黄土丘陵区人工油松林地土壤大孔隙定量研究

Quantitative studies on soil macropores under artificial Chinese pine(Pinus tabuleaformis Carr.)forest in loess hilly region

根据水分穿透曲线和Poiseulle方程原理，定量研究了黄土丘陵区人工油松林地原状土大孔隙的半径范围、个数及分布情况。黄土丘陵区人工油松林地田间持水量至饱和含水量之间的大孔隙半径为0．2～3mm．孔径〉1mm的特大孔隙仅占大孔隙总数的2．2％，表现出特大孔隙较少、小孔隙较多的特点。土壤剖面上部的大孔隙加权平均半径较大，随土层深度的增加，大孔隙半径逐渐减小。大孔隙所占过水断面面积在1．27％～18．13％之间，大部分样品大孔隙所占过水断面面积〈5％。坡位、坡度、坡形、坡向对大孔隙形成起着重要作用。大孔隙虽然占土壤体积的很小一部分，但其平均半径与水流通量和饱和导水率之间有显著幂函数关系，分别决定了水流通量的77％和饱和导水率的75％变异。植物强化土壤渗透能力的主要原因之一是根层土壤大孔隙的优势流效应。

The radius, number and distribution of soil macropores under artificial Chinese pine（ Pinus tabuleaformis Cart. ）forest were quantitatively researched by the water breakthrough curve and Poiseulle equation. The radius of soil macropore, which is defined as the pores between field capacity and saturated water content, is 0.2 - 3 mm, of which the macropores with the radius larger than lmm account for only 2. 2% of total macropore number. And there are more macropres in the upper layers of soil profiles than those in the lower layers. The weighted mean radius of macropores in the upper layers is larger, and is gradually decreased along with the soil depth. The ratio between the macropore area and water through sectional area is 1.27 % - 18.13%, and the ratio is less than 5% for most samples. The slope position, gradient, shape and direction intensively affect soil macropores. Although soil macropores account for small portion of the soil volumes, there is a remarkable power function relation between the mean radius of soil macropores and water flux, saturated hydraulic conductivity. The mean radius determines 77 % and 75 % variances of water flux and saturated hydraulic conductivity, respectively. The mechanics of intensifying soil penetration by plants is the effect of preferential flow, which is produced by soil macropores formed by roots.