Relationship between vegetation and modern pollen-rain along an elevational gradient on Kilimanjaro, Tanzania

Modern pollen-rain studies are crucial for the calibration and interpretation of fossil pollen records. In East Africa, numerous pollen records provide important insights into the impact of human populations and climate change on tropical ecosystems. However, the confident use of fossil pollen data to reconstruct vegetation and climate dynamics requires well-founded knowledge regarding the relationship between pollen deposition and modern-day vegetation, which is still deficient for large parts of the African continent and non-existent for the tropical East African Mountains. In this study, we investigated the relationship between vegetation and modern pollen-rain along the elevational gradient of Kilimanjaro. We apply multivariate data analysis to assess the relationship between vegetation and modern pollen-rain and quantify the representativeness of forest zones. We further assessed the taxonomic level needed for differentiation between forest zones based on the modern pollen-rain assemblage, biodiversity patterns and pollen and spore drift. In the montane vegetation of Kilimanjaro, it is sufficient to analyse the pollen-rain on plant family level in order to derive the forest zone of the surrounding vegetation. Along this elevational gradient, pollen and spore dispersal is strongly influenced by regional wind patterns, but their deposition reflects the diversity patterns of the surrounding vegetation. This study represents the first statistical analysis of pollen vegetation relationship along an elevational gradient in Africa. Hence, this paper improves confidence in interpretation of palynological records from the tropical East African Mountains and may refine past climate reconstructions for a more accurate comparison of data and modelling.