Responses and microbial mechanisms of greenhouse gas emissions and multifunctionality of soils at different elevations in Changbai Mountain under warming conditions

Mountains experience vertical variations in forest types and present different vegetation zones due to changes in topography and climate. Mountain environments are particularly sensitive to the effects of global warming, which has resulted in changes in the distribution of vegetation zones. Therefore, soil greenhouse gas emissions and their mechanisms in different vegetation zones under climate warming require further investigation. In this study, we conducted in-situ gradient shift warming experiments to evaluate the response of soil greenhouse gas emissions (GHGs) and multifunctionality in Changbai Mountain. Our results showed that warming increased soil CO₂ and N₂O emissions while enhancing CH₄ uptake in all four vegetation zones. The responses of soil CO₂ and N₂O emissions, as well as global warming potential, were more pronounced in coniferous forests. The sensitivity of CH₄ uptake to warming was highest in mixed coniferous-broadleaf forests. Microbial Shannon diversity was crucial for explaining the variations in CO₂ and N₂O emissions, whereas NO₃⁻-N levels primarily explained the variations in CH₄ uptake. Metagenomic analysis indicated that the functional profiles of microbial communities associated with soil carbon and nitrogen cycles changed across the four vegetation zones due to warming. Furthermore, climate warming decreased the multifunctionality of the mixed coniferous-broadleaf forest zone. PLS-PM revealed that microbial diversity and soil properties negatively impacted soil greenhouse gas emissions and positively affected soil multifunctionality, while warming positively influenced functional genes that are related to carbon and nitrogen cycles. These findings enhance our understanding of how climate warming impacts soil GHGs, carbon and nitrogen cycling, and ecosystem functions in mountain ecosystems, and are essential for mountain ecosystem management.