Examining the impacts of agricultural drainage on carbon cycling of northern peatlands

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Northern peatlands, storing about 30% of global soil carbon (C), are susceptible to climate and land-use change. They have been, and are still being, converted into agricultural and forestry lands through drainage. Land-use change and other human disturbances, which can be as large as, or larger than, the direct effect of climate change, are key uncertainties in the global C cycle. How do these drained peatlands, with different hydrology and vegetation composition from pristine peatlands, function with respect to C cycling? There is an urgent need to study these changes because the effects of drainage since 2012 have to be accounted for in national greenhouse gas inventories and therefore will become part of land management in the future. However, the peatland C cycling models cannot simulate drainage as they are only parameterized to simulate C cycling under natural conditions. To include drainage in the peatland ecosystem C models requires a greater understanding of the hydrological, ecological and biogeochemical processes of the drained peatlands, and an incorporation of that understanding into the simulation models. The long-term objective of my research program is to understand how the C cycling in northern peatlands is altered by climate and/or land-use change, and eventually to incorporate that knowledge into peatland ecosystem biogeochemical models for climate and land-use change studies. Agriculture is the most widespread use for peatlands globally, the majority being used as meadows and pasture. Canada has one of the largest areas of agriculturally used peatlands. In this study, we are mainly interested in peatlands converted to pastures. The short-term objectives of this 5-year research program are to examine the impacts of drainage on ecological and biogeochemical processes and C cycling of northern peatlands, and to parameterize these drainage impacts in the McGill Wetland Model (MWM). Initially, I will use my new pristine and drained-abandoned pasture peatland sites as my first test case, but my research will expand to other land-use changes over time. Both field measurements and modeling will be employed in my research program, where field measurements will assist in parameterizing and testing the newly developed Drainage-MWM. This study will be of great value to global change science, especially wetland C cycling science. The measurement will provide us with rigorous and continuous carbon dioxide and methane flux data from both pristine and drained peatlands for model parameterization and evaluation. Moreover, this research will provide climate change and land-use policy makers with a simulation tool for examining how agricultural drainage could potentially affect the ecosystem functions of northern peatlands in terms of carbon cycling. The first definitive results will be pertinent to policy on peatland drainage and use of peatlands as pasture in Canada.