Dead Standing Trees Characteristics Analysis of Pinus sylvestris var. mongolica Natural Forest in Honghuaerji

Objective To understand the characteristics and forming of dead standing trees of Pinus sylvestris var. mongolica natural pure forest and provide the basis for the protection and management of P. sylvestris var. mongolica natural pure forest.

Method Two plots were set up with total station in different density P.sylvestris var. mongolica natural forest with a area of 1 hm² each. All the trees with diameter larger than 5 cm were located and surveyed. The basic characteristics of sample plots, the quantitative characters and class distribution of dead standing trees were analyzed and the concept of living tree ratio was proposed to express the micro environment around dead standing in stand, at the same time, the method of stand spatial structure parameter distribution and bivariate distribution was used to analyze the relationship of the dead standing trees with the nearest 4 adjacent trees.

Result There was significant difference between amounts of seedlings and dead standing in the P. sylvestris var. mongolica natural forest with different density. The plot 1 was less in stand density, where the amounts of both seedlings and dead standing were less, while that of plot 2 were 15 280 stem·hm^-2 and 200 trees respectively. The dead standing trees of P.sylvestris var. mongolica natural pure forest were mainly small diameter and their diameter was below 11 cm. The diameter classes of plot 1 followed a continuous distribution and the range was narrow; the diameter class range of plot 2 was broad and it was discontinuous in 2022 cm, there had 2 dead standing trees which diameter was larger than 23 cm. The distribution pattern of dead standing in P. sylvestris var. mongolica natural pure forest followed a random distribution; mostly the 4 adjacent trees around the dead standing trees were living trees and their diameter larger than that of the dead standing trees in plot 1. In half case, all the 4 adjacent trees around dead standing trees were living trees and more than one-third of dead standing trees which DBH were not minimal. The dead standing trees showed the continuous distribution phenomena in plot 2. The difference of dead standing trees bivariate distribution of the uniform angle index and neighbourhood comparison were not obviously and the difference of dead standing tree bivariate distribution of the uniform angle index and mingling, and neighbourhood comparison were obviously. The proportion of 4 adjacent trees randomly distributed around dead standing trees were all living trees and their DBH larger than that of the dead standing trees were significantly higher in plot 1 than in plot 2, however, the proportion of 4 adjacent trees randomly distributed around dead standing trees were dead standing trees were significantly lower in plot 1 than in plot 2.

Conclusion Mostly, the dead standing trees in P. sylvestris var. mongolica natural pure forest are small diameter trees, the amount of dead standing trees is related to the stand density, and competition is the main reason causing the death of forest trees. When the density of P.sylvestris var. mongolica natural pure forest is too high, it is prone to suffer from pest. Therefore, P. sylvestris var. mongolica natural pure forest need to maintain a reasonable density.