Variability in modern pollen rain from moist and wet tropical forest plots in Ghana, West Africa

Abstract

How pollen moves within and between ecosystems affects factors such as the genetic structure of populations, how resilient they are to environmental change, and the amount and nature of pollen preserved in the sedimentary record. We set artificial pollen traps in two 100 m by 100 m vegetation plots, one in a wet evergreen forest, and one in a moist semideciduous forest in Ghana, West Africa. Five traps from each plot were counted annually from 2011 to 2014, to examine spatial and temporal variation in the pollen rain of the most abundant taxa shared between pollen and vegetation assemblages. Samples from the wet evergreen plot exhibited high variability within years, with the dominant pollen types changing between samples, and many pollen taxa being over-represented relative to their parent plant abundance in some traps whilst being entirely absent from others. The most abundant plant taxa of the wet evergreen plot (Drypetes and Cynometra) do, however, constitute major components of the pollen rain. There is less variation between samples from the moist semi-deciduous plot spatially, as it is dominated by Celtis, which typically comprises >70% of the pollen assemblages. We conclude that pollen rain in these tropical ecosystems is highly heterogeneous, and suggest that pollen assemblages obtained by trapping are susceptible to small-scale variations in forest structure. Conversely, this may mean that current recommendations of more than three years of trapping in tropical systems may be too high, and that space could substitute for time in modern tropical pollen trapping.

Pollen rain, vegetation and connectivity in the Tacaná volcano, Southern Mexico

“…In particular, temperate taxa were abundant in the pollen rain, and Pinus elements were disproportionately abundant, in line with previous research carried out in the highlands of Guatemala (Islebe and Hooghiemstra 1995). Pollen rain also showed an increase in the diversity of taxa at intermediate elevations, reflecting the traditional hump curve expected for intermediate elevations, and likely explained by the intermix of species of tropical and temperate affinities (Mannion et al 2014;Sch€ uler et al 2014;Adele et al 2019).…”

“…Pollen rain is a tool proved to be useful for describing vegetation in many Neotropical locations, as strong correlations of pollen signal with vegetation structure and diversity have been reported (Adele et al 2019; Hagemans et al 2019; Bush et al 2021). In addition, pollen assessments might offer both a qualitative and quantitative picture of the functional connectivity among seemingly distant sites.…”