Regional assessment of N saturation using foliar and root d15N
| Forfatter | L.H. Pardo , P.H. Templer , C.L. Goodale , S. Duke , P.M. Groffman , M.B. Adams , P. Boeckx , J. Boggs , J. Campbell , B. Colman , J. Compton , Bridget A. Emmett , Per Gundersen , O. Janne Kjønaas , G. Lovett , M. Mack , A. Magill , M. Mbila , M.J. Mitchell , G. McGee , S. McNulty , Knute J. Nadelhoffer , S. Ollinger , D. Ross , H. Rueth , L. Rustad , P. Schaberg , S. Schiff , Patrick Schleppi , J. Spoelstra , W. Wessel |
|---|---|
| Publisert i/av | Biogeochemistry |
| Utgave/nummer | 80 |
| Sidetall | 143-171 |
| Årstall | 2006 |
| Kategori | Artikler i internasjonale tidsskrifter med referee |
| Språk | Engelsk |
Abstract
N saturation induced by atmospheric N deposition can have serious consequences for forest health in many regions. In order to evaluate whether foliar d15N 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 d15N 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 d15N than the regional driver of N deposition. Foliar d15N increased non-linearly with nitrification:mineralization ratio and decreased with forest floor C:N. Foliar d15N was more strongly related to nitrification rates than was foliar N concentration, but concentration was more strongly correlated with N deposition. Root d15N was more tightly coupled to forest floor properties than was foliar d15N. We observed a pattern of decreasing foliar d15N values across the following species: American beech>yellow birch>sugar maple. Other factors that affected foliar d15N included species composition and climate. Relationships between foliar d15N 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 d15N, due to the importance of ammonium deposition in this region. Our results suggest that examining d15N values of foliage may improve understanding of how forests respond to the cascading effects of N deposition. Introduction Nitrogen saturation is the process by which chronically elevated N inputs alter forest ecosystems, ultimately resulting in increases in ecosystem N loss (Aber et al. 1989; 1998). N saturation can result in detrimental plant responses and have serious consequences for forest health (Nihlgard 1985; Aber et al. 1989; Schaberg et al. 2002) and may impact forests in many regions (Dise et al. 1998; Aber et al. 2003). Therefore, developing indicators useful for determining whether a forest is at N saturation and for predicting when a forest is nearing N saturation is valuable. Such indicators would facilitate both forest management and understanding of N cycling in forest ecosystems.
Referanse
Pardo, L.H., Templer, P.H., Goodale, C.L., Duke, S. Groffman, P.M., Adams, M.B., Boeckx, P., Boggs, J., Campbell, J., Colman, B., Compton, J., Emmett, B., Gundersen, P., Kjønaas, J., Lovett, G., Mack, M., Magill, A., Mbila, M., Mitchell, J., McGee, G., McNulty, S., Nadelhoffer, K., Ollinger, S., Ross, D., Rueth, H., Rustad, L., Schaberg, P., Schiff, S., Schleppi, P., Spoelstra, J. & Wessel, W. 2006. Regional assessment of N saturation using foliar and root d15N. Biogeochemistry 80: 143-171.