Impact of selective logging of dominant Acacia mangium trees on understory shrub diversity
[Objective]Selective cutting is a powerful tool to promote the growth and regeneration of understory shrubs.Analyzing the effect and extent of selective cutting of dominant Acacia mangium trees on shrub diversity,and constructing a predictive model for the influence range,can provide significant guidance for establishing scientifically sound selective cutting techniques for A.mangium forests.[Method]76 dominant A.mangium trees in Nanya Forestry Farm,Hainan province,were studied through a selective cutting experiment(monitored from 2014 to 2021).By setting up different plot sizes(0.6 times crown radius,0.8 times crown radius,1.0 times crown radius,1.2 times crown radius,1.4 times crown radius),the maximum influence range of A.mangium trees was determined,and the influence on understory shrub diversity across different recovery periods was analyzed,so as to construct a predictive model for the influence range of dominant A.mangium trees.[Result]The maximum influence range of dominant A.mangium trees on shrub Shannon index and Pielou index were 1.0 times measured crown width and 1.2 times measured crown width,respectively.Selective cutting of A.mangium trees significantly increased understory shrub diversity(P＜0.05),with usual shrub Shannon index and Pielou index significantly increasing within 5 years after cutting(P＜0.05),and the increase rate being not obvious after 5 years(P＞0.05).The predictive models for the influence range of the shrub Shannon index and Pielou index are best represented by Richards'curves,with their respective determination coefficients amounting to 0.702,and root-mean-square percent errors being 14.341%.[Conclusion]The selective cutting of a single A.mangium tree significantly improves understory shrub diversity within a certain range and over a certain period,and its maximum influence range is closely related to the breast height diameter of the A.mangium trees.These findings can provide effective guidance for subsequent density control and reformation of A.mangium forests.
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