Sphagnum mosses--masters of efficient N-uptake while avoiding intoxication.
Sphagnum mosses--masters of efficient N-uptake while avoiding intoxication.
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DOI：
10.1371/journal.pone.0079991
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发表时间：
2014
期刊：
影响因子：
3.7
通讯作者：
Elzenga TJ
中科院分区：
文献类型：
--
作者：
Fritz C;Lamers LP;Riaz M;van den Berg LJ;Elzenga TJ
泥炭形成的泥炭藓能够通过有效清除大气中沉积的氮（N）来防止维管植物在营养条件下占主导地位。因此，这些苔藓的氮吸收动力学预计将在泥炭地的氮利用率差异、植物竞争和碳封存中发挥关键作用。然而，人们对降雨氮浓度和暴露时间对苔藓氮吸收率的相互作用影响知之甚少。我们研究了氮浓度（1、5、10、50、100、500 µM）、氮形式（15N - 铵或硝酸盐）和暴露时间（0.5、2、72 小时）对巴塔哥尼亚（阿根廷）原始沼泽和暴露于数十年氮污染的荷兰沼泽中的麦哲伦泥炭藓吸收动力学的影响。铵的吸收率高于硝酸盐，并且吸附位点的氮结合可以忽略不计。在前 0.5 小时内，氮吸收遵循饱和动力学，显示出高亲和力 (Km 3.5–6.5 µM)。铵的吸收速度比硝酸盐快 8 倍，而在 72 小时内，吸收速度仅为硝酸盐的 2 倍。随着暴露时间的增加，吸收率急剧下降，这意味着文献中的许多短期氮吸收实验很可能高估了长期吸收率和生态系统保留。来自污染地点的泥炭藓（即长期接触氮）的吸收率低于来自原始地点的苔藓，表明适应性反应。 因此，泥炭藓似乎在利用短氮脉冲（例如原始地区的降雨）方面非常高效。这一策略具有重要的生态和进化意义：在高氮输入率下，氮毒性的风险似乎可以通过降低泥炭藓的吸收率来降低，但代价是其长期过滤能力和相对于维管植物的相关竞争优势。正如我们的概念模型所示，氮沉积和气候变化（降雨量变化）的相互作用将严重改变泥炭地的功能。
Peat forming Sphagnum mosses are able to prevent the dominance of vascular plants under ombrotrophic conditions by efficiently scavenging atmospherically deposited nitrogen (N). N-uptake kinetics of these mosses are therefore expected to play a key role in differential N availability, plant competition, and carbon sequestration in Sphagnum peatlands. The interacting effects of rain N concentration and exposure time on moss N-uptake rates are, however, poorly understood. We investigated the effects of N-concentration (1, 5, 10, 50, 100, 500 µM), N-form (15N - ammonium or nitrate) and exposure time (0.5, 2, 72 h) on uptake kinetics for Sphagnum magellanicum from a pristine bog in Patagonia (Argentina) and from a Dutch bog exposed to decades of N-pollution. Uptake rates for ammonium were higher than for nitrate, and N-binding at adsorption sites was negligible. During the first 0.5 h, N-uptake followed saturation kinetics revealing a high affinity (Km 3.5–6.5 µM). Ammonium was taken up 8 times faster than nitrate, whereas over 72 hours this was only 2 times. Uptake rates decreased drastically with increasing exposure times, which implies that many short-term N-uptake experiments in literature may well have overestimated long-term uptake rates and ecosystem retention. Sphagnum from the polluted site (i.e. long-term N exposure) showed lower uptake rates than mosses from the pristine site, indicating an adaptive response. Sphagnum therefore appears to be highly efficient in using short N pulses (e.g. rainfall in pristine areas). This strategy has important ecological and evolutionary implications: at high N input rates, the risk of N-toxicity seems to be reduced by lower uptake rates of Sphagnum, at the expense of its long-term filter capacity and related competitive advantage over vascular plants. As shown by our conceptual model, interacting effects of N-deposition and climate change (changes in rainfall) will seriously alter the functioning of Sphagnum peatlands.
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影响因子：
9.4
作者：
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通讯作者：
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