Global change and arctic ecosystems: is lichen decline a function of increases in vascular plant biomass?
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| Authors: | Cornelissen, JHC; Callaghan, TV; Alatalo, JM; Michelsen, A; Graglia, E; Hartley, AE; Hik, DS; Hobbie, SE; Press, MC; Robinson, CH; Henry, GHR; Shaver, GR; Phoenix, GK; Jones, DG; Jonasson, S; Chapin, FS; Molau, U; Neill, C; Lee, JA; Melillo, JM; Sveinbjornsson, B; Aerts, R |
| Year: | 2001 |
| Journal: | J. Ecol. 89: 984-994 Article Link (DOI) |
| Title: | Global change and arctic ecosystems: is lichen decline a function of increases in vascular plant biomass? |
| Abstract: | 1 Macrolichens are important for the functioning and biodiversity of cold northern ecosystems and their reindeer-based cultures and economics. 2 We hypothesized that, in climatically milder parts of the Arctic, where ecosystems have relatively dense plant canopies, climate warming and/or increased nutrient availability leads to decline in macrolichen abundance as a function of increased abundance of vascular plants. In more open high-arctic or arctic-alpine plant communities such a relationship should be absent. To test this, we synthesized cross-continental arctic vegetation data from ecosystem manipulation experiments simulating mostly warming and increased nutrient availability, and compared these with similar data from natural environmental gradients. 3 Regressions between abundance or biomass of macrolichens and vascular plants were consistently negative across the subarctic and mid-arctic experimental studies. Such a pattern did not emerge in the coldest high-arctic or arctic-alpine sites. The slopes of the negative regressions increased across 10 sites as the climate became milder (as indicated by a simple climatic index) or the vegetation denser (greater site above-ground biomass). 4 Seven natural vegetation gradients in the lower-altitude sub- and mid-arctic zone confirmed the patterns seen in the experimental studies, showing consistent negative relationships between abundance of macrolichens and vascular plants. 5 We conclude that the data supported the hypothesis. Macrolichens in climatically milder arctic ecosystems may decline if and where global changes cause vascular plants to increase in abundance. 6 However, a refining of our findings is needed, for instance by integrating other abiotic and biotic effects such as reindeer grazing feedback on the balance between vascular plants and lichens. |
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