Plant-climate interactions over historical and geological time

Data-model comparisons are a useful approach to elucidating the relative influence of past climate change on vegetation dynamics over various spatial global, regional, stand) and temporal (historical, geological) scales. Comparisons between changes in tree species abundance reconstructed from pollen and simulated from a forest gap model, for example, indicate that based solely on climate change over the past 1500 years, southern Scandinavian forests should be co-dominated by Tilia and Fagus. Picea has begun to more closely track changes in climate since 1000 years ago, however in the last few centuries the realised range limit of Picea has overshot the potential limit because of planting and establishment during favourable years. Not only can palaeodata-model comparisons provide practical information for forest managers, but they can help further our appreciation of the climatic catalysts underlying evolution of terrestrial ecosystems. Past changes in atmospheric CO2, independently or in combin- ation with changes in climate, may have altered vegetation form and function such that palaeoplant assemblages were much different than today, speciation may have been promoted via biological vicariance, and some species may have been pushed to extinction. A thorough understanding of modern plant-climate interactions requires consideration of how past climate and atmospheric CO2 events could have shaped physiological, biochemical and biophysical functioning of existing vegetation.