Chen et al. (2025) Drivers and thresholds of carbon and water flux dynamics in a semi-humid urban forest ecosystem

Identification

• Journal: Agricultural and Forest Meteorology
• Year: 2025
• Date: 2025-12-01
• Authors: Tuqiang Chen, Han Li, Jinhui Jeanne Huang‬‬‬‬
• DOI: 10.1016/j.agrformet.2025.110933

Research Groups

• College of Environmental Science and Engineering, Sino-Canada Joint R&D Centre for Water and Environmental Safety, Nankai University, Tianjin 300071, PR China
• Shenzhen Research Institute of Nankai University, Shenzhen 518057, China

Short Summary

This study quantified carbon and water fluxes in a semi-humid urban forest using eddy covariance, identifying their magnitudes, key environmental drivers, and nonlinear response thresholds under both drought and non-drought conditions.

Objective

• To understand the magnitude, driving factors, and environmental response thresholds of carbon and water fluxes (Gross Primary Production, Evapotranspiration, and Water Use Efficiency) in a semi-humid urban forest ecosystem.

Study Configuration

• Spatial Scale: A semi-humid urban forest ecosystem in China.
• Temporal Scale: Four consecutive growing seasons (May–October) from 2020 to 2023.

Methodology and Data

• Models used: Structural equation modeling.
• Data sources: Eddy covariance technology (for carbon and water fluxes), measurements of environmental variables including net radiation (Rn), air temperature (Ta), vapor pressure deficit (VPD), and soil water content (SWC).

Main Results

• Multi-year averages during the growing seasons were: Gross primary production (GPP) of 1177.1 g C m⁻² yr⁻¹, evapotranspiration (ET) of 520.5 mm yr⁻¹, and water use efficiency (WUE) of 2.2 g C kg⁻¹ H₂O.
• Canopy conductance (Gc), GPP, and ET were significantly higher under non-drought conditions compared to drought conditions.
• Higher soil water content partially mitigated the negative impacts of high net radiation, air temperature, and vapor pressure deficit on GPP and ET during droughts.
• Under drought conditions, GPP was primarily regulated by atmospheric demand (e.g., VPD), while ET was mainly controlled by energy availability (e.g., Rn and Ta), with soil water content positively influencing both.
• Under non-drought conditions, energy availability was the dominant regulator for both GPP and ET.
• GPP and ET exhibited nonlinear responses to environmental drivers (Rn, Ta, VPD), initially increasing but declining after reaching specific thresholds.

Contributions

• Enhances the understanding of the mechanisms governing carbon and water flux dynamics in urban forest ecosystems.
• Provides critical insights into urban forest responses to environmental stressors, particularly under drying and warming conditions.
• Identifies specific environmental thresholds for GPP and ET responses, which is valuable for urban forest management.

Funding

• Not specified in the provided text.

Citation

@article{Chen2025Drivers,
  author = {Chen, Tuqiang and Li, Han and Huang‬‬‬‬, Jinhui Jeanne},
  title = {Drivers and thresholds of carbon and water flux dynamics in a semi-humid urban forest ecosystem},
  journal = {Agricultural and Forest Meteorology},
  year = {2025},
  doi = {10.1016/j.agrformet.2025.110933},
  url = {https://doi.org/10.1016/j.agrformet.2025.110933}
}