Rapid ecosystem shifts in peatlands: linking plant physiology and succession
Rapid ecosystem shifts in peatlands: linking plant physiology and succession
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DOI：
10.1890/09-2267.1
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发表时间：
2010-10-01
期刊：
影响因子：
4.8
通讯作者：
Rydin, Hakan
中科院分区：
文献类型：
--
作者：
Granath, Gustaf;Strengbom, Joachim;Rydin, Hakan
泥炭地的地层记录表明，从富饶的沼泽(钙质沼泽)向营养丰富的沼泽的转变可以迅速发生。这一转变构成了从物种丰富的生态系统到物种匮乏、碳储量更大的生态系统的转变。在这一过程中，泥炭藓(Sphagnum)酸化沼泽物种的入侵和扩张起着关键作用。为了测试酸化沼泽物种在什么条件下可以入侵肥沃的沼泽，我们进行了三个实验，将沼泽物种S.fucsum与富饶沼泽物种S.warnstorfii和S.teres进行了对比。我们首先通过在富饶的沼泽池塘中在不同的恒定高度(HWT；2，7和14 cm)上种植这三个物种来测试石灰水的效果，并测量了最大光合速率、产量和长度生长差异作为竞争指标。在低HWT条件下，没有一种植物的光合作用能力受到负面影响，但在低HWT条件下，青霉是一个较弱的竞争对手。在我们的第二个实验中，我们将这三个物种移植到具有不同和自然变化的HWT的微生境中，在肥沃的沼泽中。在这里，当移植到低HWT(棕色苔藓地毯)时，S.fuscum几乎停止了光合作用，而它在中等水平上的表现与两个富沼泽树种(S.warnstorfii hummock水平)相似。与黑粉菌不同的是，富粉水蚤在两种生境中的表现都一样好。棕色苔藓地毯被季节性地淹没，在我们的第三个实验中，我们发现Fuscum，而不是S.teres，在富含沼泽的水中被严重破坏。我们的结果表明，影响生态系统切换的HWT有两个阈值：一个水平降低了淹没的风险，另一个水平使沼泽沼泽与富饶的沼泽物种竞争。
Stratigraphic records from peatlands suggest that the shift from a rich fen (calcareous fen) to an ombrotrophic bog can occur rapidly. This shift constitutes a switch from a species-rich ecosystem to a species-poor one with greater carbon storage. In this process, the invasion and expansion of acidifying bog species of Sphagnum (peat mosses) play a key role. To test under what conditions an acidifying bog species could invade a rich fen, we conducted three experiments, contrasting the bog species S. fucsum with the rich-fen species S. warnstorfii and S. teres. We first tested the effect of calcareous water by growing the three species at different constant height above the water table (HWT; 2, 7, and 14 cm) in a rich-fen pool and measured maximum photosynthetic rate and production and difference in length growth as an indicator of competition. In none of the species was the photosynthetic capacity negatively affected when placed at low HWT, but S. fuscum was a weaker competitor at low HWT. In our second experiment we transplanted the three species into microhabitats with different and naturally varying HWT in a rich fen. Here, S. fuscum nearly ceased to photosynthesize when transplanted to low HWT (brown moss carpet), while it performed similarly to the two rich-fen species at the intermediate level (S. warnstorfii hummock level). In contrast to S. fuscum, the rich-fen sphagna performed equally well in both habitats. The brown moss carpet was seasonally flooded, and in our third experiment we found that S. fuscum, but not S. teres, was severely damaged when submerged in rich-fen water. Our results suggest two thresholds in HWT affecting the ecosystem switch: one level that reduces the risk of submergence and a higher one that makes bog sphagna competitive against the rich-fen species.