Schulze E-D, Chapin F S, Gebauer G
Lehrstuhl Pflanzenökologie, Universität Bayreuth, D-95440, Bayreuth, Germany.
Department of Integrative Biology, University of California, 94720, Berkeley, CA, USA.
Oecologia. 1994 Dec;100(4):406-412. doi: 10.1007/BF00317862.
Natural abundances of nitrogen isotopes, δN, indicate that, in the same habitat, Alaskan Picea glauca and P. mariana use a different soil nitrogen compartment from the evergreen shrub Vaccinium vitis-idaea or the deciduous grass Calamagrostis canadensis. The very low δN values (-7.7 ‰) suggest that (1) Picea mainly uses inorganic nitrogen (probably mainly ammonium) or organic N in fresh litter, (2) Vaccinium (-4.3 ‰) with its ericoid mycorrhizae uses more stable organic matter, and (3) Calamagrostis (+0.9 ‰) exploits deeper soil horizons with higher δN values of soil N. We conclude that species limited by the same nutrient may coexist by drawing on different pools of soil N in a nutrient-deficient environment. The differences among life-forms decrease with increasing N availability. The different levels of δN are associated with different nitrogen concentrations in leaves, Picea having a lower N concentration (0.62 mmol g) than Vaccinium (0.98 mmol g) or Calamagrostis (1.33 mmol g). An extended vector analysis by Timmer and Armstrong (1987) suggests that N is the most limiting element for Picea in this habitat, causing needle yellowing at N concentrations below 0.5 mmol g or N contents below 2 mmol needle. Increasing N supply had an exponential effect on twig and needle growth. Phosphorus, potassium and magnesium are at marginal supply, but no interaction between ammonium supply and needle Mg concentration could be detected. Calcium is in adequate supply on both calcareous and acidic soils. The results are compared with European conditions of excessive N supply from anthropogenic N depositions.
氮同位素的自然丰度（δN）表明，在同一栖息地中，阿拉斯加白云杉和黑云杉与常绿灌木越橘或落叶禾本科植物加拿大拂子茅利用的土壤氮库不同。极低的δN值（-7.7‰）表明：（1）云杉主要利用无机氮（可能主要是铵态氮）或新鲜凋落物中的有机氮；（2）具有石楠状菌根的越橘（-4.3‰）利用更稳定的有机质；（3）加拿大拂子茅（+0.9‰）利用土壤氮δN值较高的更深土层。我们得出结论，在养分缺乏的环境中，受相同养分限制的物种可能通过利用不同的土壤氮库而共存。随着氮有效性的增加，不同生活型之间的差异减小。不同的δN水平与叶片中不同的氮浓度相关，云杉的氮浓度（0.62 mmol/g）低于越橘（0.98 mmol/g）或加拿大拂子茅（1.33 mmol/g）。Timmer和Armstrong（1987）进行的扩展向量分析表明，在该栖息地中氮是云杉最具限制作用的元素，当氮浓度低于0.5 mmol/g或每枚针叶氮含量低于2 mmol时会导致针叶发黄。增加氮供应对嫩枝和针叶生长有指数效应。磷、钾和镁处于边际供应水平，但未检测到铵供应与针叶镁浓度之间的相互作用。在钙质土和酸性土上钙供应充足。将这些结果与欧洲因人为氮沉降导致氮供应过量的情况进行了比较。
