Study On Spatial Structure And Stand Visualization Of Pinus Tabuliformis And Quercus Wutaishanica Mixed Forests In Huanglong Mountain

The forest area of Huanglong Mountain, located in Yan’an, Shaanxi Province, is one of the five largest forest area of Shaanxi. It is the green barrier of Weibei Plateau and Guanzhong area with the reputation "Oasis of the Yellow River". Pinus tabuliformis and Quercus wutaishanica mixed forest is one of the main forest type there. In this research, a typical natural secondary Pinus tabuliformis and Quercus wutaishanica mixed sample plot(100 m×100 m) was selected to analyze the spatial structure characteristics, spatial distribution patterns and associations of the main tree species, we also carried out a preliminary study on simulation visualization management of the stand. Some main research results as following were obtained:(1) There were 21 tree species with diameter at breast height(DBH) greater than 1 cm and the forest had abundant species and a high tree density of 2467 plants/hm2. Pinus tabuliformis, Quercus wutaishanica, Betula platyphylla and Acer ginnala were classified as the main tree species with top 4 important values of 25.16%, 20.33%, 19.82% and 8.22%respectively. The average diameter at breast height(DBH) was 9.9 cm and the average tree height is 8.2 cm of the stand. The tree diameter distribution was like an inverse "J" curve,while the tree height distribution was approximately a normal curve.(2) The average mingling degree value of the sample plot was 0.654, while the average neighborhood comparison value was 0.496 and the average angle index value was 0.548. The main tree species Pinus tabuliformis, Quercus wutaishanica, Betula platyphylla and Acer ginnala have the average mingling degree values of 0.50, 0.72, 0.69 and 0.69 respectively and the average neighborhood comparison values of 0.50, 0.52, 0.32 and 0.66 respectively.(3) Pinus tabuliformis, Quercus wutaishanica and Betula platyphylla populations all presented as cluster distribution at the total research scale, Acer ginnala population had a slightly complex spatial distribution pattern, it presented as cluster distribution at the scale of0-31 m and random distribution at the scale of 31-50 m. Pinus tabuliformis, Quercus wutaishanica and Betula platyphylla all had a trend to be random distribution at the largescale. Pinus tabuliformis and Quercus wutaishanica, Pinus tabuliformis and Betula platyphylla, Quercus wutaishanica and Betula platyphylla all had non-significant positive associations, except that Acer ginnala showed non-significant negative associations with other main tree species at the most of the research scale. The overall correlation coefficient was 1.01, so it can be concluded that the tree species presented an overall weak positive association.(4) Based on the investigating data, this research applied the tool module "Tree designer" of the stand visualization system designing the tree form of Pinus tabuliformis and Quercus wutaishanica. Also the data of a representative small sample plot of the stand was selected to implement stand visualization and the paper explored the process of stand visualization management through SVS system.