The PnET-N-DNDC process-orientated model which simulates C and N dynamics in upland forest ecosystems and the FLATWOODS (Sun et al., 1998) distributed hydrological model have been integrated to create the Wetland-DNDC model. The main structure of Wetland-DNDC is taken from PnET-N-DNDC (Li et al., 2000), with several additional functions and algorithms developed for Wetland-DNDC to represent features unique to wetland ecosystems such as anaerobic conditions, growth of mosses and herbaceous plants and water table dynamics. The model is capable of predicting carbon biogeochemical cycles in wetland ecosystems through the integration of the primary drives of climate, hydrology, soil and vegetation (Zhang et al. 2002).
Zhang et al. (2002) describes the model as consisting of four interacting components: hydrological conditions, soil temperature, plant growth and soil C dynamics. Initial conditions need to be set (e.g. for plant biomass, soil porosity, soil C content, and water table position). In addition the climate drivers are inputs to the model and some model parameters (e.g., lateral inflow/outflow parameters, maximum photosynthesis rate). The model output includes C pools and fluxes and thermal/hydrological conditions.
The model was validated by Zhang et al. (2002) against observations from three wetland sites in North America, which were in agreement with measurements of water table dynamics, soil temperature, methane (CH4) fluxes, Net Ecosystem Productivity (NEP) and annual carbon budgets. Plant photosynthesis capacity, initial soil C content, air temperature and water outflow parameters were shown to be the most critical input factors for C dynamics in wetland ecosystems through sensitivity analysis.
Wetland-DNC has had additional enhancements by (Li et al 2004) to enable changes in management practices that affect carbon sequestration to be represented, such as forest harvest, tree planting, chopping and burning and water management.