Abstract:Root distribution and its resource demands of different aged apple trees are not same. Numerous studies focused on the spatial distribution of roots of specific aged trees and however, few studies were done for different aged apple trees. The spatial distribution of the fine roots of different aged apple trees in the Weibei rainfed tableland was investigated. The fine roots of the 3-aged apple tree were distributed mainly within a range of 1.5 m, horizontally, and within a thickness of 0.5 m, vertically, while those of the 20 and 15-aged apple trees exceeded 2 m in the radial direction and 1.4 m in the vertical direction. The dominated distribution range of the 10-aged tree was greater than that of the 3-aged tree, and it was close to those of the 15 and 20-aged trees. The fine roots of the 3 and 10 aged trees were sparsely distributed, while those of the 20 and 15-aged trees were densely distributed. Evolution of root length density (RLD) of the fine roots can be divided into three stages: range expanding stage (3 and 10-aged), density expanding stage (10 and 15-aged), and density degradation stage (15 and 20-aged). Directional difference in the RLD of fine roots was not distinct. The RLDs in 0-20 cm surface soil for 10, 15, and 20-aged trees were less than those in 20-40 cm soil layer. Peak values for the trees were observed in 40-80 cm soil layer below which the RLDs decreased gradually. The RLD of the 3-aged tree in 0-20 cm surface soil was higher than those in deeper layers. Within 2 m range in radial direction, the RLDs of the 3, 15, and 20-aged trees increased with distance, while that of the 10-aged tree decreased. Some variations of RLD in radial direction were found for all aged trees.