杨树农田防护林带单木枝面积的变化

Variation of Branch Surface Area in Individual Tree for Poplar Shelterbelts

枝面积指数同叶面积指数一样,是重要的林分结构特征,但叶面积指数更受重视,而枝面积指数常被忽略（Weiskittel et al.,2006）。枝面积对总呼吸、光能辐射及降雨截留等多种生理生态过程具有重要意义（Bosceta1．，2003；Keim，2004）；枝面积及其垂直分布对森林生物多样性具有重要意义（Ingram et al．，1993）。由于受重视程度不够，

Branch surface area（BSA）,an essential crown structural characteristic,and branch surface area index（BAI）,an important forest structural attribute,have significant implications for studying forest structural and protective effects of shelterbelt.The variation in BSA was investigated for 6-year-old and 9-year-old Populus × euramericana ＂Zhonglin 46＂ stand in Henan Eastern Plain.The results showed that specific shoot area decreased significantly with increasing tree age,and averaged 12.55 and 11.36 cm2·g-1 in 6-year-old and 9-year-old trees,respectively,however,total branch surface area increased significantly with increasing tree age,and averaged 7.53,14.55 m2,respectively.In addition,surface area of the primary branch axis was significantly influenced by the position in the crown.It decreased significantly from the interior to the exterior of the crown,however,vertical distribution of surface area of the primary branch axis wasn＇t the same for 6-year-old and 9-year-old Populus × euramericana ＂Zhonglin 46＂ stand.There were different classes of lateral shoots in different stand age,three classes of lateral shoots in 6-year-old poplar and four classes of lateral shoots in 9-year-old poplar.Lateral shoot surface area decreased over successively higher order.Branch surface area on individual tree was a function of tree size and several variables representing the size and vigor of the crown.This equation was reliable to predict branch surface area at the tree-level and to estimate branch surface area and BAI at the stand-level.