Hydrogeomorphic Controls on Reduction–Oxidation Conditions across Boreal Upland–Peatland Interfaces |
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Authors: | Carl P J Mitchell Brian A Branfireun |
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Institution: | (1) Department of Geography, University of Toronto at Mississauga, 3359 Mississauga Road North, Mississauga, Ontario, L5L 1C6, Canada |
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Abstract: | The reduction–oxidation (redox) state of peatland pore waters plays an important role in many peatland biogeochemical processes.
Recent research has also shown that the interface between ecosystems, or the ecotone, may be responsible for a disproportionate
amount of biogeochemical activity when material and/or energy is hydrologically transported between ecosystems. The purpose
of this research was to examine the spatiotemporal dynamics of redox conditions across two geomorphically distinct Boreal
Precambrian Shield upland–peatland ecotones to determine the spatial and temporal scales at which these ecotones may be important.
Pore water chemistry of iron and sulphur species was monitored across two upland–peatland ecotones in northwestern Ontario
in conjunction with hydrological measurements under both stormflow and nonstormflow conditions. In addition, one upland–peatland
ecotone was instrumented to make continuous measurements of in situ redox potential (Eh) over a 12-day period to determine whether measurements at a high temporal scale could provide additional
insights into the transfer of nutrients across the upland–peatland interface. Results indicated that hydrology—specifically,
groundwater flowpath and the strength of the hydrological connection between upland and peatland—determined the spatial extent
of the ecotone as a biogeochemical hotspot. In situ Eh measurements showed that these ecotones may be most important over
a scale of only several hours and are largely affected by lateral hydrological flows from the upland. The role of both hot
spots and hot moments in biogeochemistry must be considered to accurately estimate the ability of a single ecosystem to process
chemical inputs. |
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Keywords: | reduction– oxidation hydrology peatland hillslope ecotone interface hot spot hot moment sulphate iron |
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