| The carbon cycling and carbon storage in forests play an important role in the studies of carbon cycling and climate change in global terrestrial ecosystems.A precise estimation of the carbon storage and its changes in different types of forest ecosystems can provide theoretical basis for the management of forest resources.In this study,we chosed the Castanopsis forest in Guangzhou as the research object,through the investigation and sampling analysis of the components of the ecosystem(including trees,shrubs,herbs,litters,fine roots and soil),the biomass carbon storage was estimated,and the driving factors were discussed by using the structural equation model method.Ther main conclusions of this study are as follows:1)The main dominant species of Castanopsis forest were Castanopsis fissa,Catanopsis chinensis,Castanopsis faberi,Schima superba and Castanopsis hystrix.The tree carbon content of Castanopsis forest varied with species and organs.There was no significant difference in the carbon content of the same organ among the five main dominant species,no significant difference in the carbon content of the stem and leaves of the same tree specie,but with a significant difference in the carbon content of the branches and roots.In general,the carbon content of different tree organs was in order of stems,leaves,branches,and roots,with an average carbon content value of 48.20%,47.49%,46.88%and 45.63%,respectively.The average carbon content of Machilus chinensis,Cunninghamia lanceolata and Diospyros morrisiana was 49%,while the average carbon content of Castanopsis fargesii and Castanopsis fordii was less than45%,The soil carbon content decreased with the soil depth,with a significant difference between each two soil layers.Carbon content in the soil from 0-10cm,10-20cm,20-30cm,30-50cm and50-100cm layers were about 2.1%-2.3%,1.48%-1.5%,1.1%-1.2%,0.75%-0.8%,0.6%-0.7%,respectively.2)Forest origin and stand age have great influence on carbon storage of Castanopsis forest in Guangzhou.In terms of different forest origin,The ecosystem carbon density in natural forest(202.53 t/hm~2)was higher than the planted forest(178.86 t/hm~2),and the carbon density of vegetation and soil were not significantly different in size and percentage.In terms of different forest ages,the carbon density of vegetation of planted forest differs greatly from that of soil,which is about 62.77 t/hm~2,while the carbon density of vegetation of natural forest differs little from that of soil,which is about 22.38 t/hm~2.The carbon density of natural forest and planted forest of Castanopsis forest increases with the growth of forest age,and the soil carbon density of natural forest of Castanopsis forest has similar trend(except for near-mature forest),but there is no significant difference in the carbon density of soil of planted forest.The vegetation carbon density of natural forest was higher than that of planted forest,which was dominated by arbor layer(accounting for more than 80%),while the undergrowth layer(fineroost layer,litter layer,herb layer and shrub layer)accounted for less.There was little difference in total soil carbon density between natural forest and planted forest(100cm deep),which was close to 100 t/hm~2.The carbon sink capacity of planted forest vegetation is higher than that of natural forests,and the carbon sink capacity of each forest age vegetation was in the order of young forest,mature forest and immature forest,with the value of 6.00±2.91 t/hm~2·a,5.50±2.01 t/hm~2·a,5.32±2.31t/hm~2·a,respectively.The latter two values are close.There is a strong correlation between the increase of carbon density of vegetation in Castanopsis forest and its own carbon density.3)The vegetation carbon density of the Castanopsis forest in Guangzhou was influenced by the forest structure,climate,soil properties and the human disturbance intensity,among which the forest structure and soil properties showed the direct effects,while the climate and the human disturbance intensity showed the both direct and indirect effects. |
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