低丘红壤区农林间作系统水分利用竞争性评价

农林复合系统由于其复杂的物种配置、下垫面差异及土壤水力学性质的空间变异,可能影响土壤水分运动及水量平衡,并决定物种间水分竞争性。本文研究了南方低丘红壤区花生南酸枣农林复合系统中土壤水分的时空动态、土壤水流通量和方向的二维变化;结合土壤水量平衡,评价了农林复合系统组分间的土壤水分竞争关系。研究结果表明:农林复合系统能够利用50～100 cm土层土壤水分,对干旱有一定缓冲作用;但在季节性干旱土壤水分期向树行运动,说明南酸枣与花生间作系统也存在着水分竞争,竞争同树龄和空间距离有关。花生的种植减小了地表径流却加剧了土壤的流失。农林复合系统改变了土壤水量平衡,复合后系统蒸散量提高5%～12%,而净渗漏量及土壤水分贮存量减小。农林复合系统减小了30～100 cm土壤水分运动通量,引起土壤水分运动方向变化,影响了作物水分利用体系,需在设计优化管理水资源的农林复合模式时充分考虑这些因素。

Competitive assessment of water use in alley cropping system in low hilly red soil region

Alley cropping system may influence water movement and balance owing to its complex interactions between crop and tree rooting systems as well as spatial variation of landscapes and characteristic of soil hydraulics. The objective of this study is to analyze the temporal and spatial variations of soil water regime, to quantify two dimensional water fluxes and directions and to evaluate water use in one alley cropping system, consisting of Choerospondias axillaris and peanut (Arachis hypogaea) in subtropical China. A multi-layered water balance model, with water movement between layers along soil water potential was applied. The test period was from March 1999 to December 2002 in fifteen experimental plots. The result showed Choerospondias axillaris could utilize soil water in deep soil (50-100 cm depth) and alleviate the seasonal drought. The direction of soil water movement indicated that soil water moved to hedgerow of Choerospondias axillaris, which indicated that Choerospondias axillaris also competed with peanut for water in the tested alley cropping systems especially in seasonal drought. Water competition was related to the tree spacing and tree age. The alley cropping system increased 5%-12% of evapotranspiration, decreased net drainage and water storage, and decreased 50%-60% of runoff after cultivation of peanut. The alley cropping system can change soil water balance and water use patterns, which is needed to be considered in the ecological construction.