Washita Battlefield National Historic Site Exotic Plants Monitoring Summary—2022

Owen, Merran; Barry, C.; Pingatore, A.; Valentine-Darby, P.

Each year, the Southern Plains Inventory & Monitoring Network (SOPN) monitors pathways of exotic plant introduction at Washita Battlefield National Historic Site (NHS) (WABA) and other network parks. The areas sampled are typically linear transects along roads, trails, boundary lines, and stream channels that are at high risk for exotic plant invasion and infestation. The transects for each park are divided into three panels, with one panel sampled each year. In select years, exotic plant data are also collected at predetermined grid points spaced 100 meters (m) apart, covering the entire park acreage, with areas excluded for safety or difficulty of access. Grid-point surveys are done to determine the extent and distribution of exotic plants within the park interior landscape. Data collected for infestations include plant species name, the size of the patch, canopy cover, number of plants present in the patch, phenology (e.g., flowering or fruiting stage), and level of site disturbance. At grid points, surveyors record the exotic plant species found within a 10-m radius of the point, as well as canopy cover and phenology for each species. The Southern Plains Network surveys for a short list of species that is customized to each park. Our intent is to document infestations for which we recommend treatment and monitor species of high concern. The monitoring list for WABA (Table 1) was drawn from the park’s Natural Resource Condition Assessment (NRCA), completed by Struthers et al. (2014). In the NRCA, exotic plants found in 2009–2012 WABA surveys were ranked across a series of factors, following a system designed by Hiebert and Stubbendieck (1993). Factors included the plant’s level of impact (current abundance, distribution, and known or perceived ecological effect), its innate pest potential (reproductive abilities, germination requirements, and competitive abilities), and the feasibility of control (the plant’s abundance versus the ease of applying control measures). The eleven highest-ranking plants were designated as high priority species for the park, all of which are included in our monitoring list. For further detail, see the WABA NRCA (Struthers et al. 2014).