黄土高塬沟壑区植被恢复对不同地貌部位土壤可蚀性的影响

通过采集不同地貌部位（塬面、塬坡和沟坡）各土地利用（农地、草地、灌木地和林地）坡面土壤和根系样品,采用综合土壤可蚀性指数（CSEI）评价了植被恢复对土壤可蚀性的影响。结果表明：（1）不同地貌部位的CSEI差异显著,沟坡CSEI较塬坡和塬面分别增加8.1%和77.7%。（2）塬面草地、灌木地和林地的CSEI较农地分别降低21.1%、29.2%和28.8%;而塬坡和沟坡林地CSEI均低于其他土地利用。（3）CSEI与粘粒含量、砂粒含量、毛管孔隙度、根重密度、根平均直径、根长密度及根表面积密度均呈极显著负相关,而与粉粒含量和土壤容重呈显著正相关关系;粉粒含量、土壤容重和根重密度是影响CSEI的关键因素,其中粉粒含量对CSEI的直接影响最大,而根重密度通过直接或间接作用对CSEI产生负相关影响。建议在塬面上以灌木作为植被恢复模式的首选,而在塬坡和沟坡上选择以乔木为优势群落的恢复模式对水土流失的控制更为有效。

Effects of vegetation restoration on soil erodibility on different geomorphological locations in the loess-tableland and gully region of the Loess Plateau

Vegetation restoration has returned a large number of steep slope farmlands to forests and grasslands, and effectively controlled soil erosion in the Loess Plateau. In the loess-tableland and gully region of the Loess Plateau, loess-tableland, hill-slope and gully-slope are widely distributed. Geomorphological location and land use may lead to differences in soil properties and vegetation root systems, and thus affect soil erodibility. However, few studies have been conducted to explore the impact of vegetation restoration at different geomorphological locations on soil erodibility, and the relationships between soil erodibility and influencing factors. This study was carried out in the Nanxiaogou watershed in the loess-tableland and gully region of the Loess Plateau. The undisturbed topsoil (0-20 cm) of farmland, grassland, shrub land and woodland was sampled on loess-tableland, hill-slope and gully-slope (no farmland on gully-slope). The comprehensive soil erodibility index (CSEI) was obtained by weighted sum method. The results indicated that: (1) The significant difference in CSEI was found among different geomorphological locations. The CSEI of gully-slope was 8.1% and 77.7% higher than those of hill-slope and loess-tableland, respectively. (2) As for the loess-tableland, the CSEI of grassland, shrub land and woodland decreased by 21.1%, 29.2% and 28.8%, respectively compared with that of farmland. For the hill-slope and gully-slopes, the CSEI of woodland was lower than that of other land use types. (3) The CSEI had significantly negative correlations with clay content, sand content, soil capillary porosity, root weight density, root mean diameter, root length density and root surface area density, but significantly positive correlations with silt content and soil bulk density. Multivariate linear stepwise regression indicates that silt content, root mean diameter and soil bulk density are the most important factors influencing CSEI, among which silt content has the greatest direct influence on CSEI, while root mean diameter exerts negative influence on CSEI through direct or indirect effects. This study suggests that shrubs should be the preferred vegetation for vegetation restoration on the loess-tableland. Revegetation with arbor as dominant community may be more effective in controlling soil and water loss on hill-slope and gully-slope.