Effects Of Forest Gap On Soil Microbial Biomass And Soil Enzyme At Different Periods In A Subalpine Picea Asperata Plantation Of Western Sichuan

Forest gap disturbance is forest ecosystems to maintain one of the important driving force for a long time, also is a kind of important forest circulation update way. To understand the effects of forest gap on Soil biological characteristics can provide the basic data for deeply comprehending the process of the forest regeneration on soil ecological processes and sustainable forest management. Influenced by seasonal snow cover, subalpine forest gap in growing season and non growing seasons of Soil biological characteristics may be different from other forest ecological system, but so far little information has been available. Therefore, a field experiment to study the dynamics of soil microbial biomass carbon and nitrogen, soil nitrate and ammonium, invertase and urease activity under gap center, gap edge and under-canopy was carried out from June 2012 to May 2013. Samples of soil in organic layer and mineral soil layer were collected in growing period (completely soil thawing stage, early stage and later stage of growing season) and freeze-thaw period (onset stage of freezing, deeply soil freezing stage and soil thawing stage).The main results were:(1) Forest gap had an different effect on microbial biomass and soil invertase activity in organic layer and mineral soil layer at different critical period. MBC content and invertase activity reached the lowest value at deeply soil freezing.Soil invertase activity in soil organic layer gap center was significantly higher than that under under closed canopy and gap edge in the growing season (TPL, EGS, LGS), While MBC under closed canopy was higher than that of gap center and gap edge.Wherase,MBC and Soil invertase activity under gap center were higher than that under under closed canopy and gap edge in freeze-thaw period.The response of MBC and invertase activity in soil of gap center, gap edge and under closed canopy were closely related with the sampling time and soil layers at the same time.(2) With the temperature and driving freeze-thaw pattern change, forest gap in different position of soil microbial biomass nitrogen, soil urease activity and soil mineral nitrogen in soil organic layer and mineral soil layer had obvious dynamic rule at different period, soil microbial biomass nitrogen,soil urease activity and soil mineral nitrogen had the lowest content at deeply soil freezing. Soil microbial biomass nitrogen and soil ammonium contents in soil organic layer under closed canopy wrer significantly higher than that under gap center and gap edge in the growing season (TPL, EGS, LGS), While soil urease activity soil nitrate content and soil mineral nitrogen under gap center were higher than that of closed canopy and gap edge. Wherase, soil urease activity and soil ammonium contents under closed canopy r were higher than that under gap cente and gap edge in freeze-thaw period.Sampling time, gap position and soil layer had significant effects on MBN, urease and nitrate nitrogen and ammonium nitrogen content.Visibly, affected by seasonal effects of freezing and thawing, environmental gradient formed by gap position affected the soil nitrogen cycle significantly on the one hand, it also shows the gap center under the influence of the environment more and more intense on the other hand, the growing season relatively higher temperature environment may significantly promote the nitrification of nitrogen, which plays a role in forest plant growth update.