COS 92-4 - The relative impacts of the surrounding landscape and local variables on aquatic macroinvertebrate communities of the Prairie Pothole Region in North Dakota

Thursday, August 11, 2011: 9:00 AM
8, Austin Convention Center
Peter J. Christensen, Biology, University of North Dakota, Grand Forks, ND and Brett J. Goodwin, Department of Biology, University of North Dakota, Grand Forks, ND

The effects of the surrounding landscape on prairie pothole wetland invertebrate community structure have not been well established. To assess the impact of landscape pattern on aquatic invertebrate communities we sampled 112 prairie pothole wetlands on US Fish and Wildlife Service lands in the Devils Lake Wetland Management District of North Dakota during the summers of 2009 and 2010. Wetlands were selected to maximize variation in wetland size, adjacent grassland patch size, grassland management strategy, and proximity to disturbance. By sampling the invertebrate communities of these wetlands, sampling for the presence of aquatic vertebrate predators, surveying the local vegetation communities, and quantifying landscape level patterns within a GIS framework, we assessed the impact of landscape pattern on wetland macroinvertebrate community characteristics. To sample the invertebrate communities we used a paired activity trap method, with one horizontal and one vertical funnel trap per pair. We used funnel style minnow traps to detect presence/absence of aquatic vertebrate predators. We characterized local vegetation directly adjacent to the sample wetland using 25 meter belt transects. To examine the role of landscape pattern and composition we created a GIS using a combination of aerial imagery and vector data from the North Dakota GIS Hub. We constructed a 2-kilometer buffer around each focal wetland to serve as a landscape. 


Invertebrate communities showed a high variation in diversity and species richness across the 112 wetlands sampled. This variability can be predicted by both local habitat variables as well as landscape level pattern variation. At the local level we found the presence of tiger salamanders in the wetland had a significantly negative impact on invertebrate species diversity. Presence of fathead minnows did not have a significant impact on species diversity, in contrast to prior research on wetland invertebrate communities.  Vegetation characteristics directly adjacent to the wetland did not show a significant effect on invertebrate species diversity.  Grassland management strategy did have an influence on diversity.  Those sites that had been reseeded with a diverse mixture of native grasses and forbs showed a significantly higher diversity than sites that were left idle, grazed, burned or seeded in dense nesting cover. The results of this study show that in a highly fragmented agricultural landscape, those sites with large blocks of undisturbed native grasslands have higher aquatic invertebrate species diversity than those sites with small grassland patches in close proximity to disturbances such as roads and agricultural operations.

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