The terrestrial program of the Arctic Challenge for Sustainability-II (ArCS II) is dedicated to clarifying the complex responses of Arctic boreal ecosystems and biogeochemical cycles to a warming climate. Focusing on ecosystem function, terrestrial greenhouse gas dynamics, and permafrost and biogeochemical cycles, ArCS II targets key challenges posed by climate change across terrestrial ecosystems. Biodiversity and ecosystem function research emphasizes the interactions between plant and soil microbial communities across Arctic boreal regions, with discoveries such as new fungal species contributing valuable information elucidating the status of Arctic ecosystems. Our study revealed that vegetation has a significant impact on the composition and network structure of microbial communities, and these interactions may influence ecosystem responses to environmental changes. Greenhouse gas dynamics were analyzed using long-term carbon and methane emissions data collected in boreal forests, tundra, wetlands, and glacial termini, as emissions from these regions can accelerate warming. Plant-mediated methane transport was identified as the primary process driving methane emission from wetlands, and elevated methane concentrations were detected in some glacial meltwaters. ArCS II advances permafrost modeling to assess the impacts of thawing on terrestrial processes, emphasizing freeze-thaw cycles and their impact on greenhouse gas dynamics. Excess ice formed within permafrost plays a role in suppressing permafrost warming and may induce anomalous variations in greenhouse gas emissions. Despite limitations imposed on field surveys by COVID-19, the ArCS II project elucidated ecosystem changes using long-term data. ArCS II terrestrial research lays a foundation for the exploration of climate impacts on Arctic boreal ecosystems.

来源平台：POLAR SCIENCE