Vortrag, Macroecology meets Biogeography - 9th Annual meeting of the Specialist Group on Macroecology & Jahrestagung AK Biogeographie, Trier: 15.03.2016 - 17.03.2016
Today’s treeline research generally focuses on physiological limitations of tree growth whereas biogeographic drivers such as isolation, continentality and mass elevation effect (MEE) often neglected or reduced as local or regional peculiarities. Even tough trees cannot avoid fundamental environmental limitations, biogeographic drivers modify treeline elevations also at the global scale. MEE, which affects regional climate conditions, and continentality have been described quite often, but these quantifications have often been unconvincing and a clear separation of both concepts is often missing. We sampled the largest global treeline data sets up to date (n=672) to investigate these biogeographic drivers using a systematic sampling design with GoogleEarth. We found a subtropical double hump of treeline elevations along the latitudinal gradient, negative isolation effects on both, island and continental mountains, a strong increase of treeline elevation with MEE and independent effects of continentality. Interestingly, besides latitude, MEE was thereby the most important of global treeline elevations. Our study shows a globally consistent effect of MEE on treeline elevations, contributing to our basic understanding of large-scale biogeographic processes governing treeline formation. Isolation may be a result of immigration; cloudiness seems to modulate the solar radiation regime thus MEE and continentality increase treeline elevations.