Evaluating carbon storage on subalpine lake deltas

Abstract

AbstractMountainous regions are important contributors to the terrestrial organic carbon (OC) sink that affect global climate through the regulation of carbon‐based greenhouse gases. However, mountain OC dynamics are poorly quantified. We quantified OC storage in subalpine lake deltas in the Washington Central Cascades and Colorado Front Range with the objectives of determining the magnitude of transient carbon storage and understanding the differences in storage between the two ranges. We used field, laboratory, and GIS techniques to determine the magnitude of and controls on the subalpine lake delta OC pool in 26 subalpine lake deltas. Soil moisture, soil texture, mean basin slope, and delta valley confinement are significantly correlated with soil carbon on deltas. Average soil OC concentration on subalpine lake deltas ranges from 3 to 41%, and stocks range from 140 to 1256 Mg C/ha. Surprisingly, the carbon content of subalpine lake deltas is not significantly different between the two regions, despite stark contrasts in their climate, vegetation, and total ecosystem carbon stocks. We present a conceptual model that invokes geomorphic and biogeochemical processes to suggest that carbon is more likely to reach subalpine lake deltas from the upstream basin in the Colorado Front Range compared with the Washington Central Cascades, thus accounting for the similarity in OC storage between the two regions despite differences in total ecosystem carbon stocks and climate. This points to a complex interaction among carbon production, transport, and stability in each region, and supports the idea that geomorphic and biogeochemical processes determine the magnitude of transient OC storage more strongly than primary productivity or climate. Copyright © 2017 John Wiley & Sons, Ltd.