An integrated model of soil, hydrology, and vegetation for carbon dynamics in wetland ecosystems

[1] Wetland ecosystems are an important component in global carbon (C) cycles and may exert a large influence on global climate change. Predictions of C dynamics require us to consider interactions among many critical factors of soil, hydrology, and vegetation. However, few such integrated C models exist for wetland ecosystems. We developed a simulation model, Wetland-DNDC, for C dynamics including methane (CH4) emissions in wetland ecosystems. The general structure of the model was adopted from PnET-NDNDC, a process-oriented biogeochemical model that simulates C and N dynamics in upland forest ecosystems. We developed new functions and algorithms to capture the unique features of C dynamics under wetland conditions. Major modifications were made which focus on quantifying water table dynamics, soil thermal dynamics, growth of mosses and herbaceous plants, and soil biogeochemical processes under anaerobic conditions. In this paper, we report new developments made for Wetland-DNDC, as well as tests against observations from three wetland sites in Northern America. Validation results show that the model’s predictions are in good agreement with measurements of water table dynamics, soil temperature, CH4 fluxes, net ecosystem productivity (NEP), and annual C budgets. Sensitivity analysis indicates that the most critical input factors include temperature, water outflow parameters, initial soil C content, and plant photosynthesis capacity. NEP and CH4 emissions are sensitive to many of the input variables required by different components of the model. These results suggest that integrated modeling with soil, hydrology, vegetation, and climate is essential to predict C cycles in wetland ecosystems.