Saturated hydraulic conductivity of soils in the Horqin Sand Land of Inner Mongolia, northern China

摘要

Water is a limiting factor to plant growth in Horqin Sand Land of China. Knowledge of soil saturated hydraulic conductivity (Ksat) is of importance because Ksat influences soil evaporation and water cycling at various scales. In order to analyze the variation of Ksat along with sand types and soil depths, and its relationship with soil physiochemical properties, six typical lands were chosen, including mobile dune, fixed dune, pine woodland, poplar woodland, grassland, and cropland, and Ksat was measured in situ by Guelph Permeameter at each type of land. Soil bulk density, organic matter content, and soil particle size distribution were determined in parallel with Ksat measurement. The results showed that (1) The averaged Ksat was decreased in the order: mobile dune > fixed dune > pine woodland > poplar woodland > grassland > cropland; changes in Ksat varied considerably as soil depth increased, e.g., the changes of Ksat along with soil depth in fixed dune was fitted by exponential model, but it was fitted by parabola model in the pine woodland and grassland. (2) The Ksat, values of fixed dune and mobile dune were varied considerably among three slope positions (dune top, windward slope, and leeward slope). (3) The relationships of Ksat and soil physiochemical property revealed that soil bulk density, organic matter content,and coarse sand fraction (2~0.1 mm) were the key factors affecting Ksat in Horqin Sand Land. Compared with clay and silt content proportion, sand fraction in this region showed a more significant positive correlation with Ksat.