湿地土壤微生物功能多样性及碳氮组分对长期氮输入的响应

氮输入对湿地生态系统碳氮循环具有重要影响,研究湿地土壤微生物功能多样性及碳氮组分对氮输入的响应,对于明确湿地土壤碳氮循环微生物驱动机制具有重要意义。依托长期野外氮输入模拟试验,利用Biolog-ECO微平板技术,分析不同浓度氮输入:N1(6 g N m^-2 a^-1)、N2(12 g N m^-2 a^-1)和N3(24 g N m^-2 a^-1)对湿地土壤表层(0-15 cm)和亚表层(15-30 cm)微生物碳源代谢活性、功能多样性和碳氮组分的影响。结果表明:N2处理显著提高了亚表层土壤微生物碳源代谢活性和McIntosh指数,N3处理显著降低了表层土壤微生物Shannon指数和Shannon-evenness指数。随氮输入浓度增加湿地表层土壤微生物对糖类的利用率显著降低,N3处理表层土壤微生物对胺类的利用率以及亚表层土壤微生物对醇类的利用率显著提高。N1处理显著提高了湿地表层土壤全氮和微生物量碳含量;N2、N3处理显著提高了土壤铵态氮、硝态氮含量;N3处理显著降低了土壤pH值。湿地土壤pH、总碳、溶解性有机碳含量是影响微生物碳源代谢活性和功能多样性的重要因素,土壤溶解性有机碳、铵态氮、全氮含量、含水率是影响微生物碳源利用变化的主要因子。

Response of soil microbial functional diversity and soil carbon and nitrogen components to long-term nitrogen input in wetlands

Wetland is a huge reservoir of carbon and nitrogen and plays an important role in the global carbon and nitrogen cycling. Soil microorganisms are the main medium for organic matter decomposition and nutrient cycle. Nitrogen input has significant effects on soil nutrient, carbon and nitrogen cycling as well as soil microbial community structure and function. Therefore, to better understand the microbial driving mechanism of carbon and nitrogen cycling in wetland soil, it is crucial to clarify the characteristics of soil microbial functional diversity as well as the carbon and nitrogen components under nitrogen input. The effects of different nitrogen input concentrations, including N1 (6 g N m^-2 a^-1), N2 (12 g N m^-2 a^-1), and N3 (24 g N m^-2 a^-1), on microbial carbon source metabolic activities, functional diversity, and carbon and nitrogen components in the surface (0-15 cm) and subsurface (15-30 cm) of wetland soil were examined using Biolog-ECO microplate technology based on long-term field nitrogen input simulation experiment. The results showed that the metabolic activity of soil microbial carbon source increased gradually with the extension of culture time under different nitrogen input treatments. The Shannon index, Shannon-Evenness index, and McIntosh index were significantly higher in surface soil than in subsurface soil under CK treatment. N3 treatment significantly decreased the microbial Shannon index and Shannon-Evenness index in surface soil, while N2 treatment significantly increased the microbial carbon source metabolic activity and McIntosh index in subsurface soil. There were differences in the utilization capacity and preference of soil microorganisms with different nitrogen concentrations. With the increase of nitrogen input concentration, the utilization rate of carbohydrates by microorganisms in wetland surface soil significantly decreased, while the utilization rates of amines and phenolic compounds by microorganisms in surface and subsurface soil were significantly increased under N3 treatment. The contents of total carbon, total nitrogen, and microbial biomass carbon in surface soil were significantly higher than those in subsurface soil under different nitrogen input concentrations. N1 treatment significantly increased the content of total nitrogen, total phosphorus and microbial biomass carbon in wetland surface soil. N2 and N3 treatments significantly increased soil ammonium and nitrate contents. N3 treatment significantly reduced soil pH. Soil pH, total carbon and dissolved organic carbon content were important factors affecting the metabolic activity and functional diversity of microbial carbon sources. The key variables influencing the shift in microbial carbon source utilization were soil dissolved organic carbon, ammonium nitrogen, total nitrogen content, and water content.