Spatial distribution pattern of Picea crassifolia population in Dayekou,Gansu Province

The purpose of this study is to obtain an understanding of the spatial distribution pattern of Picea crassifolia population,deduce the key parameters for a quantitative remote sensing inversion of largescaled P.crassifolia population and provide a basis for the protection of P.crassifolia populations and sustainable management of the forest for conservation of water supply in the Qilian Mountains,northwestern China.Based on the inventory data of a 1 hm2 sample plot in Dayekou of Gansu Province,we studied the spatial distribution patterns of a P.crassifolia population using an analytical point pattern method and investigated the spatial patterns of trees at different age classes under different spatial scales.First,a Weibull function was used to analyze the distribution of DBH (diameter at breast height).Then,the methods of point pattern analysis and aggregation indices were employed to study the spatial distribution patterns of trees at different age classes under different spatial scales.Finally,a Neymans type A distribution was used to simulate the spatial distribution pattern of P.crassifolia population.The results show that: 1) the DBH distribution of P.crassifolia conforms to the Weibull function;2) the distribution of the population is dense and follows an aggregation pattern;3 ) the spatial distribution patterns of young,small,middle and big trees all obey the aggregation distribution under different scales;4) the aggregation intensity decreases with the growth of P.crassifolia population and 5) the spatial distribution pattern of P.crassifolia conforms to the Neyman  s type A distribution.The aggregation distribution of the population could result from natural and human disturbance,environmental conditions and biological characteristics of P.crassifolia.