Pollen Rain in a Semi-Arid Area of Northeastern Brazil: Pollen Diversity, Concentrations over Two Years and Their Relationship with Ecological Aspects

Pollen rain studies are rare in arid and semi-arid regions worldwide. Interpretations related to the dynamics of plant communities and possible paleoclimatic changes in these areas face significant limitations due to this lack of data. The global biome of Seasonally Dry Tropical Forests and Shrublands (SDTFS) is represented in Northeast Brazil by the caatinga, which is composed of xerophytic vegetation. This study aimed to generate information about the pollen rain in this area and to understand its relationship with species flowering, pollination syndromes, life forms, and climatic aspects. A caatinga area in Canudos, Bahia, Brazil (09°54′ S 39°07′ W), was selected for this purpose. Artificial pollen collectors were installed and exchanged monthly over two years for palynological analyses of the collected material, using standard palynological techniques. A total of 124 pollen types were identified, with approximately 8823 pollen grains deposited per cm2 over the two years. Several vegetation components were represented in the pollen rain, reflecting local plant diversity, life forms, and physiognomies. A positive relationship was observed between increased temperature and pollen production from trees and shrubs, and new pollen types were associated with indicator species of caatinga vegetation.