Abstract: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, \[5.0mm, ∞), \[2.5mm, 5.0mm), \[1.0mm, 2.5mm), (0, 1.0mm), however, for farmland and orchard, \[10mm, 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.
