杨树农田防护林带单木叶面积的变化

Variation of Leaf Area in Individual Tree for Poplar Shelterbelts

研究豫东平原5,7年生欧美杨107杨农田防护林带单木比叶面积、叶面积的变化,建立预测林带单木叶面积的异速生长模型。结果表明:5,7年生单木比叶面积平均分别为136.6,138.2 cm2.g-1,两者差异不显著;叶面积平均分别为45.4,85.8 m2,两者差异显著。冠层位置对比叶面积、叶面积均有显著影响,从树冠的上层到下层,比叶面积显著增加;而叶面积在两林龄中垂直层次表现出差异性,在水平层次,由内层到外层,叶面积均显著增加。不同林龄林带具有不同级别的枝,各级别枝的叶面积间均有显著差异。异速生长关系表明:树高、胸径、冠长因子都能可靠地预测林带单木叶面积,相比而言,胸径和单木叶面积之间的异速生长模型在测算单木叶面积及其指数时较可靠、方便。

Leaf area （LA） as an essential part of crown structure affects both the growth of forests and protective effects of shelterbelt.The variation in specific leaf area （SLA） and leaf area with position in the crown was investigated for 5-year-old and 7-year-old Populus × euramericana cv.＂74/76＂stand in Henan Eastern Plain.Allometric equations describing the leaf area of the entire crown were developed.The results showed that SLA on individual tree were 136.6,138.2 cm2 ·g-1 in 5-year-old and 7-year-old trees,respectively.However,leaf area on individual tree was significantly influenced by tree age,on average it were 45.4,85.8 m2 in 5-year-old and 7-year-old trees,respectively.Specific leaf area and leaf area were significantly by the position in the crown.Specific leaf area increased significantly from the top to the bottom of the crown.Leaf area increased significantly from the top to the bottom of the crown for 5-year-old stand,however,it in the middle was significantly higher than that in the upper and the lower of the crown for 7-year-old stand,and both increased significantly from the interior to the exterior of the crown.There were different classes of shoots in different stand age,three classes of shoots in Populus × euramericana cv.＂74/76＂ aged 5 years and four classes of shoots in it aged 7 years.Leaf area among several orders of shoots had both significantly difference for 5-year-old and 7-year-old stand.Allometric relationships of leaf area with different tree characteristics indicated that stem diameter at breast height （DBH）,tree height （H） and crown length （CL） were reliable predictors of leaf area at the tree-level,however,the allometric relationships between DBH and leaf area at the tree-level were more reliable and convenient to predict the tree-level leaf area and to estimate leaf area index （LAI）.