HR: 0830h
AN: B31C-0309    [PDF]
TI: Enhanced N Deposition and Peatland Carbon Stocks in Boreal Alberta
AU: * Turetsky, M R
EM: mturetsky@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd. MS 962, Menlo Park, CA 94025 United States
AU: Halsey, L A
EM: lhalsey@ualberta.ca
AF: University of Alberta, Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9 Canada
AU: Vitt, D H
EM: dale.vitt@plant.siu.edu
AF: Southern Illinois University, Department of Plant Biology, Southern Illinois University, Carbondale, IL 62901 United States
AU: Wieder, R K
EM: kelman.wieder@villanova.edu
AF: Villanova University, Department of Biology, Villanova University, Villanova, PA 19085 United States
AB: Increased deposition of reactive nitrogen due to anthropogenic activities may stimulate plant growth and soil C turnover in N-limited ecosystems. Many peatland ecosystems are particularly sensitive to nitrogen deposition due their ombrotrophic nature. Here, we capitalize on a regional gradient of N deposition associated with several decades of oil sands mining. At six peatlands varying in atmospheric N loading (modeled from 1.45-3.26 kg N ha$^{-1}$ yr$^{-1}$), we measured {\it Sphagnum fuscum} net primary productivity (NPP). NPP rates were higher at Steepbank Bog (mean of 600 g m$^{-2}$ yr$^{-1}$) than at the five sites with lower N deposition (pooled mean of 182 g m$^{-2}$ yr$^{-1}$). At the site with the highest (Steepbank Bog) and lowest (Bleak Lake Bog) N loading, we quantified rates of C storage by $^{210}$Pb dating. Over the past 30 years of mining activity, rates of vertical peat accumulation were higher at Steepbank Bog (19.4 $\pm$0.4 cm) than at Bleak Lake Bog (13.9 $\pm$2.0 cm). However, there were no differences between sites in cumulative C storage over this 30-yr period (Steepbank: 5.0 $\pm$0.2 kg C m$^{-2}$, Bleak Lake: 5.0 $\pm$0.4 kg C m$^{-2}$). Together, these data suggest that increased N availability stimulates plant growth rates, leading to greater vertical accumulation of peat. However, enhanced N deposition does not appear to influence C storage in these sites, possibly due to lower peat bulk density and/or greater microbial activity.
DE: 1615 Biogeochemical processes (4805)
DE: 1803 Anthropogenic effects
DE: 1890 Wetlands
SC: Biogeosciences [B]
MN: 2003 Fall Meeting