不同立地条件下荆条根系分布规律

Researches on Root Distribution of Vitex negundo var. heterophylla(Franch.) Rehd. on Different Sites Conditions

根系分布特征有着特殊的生态意义,它反映出植物适应和改造环境的功能.采用土钻法对北京市门头沟区常见的灌木-荆条的根系特征进行调查和研究.结果表明,不同立地条件下的荆条根系分布特征具有明显的差异,不同径级(d≤1mm/d>1mm)的根系生物量随土壤深度呈指数减少;不同立地条件下根系密度的垂直分布,均表现为从土壤表层到深层逐次递减,在各土层中,0—60cm土层中分布的根系密度所占的比重最大;而根系密度的垂直分布,也均表现为随着距离树干的距离增大逐次递减,0—40cm土层中分布的根系密度所占的比重最大.阴坡立地上的根系密度和生物量均小于阳坡立地,≤1mm的根系分布深度要大于>1mm根系,有利于刺槐对深层土壤中水分、养分的吸收,适应干旱环境.

Root distribution characters have special ecological meaning as it reflected the utilizations of trees to the environments. Soil drilling method is applied for root distribution characters investigation of the common shrub [ Vitex negundo var. heterophylla （ Franch. ） Rehd. ] in Mentougou District of Beijing. The results indicate that there is obvious difference in the root distribution characters and root biomass of different diameter （ d ≤ 1 mm/d 〉 1 mm） decline exponentially with soil depth on different sites, root biomass of different diameter decline exponentially with soil depth. The vertical distribution of root density under different site conditions showed a gradually decreasing from soil top-layer to deep-layer. The ratio of root density in 0-60cm soil layer to the total was the biggest. The horizontal distribution of root density also showed a gradually decreasing with the distance from near-trunk farer-trunk. The ratio of root density in 0-40cm to the total was the biggest. Root density on northern slope is smaller than that on southern slope. And the distribution depth of d ≤ 1 mm is deeper than that of d 〉 1 mm, which is in favor of the up take of water and nutrients from deeper layers, helps the trees to adapt the arid environment.