Vulnerability of high-latitude soil organic carbon in North America to disturbance

TLDR

Climate warming in arctic, subarctic, and boreal regions can redistribute carbon among major reservoirs, potentially crossing thresholds that accelerate press disturbances, trigger pulse disturbances, and alter the net source/sink character of northern high‑latitude soils. This synthesis examines the vulnerability of North American high‑latitude soil organic carbon to climate change by identifying key factors and processes, assessing post‑disturbance feedbacks, and outlining data and research gaps. The authors classify SOC pools into near‑surface soils influenced by freeze‑thaw and moisture dynamics and deeper permafrost/peatland strata, then evaluate how press disturbances such as permafrost thaw, hydrological shifts, microbial and pedological changes, and pulse disturbances like wildfires and thermokarst can substantially alter SOC stocks. The study finds that climate warming may cross environmental thresholds, intensify press disturbances, trigger pulse disturbances, and ultimately shift northern high‑latitude soils from carbon sinks to sources.

Abstract

Abstract [1] This synthesis addresses the vulnerability of the North American high-latitude soil organic carbon (SOC) pool to climate change. Disturbances caused by climate warming in arctic, subarctic, and boreal environments can result in significant redistribution of C among major reservoirs with potential global impacts. We divide the current northern high-latitude SOC pools into (1) near-surface soils where SOC is affected by seasonal freeze-thaw processes and changes in moisture status, and (2) deeper permafrost and peatland strata down to several tens of meters depth where SOC is usually not affected by short-term changes. We address key factors (permafrost, vegetation, hydrology, paleoenvironmental history) and processes (C input, storage, decomposition, and output) responsible for the formation of the large high-latitude SOC pool in North America and highlight how climate-related disturbances could alter this pool's character and size. Press disturbances of relatively slow but persistent nature such as top-down thawing of permafrost, and changes in hydrology, microbiological communities, pedological processes, and vegetation types, as well as pulse disturbances of relatively rapid and local nature such as wildfires and thermokarst, could substantially impact SOC stocks. Ongoing climate warming in the North American high-latitude region could result in crossing environmental thresholds, thereby accelerating press disturbances and increasingly triggering pulse disturbances and eventually affecting the C source/sink net character of northern high-latitude soils. Finally, we assess postdisturbance feedbacks, models, and predictions for the northern high-latitude SOC pool, and discuss data and research gaps to be addressed by future research.