Physicochemical and Vegetative Responses of Prairie Wetlands to Local Land Covers

Abstract

Effective environmental monitoring and biological assessment initiatives require knowledge of the spatial and temporal scales at which human activities most strongly influence ecosystem conditions. I compared the environmental conditions and vegetation communities of 48 non-permanent wetlands in the Prairie Pothole Region of Alberta, Canada, to adjacent land cover measured at ten spatial extents and in four consecutive years. I found that both vegetation community composition and environmental conditions within the wetland were significantly related to variation in land cover across a wide range of spatial extents and the entire time period that I analyzed. Importantly, no spatial extent and year combination yielded land-cover data that was statistically significantly more concordant with environmental conditions or vegetation communities than the others within 1 km of the wetland boundary. Contrary to expectations, the catchments did not yield land cover significantly more concordant with wetland conditions than symmetrical buffers. I therefore conclude that concerns around having the most recent and highest-resolution land cover or most precisely-delineated catchment boundaries should be relaxed. Despite the lack of significant differences among extents and age of land cover data, I did observe consistent trends in concordance. Wetland environmental conditions were more concordant with land cover extracted from either the wetland catchments or from within a 200-500 m buffer around the wetland. The analysis also suggested a time-lag in the relationship of four years or more. Wetland vegetation communities appeared more strongly related to land cover at 500-5,000 m from the wetland and exhibited a one-year time lag; however, when I controlled for spatial autocorrelation, the strength of the concordance between vegetation and land cover from all extents decreased to insignificance. This revealed the same pattern as observed for environmental conditions, but at weaker concordance levels. Spatial autocorrelation in terms of environmental conditions, wetland vegetation and surrounding land cover may be associated with natural climatic and physiographic gradients in my study region and highlights the need for additional exploration of geographic variability within jurisdictional units. These findings raise interesting questions for science and have important consequences for wetland monitoring, management and conservation.