Abstract:

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).

Key words: leaf area;allometric relationship;within-crown position;shelterbelt;Populus ×, euramericana cv."74/76"