John, A., Pradhan, K., Case, M. J., Ettinger, A. K., & Hille Ris Lambers, J. (2024).
Forest canopy cover affects microclimate buffering during an extreme heat event.
Environmental Research: Communications, 6(9), 091015.
https://doi.org/10.1088/2515-7620/ad7705
📄 Full PDF

This study investigates whether temperate coastal forests in the Pacific Northwest (PNW) can buffer understory temperatures during extreme heat events, such as the June 2021 heat dome. The authors find that forests significantly cool understory environments—even under extreme heat—by as much as 4°C relative to regional macroclimate and 3°C relative to adjacent clear-cuts.

Key findings include:

• Greater canopy cover leads to stronger thermal buffering.
• Thinned forests provide significantly less cooling than un-thinned or old-growth stands.
• Vertical variation exists in buffering, with the coolest temperatures measured at the forest floor.

• Study Site: Ellsworth Creek Preserve, Washington, USA.
• Sensors: HOBO loggers (ground and 1.5–2m height) and Micromet stations.
• Data Sources:
  • In-situ microclimate data
  • GridMET regional climate data
  • Canopy data from The Nature Conservancy plots
• Metrics: Mean, min, max, and diel temperature variation; temperature offset (plot vs regional or clear-cut).
• Statistical Approach: Linear mixed-effects models using lme4 in R.

• Old-growth forests showed the highest buffering, especially for max temps and diel variation.
• Thinned forests showed reduced buffering, sometimes approaching clear-cut temperatures on the hottest day.

🔗 https://github.com/ajijohn/heatdomes

Lead Author:
Dr. Aji John
Department of Biology, University of Washington
✉️ [email protected]
🔗 ORCID

@article{john2024canopy,
  title={Forest canopy cover affects microclimate buffering during an extreme heat event},
  author={John, Aji and Pradhan, Kavya and Case, Michael J and Ettinger, Ailene K and Hille Ris Lambers, Janneke},
  journal={Environmental Research: Communications},
  volume={6},
  number={9},
  pages={091015},
  year={2024},
  publisher={IOP Publishing},
  doi={10.1088/2515-7620/ad7705}
}