| Summary: | Linear disturbances such as powerline rights of way, seismic lines and roads are common in areas of intensive resource development. Roads that bisect wetlands can alter their hydrologic connectivity on a local or landscape scale. These impacts were studied in a poor fen located 45 km south of Fort McMurray, Alberta, where a raised road was built across the northern fringe of the fen in 1977. Examination of the fen’s response to this impoundment provided insight into post-disturbance vegetation succession patterns and peatland development. The objectives of this study were to map the spatial and temporal extent of hydrological disturbance from road construction, to quantify the response of peatland vegetation to this disturbance and to determine the successional pathway of the system. The study site is an 8 ha poor fen situated on Stoney Mountain (~740 masl), about 45 km south of Fort McMurray in the Athabasca oil sands region of northeastern Alberta. The dominant groundcover of the fen is Sphagnum moss, with Ericaceae shrubs and Picea mariana (black spruce) also abundant. Construction of the raised road began in 1977, and the fen now drains through a culvert built under the road in the northwest corner. Complete tree dieback occurred within 220 m up-gradient of the road. Tree rings were used as a proxy for hydrological change, because depth to water table is the main limiting factor for growth in peatland trees. Forty-two living and dead black spruce trees in the peatland were sampled and used for analysis, and 18 in the surrounding upland hillslopes. Dead trees were cross-dated using a combination of the list method and skeleton plots, and verified with COFECHA. Tree ring chronologies were built in R, and correlation coefficients between climate and ring width index (RWI) values for each chronology were calculated in Dendroclim2002. Water table was measured weekly at three groundwater wells and bulk density of the peat was calculated at several locations across the fen. In sixteen 50 m2 (25x2 m) transects, ...
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