Proximity to successionally advanced vegetation patches can make all the difference to plant community assembly

Abstract

Background: We hypothesised that the relative position of surrounding vegetation patches would account for most floristic patterns observed in patches of exposed gold mine spoil (EMS) scattered over a 60-year-old, abandoned waste heap. Aims: We assessed the extent to which the structure of plant species assemblages from 53 EMS patches was related to distance from woodlands, heathlands and grasslands by controlling for the effect of spatial autocorrelation, patch size, slope and aspect. Results: The most discrepant in terms of species composition were the EMS patches located farthest away from heathlands and those embedded in woodlands. Zoochorous species richness declined with distance from the nearest heathland. Anemochorous, competitive-stress tolerant and total species richness increased with proximity to the nearest woodland. Conversely, competitive species richness and total species cover were larger in EMS patches that were farther away from the nearest woodland, but closer to grasslands. Depending on the identity of colonising species, the woodland stands could act as propagule source, ecological filters or seed dispersal amplifiers. Conclusion: The relative importance of proximity to source habitats for plant community assembly can change dramatically under the confounding or contrasting effects of ‘third-party’ habitat patches, which are interposed in the landscape.