四面山阔叶林土壤大孔隙特征与优先流的关系

Macropore characteristics and its relationships with the preferential flow in broadleaved forest soils of Simian Mountains

为研究土壤大孔隙数量、分布特征与优先流发生之间的关系,在使用亮蓝染色法划分林地优先流发生区域基础上,利用穿透曲线理论方法,对重庆四面山典型亚热带阔叶林土壤剖面染色和未染色区域内的土壤大孔隙进行了量化分析.结果表明:研究林地土壤剖面内大孔隙半径多在0.3～3.0mm,大孔隙率为6.3%～10.5%,随着土壤深度的增加,大孔隙呈现出聚集态的分布特征.各孔径范围内,染色区域的土壤大孔隙数量较未染色区域高出约1个数量级.半径>0.3mm,尤其是半径>1.5mm的大孔隙数量,是影响林地优先流发生的主要通道.森林土壤0.3～3.0mm孔径范围内,大孔隙数量与其对应的土壤水分稳定出流速率呈显著的正相关关系,其中在0.7～1.5mm和1.5～3.0mm孔径范围内大孔隙数量与稳定出流速率相关程度最大,相关系数分别为0.842和0.879.发生优先流的染色区内大孔隙联通状况优于未染色区,两区中1.5～3.0mm孔径范围内的联通大孔隙数量差异最大,相差78.3%.染色区内大孔隙数量随土壤深度的增加逐渐减少,"漏斗"状的孔隙分布特征可以形成有效的水压梯度,有利于水分优先运移.

Brilliant blue dyeing and water breakthrough curve were applied to study the number and distribution of macropores and their relations to the preferential flow in typical sub-tropic broadleaved forest soils of Simian Mountains. The radii of the macropores were mainly between 0.3 and 3.0 mm,with the macroporosities in the range of 6.3% to 10.5%,and the macropores were always distributed in aggregation with increasing soil depth. The number of the macropores in each radius interval of dye-stained areas was tenfold increase than that of blank areas. The number of the macropores with radius larger than 0.3 mm,especially larger than 1.5 mm,was the most important factor affecting the occurrence of preferential flow. Significant correlations were found between the number of macropores and the water steady effluent volume,with the highest correlation coefficients of 0.842 and 0.879 for the radii intervals of 0.7-1.5 mm and 1.5-3.0 mm,respectively. Macropore continuity in dye-stained areas was better than that in blank areas,especially in the radius interval of 1.5-3.0 mm,with the biggest difference of 78.31%. In dye-stained areas,the number of macropores decreased gradually with soil depth. The filler-like distribution of macropores formed an effective water pressure gradient,which resulted in the preferential transport of water.