Study On Dynamics Of Soil Microbial Biomass In Typical Forest In Daxing’an Mountains

Soil microbe is the most important decomposer in forest ecosystems and the most active part of soil organic matter. Soil microbe not only can regulate the landing ecosystem biogeochemical processes but also was the most sensitive part of the response to soil carbon pool with the global climate change and play a crucial role in forest carbon and nitrogen cycles. Meanwile, it was the sensitive indicator to environmental changes. Many studies have shown that forest soil microbial biomass have a significant seasonal dynamic characteristics. In this study, the fumigation-extraction method (FE) with chloroform was used to evaluated the seasonal variation of the soil microbial biomass carbon (Cmic) and nitrogen (Nmic) and the relationships between Cmic, Nmic, soil nutrient factors and soil environmental factors in Belula platyphylla forest (understory vegetation were clear-cut and undisturbed), Betula platyphylla-Larix gmelinii Mixed Forest, Pinus sylvestris var.mongolica forest and Larix gmelinii forest (understory vegetation were clear-cut and undisturbed) in Great Xing’an Mountains. We also investigated the effect on contents of Cmic and Nmic in Betula platyphylla forest and Larix gmelinii forest, after the understory vegetation were clear-cut and undisturbed.The contents of Cmic and Nmic were significantly different (P<0.01) among the six forest types. The Cmic values in the Betula platyphylla forest (understory vegetation were clear-cut and undisturbed), Betula platyphylla-Larix gmelinii Mixed Forest, Pinus sylvestris var.mongolica forest and Larix gmelinii forest (understory vegetation were clear-cut and undisturbed) were varied from81～604mg·kg-1,90～416mg·kg-1,75～606mg·kg-1,66～268mg·kg-1,86～215mg·kg-1and70～1065mg·kg-1respectively. And the Nmic values were varied from11～56mg·kg-1,8～62mg·kg-1,5～53mg·kg-1,12～33mg·kg-1,12～38mg·kg-1and15～75mg·kg-1respectively.The correlation analysis results of synchronous acquisition of the soil sample analysis of environmental factors and nutrient elements with Cmic and Nmic showed that the basic Cmic and Nmic were significantly correlated. They were also significantly correlated with soil organic carbon (SOC) contents and soil total nitrogen (TN) contents, and the influence of other environmental and nutrient factors have performed a wide diversity during different forest types. Clearing forest operations could impact the levels of soil microbial biomass carbon and nitrogen through the impact to the material conditions. The results could provide some based data for the further development of the boreal forest soil carbon cycle.