| Global temperature goes up faster than ever before because of the greenhouse effect, thecontent of CO2in atmosphere was35%higher than the period before the industrial revolution.Forest ecosystem carbon, the maximal part of the terrestrial carbon pool, plays an importantrole in the global carbon cycle and carbon balance. The previous research results show that85%terrestrial vegetation biomass is forest vegetation biomass. Forest carbon storage is thekey factor of the forest absorption and emission of CO2, the estimation of forest carbon is theessential prerequisites of revealing the missing carbon sink. This paper was intended toanalyze the distribution features of carbon density of Betula albo-senensis forest ecosystemon the southern slope of the Qinling Mountains and to determine which factors affect thosefeatures. We have investigated vegetation factors (canopy density, forest density, mean height,mean diameter of breast height) and topographical factors (elevation, gradient, slope position,slope aspect) among122plots and the area each plot is20×30m. Vegetation and soil sampleshave been tested in the laboratory for moisture content, biomass and carbon content. The mainresults were as following:The average vegetation carbon density (VCD) is (68.02±15.52) t·hm-2in the vegetationof Betula albo-sinensis forest, in virgin forest the average VCD was (84.83±6.66)t·hm-2, insecondary forest the average VCD was (61.92±12.77)t·hm-2, and the average VCD betweenthem was significant different. The average VCD was changed in different forest regions, inXunyangba forest region the average VCD was (53.51±6.77)t·hm-2, in Huoditang forestregion was (65.91±11.81)t·hm-2, in Huangbaiyuan forest region was (68.09±16.83) t·hm-2, andin Guanyinshan forest region was (84.55±4.23) t·hm-2. The average VCD on arbor layer was(57.14±14.12) t·hm-2, and on every organ the organic carbon density was different on leaf was(1.10±0.32) t·hm-2, on branch was (11.05±2.81) t·hm-2, on bark was (5.44±1.36) t·hm-2, onstem was (30.83±7.48) t·hm-2, and on root was (8.72±2.22) t·hm-2, in the rest vegetation layer,the average VCD was (1.37±0.52) t·hm-2on shrub layer,was (0.62±0.25) t·hm-2on herb layer,and was (9.08±3.12) t·hm-2on litter layer, one-way ANOVA analysis shows that the VCD ofBetula albo-senensis forest was significant dissimilar in four forest regions and differentvegetation layer. The VOCD of Betula albo-senensis forest was positively correlated with stand age, forest density and canopy density. However, the VCD of Betula albo-senensisforest was first increasing and then decreasing with the elevation and gradient increasing.Principal competent analysis result shows that elevation and stand were the first principalcompetent that affecting VCD, gradient was the second principal competent that affectingVCD, forest density and canopy density were the third principal competent that affectingVCD, and the result revealed that84.88%VCD variances came from those four principalcompetent.The average soil organic carbon density(SOCD) was (69.02±12.90) t·hm-2in the soilunder Betula albo-sinenswas forest. In virgin forest the average SOCD was (76.21±10.83)t·hm-2, in secondary forest was (65.24±12.32) t·hm-2, and the average SOCD between themwas significant different. The average SOCD was decreasing with the increment of thethickness, in layer A the average SOCD was(31.52±6.57) t·hm-2, layer B was(27.18±6.49)t·hm-2, layer C was(10.32±2.65) t·hm-2. The average SOCD was changed in different forestregions, Xunyangba forest region was (58.80±10.29) t·hm-2, Huoditang forest region was(67.95±10.25) t·hm-2, Huangbaiyuan forest region was (69.63±12.78) t·hm-2, Guanyinshanforest region was (75.82±12.30) t·hm-2.One-way ANOVA analysis shows that the averageSOCD was significantly dissimilar in four forest regions and three layers, not substantiallychanged in different slope position. SOCD between shady slope and sunny slope was notsignificantly different based on the results of t-test. Correlation analysis shows that SOCDwas positively correlated with elevation, stand age, arbor biomass and herbbiomass,negatively correlated with the gradient and forest density. Principal component analysis resultshows that elevation and gradient were the first principal component affecting SOCD, canopydensity and forest density were the second principal component, stand age was the thirdprincipal component, arbor biomass and herb biomass were fourth principal component,which account85.62%of the variance of SOCD. Stepwise regression analysis result showsthat the effect of different factors to soil organic carbon density was discrepant. However,stand age, elevation, gradient, arbor biomass and herb biomass were the primary factorsaffecting SOCD. The difference of forest soil organic carbon density was the comprehensiveresult of topographical and stand factors, using forest investigated data estimating forest soilcarbon storage at larger scales, we should consider the topographical, climatic and standfactors for improving the estimated accuracy.The ecosystem carbon density (ECD)was138.83t·hm-2in Betula albo-sinensis forest. Invirgin forest the average ECD was (158.99±15.01) t·hm-2, in secondary forest was(128.25±20.10) t·hm-2, and the average ECD between them was significant different.One-way ANOVA analysis shows that the average ECD was significantly dissimilar in four forest regions, not substantially changed in different slope position. ECD between shady slopeand sunny slope was not significantly different based on the results of t-test. Correlationanalysis shows that ECD was positively correlated with elevation and stand age, negativelycorrelated with the gradient, canopy density and forest density. Principal component analysisresult shows that elevation and stand age were the first principal component affecting ECD,canopy density and forest density were the second principal component, slope aspect, slopeposition and gradient were the third principal component, which account92.90%of thevariance of ECD. Stepwise regression analysis result shows that the effect of different factorsto ecosystem carbon density was discrepant. However, stand age and elevation were theprimary factors affecting ECD. The difference of forest ecosystem carbon density was thecomprehensive result of topographical and stand factors, using forest investigated dataestimating forest ecosystem carbon storage at larger scales, we should consider thetopographical, climatic and stand factors for improving the estimated accuracy. |
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