Effects Of Forest Tending On Carbon Payments Of Oak-pine Mixed Forest In The Qinling Mountains

The forest thinning is one of the most effective ways of anthropogenic interference,which can not only change the structure of forest, but also the forest environment, therefore,resulting in forest ecosystem carbon budget fluctuations. Based on the community surveys,combined with the universal quadratic rotation, the oak-pine mixed forest in the QinlingMountains was studied. The design of universal quadratic rotation combination was used toarrange the experiment as follows: there were five levels (25.00%,22.07%,15.00%,7.93%and5.00%) of forest thinning intensity and five levels (100.00%,85.36%,50.00%,14.64%and0.00%) of the residue removal intensity. Oka-pine mixed forest carbon density and itscarbon dynamics were tested in2012-2013, and also the estimation models of typical shrubbiomass were built and then the optimal forest tending combinaction was built. The resultsshowed:(1) The total carbon density (TCD) in the oak-pine mixed forest was231.79±8.46t hm-2,of which (111.72±6.55) t hm-2in the vegetation represented48.20%of the TCD in the wholeecosystem. The carbon sequestration in soil was (110.74±6.72) t hm-2and47.77%of carbonstock in the whole ecosystem. Carbon density of litter was (9.33±0.75) t hm-2and4.03%ofthe TCD in the whole ecosystem. Carbon density of trees was estimated to be (97.54±5.67)t hm-2, which was87.31%of the vegetation and42.08%of the whole ecosystem. The stemaccumulated47.32%of the tree TCD and shared the highest rate in tree carbon stock. Theannual net primary productivity of oak-pine mixed forest ecosystem was (5.55±0.54) t hm-2a-1and annual carbon stock was (3.04±0.32) t hm-2a-1, equal to (11.14±0.75) t hm-2a-1of CO2.(2) The majority of the best-fit regression equations were cubic equations while theothers are quadratic polynomial equations and power functions; D, D2H and CW were used asthe independent variables of the best-fit regression equations for root, stem, and leaf,respectively. The best-fit regression equations of the whole plant used the D or D2H asindependent variables. These models, which their determination coefficients mostly higherthan90%, the relative error were not more than20%, can be used to estimate the shrubbiomass. The biomass of shrubs was estimated as5017.403kg·hm-2by the best-fit regressionequations in the Huoditang forest region in the Qinling Mountains. (3) Soil respiration rates were not significantly different (P>0.05) among the differentforest thinning treatments over the study period, but showed obvious seasonal variation. Soilrespiration rate was highest in August, ranged from4.12-5.01μmol·m-2·s-1. Annual netvegetation carbon storage increment under different forest tending treatments ranged from5.28-6.74t·hm-2, and the arbor annual net carbon storage increment was the largest, followedby shrub and herb. The carbon balance of payments net change under different thinningintensities in oak-pine mixed forest ranged from0.447to11.455t hm-2. The highest netcarbon balance of payments was11.455t hm-2under treatment3; the lowest was0.447t hm-2under treatment1.(4) Net carbon sequestration was affected more significant by thinning intensitycompared to the intensity of thinning residue remove. When thinning intensity was7.19%~11.44%and thinning residue removal intensity was30.41%~69.59%, net carbon dioxidesequestration was the largest.