功能菌群丰度增加，有利于稳定土壤碳氮循环。试验结果为进一步研究设施菜田水氮管理介导的土壤碳氮循环功能菌群变化的环境驱动机制提供了一定科学依据。

Effects of Water and Nitrogen Interactions on Soil Nitrogen Composition and Bacterial Community in the Protected Vegetable Field

The interactions of water and nitrogen (N) on soil bacterial community were analyzed in a simulated indoor incubation experiment. The main factor included soil moisture (70% and 100% field capacity), and the split factor was N addition form (no N application, pure inorganic N, pure organic N, 2/3 inorganic N + 1/3 organic N, and 1/3 inorganic N + 2/3 organic N). The results showed that the interaction of water and nitrogen had significant influences on the content of soil inorganic N and the Shannon and Simpson indices of soil bacterial community. Moreover, the content of soil inorganic N in the high soil water treatment was significantly decreased (P < 0.05), while the Shannon, Ace and Chao1 indices of soil bacterial communities were significantly increased (P < 0.01). The relative abundances of Aeromonas and Flavobacterium were increased with the increase of soil moisture content. Compared to the inorganic N treatment, the organic N treatments significantly accelerated the content of soil organic N after 30 days of incubation. With the addition of organic N, the relative abundances of Cellvibrio and Devosia also increased. In conclusion, although organic N fertilization in the protected vegetable field could not be conducive to the increase of soil available N, the dominant bacterial populations changed under the appropriate water condition. Soil carbon-N cycle is supposed to tend toward stability with the increased richness of the specific carbon assimilating bacteria. The results may provide a new insight for understanding the environment-driven mechanisms for soil carbon and N cycling functional microbes, in response to the different water and N managements in the protected vegetable filed.