razilian biomes distribution: Past and futur

The Last Glacial Maximum (LGM, 26.5-19 ka) was marked by atmospheric cooling, in contrast to the current warming climate, which will probably continue in the coming decades, according to climate models projections. The LGM to pre-industrial transition provides an opportunity to test the vegetation response to a very large temperature change that can then be applied to project pre-industrial to end-of-century changes. In order to explore the changes in Brazilian biomes due to temperature change, we projected potential vegetation for both past and future scenarios. We compared biome projections with a compilation of 149 published LGM reconstructions of climate and vegetation within Brazil and adjacent areas. In addition, we evaluated the particular effects that changes in precipitation, temperature and CO2 had on vegetation by performing sensitivity experiments. Our results suggest that biomes in the western and central portions of the Amazon forest remained largely unchanged during the LGM mainly due to negative temperature anomalies, while a decrease in past precipitation was responsible for the shift from tropical evergreen forest to tropical seasonal forest in the eastern portion of the Amazon. These results are consistent with proxy reconstructions. LGM model projections and proxy reconstructions suggest expansion of grassland in the southern Brazilian highlands. Under future warming scenarios, biome changes are mostly forced by decreasing precipitation and increasing temperatures, which counteract potential biomass gain from the positive CO2 fertilization effect. Under future warming, our simulations show an expansion of Savanna/Cerrado and a reduction of tropical seasonal forest and Caatinga, with potential large impacts over biodiversity and regional climate. (AU)