No abstract

Quantification of deep drainage and the response of soil water content to rainfall patterns are critical for an effective management strategy of soil water conservation and groundwater utilization. However, there has been little information on how rainfall characteristics influence soil water dynamics and deep drainage in mobile sandy lands. We used an underground chamber to examine the responses of deep drainage and soil water content in mobile sandy lands to rainfall characteristics in Inner Mongolia during the growing seasons of 2010, 2011 and 2012. Results showed that rainfall in this area was dominated by small events (≤5 mm), which increased soil water content in the surface soil layers (0-40 cm), but did not increase soil water content in the deeper soil layers (greater than 40 cm). Soil water content at the 0-100 cm depth increased significantly when the total amount of rain was >20 mm. Rainfall amount, intensity and the duration of dry intervals were significantly related to the soil water content in different soil layers. Deep drainage was significantly correlated with rainfall amount and intensity, but not with the duration of dry intervals. The coefficients of deep drainage in the mobile sandy lands ranged from 61.30% to 67.94% during the growing seasons. Our results suggested that rainfall infiltration in the mobile sandy lands had considerable potential to increase soil water storage while recharging the groundwater in this region.

Water is a limiting factor to plant growth in Horqin Sand Land of China. Knowledge of soil saturated hydraulic conductivity (K(sat)) is of importance because K(sat) influences soil evaporation and water cycling at various scales. In order to analyze the variation of K(sat) 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 K(sat) 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 K(sat) measurement. The results showed that (1) The averaged K(sat) was decreased in the order: mobile dune > fixed dune > pine woodland > poplar woodland > grassland > cropland; changes in K(sat) varied considerably as soil depth increased, e.g., the changes of K(sat) 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 K(sat) 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 K(sat) 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 K(sat) in Horqin Sand Land. Compared with clay and silt content proportion, sand fraction in this region showed a more significant positive correlation with K(sat).