水保所知识产出(1956---)知识库

枯落物种类及覆盖量差异可能会影响坡面流水动力特性。选取黄土高原丘陵沟壑区典型草地铁杆蒿（菊科）和
白羊草（禾本科）枯落物为研究对象，通过设置 7 个枯落物覆盖量（铁杆蒿为 0～1 000 g/m 2 ，白羊草为 0～600 g/m 2 ）和
2 个降雨强度（60 和 120 mm/h），系统研究枯落物类型及覆盖量对坡面流水动力学特征参数的影响。结果表明：1）相对
裸地对照，枯落物覆盖处理坡面流平均流速、雷诺数和弗汝德数平均减小了 77.3%、18.5%和 87.4%，阻力系数增加了 315
倍；2）枯落物覆盖量的增加可有效减缓流速、流态和增加阻力系数，并且随着枯落物覆盖量的增加，平均流速、雷诺数
和弗汝德数均呈幂函数减小趋势（P＜0.01），而阻力系数呈幂函数增加趋势（P＜0.01）。总体而言，铁杆蒿枯落物对坡面
流水动力参数的影响高于白羊草枯落物。3）逐步回归结果表明各个水动力参数均与流量、枯落物覆盖量和枯落物特征参
数呈显著幂函数关系（R 2 为 0.84～0.92，NSE（Nash-Sutcliffe 系数）为 0.60～0.91，P＜0.01）；除流量和枯落物覆盖量外，
流速和阻力系数还受枯落物直径影响，流态则主要与枯落物密度和长度密切相关。本研究可为揭示枯落物的水土保持机
理，正确评价草地的水土保持效益提供科学参考。

Litter coverage maybe significantly affect hydrodynamic characteristics of overland flow. An artificially simulated
rainfall experiment was carried out to investigate the effects of litter coverage of different species and mass of different levels
on the overland flow hydraulic parameters with a bare slope as the control. There seven litter mass coverages and two rainfall
intensities in the experiment. Typical grassland litter of Artemisia gmelinii with the composite family and Bothriochloa
ischcemum ( Linn .) Keng. with the grass family were selected in the Loess hilly-gully region, the north of Shaanxi province,
China. Seven litter mass coverages were set to Artemisia gmelinii and Bothriochloa ischcemum ( Linn .) Keng. , respectively,
varying from 100 to 1 000 g/m 2 and 50 to 600 g/m 2 for each of those vegetation types and subjected to simulated two rainfall
intensities: 60 and 120 mm/h. A normal rainfall intensity 60 mm/h and a rainstorm rainfall intensity 120 mm/h as the simulated
rainfall intensities. According the extreme rainstorm event “7·26” in Zizhou and Suide, the north of Shaanxi province which
the maximum hourly rainfall was 52 mm, so 60 mm was set to simulate rainfall. During the rainfall experiment, flow velocity
and runoff were measured every three minutes, the water temperature was measured every fifteen minutes, and the Reynolds
number, Froude number and the resistance coefficient were calculated based on flow velocity, flow discharge or water
temperature. The results showed that compared with bare slope control, the flow velocity, Reynolds number and Froude
number of litter coverage treatments were reduced by 77.3%, 18.5%, and 87.4%, respectively. However, the resistance
coefficient was 314 times greater than the reference treatment. The average flow velocity, Reynolds number and Froude
number decreased with the litter mass coverage increased as a power function ( P <0.01), however, the resistance coefficient
increased with a power function ( P <0.01). As a whole, with the litter mass increased, the flow velocity, Reynolds number and
Froude number of Bothriochloa ischcemum ( Linn .) Keng. were larger than that the Artemisia gmelinii ( P <0.01), but the
resistance coefficient was opposite. The stepwise regression results showed that there was a significant ( P <0.01) power
function relationship between flow discharge, litter mass coverage, characteristic parameters of litter and the hydraulic
parameters of the slope ( P <0.01). The R 2 and NSE (Nash-Sutcliffe efficiency coefficient) ranged from 0.84 to 0.92 and 0.60 to
0.91, respectively. In addition to the flow discharge and litter mass coverage, the litter density was the key parameter to affect
the flow velocity. Furthermore, the projected area of litter and the flow pattern had a close relationship, and the litter surface
area was the main parameter for characterizing the resistance coefficient. This study can reveal the soil and water conservation
mechanism of grassland litter and correctly evaluate the soil and water conservation benefits of grassland.