作 者 ：时忠杰,王彦辉*,徐丽宏,熊伟,于澎涛,郭浩,徐大平
期 刊 ：生态学报 2008年 28卷 10期 页码：4929~4939
Keywords:Liupan Mountains, forest soil, rock fragment, macropore, steady effluent,
摘 要 ：石砾广泛分布于山地林区的土壤中，它对土壤的大孔隙及水分运动特征具有重要影响，是还较少研究的与森林水文过程有关的重要因素。基于对田间持水量与饱和含水量之间的土壤孔隙为大孔隙的定义，在宁夏六盘山南侧香水河小流域调查分析了典型植被样地土壤的石砾体积含量和大孔隙特征（半径、密度、面积比）及其之间的关系，并评价了它们对水分出流速率的影响。结果表明，土壤大孔隙的平均半径和密度都对水分出流速率影响显著，特别是半径>1.4mm的大孔隙密度的影响格外显著，虽然其密度仅占大孔隙总密度的6.86%，但可解释稳定出流速率变异的67.4%；作为综合反映大孔隙半径与密度的参数，土壤断面的大孔隙面积比能更好地解释稳定出流率变化，稳定出流速率随大孔隙面积比增大而线性增加，线性回归关系式的确定系数高达0.8361。石砾含量与稳定出流速率的关系比较复杂，在0~60cm土层内，石砾含量<15%时，稳定出流速率随石砾含量增大而增加，之后转而减少；但在60~80cm土层，则呈相反的变化趋势。石砾含量增加能导致土壤大孔隙半径增大，特别是半径大于1.4mm的较大大孔隙的密度增大，但对较小半径的大孔隙密度影响较弱，说明石砾在一定程度上通过影响土壤大孔隙的半径和密度特征来影响土壤水分出流速率。土壤稳定出流速率随土层深度而变化，在作为主根系层的0~60cm土层随土壤加深而降低，在>60cm土层则随土壤加深而提高，这是因为土壤大孔隙和稳定出流速率在主根系层更多地受植物改良土壤作用影响，在深层土壤则更多地受石砾含量增加的影响。
Abstract:The rock fragment which is widespread in the mountain forest soils, deeply affects the characteristics of soil water movement and soil macropores. However, this has been less studied in forest hydrology, although it is an important factor related with hydrological process. Based on the definition that macropores include the soil pores between field capacity and saturated water content, the rock fragments content and the macropore characteristics (radius, density, and area proportion of macropores) as well as their relations were studied, and their effects on the water effluent were evaluated in the plots with typical vegetation forms in a small watershed of Xiangshuihe, south side of Liupan Mountains in northwest China. The results indicate that the steady effluent rate is markedly affected by the mean radius and the density of macropores, especially the density of macropores with radii >1.4 mm. Though the macropores with radii >1.4 mm make up only 686% of the total density, they contribute 67.4% of the variability of the steady effluent rate. The area proportion of macropores, as a parameter synthetically reflecting the effects of radius and density of macropores, can better explain the variability of steady effluent rate. The steady effluent rate is markedly related with the area proportion of soil macropores, in a linear relation with a high determination coefficient (R2=0.8361). However, the relation between the content of rock fragments and steady effluent rate is complicated. In the main root zone of soil layer of 0-60cm, the steady effluent rate increases with the volumetric content of rock fragments until it reaches 15%, and then decreases with the rock fragments content; while the relation in the soil layer of 60-80cm is opposite. The increase of the volumetric content of rock fragments in soils induces a increased mean radius of macropores, especially the increased density of macropores with radius > 1.4 mm, but less effect on the density of macropores with radius <1.4 mm. This means the effect of rock fragments on water effluent rate (macropore flow) is operated by affecting the characteristics of soil macropores in a certain extent, such as the radius and density of macropores. The steady effluent rate varies with soil depth: firstly it decreases from soil surface to deeper layer in the main root zone of 0-60cm, and then increases with soil depth in the layers of >60cm. This is because the macropores and steady effluent rate are more affected by the soil improvement effect of vegetation in the main root zone, while more affected by the increasing rock fragment content in deeper soil layers.
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