The effect of environmental change on vascular plant and cryptogam communities from the Falkland Islands and the Maritime Antarctic

Background: Antarctic terrestrial vegetation is subject to one of the most extreme climates on Earth. Currently, parts of Antarctica are one of the fastest warming regions on the planet. During 3 growing seasons, we investigated the effect of experimental warming on the diversity and abundance of coastal plant communities in the Maritime Antarctic region (cryptogams only) and the Falkland Islands (vascular plants only). We compared communities from the Falkland Islands (51 S, mean annual temperature 7.9 degrees C), with those of Signy Island (60 degrees S, - 2.1 degrees C) and Anchorage Island (67 degrees S, -2.6 degrees C), and experimental temperature manipulations at each of the three islands using Open Top Chambers (OTCs).Results: Despite the strong difference in plant growth form dominance between the Falkland Islands and the Maritime Antarctic, communities across the gradient did not differ in total diversity and species number.During the summer months, the experimental temperature increase at 5 cm height in the vegetation was similar between the locations (0.7 degrees C across the study). In general, the response to this experimental warming was low. Total lichen cover showed a non-significant decreasing trend at Signy Island (p < 0.06). In the grass community at the Falkland Islands total vegetation cover decreased more in the OTCs than in adjacent control plots, and two species disappeared within the OTCs after only two years. This was most likely a combined consequence of a previous dry summer and the increase in temperature caused by the OTCs.Conclusion: These results suggest that small temperature increases may rapidly lead to decreased soil moisture, resulting in more stressful conditions for plants. The more open plant communities (grass and lichen) appeared more negatively affected by such changes than dense communities (dwarf shrub and moss).

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