滇西南不同土地利用方式坡地土壤大孔隙特征及与饱和导水率的关系

Characteristics of sloping soil macropores and its relationship with saturated hydraulic conductivity of different land use patterns in Southwest Yunnan

【目的】研究滇西南不同土地利用方式坡地土壤大孔隙特征与饱和导水率的变化,为控制滇西南地区坡地水土流失提供参考。【方法】以滇西南6种典型土地利用方式(荒草地、茶地、烤烟地、玉米地、甘蔗地、澳洲坚果地)坡地为研究对象,测定6种坡地不同坡位(坡上、坡下)和土层(0~15,15~30 cm)土壤的基本理化性质、水分穿透曲线、大孔隙特征及饱和导水率,分析不同土地利用方式坡地土壤大孔隙特征与饱和导水率的关系。【结果】(1)滇西南不同土地利用方式坡地土壤基本理化性质存在差异,坡位和土层深度对土壤的基本理化性质有明显影响。(2)滇西南不同土地利用方式坡地的土壤水分出流速率先增加,都在90 s之后基本趋于稳定。6种土地利用方式下0~30 cm土层土壤平均出流速率表现为玉米地>荒草地>澳洲坚果地>茶地>甘蔗地>烤烟地。(3)不同土地利用方式坡地土壤大孔隙半径、面积比与平均体积存在明显差异。荒草地、茶地、玉米地、澳洲坚果地土壤大孔隙平均半径随土层深度的增加而减小,而甘蔗地、烤烟地土壤大孔隙平均半径变化则相反。不同土地利用方式坡地土壤大孔隙面积比与平均体积由大到小均表现为玉米地>荒草地>澳洲坚果地>茶地>甘蔗地>烤烟地。(4)不同土地利用方式坡地土壤饱和导水率差异显著,其中玉米地和荒草地饱和导水率明显高于其他坡地。(5)相关性分析表明,不同土地利用方式坡地土壤大孔隙密度、平均体积与饱和导水率呈线性正相关关系,平均半径与饱和导水率之间呈指数函数关系。土壤大孔隙平均体积与稳定出流速率之间呈线性正相关关系。【结论】不同土地利用方式坡地表层(0~15 cm)和上坡位土壤大孔隙半径大、联通性好,更有利于土壤的滞水减流。

【Objective】This study explored the changes of soil macropore characteristics and saturated hydraulic conductivity of slope filed with different land use patterns in Southwest Yunnan to provide reference for controlling soil and water loss in slope field.【Method】The basic physicochemical properties,water breakthrough curve,macropore characteristics and saturated hydraulic conductivity of soil at different slope positions(up and below of slope)and soil layers(0-15 cm and 15-30 cm)were measured for six land use patterns in Southwest Yunnan(barren grassland,tea filed,tobacco filed,sugar cane filed,corn filed and macadamia filed).Then,the relationship between large pore characteristics of slope soil and saturation conductivity in different land use patterns was analyzed.【Result】(1)There were differences in basic physical and chemical properties of slope soil in different land use patterns in Southwest Yunnan.The slope position and soil depth had significant impacts on basic physical and chemical properties of soil.(2)The soil water effluent rate on slopes of different land use patterns in Southwest Yunnan increased first and stabilized after 90 s.Under the six land use patterns,the average soil outflow rate of 0-30 cm soil layer was in the order of corn filed>barren grassland>macadamia filed>tea filed>sugar cane filed>tobacco filed.(3)There were significant differences in radius,area ratio and average volume of soil macropores in slope soil with different land use patterns.The average radius of soil macropores in barren grassland,tea filed,corn filed and macadamia filed decreased with the increase of soil depth,while the average radius of soil macropores in sugar cane filed and tobacco filed changed differently.The ratio of soil macropore area and average volume of slope soil were in the order of corn filed>barren grassland>macadamia filed>tea filed>sugar cane filed>tobacco filed.(4)The soil saturated hydraulic conductivity of different land use patterns was significantly different,and the saturated hydraulic conductivity of corn field and barren grassland was significantly higher than that of other slopes.(5)Correlation analysis showed that there were linear positive correlations between soil macropore density,average volume and saturated hydraulic conductivity.There was an exponential relationship between mean radius and saturated hydraulic conductivity and there was a linear positive correlation between soil macropore average volume and stable outflow rate.【Conclusion】The surface layer(0-15 cm)and upslope of slope soil had larger soil pore radius and good connectivity in different land use patterns,which is more conducive to restrain water and reduce flow reduction.