黄土高原刺槐根系垂直分布特征研究

摘要

在中国西北黄土高原地区,水分是树木生长发育的主要限制因子.根系分布特征由于反映了树木对环境条件的利用程度而具有更加特殊的生态意义.本研究选择阳坡和阴坡不同立地上年龄一致的刺槐林调查了根系分布特征.根系垂直分布特征的调查结果表明,在所有立地上,根系生物量随着深度的增加而降低,其中细根的分布深度大于粗根的分布深度.方差分析结果表明:不同立地上不同径级根系的分布特征也有明显的差别,粗根是差异存在的主要原因,阴坡立地上的根系生物量,特别是细根生物量大于阳坡立地上的.对根系消弱系数的分析结果表明,阴坡立地上的根系消弱系数大于0.982,而阳坡立地上的根系消弱系数小于0.982,说明阴坡立地上刺槐根系的生物量在深层土壤中的分布相对量更大一些.其中细根的根系消弱系数大于粗根的,这种根系分布特征有利于根系对深层土壤水分养分的吸收利用,进而促进树木地上部分的生长发育.图3表3参15.%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 of Robinia 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(φ<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 of Robinia 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.