Effect Of Thinning Disturbance On Structure And Growth Of Coniferous And Broad-leaved Mixed Forest In Jiaohe Jilin Province

Thinning,as the main way of forest management,can create a good environment for forest growth,regulate stand structure,affect stand species diversity and productivity,and cause great disturbance to the soil under the forest.At present,there are many studies on the effects of cutting on stand growth,but there are few qualitative studies on the relationship between stand growth,species diversity and soil nutrients.In this paper,the effects of cutting on the growth process of main tree species Pinus koraiensis,Ulmus japonica var.japonica and Acer mono were analyzed.Variance analysis was used to analyze the effects of thinning on species diversity,stand structure diversity,productivity and soil nutrients in the process of stand development.The correlation coefficient was used to compare the response level of soil nutrients and species diversity,stand structure diversity,productivity to cutting.The structural equation model was used to analyze the interference degree of cutting on stand structure diversity and function.The results are as follows:1.The growth range of 3 species increased with the increase of cutting intensity after felling.In terms of annual growth,Pinus koraiensis was the highest in the cutting plot with 40% intensity,Ulmus japonica var.japonica was the highest in the control plot,and Acer mono was the highest in the cutting plot with 20% intensity.With the increase of time after felling,the growth rates of different species were different.Acer mono was the largest in the cutting plot with 40% intensity,and Pinus koraiensis and Ulmus japonica var.japonica were the largest in the plot with 60% cutting intensity.2.With the increase of time after felling,the species diversity of each plot tended to be stable,and the difference was not significant.The overall change trend of stand structure diversity was consistent with the cutting intensity,which decreased with the increase of cutting intensity,and gradually recovered with the increase of time.The proportion of small diameter trees in the felled plots increased with the increase of cutting intensity,which was higher than that in the control plot.The productivity is greatly affected by cutting,and the overall trend is to decrease with the increase of intensity.At the same time,productivity gradually increases over time,and the growth rate is getting faster and faster.The growth rate of cutting plot with 60% intensity was the fastest.The cutting intensity has a great disturbance on soil nutrients.And the response of different soil nutrients contents to cutting is different.3.The correlation degree between soil nutrients and species diversity,stand structure diversity and productivity was the highest in the control plot,and the correlation decreased with the increase of cutting intensity.Among them,the correlation between soil nutrients and stand structure diversity is stronger than species diversity and productivity.4.In the structural equation model,stand structure diversity and stand density have direct and significant positive effect on productivity.Cutting has a direct and significant negative effect on stand density and stand structure diversity.Stand density has a direct and significant positive effect on species richness and stand structure diversity.Species diversity has a direct and significant positive effect on stand structure diversity.Cutting has no direct effect on productivity,but indirectly affects productivity through stand density and stand structure diversity.Cutting has an indirect effect on species diversity through stand density.Species diversity indirectly affects productivity through stand structure diversity.Compared with species diversity,stand structure diversity has a more direct and significant effect on productivity.To sum up,in order to formulate forest management measures and to achieve the best forest growth environment and the maximum ecological benefit,attention should be paid to the protection of soil environment while maintaining biodiversity,and the stand structure should be adjusted according to the characteristics of species and the interaction among species.