PARENT SESSION
Oral Session #44: Global Change and Climate Change.
Presiding: C. Wessman
Tuesday, August 6. 1:00 PM to 4:45 PM. Grand Ballroom West, Radisson.
Patterns of nitrogen loss from a pristine old-growth forested watershed, Olympic National Park, Washington.
Edmonds, Robert*,1, McAfee, Stephanie1, Volk, Carol1, 1 University of Washington, Seattle, WA
ABSTRACT- Nitrogen inputs and outputs were determined in the West Twin Creek (WTC) watershed (58ha) in Olympic National Park from 1985-2001. Forests along the Pacific Northwest coast have historically received little N pollution from depositional events, in comparison to the elevated NO3 inputs in the eastern U.S. and in regions down-wind of urban-industrial centers. Since 1980, annual wet-only deposition along the Pacific Northwest coast has been generally <2 kg ha-1 (NADP). Although N in bulk and wet-only precipitation were similar from 1985-1993, bulk precipitation measurements of N deposition between 1993 and 1996 were >4 kg ha-1 yr-1 near Olympic National Park. Throughout most of the study, NO3-N has comprised 30-50% of annual N outputs from WTC; dissolved organic N (DON) has comprised the bulk of the remainder. Between 1993 and 1996, NO33-N comprised >65% of the total N output from the watershed, but returned to generally <50% in 1997. The rapid alteration followed by recovery in this system suggests that the N-cycle in old-growth forests may be sensitive to impact by anthropogenic pollution, but resilient enough to recover once the depositional impact is removed.
KEY WORDS: N-cycle, stream chemistry, old-growth, global change