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.

The intrusion of petroleum into soil ecosystems causes severe environmental damage. A synergistic plant-microbe-electrochemical soil remediation technology offers a strategic and eco-friendly solution to address this issue. However, the significant mass transfer resistance in soil poses a major limitation for long-distance site remediation. This research introduces a novel technique that leverages water circulation driven by plant transpiration to facilitate the long-distance migration, adsorption, and electrochemical degradation of hydrocarbons. Experimental results demonstrate that the incorporation of Iris tectorum, polyurethane sponge (as an electrode support matrix), and water-retaining agents significantly enhanced soil water circulation, enabling the migration of soluble organic carbon over distances of up to 60 cm. Additionally, the application of a weak voltage (0.7 V) to the electrode further improved total organic carbon (TOC) removal, achieving a reduction of 193 +/- 71 mg/L. After 42 days of remediation, hydrological circulation accelerated the degradation of n-alkanes and aromatics, with removal efficiencies reaching 57 % and 44 %, respectively, within the 20-60 cm range in the microbial electrochemical cell (MEC) group. The functional microbiota, enriched with electroactive microorganisms, was effectively cultivated on the anode, with the total abundance of potential hydrocarbon-degrading bacteria increasing by 42 % compared to the control. Furthermore, a scalable configuration has been proposed, offering a novel perspective for multidimensional ecological soil remediation strategies.