‘中林46杨’农田防护林单木叶面积特征

叶面积是树冠结构研究的重要内容，影响着林分的生长，对农田防护林防护效能起着现实意义。研究了豫东平原9年生‘中林46杨’农田防护林带单木树冠内叶面积的变化及各级枝叶面积间的变化，建立了预测林带单木叶面积的异速生长模型，并用来测算林带的叶面积。结果表明，冠层位置对叶面积有显著影响。在垂直尺度，叶面积表现为中层显著高于上层和下层；在水平尺度，由内层到外层，显著增加。不同分枝级别枝条的叶面积差异显著，表现为2级枝最高，5级枝最低。树高、胸径、冠长单个因子及其复合因子都能可靠地预测林带单木叶面积。相比而言，选择胸径因子来预测单木叶面积在应用上更为简便。

Leaf Area Characteristics of Populus × euramericana (Dode) Guinier CL. ‘zhonglin 46’ Trees in Shelterbelts

Leaf area （LA） as an essential part of crown structure affects both the growth of forests and protective effects of shelterbelt. The variation in leaf area with position in the crown and with 4 ranks branch were investigated from 4-row 9-year-old Populus x euramericana （Dode） Guinier CL. ‘zhonglin 46＇ sheherbelts in eastern plain of Henan. Allometric equations describing the leaf area of the entire crown were developed, and used to estimate shelterbelts leaf area. The results showed that leaf area were significantly influenced by the position in the crown. Leaf area in the middle was significantly higher than that in the upper and the lower of the crown, and increased significantly from the interior to the exterior of the crown. There were significant differences among branch classes. Leaf area from 5 ranks branch followed the sequence： secondary shoots〉 third shoots〉primary branch〉fourth shoots〉fifth shoots. Stem diameter at breast height （DBH）, tree height （H）, crown length （CL） and their compound indexes were all reliable predictors of leaf area at the tree level. In contrast, it was more convenient to apply DBHto predict leaf area at the tree-level.