Study on the occurrence and discrimination of two types of “soil reservoirs” in the ecotone between desert and grassland

Abstract

[Objective] By introducing the “soil reservoir” analysis paradigm, the nature and types of soil reservoirs in the ecotone between desert and grassland were identified and summarized, which provided a basis for the engineering management of regional soil water resources and its application in ecological restoration. [Methods] Based on the distribution law and relationship between soil texture and soil water content at the regional scale, the concepts and connotations of “characteristic soil reservoirs” and “general soil reservoirs” in the desert-grassland ecotone(central Ningxia) were proposed and analyzed based on the depth and range of relative water enrichment in the soil profile from 0 to 200 cm. [Results] The result shows that:(1) At the regional scale, there is a negative linear regression relationship between the soil moisture content of 0~20 cm, 20~60 cm, 60~140 cm and 140~200 cm and the soil sand content of 0~30 cm soil layer, and the linear relationship between soil moisture content of 20~60 cm and soil sand content of 0~30 cm is the most significant(R²=-0. 23, P≤0. 05).(2) Indicated by the soil water content and the coefficient of variation, the characteristic depth of the soil profile of the characteristic soil reservoir is 20~140 cm(desertification group) and 20~60 cm(loam group), and there is no “characteristic soil reservoir” with a fixed location in the 0~200 cm soil layer of the sandy soil group.(3) The spatial distribution of soil moisture content and surface soil sand content in the 20~60 cm soil layer shows a rotational correspondence, which is potentially consistent with the distribution of the multi-year average isoprecipitation line in the study area, highlighting the indicative significance of “general soil reservoir” in the region. [Conclusion] Soil texture is the key factor to determine the relative enrichment degree and location of local soil moisture, that is, the occurrence of soil reservoirs. Precipitation and soil texture jointly determine the occurrence of soil reservoirs on a regional scale. The occurrence of soil reservoirs in the natural ecosystem of arid areas is essentially a process of precipitation redistribution with soil as the medium. It is manifested as a higher and relatively stable water content at a certain position in the vertical section of the soil, which plays a role in the conservation and regulation of uncertain precipitation resources in arid areas.

Keywords

ecotone of desert and steppe / soil texture / soil water resources / characteristic soil reservoirs / general soil reservoirs / influence factors