Abstract

In this study, soil drilling and pot-culture methods were applied to study vertical root distributions and root drought resistance of plantation tree species on the Weibei Loess Plateau. Results indicated that site conditions had clear effects on vertical root distribution characteristics of Robinia pseudoacacia. Differences existed in vertical root distributions among the four study species, and R. pesudoacacia had the deepest roots. Results from pot-culture experiments revealed that root vigor decreased gradually with a decrease in soil moisture, and soil moisture levels below a certain level resulted in the death of seedlings. Among the four tree species used in the study, Prunus armeniaca var. ansu Maxim showed the strongest drought resistance, followed by Platycladus orientalis, R. pseudoacacia and Pinus tabulaeformis. Root vigor was affected not only by the degree of soil drought, but also drought duration. When soil moisture was lower than 40% of field water capacity for more than 30 days, growth of P. tabulaeformis was limited, but little negative effect was observed for P. armeniaca var. ansu Maxim, P. orientalis and R. pseudoacacia. Based on the analysis of root distribution and root drought resistance, it can be concluded that P. orientalis and P. armeniaca var. ansu Maxim could be planted on most sites in Chunhua County. R. pesudoacacia could be used in more sites because of its larger root distribution space, while P. tabulaeformis is more suited for sites with better soil moisture conditions, such as northern slopes and valley plains.

Key words: Soil drilling, site types, vertical root distribution, soil drying gradient, root vigor, Weibei Loess Plateau.