基于林分空间结构分析方法的土壤大孔隙空间结构研究

Study of Soil Macropore Spatial Structure Based on Stand Spatial Structure Analysis Method

土壤大孔隙的形成和分布具有重要的生态学意义,但尚未有研究者利用生态学方法研究其空间结构。以三峡库区紫色砂岩区的3种典型土地利用类型下的土壤大孔隙为研究对象,将图像处理技术与林分空间结构分析方法相结合,从形态学和生态学角度量化分析土壤大孔隙的空间结构。结果表明:3种土地利用类型的土壤大孔隙形状、空间结构复杂程度高,空间分布格局随土壤深度的增加均呈聚集分布趋势,且深层土壤的大孔隙组成较表层单一,其中草地最明显,大孔隙发育程度均随土壤深度的增加而降低;3种土地利用类型的土壤优先流发育程度由大到小为:草地、果园、农地,同一土地利用类型不同孔径范围的大孔隙所形成的优先路径的连通性、导水性和发育程度由大到小依次为:草地孔径范围[5.0 mm,∞)、[2.5 mm,5.0 mm)、[1.0 mm,2.5 mm)、(0,1.0 mm),农地和果园孔径范围[1.0 mm,2.5 mm)、[2.5 mm,5.0 mm)、(0,1.0 mm)、[5.0 mm,∞);将林分空间结构分析方法与土壤大孔隙位置密度分布、大孔隙变异度和复杂度指标进行对比,并与以往研究土壤大孔隙空间结构的方法进行比较,所得结果相同,证明该方法可以用于土壤大孔隙空间结构的分析和研究。林分空间结构分析方法简单易行,从生态学的角度完善了大孔隙空间结构的分析,弥补了目前基于物理化学方法在大孔隙结构理论分析的不足,进一步揭示了土壤大孔隙空间结构形成和分布的原因。

The soil macropores development and distribution in the field play an key ecological role in soil ecosystems, because of the complex interaction of soil＇s structures, moisture condition, stress level and biological activities. However, few researchers have used the ecological method to study the spatial structures of the soil macropores. This paper presents a new method （i. e. , combining with the ecology and morphology） to quantitatively investigate the spatial structure characteristics of macropores in purple sandstone regions the typical three land use types in Three Gorges Reservoir Area, with the stand spatial structure analysis method and image processing technology. The results demonstrated that the shapes and spatial structures of the soil macropores of three land use types were highly complicated. The soil macropores were mainly represented a gradual tendency of clumped distribution pattern and community structures （i. e. , composing of the same pore size macropore with increasing soil depth）, especially the grassland. The development degree of macropores in three land use types gradually decreased with the increase of soil depth. Three land use types＇ development degrees of the preferential flow were in this order from high to low： grassland, orchard and farmland. The spatial connectivity, the development degree and water conductivity of different preferential flow paths in same land use type were in this order from high to low： for grassland, [5.0 mm, ∞ ） , [2. 5 mm, 5.0 mm） , [ 1.0 mm, 2.5. mm） , （0, 1.0 mm） , however, for farmland and orchard, [1.0mm, 2.5mm）, [2. 5mm, 5.0mm）, （0, 1.0mm）, [5.0mm, ∞）. The analysis results of stand spatial structure analysis method were compared with distribution density of the soil macropore, variability, complexity and previous research methods. The same result proved the accuracy and applicability of stand spatial structure analysis method used to analyze the spatial structures of macropores. This new method provides an effective, convenient, rapid and more economical method for studying spatial structures of macropores, and gives us more spatial structure information from the viewpoint of ecology. Meanwhile, it compensates for the deficiency of the current methods （e. g. , dye tracer, visual liquid latex, water breakthrough curves analysis and CT technique） based on physical and chemical analysis about theoretical analysis of macropores structures, and further reveals the reasons about the formation and distribution of spatial structure of the soil macropores.