红松人工林优势木竞争指数影响因子

在温带湿润气候区东段不同立地条件下的红松人工林内设置面积为600 m~2(20 m×30 m)的70块矩形固定样地。在每个样地内，选取5颗最高且长势较好的优势木作为研究的对象木，用Voronoi图确定优势木相应的竞争木，测定每一块样地内优势木与竞争木之间的距离。采用Hegyi单木竞争指数模型，分析优势木在不同样地水平上的种内竞争强度，探讨林分生长因子、地形因子、土壤养分因子对优势木竞争指数的影响，并对这3类因子与优势木竞争指数进行相应的拟合和相关性分析。结果表明：红松人工林优势木竞争强度随着优势木胸径的增大而变小，并且两者之间的关系服从幂函数；红松优势木的竞争指数与其树高、胸径、冠幅呈极显著的相关关系(P<0.01);坡向、坡位、海拔对竞争指数影响极显著(P<0.01);红松人工林优势木竞争指数的大小与土壤氮磷钾含量均呈极显著的相关关系(P<0.01);pH值对优势木竞争指数的影响不显著。当红松人工林优势木平均胸径达到45cm,优势木平均树高和冠幅大于周围竞争木时，其对周围资源的利用程度增大，林木会发生自然稀疏现象，其所受的竞争压力减小。红松喜光性强，对水分的要求高，...

Analysis on influencing factors of competitive index of dominant trees in Pinus koraiensis plantation

In this paper, 70 fixed plots of 20 m×30 m were setting in the eastern section of Pinus koraiensis plantations under different site conditions in the temperate humid climate zone. In addition, the tree height, diameter at breast height, crown width and forest nutrients of the trees in the sample area were measured. In each sample plot, 5 dominant trees with the highest and better growth were selected as the object trees. The corresponding competitive trees of the object trees were determined by Voronoi diagram, and the distance between the dominant trees and the competitive trees in each plot was measured. Using Hegyi single-tree competition index model, we analyzed the dominant trees in different levels of intraspecific competition intensity, and explored the growth factors, terrain factors, and soil nutrient factors on the influence of the dominant tree competition index. In addition, stand growth factors, topographic factors, soil nutrient factors, and the competitive index of dominant trees were fitted and the correlation was analyzed. The results showed that the competition intensity of Pinus koraiensis decreased with the increase of the diameter at breast height of the dominant trees, and the relationship between them followed a power function. Moreover, the competitive index of dominant trees of Pinus koraiensis was significantly correlated with height, diameter at breast height and crown width (P <0.01). Slope aspect, slope position and altitude had significant effects on the competition index (P <0.01). The competitive index of dominant trees in Pinus koraiensis forest was significantly correlated with soil N, P and K content (P <0.01). The influence of pH value on the competitive index of dominant trees was not significant. When the diameter at breast height of Pinus koraiensis forest reached 45 cm, the tree height was higher than that of the surrounding competitive trees, and the crown width was larger than that of the surrounding competitive trees. With the increased of the utilization of surrounding resources, the natural thinning of trees would occur and the competitive pressure would decrease. Pinus koraiensis liked light and water, which led to its competition index in the shady slope was bigger either uphill or downhill, and the growth of Pinus koraiensis forest was better from top to bottom. By reason of the foregoing, large diameter timber cultivation of Pinus koraiensis plantations should be planted on the middle or lower slopes of semi-shady and semi-sunny slopes, with fertile soil and good permeability.