祁连山区典型草地生态系统土壤抗冲性影响因子

为探索祁连山区典型草地生态系统土壤抗冲性的影响因子及其效应,采用野外实地放水冲刷法,以一定体积的冲刷水流含沙量为指标,对土壤抗冲性进行了研究,并调查了海拔、坡度、植被高度、植被覆盖度、地上生物量、根系密度、生物多样性、土壤质地等因子,利用通径分析研究了各因子与土壤抗冲性的关系。结果表明:(1)土壤抗冲性与海拔、植被覆盖度、根系密度和土壤砂粒体积分数呈极显著正相关(P0.01),而与坡度和土壤粉粒体积分数呈极显著负相关(P0.01),与地上生物量和物种丰富度呈显著正相关(P0.05),与植被高度不具备显著相关性;(2)通径分析结果显示,植被覆盖度和根系密度是影响祁连山区典型草地生态系统土壤抗冲性的主导因素,植被覆盖度对土壤抗冲性的影响主要表现为强烈的直接作用(0.660),而根系密度对土壤抗冲性的直接作用相对较小(0.286),有较大一部分影响表现为间接作用(0.174);(3)径流含沙量随植被覆盖度和根系密度的增加明显减少,植被覆盖度与径流含沙量间的关系可用指数或对数形式表达,根系密度与径流含沙量间的关系可用指数形式表达。研究显示,在祁连山区典型草地生态系统,与海拔、坡度、地上生物量、植物多样性、土壤质地等因素相比,植被覆盖度和根系密度对土壤抗冲性的影响作用更突出,提高植被覆盖度与根系密度能够有效增强土壤抗冲性。该研究可为祁连山区的土壤侵蚀规律研究及效益评价提供依据。

Analysis of factors impacting soil anti-scourability of typical grassland ecosystems on the Qilian Mountains

As a typical ecological functional zone in northwest China, the Qilian Mountains play an important role in soil and water conservation research for alpine and semi-arid areas. Soil anti-scourability (AS) is an important indicator of the ability of soil to resist flow erosion. To investigate the AS and the factors that impact in typical grassland ecosystems on the Qilian Mountains, the sediment yield of surface runoff was set as an index, artificial field flume experiments were carried out, and correlation, regression analysis, and path analysis were used to analyze the effects of topography, vegetation, and soil properties on AS. Correlation analysis showed that the AS was positively correlated with altitude, vegetation coverage, root density, and sand content at P < 0.01, negatively correlated with slope and silt content at P < 0.01, and positively correlated with vegetation diversity and above-ground biomass at P < 0.05. However, it had no significant correlation with average height of grass. Correlation analysis also showed that there were correlations between some factors (e.g., vegetation coverage and above-ground biomass, altitude, and vegetation coverage), which suggested that there was multicollinearity among factors. To eliminate the multicollinearity and identify the crucial factors, path analysis was used. Path analysis showed that vegetation coverage and root density were crucial factors for the AS of grass ecosystems on the Qilian Mountains. The direct and indirect path coefficients of vegetation coverage were -0.660 and -0.075 respectively, and the direct and indirect path coefficients of root density were -0.286 and -0.174 respectively. This indicates that the influence of vegetation coverage on AS was mainly an intense direct effect, whereas the influence of root density had a weaker direct effect, and there were quite a few non-negligible influences with indirect effects on the AS of root density. The overall contributions of vegetation coverage and root density to the regression equation''s R² were 0.485 and 0.132, respectively. This suggests that vegetation coverage was a more crucial influence factor than root density. Regression analysis was used to determine the relationships between AS and vegetation coverage, and AS and root density. The AS increased obviously with vegetation coverage and root density, the exponential function y=19.73e^-0.02x-3.12(R²=0.57,P < 0.001)could be used to express the relationship between the sediment yield of surface runoff and vegetation coverage, and the exponential function y=11.15e^-191.57x+0.8(R²=0.69,P < 0.001)could be used to express the relationship between the sediment yield of surface runoff and root density. This research indicated that vegetation coverage and root density should be considered key factors in the search for soil erosion rules and benefit evaluations on the Qilian Mountains. Thus, it could be used to increase vegetation coverage and root density of grassland ecosystems by protecting existing vegetation and spreading seeds of plants with well-developed root systems to control soil erosion on the Qilian Mountains. It also provided valuable information for general ecological research.