Soil Water Content and Root Patterns in a Rain‐fed Jujube Plantation across Stand Ages on the Loess Plateau of China

Abstract Planting economic trees is one of the primary parts of the large‐scale ecological rehabilitation project (known as ‘Grain for Green’ project) initiated in 1999 on the Loess Plateau of China. Knowledge of soil water dynamics and fine roots patterns is critical to water management for orchards in this region. Here we investigated the distribution of root‐zone soil water variation and fine roots with a range of stand ages (2, 6, 10 and 15 years) in a rain‐fed jujube ( Ziziphus jujuba ) plantation on the Loess Plateau. Soil water in the 0‐ to 3‐m depth was monitored using portable Time Domain Reflectometry, and root samples were taken with a hand auger ( Φ = 9 cm). The results showed soil water storage in the 0‐ to 0·6‐m soil layers in all stands increased remarkably following apparent rainfall events. However, there was no clear change in soil water storage below 0·6 m throughout the growing season. Generally, fine root length density increased with the increase of stand age, which were unevenly distributed in the vertical and horizontal directions around the tree trunks in young stands (2 and 6 years), and the fine roots were uniformly distributed radically from the tree trunk in mature stands (10 and 15 years). Additionally, a high‐density zone of fine roots was observed in the middle of the inter‐row in mature stands, and the specific length of fine roots in young stands was higher than observed in mature stands. The results presented here would be helpful to water management in the rain‐fed jujube plantations on Loess Plateau and potentially for other semi‐arid orchards. Copyright © 2016 John Wiley & Sons, Ltd.