Pollen distribution and deposition in mangrove sediments of the Ranong Biosphere Reserve, Thailand

• Very complex variables can influence mangrove pollen taphonomy.
• The mangrove environment is represented by many mangrove pollen species.
• A high concentration of R. apiculata pollen is indicative of the R. apiculata community.
• The Ranong mangrove forest prograded seawards over time according to pollen records.

Pollen analyses of surface and core sediments from the Ranong Biosphere Reserve, Ranong Province, Thailand, were carried out to determine spatial and quantitative compositional fidelities of the pollen record to achieve more accuracy in the reconstruction of past mangroves. The results reveal that many taphonomic biases from both biological and physical variables can lead to misinterpretation of the pollen records. Autochthonous pollen from true mangrove species were predominant in forest sediments, suggesting that mangrove sporomorphs are potential indicators of mangrove environments, while the frequent occurrence in low numbers of allochthonous and parautochthonous palynomorphs in mangrove sediments can reflect the regional plant communities. Close relationships between pollen from Bruguiera, Rhizophora apiculata, and Sonneratia alba and their vegetation were observed. The spatial reliability of Avicennia alba, Aegiceras corniculatum, Ceriops tagal, and Xylocarpus sp. pollen was low. The sediment cores show that the mangrove forest with its plant zonation was prograding towards the sea over time. The decline in R. apiculata pollen concentrations recovered in the upper part of all sediment cores reflects a decrease in the population of this plant taxon in the forest possibly caused by logging.