Soil Organic Carbon Dynamics And General Model For The Dynamics In Several Temperate Zones Of Different Ecosystems

This paper studied the size and the dynamics of soil organic carbon in main temperate zones of different ecosystems basing on the three pool theory and simulated the general model for the dynamics(kc=α×{1+[b×(t/c)^d-1]/e^t/c} a,b,c,d are parameters to be determined ) combining with soil physical and chemical properties. Soil samples are obtained from humid subtropical grassland ecosystem,humid temperate grassland ecosystem,humid subtropical forest ecosystem,humid temperate forest ecosystem,arid temperate forest ecosystem and humid subtropical maize farmland ecosystem.The results show:there is a fast decomposition rate in the early incubation stage (about 0 - 30 days ) and a slower in the late.Decomposition quantity in the fast stage amounts to 30%- 50%of the whole decomposition quantity.The decomposition rate of topsoil organic carbon in different soil types is yellow soil＞red soil in humid subtropical grassland ecosystem;Subalpine shrub meadow soil＞alpine meadow soil＞alpine chestnut soil＞alpine coarse chestnut soil＞sierozem in humid temperate grassland ecosystem; limestone soil＞yellow soil＞red soil＞yellow brown soil in humid subtropical shrub forest ecosystem;bog soil＞albic planosol＞humus,volcanic ash soil in humid temperate birch forest ecosystem;graycinnamon soil＞dark brown soil＞subalpine meadow soil in humid temperate evergreen conifer forest ecosystem;sandy loam＞sandy soil in arid temperate red willow forest ecosystem;red clay of red soil＞red sandstone ofred soil in humid subtropical peanut farmland ecosystem;gley yellow clayey soil≈water-logging yellow clayey soil＞submerging yellow clayey soil＞bleached yellow clayey soil in humid subtropical rice farmland ecosystem;The decomposition rate of topsoil organic carbon with different vegetations in humid subtropical forest ecosystem is mixed wood＞conifer forest＞shrub forest＞evergreen broadleaf forest of red soil;shrub forest＞evergreen broadleaf forest＞conifer forest of yellow soil;mixed wood＞shrub forest of yellow brown soil.The soil organic carbon dynamics of forest ecosystem would change with hundreds of years,which shows that mature spruce forest's decomposition rate is faster than original spruce forest's in humid temperate climate.The soil organic carbon dynamics of farmland ecosystem would change with several decades,which shows that there was no significant difference between 0 year cultivation and 5 years cultivation,while 30 years cultivation's decomposition rate was significantly slower than theirs.In the vertical scale the decomposition quantity in topsoil is faster than that in second layer and the bottom layer.The pool size of active soil organic carbon is from 0.033 g/kg to 1.731 g/kg,and the proportion is from 0.45%to 42.12%.The pool size of slow soil organic carbon is from 0.083 g/kg to 64.082 g/kg,and the proportion is from 5.38%to 81.68%.The pool size of passive soil organic carbon is from 0.407 g/kg to 70.910 g/kg,and the proportion is from 17.100%to 77.320%.The mean residue time for active and slow pool are 4～161 days and 1～161 years.Because of the influence with soil types,entiroment,landuse,climate and soil layers,the proportion and mean residue time of each soil organic carbon pool in different ecosystem are discrepant.Those difference shows:frequent cultivation reduced soil carbon sequestration capacity;a lack of water is not propitious to organic carbon fixation;temperate climate is propitious to organic carbon fixation;humid temperate grassland ecosystem is the best for carbon sequestration.Simulating parameters for the general model of soil organic carbon dynamics with SAS9.0 non-linear process,the simulated curve and the mensurated curve have a good consistency.Combine parameter a,b,c,d with soil physical and chemical parameters (including total soil organic carbon,passive carbon,unpassive carbon,PH,soil clay,soil water and bulk density) to find the relativities of them:a has a significant positive correlation(R² =0.706) with total soil organic carbon,and a moderate positive correlation (R² = 0.413) with soil water;b has a moderate positive correlation(R² = 0.476) with soil clay,and a moderate negative correlation(R² =-0.415) with PH;c has a moderate positive correlation(R² = 0.428) with bulk density,and a mildly negative correlation(R²=- 0.269) with soil clay;d has a mildly negative correlation with total organic soil Carbon(R² =-0.363), unpassive carbon(R² =-0.371) and parameters c(R² =- 0.37453).set up equations to express a,b,c and d with soil physical and chemical parameters which are correlative to them,and the precisions of each equation are 0.7806,0.7894,0.4725,0.4854.