Spatio-temporal Variability Of Soil Microbial Biomass Carbon And Nitrogen In Six Forest Types In Xiaoxing’an Mountains, China

We used a chloroform fumigation extraction method to measure and to compare the soil microbial biomass carbon (MBC) and nitrogen (MBN) on the seasonal variation, and to assess the influence of environmental factors (soil nutrient content, soil water content, and soil temperature) in six forest types of mixed broadleaved-Korean pine(Pinus koraiensis) forest, valley spruce-fir (Picea-Abies) forest, selective cutting of mixed broadleaved-Korean pine forest, secondary birch (Betula platyphylla) forest, artificial larch(Larix gmelinii) plantation and artificial Korean pine forest ecosystem in Xiaoxing’an Mountains. Moreover, we explored the effect of root removed on soil microbial biomass. The results were listed as following:1) During the study period in2011, The MBC and MBN were significantly different(P<0.05) between secondary birch forest and valley spruce-fir forest. The MBC and MBN maximum occurred in secondary birch forest(MBC and MBN:687.39mg·kg-1and122.08mg·kg-1), the minimum occurred in valley spruce-fir forest(MBC and MBN:388.39mg·kg-1and63.80mg kg-1). Broadleaved forest or higher ratio of broadleaved forest types of soil microbial biomass was higher than coniferous forest or higher ratio of coniferous forest types. Both MBC and MBN decreased with the soil depth increasing for six forest types.0-10cm soil layer of MBC and MBN were higher than10-20cm layer, accounting for40%and44%of the increase, respectively.2) For all forest types, although the differences of seasonal variation curves in soil microbial biomass between2010and2011. However, the peak occurred mostly in August. Overall, the seasonal variations in the MBC and MBN were greater at the0-10cm soil layer than those at10-20cm. The seasonal variations during the growing season in2010were greater than that in2011. Root removal had no effect on soil microbial biomass pattern of seasonal variation, but there were difference degrees of reduction of soil microbial biomass for six forests.3) The plant litterfall showed similar seasonal patterns for six forests during the study period in2011. The litter input keeped a low level in the growing season for all forests, they peaked in September and October. The maximum value of total litter input occurred in mixed broadleaved-Korean pine forest (507.11g·m-2), the minimum value in the valley spruce-fir forest (317.34g. m-2).4) The MBC and MBN were positively correlated with TOC, TN and WC. In0-10cm soil layer, the MBC was positively correlated with plant litterfall in the following month to its sampling time in secondary birch forest, selective cutting of mixed broadleaved-Korean pine forest and mixed broadleaved-Korean pine forest; The MBC was positively correlated with plant litterfall in the preceding month to its sampling time in artificial Korean pine forest and valley spruce-fir forest. The MBN was positively correlated with plant litterfall in the following month to its sampling time in secondary birch forest and selective cutting of mixed broadleaved-Korean pine forest. In10-20cm soil layer, the MBC and MBN were positively correlated with plant litterfall in the preceding month to its sampling time in valley spruce-fir forest.