Institute for Applied Plant Biology, CH-4124 Schönenbuch, Switzerland.
Environ Pollut. 2010 Jun;158(6):2043-52. doi: 10.1016/j.envpol.2009.11.030. Epub 2009 Dec 16.
Effects of elevated N deposition on forest aboveground biomass were evaluated using long-term data from N addition experiments and from forest observation plots in Switzerland. N addition experiments with saplings were established both on calcareous and on acidic soils, in 3 plots with Fagus sylvatica and in 4 plots with Picea abies. The treatments were conducted during 15 years and consisted of additions of dry NH4NO3 at rates of 0, 10, 20, 40, 80, and 160 kg N ha(-1) yr(-1). The same tree species were observed in permanent forest observation plots covering the time span between 1984 and 2007, at modeled N deposition rates of 12-46 kg N ha(-1) yr(-1). Experimental N addition resulted in either no change or in a decreased shoot growth and in a reduced phosphorus concentration in the foliage in all experimental plots. In the forest, a decrease of foliar P concentration was observed between 1984 and 2007, resulting in insufficient concentrations in 71% and 67% of the Fagus and Picea plots, respectively, and in an increasing N:P ratio in Fagus. Stem increment decreased during the observation period even if corrected for age. Forest observations suggest an increasing P limitation in Swiss forests especially in Fagus which is accompanied by a growth decrease whereas the N addition experiments support the hypothesis that elevated N deposition is an important cause for this development.
使用来自瑞士的氮添加实验和森林观测样地的长期数据，评估了氮升高对森林地上生物量的影响。在钙质土和酸性土上，对幼树进行了氮添加实验，在 3 个欧洲山毛榉样地和 4 个欧洲云杉样地上进行了实验。处理持续了 15 年，包括以 0、10、20、40、80 和 160 kg N ha(-1) yr(-1)的速率添加干 NH4NO3。同一树种在永久性森林观测样地中进行了观测，观测时间跨度为 1984 年至 2007 年，模型化的氮沉积速率为 12-46 kg N ha(-1) yr(-1)。在所有实验样地中，实验氮添加导致要么没有变化，要么导致芽生长减少，叶片磷浓度降低。在森林中，1984 年至 2007 年间观察到叶片磷浓度下降，导致 71%和 67%的山毛榉和云杉样地叶片磷浓度不足，山毛榉的 N:P 比增加。即使校正了年龄因素，茎增量在观测期间仍在减少。森林观测表明，瑞士森林特别是山毛榉的磷限制越来越严重，这伴随着生长减少，而氮添加实验支持了这样一种假设，即升高的氮沉积是这种发展的一个重要原因。
