Effect Of Stand Density On Carbon Storage In Larch Plantations

Stand density decides the spatial structure of stand and plays a key role in growth and carbon pool of forest.But currently we know little about the effect of density on carbon storage of forest.Therefore,in order to investigate the effect of stand density on carbon storage in larch plantations,a study was established to estimate carbon storage in 9-year-old larch plantations with 3 densities(2000,3300,4400 plants/hm2)in Maoershan area of Heilongjiang province.We adopted the method of sample-plot survey to set 3 plots respectively in each treatment,and estimated the carbon storage of stand and influencing factors on carbon storage.The results showed:(1)The carbon storage of tree in larch plantations with 3 densities increased with stand density increasing,and carbon storage of tree layer with low density was lower significantly than middle density and high density(P<0.05).Carbon storage of tree layer with high density was twice more than low density.The carbon storage of understoiy vegetation layer decreased with stand density increasing,and the carbon storage with low density was much lower than middle and high density(P<0.05).The carbon storage of litter layer increased with density increasing,but there was no significant difference(P>0.05).The carbon storage of soil layer increased with stand density increasing,and carbon storage with high density increased 25.6%and 12.5%than low density and middle density respectively.There was significant difference between high density and low density(P<0.05).(2)The carbon storage of forest ecosystem and annual net carbon fixation of tree layer in larch plantations with 3 densities increased with density increasing,and the carbon storage with high density was much higher than low density(P<0.05).The space allocation of carbon storage in plantations with 3 densities was soil layer>tree layer>litter layer>understoiy vegetation layer.The carbon storage of tree and soil layer accounted for 96.6%-97.4%in forest total carbon storage.The carbon storage of tree layer and soil layer is the main part in carbon storage of ecosystem in larch plantations.(3)The effect of stand density on litter and temperature and moist of soil is significant.Residual rates of litter increased with density increasing,and residual rates of litter with low density was lower significantly than middle and high density during medium and later period of litter decompositing(P<0.05).The carbon concentration of residual litter increased with density increasing in the process of litter decomposition.Carbon concentration of residual litter with low density was lower significantly than middle and high density during medium and later period(P<0.05).Annual litter biomass and input of litter biomass into soil increased with density increasing.Annual litter biomass with low density was lower obviously than middle and high density(P<0.05),which decreased 29.6%and 38.4%than middle and high density respectively.In addition,soil temperature decreased with density increasing,and soil moist increased with density increasing,but there was no difference(P>0.05).(4)Available nutrition of soil in larch plantations with 3 densities changed obviously with density increasing during growing season,while total nutrition of soil,soil microbial biomass carbon and soil water-soluble organic carbon had little change in forest with different densities.