火烧和施氮对内蒙古半干旱草原土壤微生物群落碳源利用潜力的影响

Impacts of Fire and N Addition on Microbial C Utilization Potential in A Semi-arid Grassland of Inner Mongolia

火烧是草原生态系统中最常见的一种自然现象,而氮素通常被认为是干旱、半干旱地区的主要限制因子。在中国北方草原生态系统相对干旱、长期处于氮素限制条件下,对火干扰和氮沉降非常敏感。通过在内蒙古多伦县半干旱草原地区进行火烧和施氮的野外控制试验,采用BIOLOG微孔板技术探讨火烧与施氮对土壤微生物量及其碳源利用的影响。结果表明:火烧和施氮处理显著降低生长季初期土壤微生物量;但是施氮显著促进了土壤细菌类群对多聚物、糖类、酚类和胺类碳源的利用,及真菌类群对胺类碳源的利用;而且火烧与施氮处理在影响土壤细菌碳源利用上表现出明显的交互效应,火烧削弱了施氮对细菌碳源利用的促进作用。火烧与施氮对生长季初期土壤微生物的这些影响,可能通过影响有效养分的释放而影响后期植物生长,但由于火烧与施氮处理在影响土壤微生物过程中表现出来的复杂性,这种对植物后期生长的影响可能存在较大的不确定性。

Fire is one of the most common natural phenomena in grassland ecosystem.Nitrogen is generally considered as the main limiting factor in arid and semiarid environment.It has been well documented that the grassland ecosystems of northern China are very sensitive to fire and N deposition due to the situation of water deficiency and long term N limitation.Here,a field experiment with annual burning and N addition was established in the semi arid grassland of Inner Mongolia.Soil physicochemical properties,microbial biomass carbon （C） and N,and the C utilization potential of bacteria were measured using chloroform fumigation extraction method and BIOLOG microplate technique to test the responses of soil organic nutrients,microbial biomass and C utilization potential of bacteria to fire and N addition.The results showed that fire and N addition significantly decreased soil microbial biomass in the early growing season of plants.N addition largely modified the polymers carbohydrates,phenols and amines-carbon utilization of bacterial,and also promoted the amines-carbon utilization of fungi.In addition,fire and N addition had interaction effects on bacterial carbon utilization.Fire weakened the effects of N addition on improving bacterial carbon utilization.These results indicate that the effects of fire and N addition on soil microbial affect the plant growth of later stage by influencing the release of soil available nutrient.However,the interaction effects of fire and N addition on the plant growth of later stage have a greater uncertainty due to the complexity of both factors.