The abundance and distribution of a species depends on local patterns of occupancy, abundance, colonization, and extinction.  It is rare, however, for such data to be collected in more than one region of a species range, despite the fact that species are likely to experience considerable variation in habitats across broad geographic areas.  Our objective was to compare population attributes and dynamics in two locations in the range of a species using identical methods.  Population data, however, are time-consuming to collect.  In our research, we utilized roadside surveys to collect data on the annual plant Helianthus annuus; these surveys offer an efficient approach for collecting high resolution population data across large spatial scales and multiple years.  We conducted surveys in the fall at an 80m x 5 m grid cell size along 23.6 km and 18.6 km routes in northeastern Kansas and western Nebraska for six and four years, respectively.  We also recorded data on spring soil disturbance, which is likely to affect seed germination, and on landscape categories. 

Results/Conclusions  

Local plant abundance and occupancy were usually higher, but more variable, in Nebraska than Kansas.  Spring soil disturbance was positively related to plant abundance, occupancy, and colonization rates and negatively related to extinction rates; these patterns were stronger in Kansas than in Nebraska.  Similarly, variation in roadside landscape in Kansas (woods vs. grasslands) was more predictive of local plant dynamics than variation in landscape in Nebraska (crop vs. range). In contrast, spring precipitation levels were related to differences among years in abundance of plants in Nebraska but not in Kansas.  Our work illustrates how both regional climate and local site factors influence patterns of local abundance and dynamics at different parts of a species range.  Additionally, we explored the use of linear data sets for research in plant population biology.