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Pastures are composed of many plant species ranging from planted grasses and native species to invasive pest plants, and composition directly influences the quality and quantity of forage. Many factors drive plant composition of pastures including nutrient availability, disturbance (natural and human-induced) and climate.  Understanding the factors influencing pasture composition is important for informed management to maximize beneficial over pest plants.  In this study we examine seasonal differences in pasture composition across spatial scales between two pasture-types: 1) intensively managed improved pastures (IMP) and 2) less managed semi-native pastures (SNP). Plant species assessments were conducted in 12 pastures at MacArthur Agro-ecology Research Center, distributed evenly among IMP (planted with bahiagrass, fertilized, and ditched) and SNP (native grasses, not fertilized and less ditched.)  We used a modified Whittaker plot to sample vegetation; a nested design with plots at 4 spatial scales from 1m2 to 1,000m2.  Data was collected in February and June of 2011. Non-metric multidimensional scaling ordination was used to assess community similarities between pasture types, and log-log species area curves were created to compare species richness for each cumulative area sampled. As expected, there were more species found (68) in the wet summer season compared to winter (57).  In both winter and summer, perennial grasses contributed the greatest percentage of cover in each pasture type.  Certain pest species were encountered more often in the improved pastures, including thistles (10.2% of IMP plots, 2.3% of SNP plots), and smutgrass (4.9% IMP, 2.7% SNP). Other pest species like dog fennel were encountered with similar frequencies in both pasture types (5.7% IMP, 4.5% SNP). In both pasture types species richness increased significantly across all spatial scales, suggesting that species diversity is patchy and that smaller sized plots may underestimate richness in large expansive pastures. Monitoring at multiple spatial scales may also allow for the early detection of invasive species, which can allow for more target and cost-effective management. This data only provide preliminary insights into seasonal patterns and spatial scale in pasture composition. We plan to implement a more in-depth pasture monitoring program that links plant composition, pasture management, and cattle activity.