Effects Of Thinning On Stand Structure In Quercus Variabilis Artificial Forest

Quercus variabilis plantation is one of the most representative stand types of deciduous broad-leaved forests.Thinning is an important way of close-to-natural management of plantation.The effect of thinning on the stand structure of Quercus variabilis plantation was studied,which provides decision-making basis for cultivation of large-diameter timber and the sustainable management of Quercus variabilis plantation.In this paper,Quercus variabilis plantation in Dengfeng state-owned Forest Farm was used as the research object.The representative stand was selected for thinning treatment in the forest farm,and the uncultivated thinning forest was set as the control in the stand with the same growth and environmental conditions.A fixed large plot with a total area of 1 hm2(100 m × 100 m)was set in the tending stand and the uncultivated stand,respectively.Each tree was investigated and located in the sample plots,and target tree investigation was conducted to analyze the effects of thinning on the diameter structure,tree height structure,spatial structure characteristics,tree point pattern and individual distribution pattern of target trees of Quercus variabilis plantation in Dengfeng state-owned Forest Farm.This will provide data reference for sustainable management of Quercus variabilis plantation in Dengfeng state-owned Forest Farm.The main results are as follows:1.From the overall distribution characteristics of the diameter distribution and height distribution of stand in tending plot and control plot,it can be seen that the diameter structure and height structure of stand were adjusted by thinning,so that the diameter structure and height structure of the stand tend to be reasonable.The KS test and AD test were used to test the fitting goodness of tree diameter distribution and tree height distribution in tending plot and control plot.The result showed that the diameter distribution of tending plot was optimally fitted by Weibull distribution and Normal distribution.The tree height distribution of tending plot was best fitted by the Weibull distribution and the Normal distribution.2.Based on the Voronoi diagram and the Delaunay triangle network,the basic spatial structure unit of stand was determined,and the spatial structure parameters of stand were calculated.The results show that thinning is beneficial to increase tree species spatial segregation of stand.The average mingling degrees of tending plot and control plot were 0.0487 and 0.0311,respectively,which belong to weak mixing.Thinning can optimize the spatial distribution pattern of standing trees in stand,and reduce the spatial compression between trees,and make trees more random and evenly distributed.The average uniform angle indexex of tending plot and control plot were 0.3696 and 0.3815,respectively,and the average spatial density indexes were 0.5701 and 0.7159 respectively.Thinning reduced the competition intensity of stand and improved the tree dominance.Trees with pressure or growth at a disadvantage were released,which is conducive to the rapid growth of reserved trees.The average competition index of tending plot and control plot were 2.9466 and 4.7714,respectively,and the average dominance were 0.4946 and 0.4987,respectively.3.The study on the bivariate distribution characteristics of stand spatial structure parameters showed that thinning reduces the proportion of trees with the same degree of differentiation and adjacent trees with the same species,and the proportion was reduced from 90.90% of the control plot to 85.32% of the tending plot,increased the proportion of trees randomly distributed and associated with another species.Thinning increased the proportion of trees with random distribution and associated with another species,and the proportion was increased from 6.25% of the control plot to 9.98% of the tending plot.The proportion of trees with the same degree of differentiation and random distribution of the tending plot and control plot was approximately equal.4.The research on tree point pattern showed that thinning affected the spatial distribution of the whole sample plot,the dominant tree population and the individuals with different diameters of dominant trees.After the thinning,the overall spatial distribution pattern of stand was improved,and the distribution pattern of trees in the stand tended to be randomly distributed.Quercus variabilis population in tending plot showed uniform distribution on small scale(0~2 m),weak aggregation distribution on the scale of 2~16 m scale and random distribution on the scale larger than 16 m.Quercus variabilis population in control plot showed aggregation distribution pattern on a wide range of scales(0~33 m),which were randomly distributed on 33~38 m scale and weakly aggregation on larger scale larger than 38 m.5.The study on the individual distribution pattern of target trees showed that thinning promoted the growth of target trees in the stand,reduced the competitive pressure of target trees,increased the competitive radiation range of target trees,and improved the average competitive ability of target trees.The number of target trees determined in tending plot and control plot were both about 60.The average DBH and average tree height of target trees in tending plot were 16.88 cm and 13.81 m,respectively.The average CIi,ME,C,and g_CI competition indices of target trees in in tending plot were 1.6768,0.9755,10.1725,and 1.0210,respectively,which were significantly smaller than those of control plot(2.1431,1.1130,13.6165 and 1.2398)(P<0.05).