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Deep Soil Desiccation and Ecohydrological Consequences of Caragana korshinskii Plantations in the Loess Hilly Region of Southern Ningxia

Year: 2026

Type: article

Abstract: ABSTRACT Large‐scale ecological restoration on the Chinese Loess Plateau has reduced erosion and increased vegetation cover, but long‐term sustainability is constrained by deep soil water depletion in semi‐arid landscapes. The problem is acute in shrublands where precipitation is limited, groundwater is deeply buried, and deep‐rooted species can extract water stored in the thick loess vadose zone. Caragana korshinskii Kom. is widely planted for slope stabilization and soil conservation, yet the depth, severity and plant‐available status of soil water depletion under mature plantations remain poorly quantified. This study evaluated soil water status to 2600 cm in a 24‐year‐old C. korshinskii plantation in the loess hilly region of southern Ningxia, China, and compared it with adjacent rain‐fed sloping farmland. Three replicate 5 × 5 m plots were sampled in each land‐use type, with soil cores collected at 20‐cm intervals to 2600 cm depth on three occasions during 2024. Gravimetric water content and clay content were measured for every depth. A logarithmic relationship between soil water content and clay content was developed from the rain‐fed farmland data and applied to the plantation profiles to estimate the soil water content that would have been expected if the land had remained under rain‐fed cultivation. The plantation showed continuous soil desiccation from 0 to 2540 cm. The 0–2320 cm layer was classified as severe to intense desiccation, with a mean soil water content of 8.6%, whereas the 2320–2540 cm layer remained mildly to moderately desiccated. Soil water deficit peaked at 48.6% at 1540 cm, and the mean soil water supply coefficient across the profile was only 0.50. Most soil water under C. korshinskii was difficultly available to plants, whereas farmland retained intermittent layers of moderately available water. Comparison of measured plantation water content with values predicted under the rain‐fed reference indicated that long‐term shrub growth was most likely the main driver of deep depletion below 400 cm. Root sampling showed that root length density fell from 10.4 to 1.3 cm·cm −3 between the shallow and deep layers, consistent with sustained water uptake concentrated in the shallow and middle soil. These results show that mature shrub plantations can overconsume deep soil water well beyond seasonal recharge depths and that restoration in semi‐arid loess landscapes should be designed to balance vegetation cover with deep vadose zone water sustainability. Framed as an ecohydrological land‐use trade‐off, the findings indicate that vegetation restoration can shift from delivering erosion‐control benefits to imposing hidden costs on deep vadose zone water resources when plant water demand exceeds local recharge.

Source: Ecohydrology

DOI: 10.1002/eco.70253