image: Diagram of the thermal adjustment mechanism of soil microbial carbon metabolism under long-term warming.
Credit: Image by LIU Juxiu et al.
Soils release approximately 40–60 petagrams (Pg) of carbon annually into the atmosphere through microbial metabolism. Climate warming is projected to further enhance soil microbial respiration, intensifying positive carbon–climate feedback loops. However, it remains unclear whether this feedback might weaken over several years.
To address this question, a research team led by Prof. LIU Juxiu at the South China Botanical Garden of the Chinese Academy of Sciences has conducted a decade-long study that uncovered a previously unrecognized buffering mechanism in subtropical forest soils mitigating the effects of climate warming.
The team found that under long-term warming, soil microbial communities undergo fundamental reorganization, forming more stable networks that use carbon more efficiently, thereby reducing carbon emissions to the atmosphere.
Published in Science Advances on Nov. 12, the findings challenge current climate model predictions by showing that the initial surge in carbon release from warmed soils diminishes over time as microbial carbon metabolism undergoes thermal adjustment.
"What we observed is nature's sophisticated response to environmental stress," said Prof. LIU. "Microbial communities are not passive—they actively restructure their interactions to maintain ecosystem stability amid changing conditions."
The researchers demonstrated that microbial carbon use efficiency (the fraction of metabolized carbon allocated to microbial growth) became positively correlated with soil temperature after a decade of warming. This contrasts with the previously predicted negative thermal response.
Notably, this shift was not driven by changes in microbial diversity but by a restructuring of the microbial community toward more stable networks. These networks are dominated by slow-growing, efficient microorganisms (K-strategists), thereby enhancing the thermal adjustment of microbial metabolism. As a result, microbial respiration and growth returned to levels comparable to those of unwarmed soils, partially offsetting the initial carbon losses.
The findings hold implications for climate modeling and ecosystem management. The researchers noted that current Earth system models, many of which assume fixed values for microbial carbon use efficiency, may overestimate long-term soil carbon losses. Incorporating microbial network dynamics and thermal adaptation processes into these models could improve their predictive accuracy.
The study also suggests that strategies such as microbial inoculation or other management approaches to enhance soil microbial stability could be developed to boost forest resilience to climate change.
However, the researchers mentioned that this buffering capacity is not unlimited. "The positive plant growth response we observed may not necessarily occur in lowland tropical forests, where temperatures are already higher," said Associate Prof. ZHOU Shuyidan, another co-first author of the study. "Additionally, warming-induced drought could weaken or even disrupt the microbial community's capacity for metabolic thermal adjustment."
Furthermore, the study emphasizes that while subtropical forest soils possess an intrinsic buffering capacity against climate warming, this resilience has limits. Under more intense warming scenarios, this biological buffer could be overwhelmed.
This study provides new insights into refining climate models and developing nature-based solutions to address climate change.
This research was supported by the National Natural Science Foundation of China, the Guangdong Flagship Project of Basic and Applied Basic Research, and other funding sources.
Journal
Science Advances