spatial and temporal heterogeneity of macrophyte communities in thirty small, temporary ponds over a period of ten years

Ponds are important habitats within many landscapes because of the diversity of wildlife they support. This arises in part because of the heterogeneity of ecological communities found in neighbouring ponds but this variation has proved difficult to explain. Chance and unrecorded historic events have often been emphasised as explanations. This study describes the development of spatial heterogeneity and the role of historic events in the development of pond plant macrophyte communities from the ponds' creation until ten later using thirty small, adjacent temporary ponds in Northumberland. Plant communities showed significant spatial variation from the first year onwards. Metacommunity spatial patterns changed over time but even after ten years several distinct macrophyte communities persisted in different ponds. The outcome was that a greater variety of pond communities persisted than was likely if a single, larger pond had been created on the site. The spatial patterns of the plants communities were compared to spatial variation of summer dry-phase and winter inundation. Macrophyte heterogeneity appeared to result from deterministic change which would have been difficult to detect in a snap-shot survey not knowing the history of the ponds. Winter inundation showed significant spatial trends every year which mirrored the changing distribution of macrophyte communities between ponds. The proximate influence of the inundation is ultimately determined by the position of each pond in the landscape so that the marked spatial and temporal heterogeneity of plant communities was strongly influenced by small scale variation in hydrology. The results suggest that the heterogeneity of pondlife across a landscape may be deterministic when recorded over a longer time period and not due to chance, but that the determining environmental factors are highly contingent on the locality of the pond.