Research On Stand Structure Of Robinia Pseudoacacia In Weibei Loess Plateau

The indicator of stand structure which is the foundation and manifestation of stand functions is an important frame of reference which includes forest management and forest health assessment.This thesis choose the Robinia pseudoacacia in Weibei Loess Plateau as the study object,analyzing forest basis structure like diameter and height in 33 sample plots,and with the help of the method of distribution type index and method of distance to describe the forest spacing structure.Then to the smallest structural unit based on,using the spatial structure of the parameters,analyzing spacing structure from the diameter and tree height and angle scale.The results indicated that:(1) The diameter distribution of Robinia pseudoacacia forest is near to normal distribution. With the increasing of the stand density more,the skew of stand distribution decreases and the kurtosis increases. With the increasing of the stand age bigger,the skew and kurtosis of the diameter distribution decreases.The skew of the shady slope distribution is smaller than the sunny slope,but the kurtosis is bigger.The law of stand height structure indicate that the tree's height increased with the accretion of tree's diameter,then decreased dissymmetrical to the two poles;the most wood is near to the average diameter and the average height;the tree's number of small diameter class is more than big one's and the similar regulation is displayed roughly in the same tree's diameter class.And inspected byχ2,normal distribution function can precisely imitate the diameter and the height distribution.(2) The result of integrated analysis with method assemble index which related with distance shows that the young forest,middle-age forest and mature forest of Robinia pseudoacacia are aggregated distribution;nearly mature forest and over mature forest are randomized distribution.Application of the method of distribution type index that the results obtained with the method of distance slightly different rules.(3) The distribution of distanceses consistent was single-kurtosis distribution in minimum composition structure cell.(4) Based on the minimum composition structure cell,the average diameter of each age grade is not too different for the diameter.The distribution between height neighood comparison and DBH neighood comparison has a strong advantage of consistency,which has reflected the reference tree and the adjacent tree on the growth advantage.The result of angle analysis shows that the young forest,half aged forest and nearly mature forest are aggregated distribution;mature forest and over mature forest are randomized distribution.In addition,according to the basic selection principles of cutting wood,this paper took the first plot to simulated cutting as an example,then analysised the stand spatial structure after cutting.The result showed that,stand distribution is prone to random distribution after felled.It has some theoretic and practical significance for adjusting the horizontal distribution pattern of plantation stand and improving forest competition relations.