HR: 1330h
AN: B32B-0386    [PDF]
TI: Long-term Trends in Soil CH$_{4}$ Consumption at the Harvard Forest Chronic Nitrogen Addition Experiment: Implications for the Future Growth in Atmospheric CH$_{4}$.
AU: * Steudler, P A
EM: steudler@mbl.edu
AF: The Ecosystems Center Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA 02543 United States
AU: Chan, A S
EM: achan@mbl.edu
AF: The Ecosystems Center Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA 02543 United States
AU: Aber, J D
EM: john.aber@unh.edu
AF: Complex Systems Research Center University of New Hampshire, Morse Hall Rm 445, Durham, NH 03824 United States
AU: Gulledge, J
EM: jay.gulledge@louisville.edu
AF: Department of Biology University of Louisville, 139 Life Science Building, Louisville, KY 40292 United States
AU: Cavanaugh, C M
AF: Department of Organismic and Evolutinary Biology Harvard University, 16 Divinity Avenue, Cambridge, MA 02138 United States
AU: Melillo, J M
EM: jmellillo@mbl.edu
AF: The Ecosystems Center Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA 02543 United States
AB: For the past 15 years we have been conducting a field experiment designed to examine the short- and long-term effects of chronic N additions to temperate forests on a number of biogeochemical processes including soil CH$_{4}$ consumption. The N additions were begun in 1988 in a 50+ year-old mixed hardwood stand and a 70+ year-old red pine plantation. Nitrogen was applied as NH$_{4}$NO$_{3}$ at annual rates of 0, 50 and 150 kg N/ha over the six- month growing season. Forests in this region receive about 8 kg N/ha/yr from dry and wet deposition. During the first year of treatment we observed an immediate decrease in the rate of soil consumption of atmospheric CH$_{4}$ of about 23% in all of the amended plots compared to the controls. Over the next four years the overall decrease in consumption stabilized at about 36% and 62% in the hardwood and pine high N plots, respectively. We re-measured the consumption rates at these sites in 2003, after 15 years N addition. Preliminary results indicate that consumption rates have not remained constant at the levels measured in 1993, but have continued to decrease dramatically in all treatments. The greatest change was in the high N pine plot where the consumption rate was reduced by 82%, while the rate in the low N plot was reduced by 59%. The hardwood plots showed a similar pattern with a reduction in the rates in the low and high N plots by 39% and 63%, respectively. These findings are consistent with CH$_{4}$ consumption measurements in forests that have high N deposition rates in the United States and Europe. These results have important long-term implications for the CH$_{4}$ consumption capacity of temperate forest soils. It appears that even moderate levels of chronic N deposition may diminish the potential for these soils to slow the future growth in atmospheric CH$_{4}$.
DE: 0315 Biosphere/atmosphere interactions
DE: 0322 Constituent sources and sinks
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2003 Fall Meeting