Climate response, migrational lag, and pollen representation: The problems posed by Rhododendron and Acer

Abstract

Views have changed as to the relative importance of climate change and human activity on the composition of Holocene temperate forest. The ‘climate school’ maintains that temperate arboreal taxa responded swiftly to changes in Holocene climate, irrespective of dispersal mechanism, with no evidence for migrational lag or for human influence; taxa moved individualistically according to their climate response. This paper tests these tenets in two case studies. The present‐day distributions of Rhododendron and Acer in Europe are compared with earlier records, and discussed in the context of migrational lag and pollen‐climate response. Distributional data emphasise the importance of humans as a vector in aiding the spread of both Rhododendron ponticum and some Acer species in the very late Holocene. Arguably, the species concerned have exhibited extreme migrational lag; they re‐open the question as to whether the natural distributions of temperate arboreal species are in equilibrium with climate.

Key words:

• Pollen‐climate response
• migrational lag
• Rhododendron ponticum
• Acer
• northwest Europe
• Late‐Quaternary

Notes

New address: Centre For Environmental Change and Quaternary Research, Department of Geography and Geology, Cheltenham and Gloucester College, Cheltenham, GL50 4AZ, United Kingdom.