Science of the Total Environment, 15 February 2017, Vol.580, pp.1429-1438
expansion to alkaline fens has accelerated during the last decades in Europe, leading to changes in diversity, habitat distributions and carbon storage. The causes are still not clearly understood and involve an interplay between climate change, hydrology, nutrient supply and physiology. We conducted a 4-year field experiment in eight fens in Central European highlands and assessed survival and establishment of individual apical shoot fragments of , and transplanted along the microtopographical gradient. In a laboratory experiment, we tested combined effects of desiccation and high calcium bicarbonate concentration on survival. We found that in unflooded positions, living shoots of and brown mosses lowered [Ca ] and pH in their capillary water, in contrast to dead fragments; yet without differences between species. Survival and expansion of fragments, which did not die of acute calcium toxicity during first weeks/months, was negatively affected by dry weather and alkaline water chemistry, reflecting intolerance to desiccation and to combined high [Ca ] and pH. Shoot fragments expanded to patches only when precipitation was high. Interestingly, non-toxic concentration of calcium bicarbonate reduced desiccation damage in , probably through protection of membranes or other cell components. This mechanism would facilitate survival in elevated, frequently desiccated microhabitats of calcareous fens such as brown-moss hummocks. However, since water-retaining capacity of few shoots is insufficient to change water chemistry in its surroundings, surface acidification may occur only once the environment (e.g. sufficient humidity) enabled expansion to larger mats. Then, the retained rainwater together with hardly decomposable litter would separate mire surface from groundwater, speeding up successional shift towards poor fens. expansion to alkaline fens is therefore more likely in humid regions.
Fen Succession ; Sphagnum Transplants ; Desiccation ; Calcium Tolerance ; Climate Humidity ; Competition ; Environmental Sciences ; Biology ; Public Health
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