[Study on thinning to Robinia pseudoacacia forest on the Loess Plateau]

Radiation, temperature and soil moisture in the forests, the biodiversity and productivity of understory plants, and the growth of trees among 3 thinned 9-year-old Robinia pseudoacacia forests (735 individuals.hm-2, 1110 individuals.hm-2, and 1480 individuals.hm-2) and non-thinning forest (2220 individuals.hm-2) were analyzed comparatively. The results showed that thinning could improve growing condition of trees and understory plants, so that the biodiversity and biomass of understory plants and producing ability of trees were increased. When the remaining density was 1110 individuals.hm-2, the soil moisture was increased by 40% comparing with the non-thinning forest in whole growing seasons. The biodiversity and biomass of understory plants and productivity of trees were increased significantly. If the thinning intensity were increased continuously, the growth of understory plants and trees would reach the maximum and not increase any longer. Therefore, the thinning intensity with remaining density of 1110 individuals.hm-2 was optimum for black locust forest in this region.