The role of temperature on treeline migration for an eastern African mountain during the Last Glacial Maximum F. Saltré & I. Bentaleb & C. Favier & D. Jolly Received: 8 November 2011 /Accepted: 11 December 2012 # Springer Science+Business Media Dordrecht 2013 Abstract Paleo-data suggest that East African mountain treelines underwent an altitudinal shift during the Last Glacial Maximum (LGM). Understanding the ecological and physio- logical processes underlying treeline response to such past climate change will help to improve forecasts of treeline change under future global warming. In spite of significant improvements in paleoclimatic reconstruction, the climatic conditions explaining this mi- gration are still debated and important factors such as atmospheric CO 2 concentration, the impact of lapse rate decreasing temperature along altitudinal gradients and rainfall modifi- cations due to elevation have often been neglected or simplified. Here, we assess the effects of these different factors and estimate the influence of the most dominant factors controlling changes in past treeline position using a multi-proxy approach based on simulations from BIOME4, a coupled biogeography and biogeochemistry model, modified to account for the effect of elevation on vegetation, compared with pollen, and isotopic data. The results indicate a shift in mountain vegetation at the LGM was controlled by low pCO 2 and low temperatures promoting species morphologically and physiologically better adapted to LGM conditions than many trees composing the forest belt limit. Our estimate that the LGM climate was cooler than today’ s by -4.5 °C (range: -4.3 to -4.6 °C) at the upper limit of the treeline, whereas at 831 m it was cooler by -1.4 °C (range: -2.6 to -0.6 °C), suggests that a possible lapse rate modification strongly constrained the upper limit of treeline, which may limit its potential extension under future global warming. Climatic Change DOI 10.1007/s10584-012-0665-4 F. Saltré Centre de Bio-Archéologie et d’Écologie, EPHE, Institut de Botanique, 163 rue A. Broussonet, 34090 Montpellier, France I. Bentaleb : C. Favier : D. Jolly Université Montpellier 2, CNRS, IRD, Institut des Sciences et de l’Evolution, 34095 Montpellier Cedex 5, France F. Saltré (*) 104, College of Earth Ocean and Atmospheric Sciences, Administration Building, Oregon State University, Corvallis, OR 97331, USA e-mail: fsaltre@coas.oregonstate.edu