Watersheds within the Catskill Mountains, New York, receive among the highest rates of nitrogen (N) deposition in the northeastern United States and are beginning to show signs of N saturation. Despite similar amounts of N deposition across watersheds within the Catskill Mountains, rates of soil N cycling and N retention vary significantly among stands of different tree species. We examined the potential use of δ 15N of plants and soils as an indicator of relative forest soil N cycling rates. We analyzed the δ 15N of foliage, litterfall, bole wood, surface litter layer, fine roots and organic soil from single-species stands of American beech (Fagus grandifolia), eastern hemlock (Tsuga canadensis), red oak (Quercus rubra), and sugar maple (Acer saccharum). Fine root and organic soil δ 15N values were highest within sugar maple stands, which correlated significantly with higher rates of net mineralization and nitrification. Results from this study suggest that fine root and organic soil δ 15N can be used as an indicator of relative rates of soil N cycling. Although not statistically significant, δ 15N was highest within foliage, wood and litterfall of beech stands, a tree species associated with intermediate levels of soil N cycling rates and forest N retention. Our results show that belowground δ 15N values are a better indicator of relative rates of soil N cycling than are aboveground δ 15N values.
|Number of pages||8|
|State||Published - Aug 2007|
Bibliographical noteFunding Information:
Acknowledgments This study was supported by the Heinz Foundation, the Hudson River Foundation and the National Science Foundation (DEB grants 9981503 and 044895 to the Institute of Ecosystem Studies). The second to fourth authors of this paper are placed in alphabetical order since they made an equal contribution to the completion of this project. We appreciate the laboratory and Weld assistance provided by the Institute of Ecosystem Studies Analytical Laboratory, Rebecca Brown, Christopher Byrnes, Serena Ciparis, Jacob GriYn, Lee Holt, Alan LoreWce, Susan Patterson, Charles Schirmer, and Denise Schmidt.
- Above and belowground nitrogen cycling
- Forest nitrogen retention
- Natural abundance N
- Tree species
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics