Nitrogen fertilization impacts on high elevation spruce forests, Mount Ascutney, VT

PARTNERS: Cornell University; State University of New York; University of New Hampshire; University of Maine; USDA Forest Service Northern Research Station

SUMMARY: In the early 1980s, nitrogen (N) deposition (i.e., acid rain) was first postulated as a cause of N saturation and red spruce tree mortality across the northeastern U.S. N saturation occurs when more N is added to a forest than it can use. In 1988, a series of red spruce plots were established on Mount Ascutney in southeastern Vermont to test this hypothesis. Paired plots each received, in addition acid rain that falls from the atmosphere, 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 these red spruce plots were resampled to determine how the red spruce forest has changed (this included measuring nutrients in the soil and foliage and number of live and dead trees). The summer of 2010 was the last sampling year.

Changes in soil and foliage nutrients and number of trees will now be measured every four years to determine rate of red spruce stand recovery following termination of exposure to acid rain.

EFETAC'S ROLE: The Eastern Threat Center provides personnel time and cost, travel, and supplies.

STATUS: Ongoing

PROGRESS: Studies have shown, under high acid rain inputs, reductions in tree growth and increases in nitrate (nutrient for plant growth) which tend to suggest late stage N saturation. Under low acid rain inputs, results show symptoms of mid-stage N saturation, with a smaller reduction in tree growth and nutrient lost.

Project data continue to be used by Eastern Threat Center scientists and others to further understand the roles of N on the health of red spruce forests. For example, Ascutney is being used as one of three test study sites by scientists from State University of New York, Brookhaven National Laboratory, Cornell University, and University of Maine to apply a non destructive soil inventory using an Inelastic Neutron Scattering (INS) approach to test effects of atmospheric N deposition on soil carbon storage.

Long-term benefits to the Eastern Threat Center's mission: 1) A manuscript assessing response variables will be completed and submitted to Forest Ecology and Management in 2014 to determine if red spruce plots are showing characteristics of N saturation and further ecosystem decline. 2) Data from this long-term N fertilization project have been used in a series of regional assessments and meta-data analysis projects conducted by scientists at the Northeastern Ecosystem Research Cooperative (NERC). Further plot-level analysis will continue to fill data gaps on the effects of N deposition on how forests grow and facilitate local- and regional-scale database and model development.

Pictured: The control plot on Mt. Ascutney (top) experienced 4% tree mortality between 1988 and 2006. Mortality in the high nitrogen addition plot (bottom) was about 90% during the same period.

Pictured: 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. In 2016, a new display (right) will be added on the mountain to inform the public about a science and policy success story. Click to enlarge.

Boggs, J.L. and S.G. McNulty. Changes in canopy cover alter surface air and forest floor temperature in a high elevation red spruce (Picea rubens Sarg.) forest. Proceedings paper, Conference on Ecology and Management of High-Elevation Forests of the Central and Southern Appalachian Mountains. May 14-15, 2009. Slatyfork, WV. (PDF)

McNulty, S., J. Boggs, J. Aber, L. Rustad, and A. Magill. 2005. Red spruce ecosystem level changes following 14 years of chronic N fertilization. Forest Ecology and Management 219: 279-291. (PDF)

LINKS:

Related articles from CompassLive:

• "30 Years of Nitrogen Fertilization in Spruce-Fir Forest"
• "Mount Ascutney Visitors Enjoy the View and Learn Something, Too"

CONTACT: Johnny Boggs, Eastern Threat Center Biological Scientist, johnny.boggs@usda.gov or 919-549-4060

Updated July 2018