Vegetation response to climatic change. A palaeobiological perspective

Abstract

This paper reviews the patterns and processes of vegetation change in response to climatic factors, and the question of climate- vegetation equilibrium from a palacoecological perspective. At an evolutionary temporal scale, processes such as migration, species extincion, and reorganization of the ecological structure are adequately described by biotically-conditioned threshold responses. Established communities exhibit great resistance to invasion, being pre-adaptive traits of higher importance than the direction of climate change in determining the dominant group after each environmental crisis. Palaeoecological studies at the orbital scale provide a link between evolutionary and ecological processes. The Quaternary climate variation induced dispersion of plant populations, local extinctions and disaggregation of plant communities.  Climate exerted control on long-term species pool within the constraints imposed by regional evolutionary history. Vegetation responses to astronomic forces were characteristically non linear. Iberian plant communities have often behaved inertial to climate changes occurring since the last glacial maximum. Sometimes, however, they have been very sensitive, providing century- to decadal-scale responses. Abrupt vegetation changes may be related with non-climatic factors, principally changes in the fire regime. The question of climate-vegetation equilibrium is a scale problem, where the control of vegetation changes would shift from climatic to biotic controls as the temporal and spatial scales are shortened. While interpreting compositional, structural and distributional changes in plant communities, abrupt climatic changes may represent historical accidents eventually more relevant than long-term climatic trends.