Effects of terracing measures on water retention of pinus Tabulaeformis forest in the dryland loess hilly region of China

Terraces, which are distributed worldwide, play a key role in water conservation, vegetation restoration and agricultural production particularly in dryland mountainous environments. Due to the uncertainties caused by water balance dynamics and diverse terrace structures, different findings on the soil-water retention effects of terracing were identified across the globe. To further understand the effect of terraces on soil water retention, a field experiment was conducted between 2015 and 2019 in the dryland loess hilly region of China. The experiment compared the combination of Pinus tabulaeformis with natural slope (PS), zig terrace (PT), and fish-scale pit (PF). We found that terrace measures can greatly manipulate the hydrological dynamics and compounds. Compared with the non-terraced treatments, terrace fields reduced runoff (26.9 mm/a for PF and 34.6 mm/a for PT), increased interception (13.6 mm/a for PF and 12.1 mm/a for PT) and transpiration (14.8 mm/a for PF and 2.4 mm/a for PT) during five years of the experiment. The advantage of terracing in soil water retention was temporal, mainly during heavy rainfall periods (e.g., June to August). Zig terrace promoted soil infiltration and transpiration while fish scale pit suppressed evaporation but increased transpiration. The results indicated that temporal factor and terrace structure were essential in understanding its soil-water retention services.