Structural Characteristics Analysis And Optimal Adjustment Of Spruce-fir Conifer And Broadleaf Mixed Forest Stands

Reasonable analysis of forest structure can provide effective guidance for forest management.The spruce-fir conifer and broadleaf mixed forest stands is a common forest type in the Changbai Mountain area in northeast China.In this study,three plots with the same site conditions were selected,and appropriate forest structure parameters was selected to describe the stand non-spatial structural characteristics such as the tree species composition,diameter structure,and q value.At the same time,the stand spatial structure characteristics was analyzed,such as the mingling of tree species,uniform angle index,spatial advantage degree,competitions,crowing and forest layer diversity.The status of stand structure was evaluated,and then an optimized selective cutting model of stand structure was constructed to simulate and select felling of trees.The characteristics of stand structure before and after selective cutting were compared to quantify the degree of improvement in stand structure after selective cutting.Provide a theoretical reference for forest management in this area.The main research conclusions of this paper are as follows:1)There were some differences in the stand structure among different spruce and firbroadleaved mixed forest plots.The composition of tree species in different plots was different.In different plots,there were more than 13 tree species;the negative exponential function can better fit the diameter structure distribution of three plots;There was a gap between the q value and the ideal q value of the three plots,and a reasonable optimization of the diameter structure was needed.2)The average stand mixing degree was relatively high;Randomly distributed forests was dominant in the plots.The basal area of randomly distributed forests accounted for more than 50% of the total basal area of sample plots;The number of dominant trees is relatively high.The crowding degree of trees was high,and the diversity of forest layers was low.It is necessary to further optimize the stand spatial structure.3)By analyzing the intra-and inter-specific competition of dominant tree species in each plot,the side competition of the dominant tree species was greater than the above competition.Intra-species competition of fir was higher in plot 01 and plot 03.Intra-species competition of tilia amurensis was higher in plot 02.Besides,the dominant tree species and other tree species also had relatively fierce inter-species competition.4)The ternary distribution of the structural parameters contains much more information and can describe the spatial structure characteristics of stands in more detail.As a result,in the plot 01,when the structural parameters were combined into intensity mixed(M = 0.75),random distribution(W = 0.5),and mean state(U = 0.5),the number of trees was largest.In the plot 02,when the structural parameters were combined into extreme intensity mixing(M = 1),random distribution(W = 0.5),and dominant state(U = 0),the number of trees was largest.In the plot 03,when the structural parameters were combined into moderately mixed(M = 0.5),random distribution(W = 0.5),and disadvantaged state(U = 0.75),the number of trees was largest.5)A spatial structure optimization selective cutting model was developed,and then simulate selective cutting on the plot.It was determined that there were 86 selective cutting trees in plot 01,and 72 selective cutting trees in plot 02.The species diversity and diameter structure diversity after selective cutting have remained unchanged,the q value has been adjusted to a reasonable distribution range,the degree of tree species mingling and forest layer diversity have further increased,and the degree of competition and crowding have been decreased.The horizontal distribution pattern of stands tends to be more randomly distributed.The comprehensive selective cutting index of plot 01 and plot 02 increased by 74.20% and 141.94% respectively compared with those before the harvest.The forest structure optimization effect is obvious,and it has reference significance for guiding the forest management in this area.