抚育间伐对针阔混交天然次生林生物量及碳密度的影响

选取2012年经3种间伐强度(15%、25%、35%)进行抚育间伐的小兴安岭试验样地及对照样地(间伐强度为0),于2019年测定抚育间伐8 a后试验样地的生物量、碳质量分数、碳密度,分析不同间伐强度对林分生物量、碳密度的影响。结果表明:在间伐强度为0、15%、25%、35%时,林分地上部分生物量随间伐强度的增加呈"J"型变化。间伐改变了林木各器官生物量的分配,使树干生物量所占比例整体增大,在间伐强度为15%、25%、35%时,树干生物量所占比例先增大再减小;树枝则相反,间伐使树枝生物量整体减小,并且随间伐强度的增加,树枝生物量所占比例呈先减小再增大的趋势。间伐8 a后,35%间伐强度,林分地上部分的生物量大于对照样地,且碳密度与对照样地无显著差异。15%、25%间伐强度林分生物量,显著小于对照林分、35%间伐强度林分的生物量。间伐8 a后,35%间伐强度样地,树种组成最优,为4色2青3云1冷,阔叶树种和针叶树种生物量分别占总生物量的52.25%、47.75%,且林木竞争压力得到释放,中大径级林木比例增大,有利于林分结构优化。说明试验区以35%强度间伐后,树种组成为4色2青3云1冷的小兴安岭针阔混交天然次生林的中大径级林木比例增大;与对照样地相比,林分生物量增加,碳密度不会显著降低,因此生态系统碳储量不会减少,有利于森林生态系统的碳汇。

Effect of Thinning on Biomass and Carbon Density of Mixed Conifer and Broadleaf Secondary Natural Forest

In 2012, Xiaoxing’an Mountains was selected to carry out thinning experiments of three kinds of intensities and control area. The plot numbers were: CK(control area, unthinned), T15(thinning intensity was about 15%), T25(thinning intensity was about 25%), and T35(thinning intensity was about 35%). In 2019, the effects of different thinning intensities on stand biomass and carbon density were analyzed through field survey and experimental determination. The results showed that when the thinning intensities were 0, 15%, 25% and 35%, the aboveground biomass of the stand showed a J type change with the increase of thinning intensities. Thinning changed the forest biomass distribution of each organ and increased the overall biomass of the trunk. When the thinning intensities was 15%, 25%, and 35%, the proportion of the trunk biomass first increased and then decreased. However, branches were on the contrary. Thinning reduced the overall biomass of branches, and as the intensity of thinning increased, the proportion of branch biomass first decreased and then increased;After 8 a, the aboveground biomass of 35% thinning plot was greater than that of the unthinning plot, and there was no significant difference with the CK plot in carbon densities. The biomass of 15% and 25% thinning intensity plots were significantly lower than that of CK and 35% thinning intensity plots. The composition of dominant tree species of 4 Acer mono 2 Acer tegmentosum 3 Picea asperata 1 Abies fabri of 35% thinning intensity plot was the best composition tree species, and the biomass of broadleaf and conifer tree species accounted for 52.25% and 47.75% of the total biomass, respectively. The 35% thinning intensity released the competitive pressure of trees and increased the percentage of trees with large and medium diameter grades, which was beneficial to the optimization of stand structure. After 8-a treatment with different thinning intensities, the proportion of small DBH trees in the 15% and 25% experimental areas increased, however, the forest biomass and carbon densities decreased. The 35% intensity thinning area with tree species composition of 4 Acer mono 2 Acer tegmentosum 3 Picea asperata 1 Abies fabri, the percentage of middle-diameter and large-diameter trees increased in Xiaoxing’an Mountains, the stand biomass increased, and the carbon density didn’t significantly decrease, so the carbon reserve of the ecosystem didn’t decrease. Therefore, after 8 years, 35% thinning intensity was beneficial to the carbon sink of forest ecosystem.