Soil-water deficit in deep soil layers results from the planted forest in a semi-arid sandy land: Implications for sustainable agroforestry water management

Abstract

Forest planting is a common practice in semi-arid sandy land restoration, but problems may appear associated with forest age like higher soil water consumption that threatens restoration program’s success. This study quantified the distribution and variation of soil water storage in a Pinus sylvestris (P. sylvestris) plantation under various stand ages (20, 30, 40, 50 and 60 years) along 0–1000 cm soil profile in the Mu Us sandy lands (North China). Results indicated that the 20-yr forests mainly consumed the soil water of the 0–200 cm depth soil profile, the 30-yr and 40-yr forests mainly consumed the soil water of the depth of 0–400 cm, whereas the oldest (50–60-yr) pines mainly consumed the soil water located at the deepest soil profile (500–700 cm). Variation of soil water storage (△SWS) was decreased with stand ages, reaching the minimum value in the 30–40-yr stands, and then gradually increased in the 50–60-yr stands. The △SWS was relatively uniform on the 50-yr and 60-yr stands. this pattern was associated with soil desiccation and soil-water depletion. The lower △SWS indicated lower soil water storage which was associated with soil desiccation and soil-water depletion. These findings proved that planted forest gradually aggravated soil water consumption along the increasing forest age, caused a serious soil water deficit in the 200–700 cm depth soil layer, which may be exceeding the water environmental carrying capacity. Therefore, we suggest that forest should be thinned on the periods with the highest △SWS, which would maintain long-term forest sustainability by minimizing soil desiccation for planted forest management in semi-arid sandy lands.