黄土高原丘陵区冰草和柳枝稷土壤细沟可蚀性季节动态

Seasonal dynamics of soil rill erodibility under wheatgrass and switchgrass vegetation in the hilly-gully region of Loess Plateau

为了评价黄土高原丘陵区退耕还草水土保持效应,本研究以黄土丘陵区冰草(Agropyron cristatum)和柳枝稷(Panicum virgatum)为研究对象,在不同坡度(S=17.36%~42.26%)和流量(Q=1.0~2.5L·s^(-1))条件下,采用变坡试验水槽测定土壤的分离能力,利用线性回归方法,结合土壤侵蚀过程,运用WEPP模型推求土壤细沟可蚀性(Kr),分析了冰草和柳枝稷生育期内土壤Kr的季节变化规律。结果表明,黄土丘陵区冰草生育期内土壤Kr具有显著的季节变化(P<0.05),总体呈下降趋势;柳枝稷生育期内土壤Kr无显著季节变化(P>0.05)。冰草土壤Kr表现为下降的季节变化,变化范围为0.002 1~0.022 4s·m^(-1);柳枝稷土壤Kr表现为先升高后降低的季节变化,变化范围为0.003 2~0.021 9s·m^(-1)。土壤黏结力、水稳性团聚体和根重密度是影响冰草和柳枝稷生育期内土壤Kr季节变化的主要因素。土壤细沟可蚀性与土壤黏结力、水稳性团聚体及根重密度间呈显著负相关关系。此外,用土壤黏结力和根重密度能够较好地模拟黄土丘陵区冰草和柳枝稷生育期内土壤细沟可蚀性的季节变化。冰草和柳枝稷土壤细沟可蚀性季节变化主要由根系生长和土壤黏结力变化所致。土壤细沟可蚀性与土壤黏结力、水稳性团聚体和根重密度间呈显著负相关关系。用土壤黏结力和根重密度等参数能够较好地模拟冰草和柳枝稷土壤细沟可蚀性的季节变化规律。

In order to evaluate soil and water conservation status in the restored grasslands in ＂Grain for Green＂ history in the hilly-gully region of Loess Plateau, wheatgrass and switchgrass plots were studied. The scouring experiments were carried out in a laboratory to simulate soil detachment by concentrated flow under six slopes （S=17.36%- 442.26%） and discharges （Q= 1.0-2.5 L s-1 ）. Soil rill erodibility （Kr） was estimated by WEPP model. The seasonal dynamics of soil rill erodibility under wheatgrass and switchgrass vegetation were studied during the growing season. Soil rill erodibility under wheatgrass in the hilly-gully region of Loess Plat- eau varied significantly with season （P〈0.05）, revealing a significant decline during the growing season. In contrast, soil rill erodibility under switchgrass cover had no clear seasonal dynamics during the growing season （P〈0.05）. Kr values in wheatgrass plots varied from 0.002 1 to 0.022 4 s m-1. Soil rill erodibility in switch- grass displayed a pattern of seasonal dynamics, including an initial increase, followed by decline. Kr values in switchgrass plots varied from 0.003 2 to 0.021 9 s m-1. The seasonal dynamics of soil rill erodibility of wheat- grass and switchgrass were affected by seasonal changes in soil cohesion, water-stable aggregate content, and grass root density. Significant negative correlation between soil rill erodibility and soil cohesion, water-stable aggregate content, and grass root density were found. In addition, the dynamics of change in soil rill erodibility of wheatgrass and switchgrass plots could be predicted based on with soil cohesion and grass root density. The growth of grass root system and the seasonal change in soil cohesion emerged as the main factors affecting the dynamics of soil rill erodibility of the restored grasslands in the hilly-gully region of Loess Plateau. Soil rill erodibility of the two types of grasslands showed significant negative correlation with soil cohesion and water- stable aggregate content, which are important parameters for simulating the dynamics of soil rill erodibility of the restored grasslands in this region.