抚育间伐对红桦林生态系统碳密度的影响

以秦岭南坡红桦林为对象,设置5个抚育间伐强度(5%、10%、15%、20%和25%)的研究样地以及未间伐对照样地(CK),通过野外调查、样品采集和室内分析,研究抚育间伐5a后红桦林植被层和土壤层以及总有机碳密度的变化规律和差异,以期为秦岭南坡红桦林进行科学抚育经营提供理论支撑和依据。结果表明:1)乔木层碳密度随抚育间伐强度的增大而降低,但当间伐强度>15%时,乔木层碳密度降低趋于平缓;对照分别与间伐强度10%、15%、20%及25%的林分乔木层碳密度之间呈显著、极显著差异;在不同间伐强度间,间伐强度5%林分乔木层碳密度分别与15%、20%和25%呈极显著差异,而其他间伐强度间呈无显著性差异。2)灌木层和草本层碳密度随着间伐强度的增大而增加,但当间伐强度>15%时,灌木层与草本层碳密度增加而趋于降低;灌木层碳密度在CK和不同间伐强度相互间均呈无显著差异;间伐强度10%分别与15%、20%及25%的林分草本层碳密度呈显著、极显著性差异。3)土壤和枯落物层碳密度几乎不受间伐强度的影响,各强度相互之间均呈无显著差异。4)红桦林总碳密度随着抚育间伐强度的增大而降低,抚育间伐强度越大,红桦林的总碳密度降低程度越高。与CK相比,间伐强度5%、10%、15%、20%和25%红桦林总碳密度分别降低了5.56%、14.72%、19.47%、19.15%和26.77%。由此说明,抚育间伐在一定程度上降低了红桦林乔木层的碳储量,而增加了灌木层和草本层的碳储量,对土壤和枯落物层碳储量的影响甚微;当间伐强度为15%时有利于提高红桦林的碳密度。

Effects of Thinning on Carbon Density of Betula albo-sinensis Ecosystem

Taking the Betula albo-sinensis forest occurring in the south slope of Qinling Mountains as research object,6 thinning intensities were set up:0 (control),5%,10%,15%,20% and 25%,through field surveys,sample collection and indoor analysis,change rules of vegetation layer and soil organic carbon density were analyzed in the 5 th year of intemediate cutting to provide a theoretical basis for planning the forest cultivation.The results showed that 1) in the tree layer,the carbon density decreased with thinning intensity.When the thinning intensity was greater than 15%,the carbon density tended to decrease.Difference in the carbon density was significant between the control and the thinning intensity of 10%,extremely significant between the control and the intensities of 15%,20%,and 25%.Among the different thinning intensities,the carbon density of 5% thinning intensity was significantly different with the intensities of 15%,20% and 25% in the tree layer,while there was no significant difference among the the intensities of 15%,20% and 25%.2) In the shrub and herb layer,the carbon density increased with thinning intensity.When the thinning intensity was greater than 15%,the carbon density tended to decrease.There was no significant difference in carbon density between the control and different thinning intensities.The differences in the carbon density between the thinning intensities of 10% and 15%,and 20% was significant,extremely significant between 10% and 25%.3) In the soil and litter layer,the carbon density was almost unaffected by the thinning intensity,and no significant difference was observed between different thinning intensities.4) The total carbon density decreased with the increase of thinning intensity,the greater the thinning intensity,the higher the degree of reduction of total carbon density.Compared with the control,the total carbon densities of 5%,10%,15%,20% and 25% reduced by 5.56%,14.72%,19.47%,19.15%,and 26.77%,respectively.It was concluded that tending thinning reduced carbon storage in the tree layer increased carbon storage in the shrub and herb layer,there was little effect on carbon storage in soil and litter layer.When the thinning intensity was 15%,it could improve the carbon density of the B.albo-sinensis forest.