Wang et al. (2026) Conversion from farmland to orchard reshapes moisture recycling: Mechanistic insights and implications for water management on the Loess Plateau

Identification

• Journal: Agricultural Water Management
• Year: 2026
• Date: 2026-01-12
• Authors: Jiaxin Wang, Jiahui Ha, Furong Zhang, Xueyan Zhang, Zhiming Han, Bingbing Li, Zhi Li
• DOI: 10.1016/j.agwat.2026.110136

Research Groups

• State Key Laboratory of Soil and Water Conservation and Desertification Control, College of Natural Resources and Environment, Northwest A&F University, Yangling, China
• School of Architecture Engineering, Yulin University, Yulin, China

Short Summary

This study investigates how converting farmland to orchards on the Loess Plateau reshapes land–atmosphere water cycling, revealing that deep-rooted trees enhance local moisture recycling through increased transpiration but at the cost of significant deep soil water depletion and reduced groundwater recharge.

Objective

• To integrate atmospheric moisture budget analysis with stable isotope measurements to estimate moisture recycling rates and source contributions for farmland and orchards of different ages.
• To use multiyear field observations to quantify differences in water balance components—evaporation, transpiration, deep percolation, and changes in soil water storage—between farmland and orchards of different ages.
• To develop a Recycling Efficiency Index (REI) to diagnose the water consumption and compensation trade-off associated with establishing orchards.

Study Configuration

• Spatial Scale: Changwu Loess Tableland (107°41′E, 35°14′N), China, a representative region of loess mesas and gullies with a mean elevation of 1219 meters and loess deposits over 200 meters thick. The study involved three adjacent, non-irrigated plots: farmland (F), a 17-year-old apple orchard (A17), and a 23-year-old apple orchard (A23).
• Temporal Scale: Precipitation collected from 2018 to 2024. Soil and plant xylem samples collected monthly from May to October in 2023 and 2024. Tritium tracing analysis covered the period from 1963 to 2023. Water balance components are expressed as multi-year mean annual fluxes.

Methodology and Data

• Models used:
  • Three-end-member mixing model (for partitioning precipitation sources: advection, transpiration, evaporation).
  • Craig–Gordon model (for estimating isotopic composition of soil evaporation vapor).
  • Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model (for simulating air mass trajectories and identifying advected vapor sources).
  • Rayleigh fractionation model (for estimating isotopic composition of advected vapor).
  • Soil water balance equation (P = E + T + ΔS + D + R, with R neglected).
  • Recycling Efficiency Index (REI) (REI = fre / |ΔS|).
• Data sources:
  • Stable isotope tracing (δ²H and δ¹⁸O) of precipitation, soil water (0–20 m depth), and plant xylem water (maize and apple trees).
  • Tritium tracing (for estimating deep drainage in farmland).
  • Soil water content determined by oven-drying method.
  • Soil bulk density measurements.
  • Meteorological data (NCEP GDAS) for HYSPLIT model simulations.

Main Results

• Soil water storage (0–20 m depth) in orchards declined by 9–20 % compared to farmland, with older orchards showing greater reductions.
• Deep percolation decreased from 28 mm⋅yr⁻¹ in farmland to almost zero in orchards, implying negligible groundwater recharge under orchards.
• Annual soil water deficits in orchards reached up to 36 mm.
• Actual evapotranspiration (ETa) in orchards (105–106 % of annual precipitation) exceeded annual precipitation, indicating reliance on soil water storage, whereas in farmland, ETa was 95 % of annual precipitation.
• The transpiration to actual evapotranspiration ratio (T/ETa) increased from 82 % in farmland to 88 % in orchards.
• The proportion of recycled moisture in precipitation (fre) increased from 20 % in farmland to 25 % in orchards.
• This enhanced recycling was driven by a decline in soil evaporation contribution (fE) and a rise in transpiration contribution (fT), with fT accounting for approximately 80 % of fre in orchards (compared to 70 % in farmland).
• The proposed Recycling Efficiency Index (REIstandardized) for orchards (A17: 0.88; A23: 0.69) was lower than the cropland benchmark (1), indicating a high risk of soil water deficit and suboptimal recycling benefits per unit of soil water consumption.

Contributions

• Quantified the impact of farmland-to-orchard conversion on local moisture recycling and its source composition on the Loess Plateau, providing mechanistic insights into the coupled land-atmosphere water cycle.
• Established a process-based framework revealing a chain of vertical water cycle changes: deep-water extraction → weakened recharge → ETa shifted toward transpiration → enhanced and restructured moisture recycling.
• Integrated stable isotope tracing with soil water balance partitioning, offering a comprehensive approach to assess water consumption and recycling trade-offs.
• Developed the Recycling Efficiency Index (REI) as a novel metric to diagnose the trade-off between enhanced moisture recycling benefits and soil water consumption, providing a tool for sustainable agricultural water management.
• Utilized direct measurements of plant xylem water isotopes, improving the accuracy of transpiration source partitioning compared to studies relying solely on precipitation isotopes.

Funding

• National Natural Science Foundation of China (42407491, 42477510, 42501039, and 52309036).

Citation

@article{Wang2026Conversion,
  author = {Wang, Jiaxin and Ha, Jiahui and Zhang, Furong and Zhang, Xueyan and Han, Zhiming and Li, Bingbing and Li, Zhi},
  title = {Conversion from farmland to orchard reshapes moisture recycling: Mechanistic insights and implications for water management on the Loess Plateau},
  journal = {Agricultural Water Management},
  year = {2026},
  doi = {10.1016/j.agwat.2026.110136},
  url = {https://doi.org/10.1016/j.agwat.2026.110136}
}