Changes in Subsoil Water Content After Withdrawing Crop Production in the Hilly Loess in Northwestern China

Abstract

【Background and objective】 Withdrawing crop production to restore ecological functions of the loess plateau in northwestern China has greatly increased vegetation coverage since 1999, but there is a lack of understanding of how subsoil water content responded to such land use changes. The purpose of this paper is to fill this knowledge gap. 【Method】 Soil water content in the depths from the soil surface to 1000 cm was measured from slopped farmland, grassland and jujube orchard at a small watershed in the Yuanzegou waterhead in a loess hilly region. 【Result】 ①The average moisture content in the 0~1 000 cm soil in different ecosystems was ranked in the order of jujube orchard grassland >jujube orchard, with their associated average value being 148.78 mm, 145.28 mm and 121.11 mm, respectively. Waters stored in the farmland and grassland were comparable, both being significantly higher than that in the jujube orchard (p<0.05). ③Jujube took up more water from the 200~1 000 cm soil than the grasses (p<0.05), with the water consumed by the jujube ranging from 21.67 mm to 32.97 mm compared to -4.47 mm to 10.32 mm used by the grasses. ④Subsoil water content was positively correlated with clay while negatively related to sand particles and organic carbon mass fraction, all at significant levels. 【Conclusion】 Withdrawing crop production significantly reduced soil water content and water storage in the subsoil, especially when returning to forests. Jujube took a significant amount of water from the subsoil, followed by the grasses. Therefore, managing vegetation coverage after sparing cropped land is critical to restoring ecological functions of the hilly loess landscape in northwestern China.

Keywords

• withdrawing crop production
• subsoil water content
• forests and grasslands
• jujube orchard