Cottonwood distributions across the Rolling Plains of Texas and Kansas
Walker, Ryan Nicholas
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The presence of trees is a limiting factor for wild turkeys (Meleagris gallopavo) throughout the arid and semiarid portions of their range. Any long-term changes that occur to local tree populations will likely impact local wild turkey populations. Cottonwoods (Populus spp.) are the primary riparian tree of western North America and are linked to the flow regime of the river system. From 2000 through 2006, we measured 3,832 Plains cottonwoods (P. deltoides ssp. monilifera) at four sites in the Rolling Plains of Texas and Kansas. Only 132 (3.4%) of these cottonwoods were <10 cm in diameter at breast height. We documented large declines in daily flow following dam completion along the Canadian River, Texas. We documented small declines in daily flow following dam completion along the Salt Fork of the Red River, Texas. We documented low or intermittent flows along the Cimarron River, Kansas. The large declines in flow rate along the Canadian River have led to channel narrowing and vegetation encroachment throughout the floodplain. The small declines in flow rate along the Salt Fork of the Red River did not alter the meandering status of the river, sheltering it from the changes that occurred along the Canadian River. The sporadic flow along the Cimarron River suggested this river was more unstable than the other rivers. Regardless of river flow status, we failed to detect large quantities of cottonwood regeneration across the study area. This leaves the future unclear for cottonwoods and wild turkeys in this region. We were concerned by the limited regeneration of riparian cottonwoods and wanted to examine a period >7 years. We used Landsat satellite imagery to identify changes, from 1973 to 2005, in riparian trees that may have occurred concurrently with changes in local wild turkey populations. Our supervised classification accuracies ranged from 0.9 to 64.0%, which were insufficient for us to complete our objectives. Landsat imagery was not sufficient to identify changes in riparian trees in our study area. Other satellite-based systems provide improved spatial resolution, but currently lack the necessary temporal resolution to be effective. We suggest aerial photography and ground-based surveys remain the most useful tools for documenting changes in riparian trees.