Contrasting growth responses of dominant peatland plants to warming and vegetation composition
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There is growing recognition that changes in vegetation composition can strongly influence peatland carbon cycling, with potential feedbacks to future climate. Nevertheless, despite accelerated climate and vegetation change in this ecosystem, the growth responses of peatland plant species to combined warming and vegetation change are unknown. Here, we used a field warming and vegetation removal experiment to test the hypothesis that dominant species from the three plant functional types present (dwarf-shrubs: Calluna vulgaris; graminoids: Eriophorum vaginatum; bryophytes: Sphagnum capillifolium) contrast in their growth responses to warming and the presence or absence of other plant functional types. Warming was accomplished using open top chambers, which raised air temperature by approximately 0.35 °C, and we measured air and soil microclimate as potential mechanisms through which both experimental factors could influence growth. We found that only Calluna growth increased with experimental warming (by 20 %), whereas the presence of dwarf-shrubs and bryophytes increased growth of Sphagnum (46 %) and Eriophorum (20 %), respectively. Sphagnum growth was also negatively related to soil temperature, which was lower when dwarf-shrubs were present. Dwarf-shrubs may therefore promote Sphagnum growth by cooling the peat surface. Conversely, the effect of bryophyte presence on Eriophorum growth was not related to any change in microclimate, suggesting other factors play a role. In conclusion, our findings reveal contrasting abiotic and biotic controls over dominant peatland plant growth, suggesting that community composition and carbon cycling could be modified by simultaneous climate and vegetation change.
KeywordsCalluna vulgaris Competition Eriophorum vaginatum Facilitation Microclimate Open top chambers Peatlands Sphagnum
This research was supported by a Natural Environment Research Council (NERC) CASE Studentship between The University of Manchester and Centre for Ecology and Hydrology (CEH) Lancaster, and made use of an experiment set up with funding from a NERC EHFI Grant (NE/E011594/1) awarded to R.D.B. and N.J.O. We thank colleagues from Lancaster University and CEH Lancaster, and in particular Caley Brown and Simon Oakley, for help in the field. We also thank Natural England and the Environmental Change Network, CEH Lancaster, for access to the site and meteorological data.
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