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Regional Assessment of N Saturation using Foliar and Root ?15 N

TitleRegional Assessment of N Saturation using Foliar and Root ?15 N
Publication TypeJournal Article
Publication Year2006
Publication Date10/2006
Pagination143 - 171
AuthorsPardo, LH, Templer, PH, Goodale, CL, Duke, S, Groffman, PM, Adams, MB, Boeckx, P, Boggs, J, Campbell, J, Colman, B, Compton, J, Emmett, B, Gundersen, P, ønaas, J, Lovett, G, Mack, M, Magill, A, Mbila, M, Mitchell, MJ, McGee, G, McNulty, S, Nadelhoffer, K, Ollinger, S, Ross, D, Rueth, H, Rustad, L, Schaberg, P, Schiff, S, Schleppi, P, Spoelstra, J, Wessel, W
AbstractN saturation induced by atmospheric N deposition can have serious consequences for forest health in many regions. In order to evaluate whether foliar d 15 N may be a robust, regional-scale measure of the onset of N saturation in forest ecosystems, we assembled a large dataset on atmospheric N deposition, foliar and root d 15 N and N concentration, soil C:N, mineralization and nitrification. The dataset included sites in northeastern North America, Colorado, Alaska, southern Chile and Europe. Local drivers of N cycling (net nitrification and mineralization, and forest floor and soil C:N) were more closely coupled with foliar d 15 N than the regional driver of N deposition. Foliar d 15 N increased non-linearly with nitrification:mineralization ratio and decreased with forest floor C:N. Foliar d 15 N was more strongly related to nitrification rates than was foliar N concentration, but concentration was more strongly correlated with N deposition. Root d 15 N was more tightly coupled to forest floor properties than was foliar d 15 N. We observed a pattern of decreasing foliar d 15 N values across the following species: American beech>yellow birch>sugar maple. Other factors that affected foliar d 15 N included species composition and climate. Relationships between foliar d 15 N and soil variables were stronger when analyzed on a species by species basis than when many species were lumped. European sites showed distinct patterns of lower foliar d 15 N, due to the importance of ammonium deposition in this region. Our results suggest that examining d 15 N values of foliage may improve understanding of how forests respond to the cascading effects of N deposition.
Short TitleBiogeochemistry
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