The biogeochemical heterogeneity of peatlands

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Peatlands are a type of wetland that cover about 12% of Canada's land area. They are characterized by the peat over which they form, a soil that is entirely made of the dead remains of plants and other organic matter. This peat can reach several meters high and it stores large amounts of carbon since about 50% of the peat's dry weight is carbon. It is therefore estimated that approximately one third of all the soil carbon on the planet is stored in peatlands, although they only cover about 2-3% of the global land area. This peat forms because peatlands are consistently wet, limiting the rate at which organic remains decompose. While this carbon storage has been intensively studied over the last two decades, much less is know about the role of nitrogen and phosphorus in peatlands, the two main nutrients upon which plant growth depends. The amount of nutrients available in some types of peatlands is very limited, and any change in the amount of nutrients they receive may change their vegetation composition and affect their capacity to accumulate carbon. Research on peatlands often concentrates on the central and uniform portions of these wetlands, considered to be representative of the processes occurring elsewhere. However, peatlands are not uniform. Their margin, which can be of variable width (from a few meters to more than a hundred meters) is a transition area that has unique chemical and hydrological characteristics that have seldom been studied. Many peatlands are also dotted with open water pools, small ponds that seem to be completely independent from one another and have also been seldom studied in the past. These ponds have been shown to emit carbon while the peat around it stores carbon. Peatlands that have been disturbed by peat extraction, often for horticultural uses, are often restored once the extraction stops, and in some test sites, pools have been re-created. In this research, I will try to understand how processes related to carbon, nitrogen and phosphorus cycling vary between different components of peatlands that have seldom been studied, margins and pools. I will also determine how do pools from restored peatlands chemically compare to pools from undisturbed peatlands. Finally, I will describe how the carbon, nitrogen and phosphorus content of peat varies worldwide and determine if these variations may inform us on the human disturbances to which the peatlands are exposed.