Soil Organic Carbon Pool And Mineralization Characteristics Of Forest Stands In Haituo Mountain

Forest plays an important role in carbon sink in the global carbon cycle.Haituo Mountain is one of the important forest areas in Huabei region.The research selected four different typical forest stands Chinese pine(Pinus tabuliformis Carriere.),elm(Ulmus pumila L.),white birch(Betula platyphylla Suk.),aspen(Populus davidiana Dode.),choose different sample sites,collected soil sample from different soil layer(0?100cm),determined the characteristics of soil organic carbon(SOC)content and density and their relation to soil physi-chemical properties.Laboratory constant-temperature incubation was conducted to measure mineralization rate and cumulative mineralization of soil organic carbon,and the data from the incubation experiment were fitted to a three-pool first-order model.Aimed to accurately evaluate the forest soil carbon pools and provide scientific information for assessment of the forest ecosystem services in North China,Main results are as follows:(1)Soil organic carbon content was between 2.76?46.82g·kg^-1.The mean SOC content of the stands was in the following descending order:white birch,elm,Chinese pine,aspen.Stands type had a significant effect on SOC content(p<0.05).All stands showed similar tendency vertical distribution in SOC content:decreasing from top horizon to bottom,with a higher concentration on the top horizon(0?20cm horizon accounted for(45%).(2)The SOC density ranged 3.67?88.18t·hm^-2 within 100cm in all studied forest stands.The mean SOC densities of the studied stands was in the following descending order:white birch,elm,aspen,Chinese pine.The SOC density decreasing from top horizon to bottom,with a higher density on the top horizon(0?20cm horizon accounted 36%?64%).SOC content in all studied stands had significant positive correlation to total nitrogen content(r=0.880?0.999),and significant negative correlation to bulk density(r=-0.948?-0.998)(p<0.01).(3)All studied forest stands had similar decomposition dynamic pattern with the rapid decomposition in the initial incubation stages(0?13d)and slowly declined(30?50d)and in the end to a steady state in the end(50?90d).Soil active carbon pool and slow carbon pool decreased with soil depth,while their proportions in SOC in the order of elm>white birch>aspen>Chinese pine.The mean retention time in field(MRTa)of soil active carbon pool ranged from 36 to 86 d,while the MRTs of slow carbon pool varied between 19 to 118a.Stand type was proved one of the significant factors controlling SOC mineralization process,and its effect tended to decreasing with soil depth.The organic carbon pool of the broad-leaved forest soil was generally more actively turnover and had a higher slow carbon pool use efficiency than that of the coniferous forest.In summary,in forest stand,soil organic carbon characteristics of content,density,mineralization rate and quantity controlled by a varity of factors,but forest stands have remarkable effects on soil organic carbon pool and mineralization processes.