PS 33-44
The effects of microtopography on ephemeral pond and permanent wetland plant species richness at multiple scales
The purpose of this study was to determine the relationship between microtopography and plant species richness in wetlands of the Chippewa Moraine, Wisconsin, USA. Ephemeral ponds (EPs) are unique temporary wetlands that host a wide variety of life, but few studies have investigated their vegetation. The relationships between microtopography and wetland species richness were examined at two scales: within and among wetlands. Microtopography was assessed using quadrat microtopographic score (QMS). Quadrats with high QMS had hummocks or stumps, while low QMS indicated pool or flat. We hypothesized that wetlands with deeper water and higher QMS scores would have higher species richness. We also hypothesized the QMS-richness relationships would be stronger within permanent wetlands (PWs) as opposed to ephemeral ponds.
Results/Conclusions
At the within-wetland (quadrat scale), QMS showed a significant positive relationship with quadrat species richness in 37% of wetlands. Significant relationships were significantly more frequent in PWs and in wetlands with fluctuating water levels than they were in EPs. Microtopography may not play a large role in structuring richness within EPs because the species that can tolerate the EP environment may be more generalist species that can survive in many microtopographic settings. Within PWs, the results suggest that wetlands containing more hummocks and logs sustain more richness in plant species. Among wetlands, even when excluding PWs, mean QMS had a significant positive relationship and wetland water depth had a significant negative relationship with wetland plant species richness. Wetlands that are too deep will not have as much exposed microtopography, and fewer species can tolerate the stress of deep water levels. In addition, microtopography may create more variation in wet and dry areas in a season, allowing plants with diverse requirements to flourish.