The Study On Root Decomposition And Biomass Characteristics Of Three Forest Community Types In Xiao Xing An Mountains

Root decomposition is an important part of the cycle of C and nutrient in forest ecosystem.This research adopts the buried bag sampling method of the Mongolian oak forest secondary forest spruce and fir Korean pine,white birch,three main building group of community types were kind of Mongolian oak(Quercus mongolica Fisch.ex Ledeb),birch(Betula platyphylla Suk.)spruce and fir(Abies nephrolepis Maxim.)of different level root diameter in different soil layer decomposition rate and nutrient dynamic change.The results showed that:The weight retention rate of all three species decreased rapidly(0-64d)and relatively slowed(65-451d).In processing of the decomposition,negative root decomposition occured due to experimental error and spatial heterogeneity.In decomposition coefficient k by Olson exponential attenuation model fitting,the results showed that Quercus mongolica’s root decomposition rate were significantly higher than that Betula platyphylla and Picea spp.-Abies nephrolepis(P<0.05),Quercus mongolicca’s root decomposition rate was basic level as the root diameter increased,as the soil increased.Root decomposition rates of Betula platyphylla and Picea spp.-Abies nephrolepis are basically reduced with increasing of root diameter and soil layer,and the soil layer and the root diameter have significantly influences on root decomposition(P<0.05).In the process of root decomposition,Quercus mongolica,Betula platyphylla,Abies nephrolepis diameter level root system at various levels in different layers of decomposition process,C concentrations generally show a consistent regularitions:general first increases slightly(0-123d),after the basic unchanged(123-349 d),and finally the trendency of the rose(349-451d);The concentration of N concentration was rapidly increased(0-123d)at the initial stage,and the trendency of the stable and slightly decline(123-45 1d).Soil drilling sample method is used for Quercus mongolica、Betula platyphylla、Abies nephrolepis in different depths(0-30 cm)root biomass and soil physical and chemical properties were studied.the results showed that the highest total root biomass is Quercus mongolica,it is 7.47 t/hm2,significantly higher than Betula platyphylla and Abies nephrolepis,they’re total root biomass were followed by 5.80 t/hm2、5.77 t/hm2(P<0.05).The three species are the highest in fine root biomass,showed that the fine root biomass occupies an important position in the total root system.The total root biomass of 3 tree species decreased gradually with the deepening of soil layer,Quercus mongolica’s 78.06%,Betula platyphylla’s 69.01%and Abies nephrolepis’s 82.47%was distributed in the soil layer of 0-20cm.Correlation analysis on soil physical and chemical characteristics showed that:root biomass and soil total organic C content、total N content in soil and soil bulk density were significantly negative correlation(P<0.05),and the soil pH value has significant positive correlation(P<0.05),soil total organic C and total N are less in soil,lower the soil bulk density,soil pH value is more moderate,the root biomass is higher.After analysised,due to larger plantation age,litter hard to be decomposed,thus affected the soil nutrient content,especial organic C and total N,had negative correlation,they have great a influence on root biomass.