Contrasts in Carbon and Nitrogen Ecosystem Budgets in Adjacent Norway Spruce and Appalachian Hardwood Watersheds in the Fernow Experimental

We constructed watershed mass-balance budgets of carbon (C) and nitrogen (N) and measured seasonal net N mineralization in an attempt to account for nearly 40 years of large discrepancies in stream NO,-N export in two adjacent, gauged watersheds at the U.S. Department of Agriculture Forest Service's Fernow Experimental Forest, WV. These watersheds have similar management histories, varying primarily by vegetation cover, where one watershed is a monoculture of Norway spruce (Picea abies) and the other has regenerated to native Appalachian hardwoods. Long-term stream chemistry indicates that the hardwood watershed has approached N-saturation, with relatively high stream export of nitrate-N (15 kg N03--N/halyr), whereas the spruce watershed exports virtually no nitrate-No We estimated the pool size ofC and N within the mineral soil, forest floor, litter, above-and below-ground tree biomass, and stream dissolved organic N. We were unable to account for long-term differences in N03-N export via streamflow by estimating these pools. Total C and N pools were 28 percent and 35 percent lower in the spruce watershed, respectively. Though historic organic C and N were never measured in the long-term stream chemistry, the discrepancy in C and N budgets between the two watersheds suggests that the spruce watershed may have been subjected to a period of large losses of C and organic N from deeper subsurface soils. Such large losses suggest that species conversion has the potential Kelly is a research associate and Schoenholtz is Director, both with the Virginia Water Resources and Research Center. Email: kelbcnidvt.ec.l.l!..Adams is a soil scientist with the U.S. Forest Service Timber and Watershed Lab, WV. to significantly alter ecosystem C and N budgets, with implications for long-term productivity, C sequestration, and water quality