Templer Pamela H, Arthur Mary A, Lovett Gary M, Weathers Kathleen C
Department of Biology, Boston University, 5 Cummington Street, Boston, MA 02215, USA.
Oecologia. 2007 Aug;153(2):399-406. doi: 10.1007/s00442-007-0746-7. Epub 2007 May 4.
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 delta (15)N of plants and soils as an indicator of relative forest soil N cycling rates. We analyzed the delta (15)N 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 delta (15)N 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 delta (15)N can be used as an indicator of relative rates of soil N cycling. Although not statistically significant, delta (15)N 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 delta (15)N values are a better indicator of relative rates of soil N cycling than are aboveground delta (15)N values.
纽约卡茨基尔山脉内的流域，其氮（N）沉降速率在美国东北部地区位居前列，并且已开始显现出氮饱和的迹象。尽管卡茨基尔山脉内各流域的氮沉降量相似，但不同树种林分的土壤氮循环和氮保留速率差异显著。我们研究了植物和土壤的δ（15）N作为相对森林土壤氮循环速率指标的潜在用途。我们分析了美国山毛榉（Fagus grandifolia）、东部铁杉（Tsuga canadensis）、红栎（Quercus rubra）和糖枫（Acer saccharum）单树种林分中树叶、凋落物、树干木材、地表凋落物层、细根和有机土壤的δ（15）N。糖枫林分中细根和有机土壤的δ（15）N值最高，这与较高的净矿化和硝化速率显著相关。本研究结果表明，细根和有机土壤的δ（15）N可作为土壤氮循环相对速率的指标。虽然不具有统计学显著性，但δ（15）N在山毛榉林分的树叶、木材和凋落物中最高，山毛榉是一种与中等水平的土壤氮循环速率和森林氮保留相关的树种。我们的结果表明，地下δ（15）N值比地上δ（15）N值更能作为土壤氮循环相对速率的指标。
