Response Of Soil Microbial Biomass And Nutrient To Simulated Warming And Nitrogen Application In Songnen Grassland

With the growing warming and nitrogen deposition , Physical and chemical properties of soil is bound to be destroyed. Soil microbial properties play a key role in belowground ecosystem functioning, but are not well understood in grassland ecosystems under global changes. We simulated warming and nitrogen (N) application to discuss the variation of soil microbial biomass and soil nutrients(SOC,nitrogen and phosphorus) in different treatments: Ambient (CK), Warming (W), N application (N) and Warming plus N application (W+N) in Songnen plain.Results indicated that W,N,W+N had considerable effects on soil microbial biomass carbon (SMBC),soil microbial biomass nitrogen (SMBN) and soil nutrients. The changes of SMBC and SMBN were: N increased SMBC by 22.6% and SMBN by 36.8%; Warming decreased them then increased. Responded to N and CK Microbial biomass were higher in May than that in August and October , while were not different under W and W+N .Further analysis indicated that treatment and sampling date had obvious influence on the SMBC, SMBN and there were significant interactions(P<0.01).The effect of W,N and W+N on ratio of SMBC/SMBN were significant(P<0.05).Different treatments had no significant impact on the content of soil organic carbon (SOC), W was decreased SOC by 5.5%, N was increased by 21.6%. N treatment significantly increased the content of total nitrogen (TN) by 20.4%,available nitrogen by 33%, and N mineralization rate(NMR) by 17.4%; W decreased TN by 9%; W+N also increased TN and NMR, but not significantly. The seasonal variation showed that the content of soil nutrients increased first then decreased, reached its peak in August. And there were significant interactions between treatments and sampling date(P<0.05,except soil available N).A correlation analysis showed that SMBC, SMBN, TN, SOC, and available N were all positive correlated. The significantly and positively correlation between SMBC and SMBN suggested the contents of SMBC and SMBN were the sensitive indicators for characterizing of changes of soil fertility.