Landscape classification and impact of cattle grazing on vegetation and range condition in the Dundurn Sand Hills, Saskatchewan
Houston, William Samuel Lewis
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Range condition assessment for dune sand range sites in Saskatchewan is challenging because of landscape heterogeneity and limited information regarding plant responses to disturbances. These assessment challenges prompted the initiation of this research project with the following objectives to: 1) develop a system to classify native rangeland in the Dundurn Sand Hills into patch types based on vegetation structure and topography; 2) determine the impact of cattle grazing on native vegetation in the Dundurn Sand Hills, and; 3) improve the method of range condition assessment for native rangeland in the Dundurn Sand Hills. Plant community composition, yield, soil particle size, and soil organic carbon were assessed on 14 grazed and 10 ungrazed sites within the Dundurn Sand Hills in 1996 and 1997. The dune sand range site was subdivided into five major patch types: herbaceous, prostrate shrub, short shrub, tall shrub, and tree. Response to cattle grazing for each species was determined by comparing abundance on grazed and ungrazed sites for each patch type. Significant differences were determined using the Kruskal-Wallis test. Analyses showed that grazing responses of plants were variable. Some species responded as predicted by existing standards, for example, Koeleria cristata (June grass), whereas other species, such as, Calamovilfa longifolia (sand grass), had grazing responses that contradicted the existing standard. Grazing responses for many species were previously unknown but have now been identified. Some species such as Carex obtusata (blunt sedge) responded differently among patch types. No grazing response was identified for most species. Canonical Correspondence Analysis (CCA) was employed to isolate a grazing pressure gradient and indicated that only a small proportion (6 to 10%) of the total variation in species composition is explained by the grazing pressure axis for each patch type. Division of the dune sand range site into different patch types and identification of grazing responses provides an improved method of range condition assessment for the Dundurn Sand Hills. This improved assessment method combined with the revised stocking rate information presented will facilitate better management of dune sand range sites in Saskatchewan.