Effects of land use types on deep soil water content in the loess hilly area of the north Shaanxi Province, China

Abstract

This study explored the differences of soil water content at 0-20 m soil depth at three locations, including economical plantation in Mizhi, reforestation area in Shenmu, and wind break and sand fixation forest district of Yuyang, and for clarifying the impacts of different land use types on deep soil water distribution and storage characterization, as well as its eco-environmental effect on the loess hilly area. The results showed that in the soil profile of 0-20 m, land use patterns had a significant impact on soil moisture distribution. There were significant differences of soil water sto-rage for the economical plantation, pruning Ziziphus jujuba plantation ＞ Z. jujuba plantation with 587.9 mm difference. There was no significant difference in soil water storage between Caragana korshinskii plantation and degraded artificial vegetation or between pine forests and natural grass field, degraded artificial grassland ＞ C. korshinskii plantation with 98.8 mm difference at Shenmu, and natural grassland ＞ Pinus sylvestris var. mongolica plantation with 7.5 mm difference at Yuyang. The pruning Z. jujuba tree reduced soil water consumption and was beneficial to sustainable use of soil water due to the decreased crown width and thus reduced transpiration. There were no obvious differences of soil water content between C. korshinskii plantation and degraded artificial grassland due to the historical alfalfa planting which was characterized by high water consumption due to its deep root distribution and large biomass. In contrast, P. sylvestris var. mongolica plantation and na-tural grassland had similar and low averaged soil water contents with 3.4% and 3.6%, respectively, mainly due to the sandy soil texture and weak soil water holding capacity. In addition, with increa-sing soil depth, soil water content increased in this area, indicating the effect of plants on water moisture of deep soil was very limited. Except for the underlying control of soil texture on soil water content in the soil profile, different vegetation played a key role in the dynamics of soil water content due to the difference of root zones. It was very important to choose the suitable type of vegetation regarding the protection and sustainable use of deep soil water.