Cryptic Carbon: Improving Wetland Representation and Soil Carbon Characterization across Forested Landscapes

Abstract

Inland freshwater wetlands disproportionately contain soil organic carbon (SOC), storing greater than 30% of the total global pool but only cover 6% of the land surface. However, many of these wetlands, especially in the Pacific Northwest, are hidden under forest canopy and excluded from maps of wetland extent, estimates of landscape SOC stock, and under-evaluated in broader soil science. Chapter 1 shows that implementing a new wetland mapping tool, the wetland intrinsic potential (WIP) tool, to identify hidden “cryptic” wetlands can improve estimates of landscape SOC stocks and identifies approximately 5-fold wetland SOC stock than previous estimates. Chapter 2 describes how the WIP wetland identification can be applied in models across regional scales, producing consistently higher landscape and wetland SOC measurements. This shows that the patterns of landscape soil moisture regimes with WIP is significant driver of SOC stock but not mineral soil SOC% across regional scales with climatic variation. Chapter 3 further investigates the mineral associations with soil organic matter (MAOM) and evaluates the SOC stability in forested wetlands and uplands finding that forested wetlands have lower MAOM SOC content (MAOM-C) compared to dry uplands but the radiocarbon dating of the MAOM-C (MAOM-∆14C) in forested wetlands was much older. The results suggest that landscape class, Fe, pH and SOC% are drivers of the MAOM-C and MAOM-∆14C. Overall this dissertation reveals new insights into the spatial distribution of inland freshwater wetlands and wetland SOC as well as how well this SOC is preserved.