The role of soil water retention functions of near-surface fissures with different vegetation types in a rocky desertification area

Aims Soil water deficits have presented challenges to vegetation restoration in rocky desertification areas. In the field, small volumes of soil resources are present only in near-surface crevices, fissures, and other similar features. Water stored in the soil in near-surface fissures can help plants grow in such areas. The goals of this study are to discuss the soil water retention functions of near-surface fissures in terms of soil structure, water infiltration and water storage capacity and to define the role of fissure water in the growth of plants in rocky desertification areas. Methods Several near-surface fissures with four types of vegetation (i.e., crops, grass, shrubs and trees) within a rocky karst desertification area on the Karst Plateau in Guizhou Province, China, were examined. Soil physicochemical property analysis and stable isotope techniques were applied. Results Fissures with shrubs and trees present high levels of soil porosity, while fissures with crops and grasses present low levels of soil porosity. The water infiltration rates of the soil in all of the examined fissures are higher than the rainfall intensity of the maximum daily rainfall for this province. Consequently, most rainwater infiltrates through the fissure soils. Compared to the other fissures, fissures with crops present higher levels of usable soil storage capacity in the surface soils (0-20 cm), which are affected by tillage (ploughing), but exhibit lower capacities in the bottom soil layer. Additionally, tree and shrub fissures present higher usable soil storage capacities in bottom soil layer than other types of fissures. Conclusions The main source of water for Ligustrum and Pyracantha in the dry season is fissure water, which accounts for 44.7% and 58.2% of all the water utilized by these species, respectively. Fissure water may represent the most important source of water for plants growing in near-surface karst fissures.