On the Loess Plateau, water is the main limiting factors for vegetation growth. Root distribution characters have special ecological meaning as it reflected the utilizations of trees to the environments. Even-aged stands ofRobinia pseudoacacia on slope lands facing south and north were selected as sampling plots for root distribution investigation. Investigatiing results showed that indicated that on all sites, root biomass decreased with depth, and the distribution depth of fine root was deeper than that of coarser root. The results of variance analysis indicated that there were great differences in root biomass among different diameter classes, and coarser root was the main sources of variance, and the root biomass, especially fine root (?<3mm) biomass on northern exposition sites was bigger than that on southern exposition sites. Analysis of the vertical root distribution parameters, root extinction coefficient, β indicated that the value of β on northern exposition was more than 0.982, while the value of β on southern exposition was less than 0.982, which indicated that the vertical root distribution depth ofRobinia pseudoacacia on southern exposition was deeper than that on southern exposition. And the distribution depth of fine roots (Φ<1mm) was deeper than that of thicker roots(Φ<3mm), which was in favor of the uptake of water and nutrients from deeper layers, helped the trees to adapt the arid environment, and promoted the growth of the upper parts of the tree. Keywords Root diameter classes - Variance analysis - Root extinction coefficient - Vertical distribution characters - Site conditions - Loess Plateau CLC number S792.27.01 Document code A Foundation Item: This research was supported by National Natural Science Foundation of China (30371150 and 40371075).Biography: LI Peng (1974-) male, post: Ph. D. in Northwest Scientific & Technological University of Agriculture and Forestry, Yangling 712100, Shaanxi Province, P. R. China. Tel: 029-82312651.Responsible editor: Chai Ruihal
采用土钻法对黄土高原地区主要造林树种刺槐的根系分布特征进行调查,结果表明不同立地上刺槐根系的空间分布特征具有明显差异.阴坡立地上,刺槐根系随距树干距离的增加表现出了先增加后减少的趋势,并且不同深度土层的分布相对比较均匀,这一分布特征扩大了刺槐根系的吸收空间范围,有利于树木地上部分的生长;而阳坡立地上的刺槐根系随距树干距离的增加呈降低趋,并且各处根系集中分布在40～80 cm的土层中,这一分布特征限制了根系在土层中的吸收空间,进而树木地上部分的生长也产生了一定的限制作用.对不同径级根系生物量分布特征的分析结果表明,不同立地上根系存在的差异主要是由于大径级根系生物量而引起的,阴坡立地上的细根生物量更大一些.在两个立地上,直径为1 mm
