[Distribution patterns of root systems of main planting tree species in Weibei Loess Plateau].

The vertical patterns of root systems of Pinus tabulaeformis, Robinia pseudoacacia, Platycladus orientalis, Pinus sylvestris var. mongolica, Pinus armandi, Prunus armeniacia var. ansu planted in the Weibei Loess Plateau were studied with soil auger. Site conditions had a significant effect on the vertical root distribution of R. pseudoacacia, of which, soil moisture is the key factor. Soil species and soil structure also had great effect on the distribution. P. tabulaeformis had a maximum rooting depth at its young stage(8 years old), but the root density increased with age. There was a great difference in vertical root distribution among the tree species, of them, R. pseudoaccia rooted deepest, which negated the opinion that R. pseudoacacia is a shallow rooted tree species. According to the vertical root distribution of the tree species, the productivity of these species in the south-facing site of yellow loess soil would be in order of R. pseudoacacia > Prunus armeniacia var. ansu > P. tabulaeformis > P. sylvestris var. mongolica > P. armandi > Platycladus orientalis.