Pollen-based 17-kyr forest dynamics and climate change from the Western Cordillera of Colombia; no-analogue associations and temporarily lost biomes

• A 17-kyr pollen record from 3460 m elevation shows vegetation and climate change.
• A 700 m upslope timberline migration in 200 yr punctuated the start of the Holocene.
• Rapid upslope forest shifts caused temporarily loss of subpáramo after rapid warming.
• Postglacial composition and abundance changes reflect no-analog forest associations.
• Clearing of Quercus, Podocarpus and Weinmannia since 620 cal yr BP shows human impact.

A 17 kyr long pollen record from the unexplored Western Cordillera of Colombia (Páramo de Frontino; 3460 m elevation) shows vegetation change and inferred climate dynamics at ~ 125 yr resolution. The cold and wet Lateglacial showed well-defined stadials and interstadials. At the transition to the Holocene the upper forest line (UFL) shifted within 200 years 700–800 m upslope reflecting a temperature increase of ~ 4.5 °C. Dead wood in the forests may have caused frequent fires. Individual taxa show clear and discrete successive expansion events, such as Podocarpus around 15 cal ka, Quercus, Melastomataceae, Myrsine, Weinmannia, and Hesperomeles around 11.5 cal ka, and Alnus around 9 cal ka showing the floristic composition of the montane forest changed during its upslope migration. After forest had reached around 9 cal ka a quasi-stable altitudinal interval forest taxa continued to change proportions showing that upslope forest migration caused significant internal forest dynamics. Forest stability is not found suggesting that an equilibrium between forest composition and environmental variables was not reached. We hypothesize trees migrated faster upslope than the shrubs causing a temporarily loss of this shrub biome. During most of the Holocene the UFL varied between 3500 and 3700 m indicating warmer temperatures than today. High upper limits of subandean forest suggest that the lowermost level of significant night frost was at higher elevations than today. Driest pulses were registered ~ 9170 and ~ 8200 cal ka since 620 cal ka deforestation of Quercus, Podocarpus and Weinmannia in particular shows anthropogenic impact. Comparisons with other Andean climate records show a climatic asymmetry mainly related to migrations of the ITCZ. An implication of the present benchmark records of vegetation and climate variability and modeling is that new records should be analyzed at better than century resolution.