Limpens Juul, Heijmans Monique M P D
Nature Conservation and Plant Ecology Group, Wageningen University, Droevendaalsesteeg 3a, 6708 PB Wageningen, The Netherlands.
Oecologia. 2008 Aug;157(1):153-61. doi: 10.1007/s00442-008-1046-6. Epub 2008 May 9.
Although numerous studies have addressed the effects of increased N deposition on nutrient-poor environments such as raised bogs, few studies have dealt with to what extent, and on what time-scale, reductions in atmospheric N supply would lead to recovery of the ecosystems in question. Since a considerable part of the negative effects of elevated N deposition on raised bogs can be related to an imbalance in tissue nutrient concentrations of the dominant peat-former Sphagnum, changes in Sphagnum nutrient concentration after excess N supply may be used as an early indicator of ecosystem response. This study focuses on the N and P concentrations of Sphagnum magellanicum and Sphagnum fallax before, during and after a factorial fertilization experiment with N and P in two small peatlands subject to a background bulk deposition of 2 g N m(-2) year(-1). Three years of adding N (4.0 g N m(-2) year(-1)) increased the N concentration, and adding P (0.3 g P m(-2) year(-1)) increased the P concentration in Sphagnum relative to the control treatment at both sites. Fifteen months after the nutrient additions had ceased, N concentrations were similar to the control whereas P concentrations, although strongly reduced, were still slightly elevated. The changes in the N and P concentrations were accompanied by changes in the distribution of nutrients over the capitulum and the stem and were congruent with changes in translocation. Adding N reduced the stem P concentration, whereas adding P reduced the stem N concentration in favor of the capitulum. Sphagnum nutrient concentrations quickly respond to reductions in excess nutrient supply, indicating that a management policy aimed at reducing atmospheric nutrient input to bogs can yield results within a few years.
尽管众多研究探讨了增加氮沉降对诸如高位沼泽等养分贫瘠环境的影响，但很少有研究涉及大气氮供应的减少在何种程度以及在何种时间尺度上会导致相关生态系统的恢复。由于氮沉降增加对高位沼泽的相当一部分负面影响可能与优势泥炭形成植物泥炭藓组织养分浓度的失衡有关，过量氮供应后泥炭藓养分浓度的变化可作为生态系统响应的早期指标。本研究聚焦于在两个背景总沉降量为2克氮每平方米每年的小型泥炭地中，对泥炭藓和锈色泥炭藓进行氮和磷的析因施肥实验之前、期间和之后的氮和磷浓度。连续三年添加氮（4.0克氮每平方米每年）增加了泥炭藓中的氮浓度，添加磷（0.3克磷每平方米每年）相对于两个地点的对照处理增加了泥炭藓中的磷浓度。停止添加养分15个月后，氮浓度与对照相似，而磷浓度虽然大幅降低，但仍略有升高。氮和磷浓度的变化伴随着养分在头状体和茎中的分布变化，并且与转运变化一致。添加氮降低了茎中的磷浓度，而添加磷降低了茎中的氮浓度，有利于头状体。泥炭藓养分浓度对过量养分供应的减少迅速做出反应，这表明旨在减少沼泽大气养分输入的管理政策可在几年内产生效果。
