Li et al. (2026) Seasonal divergence in GPP- and ET-pathway regulation of ecosystem water use efficiency across vegetation types in water-limited ecosystems

Identification

• Journal: Journal of Hydrology Regional Studies
• Year: 2026
• Date: 2026-09-06
• Authors: Xiang Li, Kangle Mo, Guodong Jia, Lixin Chen, Zhiqiang Zhang
• DOI: 10.1016/j.ejrh.2026.103949

Research Groups

• College of Soil and Water Conservation, Beijing Forestry University, Beijing, China
• Forest Ecosystem Studies, National Observation and Research Station, Jixian, Shanxi, China
• State Key Laboratory of Efficient Production of Forest Resources, Beijing Forestry University, Beijing, China
• National Positional Observatory for Forest Ecosystems in the Metropolitan Area, Beijing Forestry University, Beijing, China
• The National Key Laboratory of Water Disaster Prevention, Nanjing Hydraulic Research Institute, Nanjing, China
• Center for Eco-Environment Research, Nanjing Hydraulic Research Institute, Nanjing, China

Short Summary

This study investigates the seasonal divergence in gross primary productivity (GPP) and evapotranspiration (ET)-pathway regulation of ecosystem water use efficiency (eWUE) across different vegetation types in water-limited ecosystems. The findings reveal that eWUE is highest in autumn and lowest in spring, with extreme responses primarily associated with vapor pressure deficit (VPD) and downward shortwave radiation (DSR) in spring and summer.

Objective

• Characterize the spatial patterns and seasonal heterogeneity of eWUE across different vegetation types in growing seasons.
• Quantify GPP versus ET statistical importance to overall variance of eWUE, identifying the important physiological mechanism and revealing the woody-herbaceous divergence in seasonal strategies.
• Resolve the seasonal hierarchy of key environmental drivers in controlling eWUE and decompose their driver-specific transmission pathways.

Study Configuration

• Spatial Scale: The study focuses on the Loess Plateau region in China, encompassing approximately 6.3 × 10⁵ km² across the central and upper sections of the Yellow River watershed.
• Temporal Scale: The study period spans from 2001 to 2019.

Methodology and Data

• Models used: Spatial Random Forest (RF) model with partial-derivative decomposition.
• Data sources: PML-V2 coupled water–carbon flux dataset, MODIS/Terra Leaf Area Index/FPAR 8-Day L4 Global 500 m SIN Grid, MOD15A2H product, National Tibetan Plateau Data Center, HiMIC-Monthly dataset.

Main Results

• eWUE is highest in autumn (1.39 gC⋅m⁻²⋅mm⁻¹) and lowest in spring (1.08 gC⋅m⁻²⋅mm⁻¹).
• Extreme responses are primarily associated with VPD and DSR in spring and summer.
• Pathway attribution is driver-specific rather than a uniform seasonal switch.

Contributions

• This study provides a mechanistic basis for predicting eWUE responses to climate variability.
• The findings reveal the importance of considering both GPP and ET pathways in understanding eWUE dynamics.

Funding

• National Key Laboratory of Water Disaster Prevention, Nanjing Hydraulic Research Institute, China (grant number: [insert grant number]).
• State Key Laboratory of Efficient Production of Forest Resources, Beijing Forestry University, China (grant number: [insert grant number]).

Citation

@article{Li2026Seasonal,
  author = {Li, Xiang and Mo, Kangle and Jia, Guodong and Chen, Lixin and Zhang, Zhiqiang},
  title = {Seasonal divergence in GPP- and ET-pathway regulation of ecosystem water use efficiency across vegetation types in water-limited ecosystems},
  journal = {Journal of Hydrology Regional Studies},
  year = {2026},
  doi = {10.1016/j.ejrh.2026.103949},
  url = {https://doi.org/10.1016/j.ejrh.2026.103949}
}