植物根系强化黄土土层化学风化速率的作用

Intensifying Impacts of Roots of Woody and Grass Species on Chemical Weathering of Soil on Loess Plateau

黄土的风化主要为植物群落根系的物理作用及其所引起的生物化学作用。利用原状土柱淋滤实验装置及大型挖掘剖面壁法,在陕北黄土丘陵沟壑区进行野外实验研究,定量分析了林、草和农地土壤化学风化的剖面特征及动力学过程。研究结果表明,黄土土层的化学风化具有明显的垂直剖面分异特征,即风化速率随土层深度增加而递减。土壤化学风化的动力学过程可划分为急剧减小和稳定状态两个阶段。不同植被类型土壤风化速率及主导风化矿物组合类型的剖面差异主要受制于直径≤1mm的须根在剖面中的缠绕分布特征。植物根系对土壤风化作用的强化效应为油松林群落>白草群落;油松林群落和白草群落根系显著提高矿物风化速率的稳定土层深度范围分别为0～45cm和0～30cm,有效根密度分别在17根/100cm2和60根/100cm2以上。

Weathering of loess soil is physical and biochemical processes mainly controlled by the root systems of plant community. With the method of a large-size profile for measuring root density and the equipment of undisturbed monolith soil for measuring minerals weathering rates, we investigated effects of roots of woody and grass species on intensifying minerals weathering rates in soil profiles on the Chinese Loess Plateau. The results obtained suggested that minerals weathering had significant variance in the soil profile. The minerals weathering rates decreased with the increase of the soil depth. The dynamic process of mineral weathering could be divided into two phases of sharp decrease and stable phase. For the same vegetation type, minerals weathering rates and differences of the dominant weathering minerals type in soil profiles were mainly depended on the distribution and winding characteristic of plant roots of ≤1 mm in diameters.Intensifying effect of root systems of wood species on minerals weathering rate in soil profiles was greater than that of grass species. The soil depths of plant roots significantly intensifying minerals weathering rates were 0~45 cm for wood and 0~30 cm for grasses. The effective root density of woodland and grassland on minerals weathering rates of soil were 17 roots per 100 cm^2 and 60 roots per 100 cm^2 in soil profile.