What is the optimal number of leaves when measuring leaf area of tree species in a forest community?北大核心CSCD

Aims Leaf size, as one of the easier measured plant morphological traits, reflects response and adaptation of plants to environment and indicates functions and processes of ecosystem. When measuring leaf size (the leaf area, LA) on the field, the common accepted practice considers that the number of leaves picked off is often 10–20. However, what is the optimal number of leaves remains unknown. In this study, we attempt to determine how many leaves should be investigated when the leaf size of a tree is measured. Methods This study selected two dominant tree species (Schima superba, Ss and Liquidambar formosana, Lf) from a broadleaved evergreen and deciduous mixed forest in Jinhua Mountain of Zhejiang Province, eastern China. On the basis of sampling (>2 500 leaves for each tree) in five classes of the diameter of breast height (DBH) of tree species and at six directions for each individual, variations of LA in the two tree species are statistically analyzed. The optimal number of leaves, which can mostly represent the common leaf size feature, is further investigated. Important findings Mean LA of the evergreen tree Ss was smaller than that of the deciduous tree Lf. The former was (41.60 10.88) cm2 (16.74–100.80 cm2) and the latter was (57.65 19.35) cm2 (11.31–129.51 cm2). LA of Lf was significantly related to the DBH, but LA of Ss was not. LA of both trees in the middle DBH class (15–20 cm) was not significantly different from their means. LA of two trees have no significant correlations with the sampling directions, but LA at the east, west and bottom had no significant relationships with their means. Considering the representativeness and practicality in the field sampling, the priority of selecting leaves can target the bottom direction of middle diameter mature trees. Random sampling analysis indicated that, the optimal number of leaves for tree LA measurement is species specific. The optimal number of leaves for Ss is 40 and for Lf is at least 170, respectively. Therefore, when measuring leaf area in a forest community, the optimal sampling number of leaves should not be limited to 10–20 leaves. Under sufficient labor, material and time, more leaves should be measured. © Chinese Journal of Plant Ecology.