Using Relationships Between Vegetation and Surface Soil Biogeochemical Properties to Assess Regional Soil Carbon Inventories for South Baffin Island, Nunavut, Canada.

As Arctic regions warm rapidly, it is unclear whether high‐latitude soil carbon (C) will decrease or increase. Predicting future dynamics of Arctic soil C stocks requires a better understanding of the quantities and controls of soil C. We explore the relationship between vegetation and surface soil C in an understudied region of the Arctic: Baffin Island, Nunavut, Canada. We combined soil C data for three vegetation types—polar desert, mesic tundra, and wet meadow—with a vegetation classification to upscale soil C stocks. Surface soil C differed significantly across vegetation types, and interactions existed between vegetation type and soil depth. Polar desert soils were consistently mineral, with relatively thin organic layers, low percent C, and high bulk density. Mesic soils exhibited an organic‐rich epipedon overlying mineral soil. Wet meadows were consistently organic soil with low bulk density and high percent C. For the top 20 cm, polar desert contained the least soil C (2.17 ± 0.48 kg m−2); mesic tundra had intermediate C (8.92 ± 0.74 kg m−2); wet meadow stored the most C (13.07 ± 0.69 kg m−2). Extrapolating to the top 30 cm, our results suggest that approximately 44 Tg C is stored in the study region with a mean landscape soil C stock of 2.75 kg m−2 for non‐water areas. Combining vegetation mapping with local soil C stocks considerably narrows the range of estimates from other upscaling approaches (27–189 Tg) for soil C on South Baffin Island. Plain Language Summary: Warming in the High Arctic may destabilize organic carbon stored in these high‐latitude soils. One challenge to estimating the amount of carbon stored in the Arctic is that data representing all major regions of the Arctic are limited. We estimate how much carbon is stored in an understudied region of the Arctic by measuring how vegetation type is related to the development of soil carbon and combining these soil data with satellite imagery to make regional estimates of soil carbon storage. On South Baffin Island, Nunavut, Canada, three major vegetation types capture the pattern of soil carbon storage. The wettest vegetation type dominated by grasses and mosses stored the most carbon, followed by a shrub‐dominated vegetation type with moderate moisture. The driest vegetation type, characterized by a sparse cover of lichens and shrubs, stored the least soil carbon. Our regional estimate of soil carbon differed from other databases that predict vegetation and soil carbon. Broadly, our results suggest vegetation and hydrology are important factors for predicting how soil carbon stocks in the Arctic will change in response to climate change. Key Points: Vegetation type, soil composition, and soil organic depth are important controls on soil carbon stocks in this arctic study regionApproximately 44 Tg C is stored in the study region, differing from estimates calculated from circumpolar inventoriesCircumpolar upscaling inventories could benefit from accounting for the relationship between vegetation and soil C at fine scales [ABSTRACT FROM AUTHOR]