Residual canopy cover provides buffering of near-surface temperatures, but benefits are limited under extreme conditions
In response to recent extreme heat events, such as the 2021 heat dome over the Pacific Northwest, researchers have been examining how heat waves and other future climate conditions might affect forest canopy cover’s influence on temperatures near the ground in recently thinned stands. In a recent study, scientists measured temperature-induced stress to conifer seedlings and germinating seeds under different canopy conditions. The results of this study show that while overstory canopy cover may help buffer temperature stress experienced by seedlings, extreme heat events and climate change still pose significant challenges. For example, during the 2021 heat dome, the highest temperature recorded near the soil surface, under the forest canopy, was 57.4 degrees Celsius, or just over 135 degrees Fahrenheit—temperatures which can be fatal to seedlings. They also found that wildfire smoke reduced near surface temperatures by roughly 2oC, which is equivalent to an additional 15% canopy cover. Widespread smoke from wildfires can lead to unanticipated beneficial effects by reducing sunlight at the surface and thus lowering the temperatures experienced by vulnerable tree seedlings. This work highlights that climate adaptation tools need to address impacts of extreme events like heat waves as well as general warming, and that as disturbance regimes and regional climate conditions shift under global change, new dynamics and interactions will arise.
Residual canopy cover provides buffering of near-surface temperatures, but benefits are limited under extreme conditions. Brackett, Amanda E.; Still, Christopher J.; Puettmann, Klaus J. 2024. Residual canopy cover provides buffering of near-surface temperatures, but benefits are limited under extreme conditions. Canadian Journal of Forest Research. 54(9): 1018-1031. doi:https://doi.org/10.1139/cjfr-2023-0268