Canopy Photosynthesis Shows Signs of Acclimation to Rising Temperatures: A Warming World Silver Lining?

   New research highlights that plants are acclimating their photosynthesis in response to warming, though water availability remains a crucial factor

 Amid growing concerns about the impact of global warming on terrestrial ecosystems, new research published in Nature Plants led by a team from Seoul National University (Professor Youngryel Ryu’s group, with Dr. Jiangong Liu as the lead author), in collaboration with the international LEMONTREE project consortium, which includes members from China, Germany, Singapore, Switzerland, the UK, and the US, presents observation-based evidence that plants are not defenseless against rising temperatures. The study, encompassing over 200 observation sites globally, reveals that plants can acclimate their canopy photosynthesis—essentially, their maximum ability to absorb carbon dioxide—to higher growth temperatures. This finding provides a nuanced perspective on how warming may influence carbon uptake in ecosystems worldwide.

“The Good News: Plants Are Acclimating”

 The study, based on data from the FLUXNET2015 global network of ecosystem-scale carbon fluxes, shows that plants across diverse environments, from forests to grasslands, are adjusting their photosynthetic capacity to align with local growth temperature increases. This ability to acclimate helps plants maintain or even improve their photosynthetic efficiency as temperatures rise, potentially aiding in carbon absorption.

"Our study shows widespread acclimation to temperature at the canopy level, a phenomenon previously observed mainly in individual leaves or controlled environments," explains Liu. "This suggests that some certain types of plants may benefit from warming, which could influence how much carbon they can capture from the atmosphere."


Figure: An international team shows observation-based evidence of vegetation thermal acclimation across both space and time.

“But Heat and Water Still Matter”

 However, the study underscores that acclimation has its limits. While plants can acclimate to warmer temperatures, their photosynthetic benefit hinges on not having heat or water stresses. In regions experiencing high growth temperature, droughts or prolonged dry spells, plants are less able to maintain this adaptive response, which could counterbalance any positive effects of acclimation in a warmer world.


Implications for Vegetation Function Modeling

 Understanding plant acclimation at the canopy scale is crucial for land surface and vegetation models that predict future carbon absorption by ecosystems. Models incorporating thermal acclimation will better reflect how plants may respond under varied climate scenarios, especially regarding seasonal carbon cycles. Yet, as water scarcity increases with climate change, regions already prone to drought may face diminishing returns on these acclimative benefits.

A Step Toward Resilience

 Ultimately, while the results offer some hope, the researchers' caution that warmer temperatures coupled with limited water could still hinder plant growth and carbon absorption. Liu adds, "These findings point to the importance of conserving water resources in tandem with climate adaptation efforts, to support natural ecosystems under the stress of rising temperatures.". Ryu adds, “Plants are not passive; they are remarkably acclimated to a warmer world, from the scale of individual leaves to entire canopies, across ecosystems ranging from the tundra to the tropics.”