金沙江干热河谷区不同坡位引种巨菌草(Cenchrus fungigraminus)对土壤物理性质与水分特征的影响

Effects of the introduction of Cenchrus fungigraminus in different slope positions on soil physical properties and moisture characteristics in the dry hot valley of the Jinsha River

金沙江干热河谷区土壤侵蚀剧烈,生态环境极度脆弱,其坡面植被治理与土壤属性备受关注.选择巨菌草样地为研究对象,以裸地为对照,比较旱雨季不同坡位各层土壤物理性质与水分特征差异.结果表明,巨菌草样地砂粒含量与容重显著低于对照,黏粒含量、孔隙度、含水量及持水量均高于对照.巨菌草的种植明显增大了各坡位间土壤机械组成、容重、孔隙度、含水量及持水量差异的幅度.随着坡位由上至下,巨菌草样地容重分别为1.26 g/cm^(3)、1.16 g/cm^(3)、1.21 g/cm^(3),即上>下>中坡位;总孔隙度、含水量、最大持水量、毛管持水量分别为39.48%、6.82%、31.69%、26.62%与54.03%、11.09%、47.56%、35.62%及47.13%、8.48%、39.73%、27.60%,即中>下>上坡位;毛管孔隙度分别为33.19%、40.51%、32.83%,即中>上>下坡位;非毛管孔隙度、非毛管持水量分别为6.29%、5.07%与13.52%、11.94%及14.29%、12.13%,即下>中>上坡位.同坡位巨菌草样地随土层加深,砂粒含量与容重增加,其余指标相反;含水量在旱季显著低于雨季,最大持水量、毛管持水量在旱季显著高于雨季,且均在巨菌草样地中较对照样地更为明显.整体而言,种植巨菌草可改善该区土壤物理性质与水分特征,中坡位改良效果最好,上坡位最差.

Soil erosion in the dry hot valley area of the Jinsha River is severe,and the ecological environment is extremely fragile.Management of slope vegetation and soil properties in this area has attracted considerable attention.In this study,the soil of plots with Cenchrus fungigraminus was selected as the research object and bare land was used as the control to compare the differences in soil physical properties and moisture characteristics at different layers on different slope positions during the dry and rainy seasons.The results showed that the contents of soil gravel and soil bulk density in the Cenchrus fungigraminus plots were lower than those in the control,and the contents of soil clay,porosity,natural capacity,and water-holding capacity in the Cenchrus fungigraminus plots were all higher than those in the control.Planting Cenchrus fungigraminus significantly increased the differences in soil mechanical composition,bulk density,porosity,natural capacity,and water-holding capacity among different slope positions.With the change of slope position from upper to lower in the Cenchrus fungigraminus plots,the bulk density was 1.26 g/cm^(3),1.16 g/cm^(3),and 1.21 g/cm^(3),respectively,showing an order of upper>lower>middle slope position;total porosity,natural capacity,maximum water-holding capacity,and capillary water-holding capacity were 39.48%,6.82%,31.69%,26.62%,and 54.03%,11.09%,47.56%,35.62%,and 47.13%,8.48%,39.73%,and 27.60%,respectively,showing an order of middle>lower>upper slope position;capillary porosity was 33.19%,40.51%,and 32.83%,respectively,showing an order of middle>upper>lower slope position;non-capillary porosity,and non-capillary waterholding capacity was 6.29%,5.07%,and 13.52%,11.94%,and 14.29%and 12.13%,respectively,showing an order of lower>middle>upper slope position.For each slope position,the soil gravel content and soil bulk density increased with soil depth,whereas the opposite was true for soil clay content,porosity,natural capacity,and water-holding capacity.For each slope position,the natural soil capacity during the dry season was significantly lower than that during the rainy season,and the maximum and capillary water-holding capacities during the dry season were significantly higher than those during the rainy season.Moreover,all the regularities were more evident in the Cenchrus fungigraminus plots than in the control plots.In summary,our study revealed that the physical properties and moisture characteristics of soil can be improved by Cenchrus fungigraminus planting in dry hot valleys of the Jinsha River area.The improvement effect changed with the slope position,and the soil structure and ecohydrological function were best at the middle slope,followed by the lower slope;the upper slope had the worst soil properties.