Talk, Integrating Mechanisms into Macroecology - 8th Annual Meeting of the Specialist Group for Macroecology of the Ecological Society of Germany, Austria, and Switzerland (GfÖ), Halle (Saale): 2014-03-04 - 2014-03-06
Treelines have been an important research focus in ecology and biogeography for decades. Island treelines are suggested to experience specific drivers unique to island ecosystems. We empirically test how the latitude-treeline elevation relationship of islands relate to mainland treeline elevation, and to what extent island treeline patterns are driven by island characteristics and/or latitude. We collected a global dataset (n=87) by applying a stratified design using GoogleEarth to identify island treeline elevations and gather island characteristics. Island treeline elevation followed a hump-shaped distribution with latitude. Treeline elevation decreased from the mainland through continental islands to oceanic islands. The highest island treelines were found in the tropics (vs. mainland maxima in the subtropics). Low species pool and oceanic climates are likely to have negative effects on island treeline elevation. Surprisingly, maximum island elevation was the best single predictor of island treelines, not latitude. Probably, the possibility of range shifts during climatic fluctuations, the summit syndrome and the increasing cloud layer altitude with island elevation are responsible for the maximum islands elevation-effect. Investigating islands in treeline research enables to disentangle the global effect of latitude on treeline elevation from the variation created in continental mountains by continentality or the mass elevation effect.