Carbon cycle feedbacks of temperate forested wetlands under a changing climate
Forested wetlands (swamps) support carbon (C) storage in their living biomass and in some cases they also accumulate C in the form of peat. Carbon storage and other C cycling processes in swamps rely on unique hydro-climatic conditions that may be altered under climate change (CC), thus distorting the C balance of this ecosystem. In particular, ~1.1 billion tonnes of C stored in forested wetlands across Southern Ontario (SON) are susceptible to CC impacts that may contribute a positive climate feedback. To understand the C dynamics of temperate forested wetlands under CC, this study assessed the response of swamp C flux to future climate conditions at a forested wetland in SON. A processed-based ecology model (CoupModel) was initialized to reproduce the swamp’s historic C flux and its associated thermal and hydrological conditions. Thereafter, the model was forced with future climate projections to quantify how changes in existing hydro-climatic conditions will affect the swamp’s net ecosystem exchange (NEE) of CO2. Historic soil temperature and water table levels of the swamp were reasonably simulated by CoupModel with coefficient of determination (R2) values of 0.81& 0.62 respectively, when validated with field measurements. For future projections, 2-3 oC increase in mean air temperature and 10% increase in annual evapotranspiration accelerated heterotrophic respiration and C loss from swamp soils by mid-century. However, this loss was balanced by greater gross primary productivity as a result of prolonged growing season and increased atmospheric CO2 concentration. The bidirectional feedbacks resulted in minimal future NEE changes in the swamp.