The detailed field survey data of the samples

hree plots with typical characteristics in the late stage of the natural secondary changed series were arranged, i.e., Plot I for P. tabulaeformis forests; Plot II for Pinus+Quercus mixed forests; Plot III for Q. wutaishansea forests. Each forest was sampled on both a southern slope and a northern slope (with a due east-due west line as the boundary, the slope at the southern boundary is the sunny slope and the slope at the northern boundary is the shaded slope). With a canopy density of approximately 0.8 based on the adjacent gridding method, the plot was divided into 25 20 m × 20 m small plots. In each small plot, the coordinates (x and y), diameter at breast height in 1.3m (DBH), height (h), and the crown width of adult trees (DBH >3 cm) were measured (Table 1). In addition, 5 2 × 2 m2 bush quadrats and 5 1 × 1 m2 plant quadrats (1 m × 1 m) were respectively arranged at the four corners and at the center of the subplot.