Diameter and height class structure distribution of Parashorea chinensis Wang Hsie.plantations in different slope directions

ObjectiveDiameter and height class structure distribution of Parashorea chinensis Wang Hsie. plantations in different slope directions was analyzed to reveal the growth and development laws of P. chinensis,and provide reference for the selection of site conditions and the estimation on tree height of P. chinensis.MethodRepresentative sample plots of P. chinensis plantations were respectively selected from north and south slope directions and every tree was measured. The upper limit exclusive method was used to divide the diameter and height class,and analyze the diameter and height class structure distribution in north and south slope directions. Six models including linear function,logarithmic function,quadratic function,power function,exponential function and Logistic model were used to fit the diameter at breast height(D)-plant height(H)curve.ResultThe differences of diameter class distribution of P. chinensis plantations were not obvious between the north and south slopes. Ⅵ diameter class on both north and south directions had the most numerous trees(32.00 cm≤D<36.00 cm),which accounted for 32.26% and 35.09% of the total respectively. As a whole,the distribution was normal distribution. The tree number was small in low and high diameter classes,and tree number was large in medium diameter class. The height class structure distribution in north slope of P. chinensis plantations presented normal distribution and the peak of height class distribution appeared at Ⅴ class(27.00 m≤H<30.00 m). While right-deviated normal distribution appeared in height class structure of P. chinensis plantations in south slope,with the peak of height class structure distribution at Ⅶ class(33.00 m≤H<36.00 m). It was obviously higher than the peak of height class in north slope. Power function H=3.096D0.656(R2=0.809)was the optimal equation to fit D-H of P. chinensis plantations in north and south slopes.ConclusionSouth slope has certain promoting effects on the plant height growth of P. chinensis plantations.The power function H=3.096D0.656(R2=0.809)can be used as D-H growth curve of P. chinensis plantations,which is used to select afforestation site and estimate plant height.