Structure Characters of Pinus tabulaeformis Natural Forest on Xiaolong Mountain

The structure characters of Pinus tabulaeformis natural forest on Xiaolong Mountain,Gansu Province was studied by fixed sample survey of each tree positioning data with statistical software,the result showed that the tree composition of Pinus tabulaeformis natural forest was abundants,there had 18 tree species in community dominated by P.tabulaeformis,however,the degree of tree species segregation was lower and the average value of mingling was weak.The diameter at breast height(DBH) distribution of forest stand followed a multi-shaped peak curve and the DBH distribution of P.tabulaeformis population approximated to normal distribution and it was well fitted by Weibull function,the tree height increased with the tree DBH increasing and the relationship between tree height and DBH was well fitted by power function.The individual size of DBH,tree height and crown width of P.tabulaeformis in stand was significantly differentiated;the average state belonged to medium.Both the horizontal distribution patterns of stand and P.tabulaeformis population were random distributed.