Yang et al. (2025) Agroforestry buffers drought stress by enhancing hydrological redistribution in dryland apple orchards

Identification

• Journal: Agricultural Water Management
• Year: 2025
• Date: 2025-11-22
• Authors: Min Yang, Lianhao Zhao, Xiaodong Gao, Jinlong Zhu, Shaofei Wang, Hailong He, Yaohui Cai
• DOI: 10.1016/j.agwat.2025.110008

Research Groups

• College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi, China
• State Key Laboratory of Arid land Crop Science, College of Agronomy, Gansu Agricultural University, Lanzhou, China
• State Key Laboratory of Soil and Water Conservation and Desertification Control, Northwest A&F University, Yangling, Shaanxi, China
• College of Soil and Water Conservation Science and Engineering, Northwest A&F University, Yangling, Shaanxi, China
• College of Water Resources and Architectural Engineering, Northwest A&F University, Yangling, Shaanxi, China
• Department of Soil Science, University of Manitoba, Winnipeg, MB, Canada

Short Summary

This study investigated the hydrological benefits of apple tree–oil crop (ATOC) intercropping systems under varying drought severities on China’s Loess Plateau, combining a four-year rainfall exclusion experiment with MAESPA modeling. It found that agroforestry enhances water-use efficiency and buffers moderate drought stress by promoting deeper water uptake and optimizing water partitioning, but its buffering capacity is overwhelmed under severe drought.

Objective

• To investigate the effects of apple tree–oil crop (ATOC) systems on hydrology in dryland environments.
• To examine how prolonged droughts impact key water balance components (evaporation, transpiration, deep percolation, and soil water storage) under different precipitation regimes.

Study Configuration

• Spatial Scale: Field experiment in Mizhi County, northern Loess Plateau of China (37°40′–38°06′N, 100°15′–110°16′E, 960 m above sea level). Experimental plots measured 4 meters × 10 meters, with impermeable barriers installed to 1 meter depth. Soil profile monitored down to 2.8 meters.
• Temporal Scale: Four-year rainfall exclusion experiment conducted during the growing seasons (May to October) from 2019 to 2022. Sap flow monitored from 2020, and physiological measurements from 2020 to 2022.

Methodology and Data

• Models used: MAESPA model (3D process-based ecohydrological model integrating canopy radiation, photosynthesis, and water-energy balances).
• Data sources:
  • Rainfall exclusion experiment with moderate (15% reduction) and severe (25% reduction) precipitation exclusion.
  • Automatic weather station data: precipitation, air temperature, relative humidity, vapor pressure deficit.
  • Soil volumetric water content (SWC) measured in situ using TDR sensors at 20 centimeter depth intervals down to 2.8 meters.
  • Apple tree sap flow density (SFD) monitored using thermal dissipation probes (FLGS-TDP XM1000).
  • Canopy morphological parameters: crown diameter, tree height, new shoot length, plant height, basal diameter, aboveground biomass, and leaf area index (LAI).
  • Physiological traits: net photosynthetic rate, stomatal conductance, electron transport rate, maximum rate of Rubisco carboxylation, and leaf water potentials.
  • Soil characteristics: bulk density, porosity, saturated hydraulic conductivity, field capacity, and water retention curves from soil cores.
  • Fine root length density (FRLD) for apple trees, soybean, and canola.

Main Results

• The MAESPA model accurately simulated soil water content (KGE > 0.88) and transpiration rates (KGE 0.92–0.99).
• Under natural precipitation, the ATOC system increased soil water content by 3.5%, transpiration by 39%, and deep percolation by 11%, while reducing soil evaporation by 10% compared to apple monoculture.
• Under moderate drought, the ATOC system experienced declines in SWC (-10%), transpiration (-26%), and deep percolation (-17%) relative to non-drought agroforestry. However, transpiration remained 11–15% higher than in monoculture during normal and wet years due to a shift in water uptake to deeper soil layers.
• Under severe drought, the buffering capacity of the ATOC system was overwhelmed, leading to substantial reductions across all water balance components, including SWC, transpiration, and deep percolation.
• Root water uptake patterns showed an adaptive shift: in normal years, shallow soil layers (0–80 cm) contributed 70–73% of root water uptake in monoculture, which was reduced to 66–68% in ATOC-ND. Under extreme drought, all treatments increasingly relied on deeper soil (>80 cm), with agroforestry and drought treatments showing significantly higher subsoil dependency (37–39%) compared to monoculture (30%).
• Cumulative deep percolation over the four-year study period was 74.7 mm (monoculture), 83.4 mm (ATOC-ND), 68.1 mm (ATOC-MD), and 59.4 mm (ATOC-SD), demonstrating enhanced deep percolation in ATOC-ND under natural conditions.

Contributions

• Provides a mechanistic and quantitative understanding of how agroforestry systems redistribute soil water among evaporation, transpiration, and deep percolation under prolonged drought conditions.
• Elucidates the conditional mechanisms through which agroforestry systems buffer drought stress, highlighting benefits under moderate drought but vulnerability under severe drought.
• Demonstrates the adaptive shift in apple tree water uptake towards deeper soil layers as a key drought response in agroforestry systems.
• Offers crucial insights for designing climate-resilient water management strategies in dryland landscapes, including practical adaptive measures such as moderate canopy pruning, optimizing intercrop density, and employing land engineering interventions.

Funding

• National Key R&D Program of China (2023YFF1305103)
• Key Research and Development Program of Shaanxi Province (2023-ZDLNY-49)
• National Natural Science Foundation of China (grants no. 42407624, 42125705)
• China Postdoctoral Science Foundation (grants no. 2024M752640, 2025M770364)
• Postdoctoral Research Project Funding in Shaanxi Province (2024BSHSDZZ181)

Citation

@article{Yang2025Agroforestry,
  author = {Yang, Min and Zhao, Lianhao and Gao, Xiaodong and Zhu, Jinlong and Wang, Shaofei and He, Hailong and Cai, Yaohui and Zhao, Xining},
  title = {Agroforestry buffers drought stress by enhancing hydrological redistribution in dryland apple orchards},
  journal = {Agricultural Water Management},
  year = {2025},
  doi = {10.1016/j.agwat.2025.110008},
  url = {https://doi.org/10.1016/j.agwat.2025.110008}
}