采伐干扰对吉林蛟河针阔混交林生产力稳定性的影响

Effects of Disturtance by Thinning on Productivity Stability of Conifer-Broadleaf Mixed Forest in Jiaohe,Jilin Province

【目的】研究采伐干扰对吉林蛟河天然次生针阔混交林林分生产力稳定性的影响,以期为针阔混交林的可持续经营提供理论依据。【方法】2011年7月在吉林蛟河建立4块1 hm^(2)的针阔混交林采伐样地,2011年12月进行抚育采伐,采伐强度为2.7%~77.6%,平均值为39.2%,并于2013、2015和2018年复测保留木,利用样地中100个连续样方的木本植物数据,通过线性回归模型分析采伐强度、林分密度、土壤养分、林木大小分化(胸径Shannon-Wiener指数)和物种多样性(物种Simpson指数)与生产力稳定性的相关性;运用方差分解分析比较不同变量对生产力稳定性的贡献;进而利用结构方程模型探讨采伐对林木大小分化、物种多样性和生产力稳定性的影响及林木大小分化、物种多样性和生产力稳定性之间的关系。【结果】采伐强度与生产力稳定性无显著关系,物种多样性和林木大小分化与生产力稳定性均呈显著正相关(P<0.05),林分密度对生产力稳定性有显著负影响(P<0.05)。在方差分解中,物种多样性单独解释生产力稳定性的19.5%;林分密度和林木大小分化对生产力稳定性的贡献率分别为7.0%和7.6%。采伐强度对林分密度、土壤养分(土壤碳、氮、磷、钙含量的第一主成分)、林木大小分化有极显著的负向影响(P<0.001),路径系数分别为-0.629、-0.316和-0.255,而对物种多样性和生产力稳定性没有显著影响;林分密度、物种多样性和林木大小分化对生产力稳定性都有显著影响(P<0.05),路径系数分别为-2.063、1.652和1.463。林分密度、林木大小分化对生产力稳定性有显著的负向总效应(P<0.05),路径系数分别为-2.365和-0.556,物种多样性对生产力稳定性有显著正向总效应(P<0.05),路径系数为1.652;土壤养分对生产力稳定性无显著的负向总效应的效应;采伐强度对生产力稳定性没有直接显著影响,通过物种多样性和土壤养分对生产力稳定性的间接影响也不显著,而是主要通过林分密度和林木大小分化来影响生产力稳定性的变化,采伐强度对生产力稳定性有显著(P<0.05)的负向总效应,路径系数为-0.290。【结论】采伐强度对生产力稳定性没有直接影响,与生产力稳定性直接相关的影响因素是林分密度、林木大小分化和物种多样性,而采伐是通过调整林分密度和林木大小分化来间接影响生产力稳定性,从而影响森林生产力的变化。因此,在森林经营管理中,合理进行采伐干扰对促进森林生产力稳定性具有重要意义。

【Objective】This paper aims to explore the effect of thinning disturbance on the productivity stability of stand productivity in a secondary natural mixed conifer-broadleaved forest in Jiaohe in Jilin province,in order to provide a theoretical basis for the sustainable management of mixed carboniferous forest.【Method】Four sample plots with an area of 1 hm^(2) were established in the mixed forest in July 2011,thinning was conducted in December 2011 with a thinning intensity ranged from 2.7%to 77.6%with an average of 39.2%.The retained trees were measured in 2013,2015 and 2018.using the data of woody plants obtained from 100 consecutive sample plots,the correlations of the thinning intensity,stand density,soil nutrient,tree size differentiation(DBH Shannon-Wiener index),species diversity(Species Simpson index)and the productivity stability were analyzed by using a linear regression model.Analysis of variance components was used to compare the contributions of different variables to the productivity stability.Furthermore,the effects of thinning on the tree size differentiation,the species diversity and the productivity stability and their inter-relations were analyzed by using structural equation model.【Result】There was no significant correlation of the thinning intensity with the productivity stability,but a significant positive correlation of the species diversity and the tree size differentiation with the productivity stability(P<0.05).The stand density had a significant negative impact on the productivity stability(P<0.05).Among the variance components,that of species diversity alone contributed 19.5%of the productivity stability,those of the stand density and the tree size differentiation contributed to the productivity stability by 7.0%and 7.6%respectively.The thinning intensity had a significant negative effect on the stand density,the soil nutrients(the first principal component of soil carbon,nitrogen,phosphorus and calcium content)and the tree size differentiation(P<0.001),and the path coefficients were-0.629,-0.316,and-0.255 respectively,but had no significant effect on the species diversity and the productivity stability.The stand density,the species diversity,and the tree size differentiation had significant effects on the productivity stability(P<0.05),and the path coefficients were-2.063,1.652 and 1.463 respectively.The stand and the tree size differentiation had significant negative effects on the productivity stability(P<0.05),path coefficients were-2.365 and-0.556,and the species diversity had a significant positive effects on the productivity stability(P<0.05),with a path coefficient of 1.652;the soil nutrients had no significant effects on the productivity stability;The thinning intensity had no significant direct impact on the productivity stability,neither indirect impact on the productivity stability through the species diversity and soil nutrients,but had significant indirect impact mainly through the stand density and the tree size differentiation.The thinning intensity has a significant negative effect on the productivity stability(P<0.05),with a path coefficient of-0.290.【Conclusion】The thinning intensity has no direct impact on the productivity stability.The stand density,the tree size differentiation and the species diversity have direct impact on the productivity stability.The thinning intensity indirectly influences the productivity stability through adjusting the stand density and the tree size differentiation,and further influences the variation of forest productivity.Therefore in forest management,a reasonable thinning interference is of great importance for promoting the stability of forest productivity.