Existing Soil Carbon Models Do Not Apply to Forested Wetlands
When assessing the biological,geological,and chemical cycling of nutrients and elements — or when assessing carbon dynamics with respect to global change — modeling and simulation are necessary. Although wetlands occupy a relatively small proportion of Earth’s terrestrial surface (<3 percent), they contain a disproportionate share of the terrestrial carbon pool (15 to 22 percent). Models that do not accurately represent wetland soil processes cannot,therefore,provide reasonable simulations. We evaluated 12 widely used soil C models to determine their applicability to wetland ecosystems: CANDY, CENTURY, DAISY, DNDC, ITE, MBL-GEM, NCSOIL, QSOIL, ROTHC, SOMM, VVV, and WMEM. Only three (CENTURY, DNDC, and WMEM) allow for anaerobic conditions; none contains components for anoxia,ground water hydrology, multiple organic and physical soil layers,or a daily time-step, all of which are necessary when modeling soil C in wet soils.Accordingly for any land area that includes wetlands, none of the individual models would produce reasonable simulations based on soil processes. We present a wetland soil C model framework based on desired attributes, the DNDC model,and components of the CENTURY and WMEM models. Our proposed synthesis would be appropriate when considering soil C dynamics at multiple spatial scales and where the land area considered includes both wetland and upland ecosystems.