华北土石山区森林土壤大孔隙对土壤理化性质及根系的响应

土壤大孔隙是土壤水分、空气、化学物质及污染物优先运移的主要通道,对其形成机制的研究至关重要。以往对大孔隙的量化局限于传统方法,大孔隙三维形态特征的量化分析及其影响因素是目前大孔隙的研究重点。利用CT扫描及图像处理分析技术量化大孔隙三维形态特征参数,同时测定土壤基本理化性质及根长密度,分析土壤大孔隙三维特征对土壤理化性质及根系的响应。结果表明:土壤密度及土壤砂粒含量与大孔隙特征参数不存在相关关系;土壤有机质含量、土壤根长密度与大孔隙体积密度、大孔隙表面积密度、大孔隙数量密度呈现显著正相关关系,与大孔隙平均迂曲度呈现显著负相关关系。林木根系与土壤有机质对土壤大孔隙三维特征产生积极影响,表现为根系及土壤有机质含量越多,则大孔隙含量也越多,并具有更差的弯曲度。在今后对山地森林抚育管理、土壤水分运动机理及地下水污染评估等研究过程中不能忽略根系及土壤有机质差异对土壤大孔隙的重要影响。

Response of Soil Macropore to Soil Phychemical Properties and Root in Forest in Rocky Mountain Area of North China

Soil macropore is the main channel for preferential transport of soil moisture, air,chemical substances and pollutants, so the studies on its formation mechanism are of great importance. In the past, the quantification of macropore was limited to the traditional methods. But nowadays, quantitative analysis of three-dimensional morphological characteristics of soil macropore and its influencing factors are the research focus. In this paper, CT scanning and image processing techniques were used to quantify the 3-D characteristic parameters of macropore, and the basic physical and chemical properties of soil and root length density were also determined. The correlations between soil physicochemical properties, soil roots and the 3-D characteristics of soil macropore were analyzed. The results showed that there was no correlation between soil density, soil sand contents and characteristic parameters of macropore; soil organic matter contents and root length density were significantly positively correlated with volume density, surface area density and number density of macropore, and significantly negatively correlated with mean tortuosity of macropore. Soil organic matter and roots had a positive impact on the 3-D characteristics of soil macropore, the more roots and organic matter contents, the more macropore contents, and the worse bending degree of macropore. In the future, the effects of root system and organic matter should not be neglected in the studies of forest tending and management, soil water movement mechanism and groundwater pollution assessment.