不同坡位香椿人工林生长和林分结构差异

研究香椿人工林在不同坡位的生长差异，为香椿人工林的培育生产提供参考。以32~39年生香椿人工林为对象，按照不同坡位（上、中、下）设置样地，测定样地内的香椿生长指标；使用Weibull函数对不同坡位林分直径分布结构进行分析；通过林木分级统计并分析各样地林分特征；解析不同坡位香椿人工林的生长过程。结果表明，试验区香椿人工林呈中高度郁闭，下坡位香椿平均树高为13.71 m，胸径为21.32 cm，南北冠幅为5.29 m，均显著最高，而上坡对应各生长指标显著最低。不同坡位香椿人工林径阶分布的Weibull模型拟合效果为下坡＞上坡＞中坡，拟合形状参数c均在1.0~3.6，为单峰左偏状分布，c_下坡＞c_上坡＞c_中坡，下坡趋向于竞争期更稳定的自然稀疏后期。下坡林分林木分级集中在Ⅱ、Ⅲ级，占81.48%，而上坡Ⅰ、Ⅱ、Ⅲ、Ⅳ级林木占比分别为19.23%、21.79%、37.18%、20.51%，并存有少量Ⅴ级木，林木分级分布相对分散。解析香椿人工林生长过程显示，胸径、树高、材积总生长量均为下坡＞中坡＞下坡。试验区下坡的香椿人工林树高、胸径及冠幅均有生长优势。全试验区林分径阶分布呈单峰左偏状分布，下坡林分趋向于更稳定的自然稀疏后期，且林木分级多集中于Ⅱ、Ⅲ级，胸径、树高、材积总生长量最高。

Growth and Stand Structure Differences of Toona sinensis Plantation from Different Slope Positions

In order to provide reference for the cultivation and production of Toona sinensis plantation,the growth of T.sinensis plantation from different slope positions were studied.The plots were set according to different slope positions (upper,middle and lower).The growth indices of 32-39-year-old T.sinensis trees in the plots were measured.The Weibull function was used to analyze the diameter distribution structure of the T.sinensis plantation with different slope positions.The tree classification of forest stand was analyzed statistically.And the growth processes of different standing forests were studied by analyzing the parse tree.T.sinensis plantation showed a moderately high degree of canopy closure in experimental area.The average tree height,DBH and north-south crown in lower slope was the highest among three slope positions,they were 13.71,21.32,and 5.29 m,respectively,while these growth index in upper slope were the lowest.The imitative effect of Weibull model of the T.sinensis plantation diameter distribution in different slope positions was lower>upper>middle.In the experimental area,the values of fitting shape parameter c were between 1.0 and 3.6,which explained that the stand DBH appeared to be inclined to left side mountain-liking curve.And the lower-slope plantation tended to be more stable in the later stage of natural sparsity due to c_lower>c_upper>c_middle.As for tree classification,the tree grades of T.sinensis plantation in lower slope were concentrated in grade Ⅱ and Ⅲ,accounting for 81.48%.The proportion of grade Ⅰ,Ⅱ,Ⅲ and Ⅳ trees on the upper slopes was 19.23%,21.79%,37.18% and 20.51%,respectively,and there were a small amount of grade Ⅴ trees.It indicated that the tree grade distribution was relatively dispersed.Analysis of the growth process showed that the total DBH,height and volume were lower>middle>upper.In experimental area,the height,DBH and crown width of T.sinensis plantation in lower slope had growth advantages.The forest stand distribution in the whole experimental area showed a left side mountain-liking distribution,and the low-slope tree stand tend to be more stable.The mostly grade in low slope were grade Ⅱ and Ⅲ.Furthermore,the total growth of DBH,tree height and volume in lower slope were the highest.