Liu et al. (2025) Interannual Variations in Water Budget and Vegetation Coverage Dynamics in Desert Ecosystems of Heihe River Basin

Identification

• Journal: Water
• Year: 2025
• Date: 2025-09-09
• Authors: Jingpeng Liu, Wenyang Cao, Yuan Yuan, Siying Li, Pei Wang
• DOI: 10.3390/w17182660

Research Groups

• School of Natural Resources, Faculty of Geographical Science, Beijing Normal University, Beijing, China
• State Key Laboratory of Earth Surface Processes and Hazards Risk Governance, Faculty of Geographical Science, Beijing Normal University, Beijing, China

Short Summary

This study investigates interannual variations in water budgets and vegetation dynamics in two contrasting desert ecosystems of the Heihe River Basin (2016-2021), revealing divergent ecohydrological responses and vegetation-water coupling mechanisms driven by precipitation gradients, species adaptations, and the critical role of groundwater.

Objective

• To quantify interannual variations in ecosystem water budgets and their impacts on vegetation patterns across contrasting desert environments.
• To elucidate the mechanistic responses of key desert shrubs to fluctuating water availability, including their adaptations to groundwater depletion and precipitation variability.

Study Configuration

• Spatial Scale: Heihe River Basin, China, focusing on two specific desert sites: Huazhaizi (midstream, Kalidium foliatum desert) and Huangmo (downstream, Reaumuria songarica desert).
• Temporal Scale: 2016 to 2021.

Methodology and Data

• Models used:
  • Simplified ecosystem water balance equation: P + GW(I) = ET + ΔQ
  • Soil water storage (Q) calculation: Trapezoidal method
  • Soil water residence time (τ) estimation
  • Penman–Monteith formula for potential evapotranspiration (ET₀)
• Data sources:
  • Meteorological and Eddy Covariance Data: National Tibetan Plateau Data Center (TPDC)
    • Precipitation: TES25MM tipping-bucket rain gauge
    • Evapotranspiration (ET): Eddy covariance systems (CSAT3 sonic anemometer, LI-7500 open-path CO₂/H₂O analyzer)
    • Air temperature and humidity: HMP45AC ventilated thermometer and hygrometer
  • Soil Moisture: ML3 ThetaProbe soil moisture sensors installed at 7 depths (2, 4, 10, 20, 40, 60, and 100 cm).
  • Vegetation Monitoring: Monthly Fractional Vegetation Cover (FVC) data from the China Regional 250 m Vegetation Coverage Dataset (2000–2023), validated by ground surveys.
  • Field Surveys: Systematic field quadrat surveys for vegetation structural differences (plant density, canopy architecture).

Main Results

• Ecohydrological Contrast:
  • The midstream K. foliatum desert (mean annual precipitation: 133.7 mm, ET: 240.05 mm) exhibited substantial soil moisture variability (10-50 cm depth) and a pronounced soil water deficit.
  • The downstream R. songarica desert (mean annual precipitation: 29.7 mm, ET: 77.74 mm) maintained minimal moisture fluctuation (deeper layers 40-100 cm stable) and recorded a slight water surplus (mean annual ΔQ: 0.47 mm).
• Vegetation-Water Coupling:
  • In the K. foliatum desert, monthly vegetation coverage showed significant nonlinear correlations with soil water storage (R² = 0.33, p < 0.01), precipitation (R² = 0.21, p < 0.05), and evapotranspiration (R² = 0.20, p < 0.05), indicating dependence on recent hydrological inputs.
  • In the R. songarica desert, no significant correlation was observed between monthly hydrological factors and vegetation coverage (p > 0.05), suggesting a pulsed response to episodic rainfall and reliance on deeper water sources.
• Water Budget Components: Both ecosystems experienced overall water deficits (ET > P), averaging 106.35 mm/year for K. foliatum and 48.04 mm/year for R. songarica.
• Groundwater Role: Groundwater recharge emerged as a key compensatory mechanism against rainfall shortages, particularly in the downstream region, with external water inputs averaging 104.72 mm/year (midstream) and 48.13 mm/year (downstream).
• Soil Water Residence Time: The average soil water residence time was 105 days for K. foliatum and 102 days for R. songarica.
• Atmospheric Controls: Vapor pressure deficit (VPD) was the dominant atmospheric constraint on vegetation coverage in both ecosystems, explaining 45% of variability (p < 0.01).

Contributions

• Provides a comprehensive, multi-year (2016-2021) analysis of interannual ecohydrological dynamics using high-resolution field observations in two contrasting desert ecosystems.
• Quantifies species-specific water-use strategies and reveals fundamentally divergent vegetation-water coupling mechanisms (continuous vs. pulsed responses) under shared climatic conditions.
• Highlights the critical role of groundwater and human-derived water inputs (e.g., irrigation subsidies, oasis water vapor diffusion) in sustaining desert vegetation beyond precipitation limits.
• Demonstrates the limitations of conventional monthly-scale monitoring in capturing rapid, pulsed ecohydrological responses characteristic of hyper-arid environments.
• Offers science-backed recommendations for differentiated water management strategies, including optimizing irrigation in midstream oasis-desert ecotones and implementing groundwater conservation downstream.

Funding

• Joint Fund Project of the National Natural Science Foundation of China (U21A2001)

Citation

@article{Liu2025Interannual,
  author = {Liu, Jingpeng and Cao, Wenyang and Yuan, Yuan and Li, Siying and Wang, Pei},
  title = {Interannual Variations in Water Budget and Vegetation Coverage Dynamics in Desert Ecosystems of Heihe River Basin},
  journal = {Water},
  year = {2025},
  doi = {10.3390/w17182660},
  url = {https://doi.org/10.3390/w17182660}
}