BEIJING, June 18 (Xinhua) -- An international research team led by Chinese scientists has for the first time proposed a theoretical model to explain and predict the thermal adaptation of tree trunk respiration.

The team established a global database of plant trunk respiration, and confirmed the widespread existence of thermal adaptation in this process. Their findings have been published online in the journal Science.

The study projects that by 2100, thermal adaptation in trunk respiration could reduce carbon emissions from terrestrial ecosystems by 24 percent to 46 percent, holding significant implications for mitigating climate change, said Wang Han, an associate professor at the Department of Earth System Science, Tsinghua University, and the corresponding author of the study.

Carbon dioxide (CO2) released by trunk respiration is a major source of carbon emissions in terrestrial ecosystems. Conventional understanding held that rising temperatures significantly increase tree respiration, thereby accelerating climate warming.

However, recent research indicates plants can mitigate their respiratory response to warming through thermal acclimation.

While thermal acclimation in leaves and roots has been extensively studied, key questions remained: Does similar thermal acclimation occur in trunks? What are the underlying physiological mechanisms? And how does this adaptation impact the global carbon cycle under long-term climate warming? Answers are crucial for accurately predicting future climate change.

The research team proposed a novel theoretical model based on the Ecological Evolutionary Optimality (EEO) principle, Wang said.

This model yielded key predictions about the thermal sensitivity of trunk respiration: for every one degree centigrade increase in ambient temperature, the basal respiration rate per unit mass decreases by approximately 10.1 percent, and the respiration rate at growth temperature decreases by about 2.3 percent.

To validate the theory, the team constructed a global trunk respiration database, including 8,782 sets of observational data from 68 field sites across global climate zones, covering 187 species, and data from a warming experiment.

The observation results are highly consistent with the theoretical predicted values, strongly confirming the reliability of the theoretical model.

Through seasonal observations and a greenhouse warming experiment, the team also verified the phenomenon of trunk respiration thermal acclimation at the individual tree scale.

The team further assessed the impact of trunk respiration thermal acclimation on global terrestrial ecosystem carbon fluxes.

The results show that the current annual carbon emissions from tree trunk respiration worldwide amount to approximately 27 billion tonnes, which is applied to the analysis of future climate change in both low-emission and ultra-high-emission scenarios.

The study suggests that existing Earth System Models (ESMs), by neglecting stem respiration thermal acclimation, may significantly overestimate the climate-carbon positive feedback effect. This new discovery provides a critical theoretical foundation and data support for revising global carbon budgets and climate predictions.

Next, the team will investigate the influence of environmental factors like soil water and CO2 concentration, as well as intrinsic factors like plant hydraulic traits, to elucidate the specific mechanisms of trunk respiration thermal acclimation. They will also integrate the EEO theoretical framework and the thermal acclimation characteristics of trunk respiration into ESMs.

The team's work is expected to significantly enhance the accuracy of global carbon cycle simulations and support climate governance decisions.

Collaborators from Western Sydney University, the University of Reading, Imperial College London, the University of Exeter, the University of California, Berkeley, and other research institutions participated in the study. ■