PARTNERS: USDA Forest Service Northern Research Station, University of New Hampshire

SUMMARY: In the early 1980s, nitrogen deposition was first postulated as a cause of N saturation and spruce mortality across the northeastern U.S. In 1988, a series of high elevation spruce-fir forest nitrogen addition plots were established on Mt. Ascutney in southeastern Vermont to test this hypothesis. The paired plots each received, in addition to ambient nitrogen deposition, 15.7 kg N ha^-1 yr^-1 (low N addition), 31.4 kg N ha^-1 yr^-1 (high N addition), or no nitrogen addition (control). Every four years, ecosystem response variables are measured on each plot, including potential and annual in situ forest floor net nitrogen mineralization and net nitrification, foliar and forest floor elemental concentrations, and basal area growth by species. An assessment of these response variables will be completed to determine if they are showing characteristics of nitrogen saturation and ecosystem decline.

STATUS: Ongoing

PROGRESS: Studies have shown, under high N inputs, reductions in live basal area and increases in net nitrification which tend to suggest late stage nitrogen saturation. Under lower nitrogen inputs, results show symptoms of mid-stage nitrogen saturation, with a smaller reduction in live basal area and net nitrogen mineralization and a smaller increase in net nitrification.

In June 2008, two interpretive display panels were installed on Mount Ascutney to inform the general public including hikers, hang gliders, bikers, runners, and campers about this long-term research project and findings.

Steve McNulty, Johnny Boggs, John Aber, Lindsey Rustad, and Allison Magill. 2005. Red spruce ecosystem level changes following 14 years of chronic N fertilization. Forest Ecology and Management 219: 279-291. (PDF)

LINKS:

USDA Forest Service Northern Research Station

University of New Hampshire

CONTACT: Johnny Boggs, EFETAC Southern Global Change Program Biological Scientist, jboggs@ncsu.edu or 919-513-2973