Local-scale analysis of plant community from the Early Cretaceous riparian ecosystem of Hautrage, Belgium

Diversity properties and relative taxon abundance are explored to describe plant community local-scale spatial and temporal patterns during four ecological stages from the middle Barremian continental aquatic ecosystem of Hautrage, Mons basin, western Belgium. Taxon co-occurrence and correlations of taxon abundance are also analyzed to describe the main patterns of plant association within each stage and through time. Diversity, relative taxon abundance and taxonomic inventory greatly vary laterally and between ecological stages. Two of these stages show gradients in taxon richness and abundance reflecting probable edge effects. A reconstruction of the plant community evolution based on these four stages plus seven previously reported stages reveal a plant community mainly composed of the conifers Arctopitys, Brachyphyllum, Frenelopsis, and Pagiophyllum, and the ferns Gleichenites and Phlebopteris, maintained through time. Two main taxon association patterns are observed over space and time: 1) Arctopitys and Phlebopteris, and 2) Brachyphyllum, Gleichenites, Pagiophyllum. Conifer type 1, Elatides and Sphenopteris appear to have been spatially associated, whereas inverse relations between Cladophlebis and Phlebopteris and between Onychiopsis and Sphenopteris reflect possible niche overlap and competitive exclusion pressures. Three different successional stages are identified by the proportion of herbaceous and woody taxa and the presence/absence of Frenelopsis. Frenelopsis was a dominant taxon in mature community stages probably forming closed canopies, and having a negative effect on richness and abundance of other taxa. Our results evidence four intense and two less intense fire events through the series, suggesting that wildfires played an important role in the ecological succession of the plant community of Hautrage. Weichselia reticulata most probably played a key role in early successional stages, contributing in the regeneration of plant communities after wildfire disturbance events.