亚热带红壤区不同土地利用方式下的土壤剖面水流特征

以江西省鹰潭市的典型旱地、稻田和林地为研究对象,采用野外亮蓝染色示踪试验结合室内图像处理的方法,量化了各样地土壤剖面染色特征参数,明确了水流类型的剖面分布规律,并揭示了土壤理化性质对水流特征的影响机制。结果表明:染色面积比(SAR)随着土层深度的增加急剧降低,0—60 cm土层的平均SAR表现为稻田(28.16%)高于旱地(21.95%)和林地(18.64%),SAR差异主要体现在5—25 cm土层;染色路径数(SPN)随着土层深度的增加先增加后减小,整个剖面的平均SPN为稻田最多(20条),旱地其次(12条),林地最少(9条)。各样地0—20 cm土层染色路径宽度(SPW)均以1—10 cm为主,水流类型从上至下依次为均质流、非均质指流和高相互作用大孔隙流;对于20 cm以下土层,旱地和稻田的SPW以1 cm为主,水流类型分别以低相互作用大孔隙流和混合作用大孔隙流为主,林地以1—10 cm的SPW为主,主要水流类型为高相互作用大孔隙流。有机质含量、根系密度和土壤机械组成等性质影响了土壤的孔隙特征,进而影响了土壤的饱和导水率和水流特征。为提高红壤区的水分利用效率、减少水土流失,可以通过破除旱地犁底层、减少稻田干湿交替下的裂隙发育,以及增加林地植被多样性等多种方式实现。

Characteristics of Red Soil Water Flows Under Different Land Use Types in the Subtropics Zone

In this study, the water flow of red soils in upland field, paddy field, and forest in Yingtan city were studied by the dye tracing experiment and digital image analysis. The parameters of dye distribution characteristics in three fields were quantified and their water flow patterns were defined. The effects of soil physiochemical properties on the water flow patterns were revealed. The results showed that the staining area ratio (SAR) decreased sharply with increasing soil depth. The higher average SAR of 0-60 cm soil layer was observed in paddy field (28.16%) than that in upland field (21.95%), and forest (18.64%), and these differences in SAR mainly happened in 5-25 cm soil layer. The staining path number (SPN) in three fields increased from soil surface to 15 cm soil depth, and then decreased continuously along the soil profile. The highest average SPN of 0-60 cm soil profile was observed in paddy field (20), followed by upland field (12) and forest (9). The soil layer of 0-20 cm depth in three fields were mainly occupied by the type of 1-10 cm staining path width (SPW), and their water flow patterns were defined as the homogeneous matrix flow, heterogeneous matrix flow, and high interaction macropore flow successively along the soil profile. For the soil layers underneath 20 cm, the upland field and forest were mainly occupied with SPW of<1 cm and water flow pattern of low interaction macropore flow and mixed interaction macropore flow. However, the SPW of 1-10 cm and the water flow pattern of high interaction macropore flow were mainly defined for the forest soil below 20 cm depth. The soil saturated water conductivity and water flow characteristics in three fields were strongly depended on the soil pore characteristic, which was mainly affected by the organic matter content, root density and soil particle size. In order to improve the water use efficiency and reduce soil erosion in the red soil area, the methods of breaking the plough pan of upland field, reducing soil crack formation in paddy field by rational irrigation management, and increasing the vegetation diversity of forest would be efficient.