Study On The Effect Of Site Factor And Stand Structure On Regeneration Of Evergreen Broad-leaved Forest In Tianmu Mountain

Natural regeneration is an important ecological process to maintain the stability of forest community structure through population reproduction without human interference.Most of the previous studies focused on the analysis of the direct effects of site factor or stand structure on natural regeneration,while ignoring interaction between them and their indirect effects on natural regeneration.With evergreen broad-leaved forest in Tianmu Mountain of Zhejiang Province as the research object.Based on the data of large-scale fixed sample review in 2020,the factor analysis method was firstly used to comprehensively evaluate the regeneration status of evergreen broad-leaved forest in Tianmu Mountain.Secondly,the stand structure characteristics of evergreen broad-leaved forest in Tianmu Mountain were quantitatively analyzed,and the spatial structure heterogeneity of the stand was evaluated.Finally,the redundancy analysis method was used to screen the dominant factors affecting the regeneration of the forest from site factors and stand structure factors.Based on this,the structural equation model was established to explore the effect of the dominant factors on the regeneration of evergreen broad-leaved forest.The main research conclusions are as follows:(1)The general renewal status of evergreen broad-leaved forest in Tianmu Mountain was good.The species diversity of new generations was the main factor in the regeneration evaluation,followed by its own growth status,individual density and distribution pattern.(2)The tree species diversity was high in the evergreen broad-leaved forest of Tianmu Mountain.The DBH structure and tree height structure of the stand were consistent with the distribution characteristics of uneven aged forest.The complete mixing,competition index,opening degree and storey index were medium,the density degree was relatively dense,and the spatial distribution pattern was weak aggregation distribution.The spatial structure heterogeneity of the forest was medium,and the diversity and stability of the stand structure presented general status,so there was a great room for optimization and adjustment.(3)The redundancy analysis found that the dominant site factors affecting stand structure were soil organic matter and elevation,while the dominant site factors affecting regeneration were elevation,p H value and aspect.The dominant stand structure factors affecting regeneration were average tree height,aggregation index,complete mixing,average DBH and average crown width.(4)The structural equation model analysis showed that elevation,average tree height,p H value and aspect had a great influence on regeneration,and the direct influence was the main way.The effect of soil organic matter on regeneration was mainly indirect.However,the average crown width has significant negative direct and positive indirect effects on regeneration.The density and tree height of new generations were most affected by dominant factors,and with the growth of new generations,the significantly affected regeneration indexes decreased gradually.(5)In the management process of evergreen broad-leaved forest in Tianmu Mountain,the spatial structure heterogeneity can be improved by increasing the uniformity of forest spatial distribution,the degree of tree species isolation,and appropriately reducing the competition and density among trees.Under certain site conditions,reasonable regulation of the stand non-spatial structure is an important management strategy for improving the artificial regeneration of evergreen broad-leaved forest in Tianmu Mountain.