Changes in distribution of the Iberian vegetation since the Last Glacial Maximum: A model-based approach

Abstract

Understanding past potential vegetation distribution across different spatial and temporal scales is a fundamental goal in palaeobotany and the study of past human societies. Additionally, this understanding is crucial in various ecological fields, including vegetation management, conservation and restoration. Our knowledge of past vegetation history mainly relies on palaeobotanical records. However, these records sometimes cover only short time spans and/or lack sufficient chronological control. Moreover, there are still large areas with limited available records. To help address these gaps, this study employs ecological niche modelling fed with inputs from high-resolution present and past climatic data, along with data on soil and current potential landscapes, to simulate the dynamics and distribution of the main vegetation types in the Iberian Peninsula since the Last Glacial Maximum (22,000 years BP). The simulations show significant changes in the extent of each vegetation type through time. Overall, the known vegetation dynamics inferred from fossil botanical data for the Eurosiberian and Mediterranean regions are well reproduced and enhanced by our models, stressing the central role of climate in the distribution of vegetation of the Iberian Peninsula. General biogeographic trends that have been recognised in fossil records, such as the massive expansion of non-forested vegetation mainly consisting of steppes during the Last Glacial Maximum and the Lateglacial; the expansion of deciduous forests during the early and mid-Holocene; and the altitudinal shifts of the vegetation belts in the main mountain ranges, are reflected in our models with great level of detail. Various areas are suggested to have been prominent as refugia for thermophilous vegetation, including the northeast of the Iberian Peninsula and the Atlantic coast of northern Spain and Portugal. The simulations presented here also provide new insights into the postglacial pathways of various vegetation types and offer a historical explanation for the present-day relict presence of taxa that remained unexplained or unexpected until now. Multiple palaeobotanical records are presented to validate the biogeographic patterns indicated by the simulations.