Development law of soil cracks in karst peak-cluster depressions under dry and wet alternations

Abstract

In an experiment with alternating dry and wet conditions of soil in cultivated land, orchards and forest lands with limestone and dolomite in karst peak depression, combined with digital image processing technology, we investigated the development law of soil surface cracks under alternating dry and wet condition. The results showed that with the alternation of wet and dry, the average width of cracks decreased at a fast-slow-slower rate, with an order of limestone > dolomite under the same land use, and orchard > cultivated land > forest soil under the same soil-forming parent rock. In the first four dry and wet alternations, the degrees of soil fragmentation and connectivity were higher in dolomite development than in limestone, with significant differences in fracture development rose diagrams. In the subsequent cycles, soil fragmentation of most samples increased, the difference dominated by parent rock gradually decreased, the crack development rose diagram converged, and the connectivity showed the pattern of forest land > orchard > cultivated land. After the fourth cycle, the alternations of dry and wet seriously damaged soil structure. The physical and chemical properties of capillary porosity and non-capillary tube porosity were dominant in the development of cracks before that, but it was more dependent on the organic matter content and the sand composition after that.