Estimates of soil taxonomic change due to near-surface permafrost loss in Alaska

Gelisols (permafrost-affected soils in U.S. Soil Taxonomy) are extensive in Alaska, currently occurring on approximately 45% of the land area of the state. Gelisol taxonomic criteria rely on the presence of near-surface (less than 2m deep) permafrost, but ongoing climatic and environmental change has the potential to affect the presence of near-surface permafrost across much of Alaska throughout the 21st century. In this study, we utilized scenarios of near-surface permafrost loss and active layer deepening through the 21st century under low (SRES B1, RCP 4.5), mid- (SRES A1B) and high (SRES A2, RCP8.5) emissions scenarios, in conjunction with the statewide STATSGO soil map, to generate spatially-explicit predictions of the susceptibility of Gelisols and Gelisol suborders to taxonomic change in Alaska. We find that 15-53% of Alaskan Gelisols are susceptible to taxonomic change by mid-century and 41-69% of Alaskan Gelisols are susceptible to taxonomic change by the end of the century. The extent of potential change varies between suborders and geographic regions, with Gelisols in Northern Alaska being the most resilient to taxonomic change and Western and Interior Alaskan Gelisols most susceptible to taxonomic change. The Orthel suborder is likely to be highly restricted by the late 21st century, while Histels and Tubels are more likely to be of greater extent. These results should be taken into consideration when designing initial survey and re-mapping efforts in Alaska, and suggest that Alaskan Gelisol taxa should be considered threatened soil taxa due to the proportional extent of likely loss.