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Red spruce ecosystem level changes following 14 years of chronic N fertilizationAuthor(s): Steven G. McNulty; Johnny Boggs; John D. Aber; Lindsey Rustad; Allison Magill
Source: Forest Ecology and Management, Vol. 219: 279-291
Publication Series: Miscellaneous Publication
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DescriptionIn the early 1980s, nitrogen (N) deposition was first postulated as a cause of N saturation and spruce mortality across the northeastern US. In 1988, a series of high elevation spruce-fir forest N addition plots were established on Mt. Ascutney (southeastern) Vermont to test this hypothesis. The paired plots each received, in addition to ambient N deposition, 15.7 kg N ha-1 year-1 (low N addition), 31.4 kg N ha-1 year-1(high N addition) or no N addition (control) from 1988 to 2002. Over the years, potential and annual in situ forest floor net N mineralization and net nitrification, foliar and forest floor elemental concentrations, and basal area growth by species were measured on each plot. Live basal area decreased by 18% on the low N addition plots, and by 40% on the high N addition plots between 1988 and 2002, while the control plots had a 9% increase in basal area over the same time period. Initially, none of the plots had measurable rates of in situ nitrification, but by 2002,21% of the mineralized N was being annually nitrified on the high N addition plots, compared to no net nitrification on the control plots. We also observed a significant increase in forest floor N concentration on the high N plots from 1988 to 2000. Reductions in live basal area, and increased net nitrification suggest that we induced late stage N saturation on the high N addition plots. The low N addition plots exhibited symptoms of mid-stage N saturation, with a smaller reduction in live basal area and net N mineralization, and a smaller increase in net nitrification compared to the high N addition plot values. Other correlations between forest floor and vegetation composition and function, and N saturation will be discussed in the paper.
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CitationMcNulty, Steven G.; Boggs, Johnny; Aber, John D.; Rustad, Lindsey; Magill, Allison. 2005. Red spruce ecosystem level changes following 14 years of chronic N fertilization. Forest Ecology and Management, Vol. 219: 279-291
KeywordsN saturation, red spruce, fertilization
- Spruce-fir forest changes during a 30-year nitrogen saturation experiment
- Nitrogen saturation in a high elevation New England spruce-fir stand
- Nitrogen mineralization and nitrification in a mixed-conifer forest in southern California: controlling factors, fluxes, and nitrogen fertilization response at a high and low nitrogen deposition site
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