Modern pollen rain, vegetation and climate in Bolivian ecoregions

The aim of this study was to improve our understanding of the relationship between modem pollen rain, vegetation and climate in Bolivia, and to provide a link to interpret the fossil pollen record. Ten ecoregions were investigated: southern Puna, northern Puna, Yungas, pre-Puna, Gran Chaco, Chaco Chiquitano, Tucuman forest, inter-Andean dry forest, flooded savanna, and southwest Amazon forest. Forty soil surface samples were collected along an elevational transect from 4588 m to 160 m in 10 ecoregions and 16 sub-ecoregions. The vegetation in each sampling plot was described and the statistical analyses were performed on the pollen data set. Each ecoregion was distinguished by its pollen content and indicators. Statistical analysis performed on 26 selected pollen taxa enabled us to identify seven groups of pollen assemblages. Taxa transported out of their source ecoregion were also identified. The two Punas were grouped in one group and all the dry forests were grouped together. Statistical regressions between pollen indicators and elevation, precipitation, and temperature were computed. These data revealed clearly separated Asteraceae (high elevation, low precipitation and low temperature) from Arecaceae (low elevation, high precipitation and high temperature). Multivariate analyses of the whole pollen data set (including all the taxa) attest to the distribution of the 10 ecoregions as a function of climate. This good predictability is promising for future fossil analysis and vegetation mapping