The Distribution and Controls of Deep Mineral Soil Carbon in Alaska

Abstract:

Substantial amounts of carbon are currently stored in the mineral and organic soils of Alaska. Frozen carbon in soils, if released through warming, could affect the global carbon balance and climate change. However, their spatial and vertical distributions remain a challenge to explain and map, even with improved spatial datasets. Previous studies revealed the coupling between organic layer depth and permafrost distribution in Alaska, but one knowledge gap remains in the quantity and controls of soil carbon in deeper mineral soils. We gathered together data from more than 700 soil profiles in Alaska and estimated their carbon content in the 0 to 100 cm of mineral soil as well as their organic horizons. The frozen component of the profiles in the Arctic and Boreal regions was strongly correlated with the profile’s organic layer depth and mean annual temperature. Differences were also found when the profiles were grouped according to their topographic position, parent material and ground cover. For example Rocky Uplands and Sandy Lowlands generally held the lowest frozen mineral carbon in the Boreal region while Silty landforms held the highest. Understanding the distribution of the mineral soil carbon pool in Alaska helps improve our ability to model processes the impacts of the change in mineral soil carbon at larger scales.