Invasive Species Monitoring in Select National Park Units in the Cumberland Piedmont Network: Data Summary 2011–2024

Moore, Bill

doi:10.36967/2320080

Park managers within the National Park Service’s Cumberland Piedmont Network identified forest communities as a long-term monitoring priority and began forest monitoring in 2011. This report summarizes one component of that effort: invasive plant status and trends in 252 permanent forest plots in 11 of the network’s 14 park units. The permanent plots were established and sampled from 2011 to 2014, then resampled from 2016 to 2019 and 2020 to 2024. Across 756 sampling events, crews recorded more than 40,000 vascular plant observations and identified 967 taxa to species; 110 of these were exotic. Of these, 27 species have been designated as high priority exotic species for forest monitoring. High priority exotic species (aka forest invasives) were widespread across the parks in this report. During the most recent sampling cycle, approximately two-thirds of sampled plots contained at least one high priority exotic species, and six of the 11 parks averaged two or more per plot. Abundance of these species varied substantially among park units, from parks where all sampled plots contained invasives to parks with comparatively low occurrence and cover. Japanese honeysuckle (Lonicera japonica), Chinese privet (Ligustrum sinense), and Japanese stiltgrass (Microstegium vimineum) were the most widespread and consistently encountered invasive species. Japanese honeysuckle occurred in more than half of sampled plots during the most recent cycle (54.8%) but generally at low cover. Chinese privet was detected in fewer plots (41.7%) but reached estimated cover as high as 61% in individual plots. Japanese stiltgrass showed the strongest evidence of expansion, increasing from the first to the third cycle in plot occurrence (+15.5%), within-plot frequency (+8.6%), and estimated cover (+5.8%). These results indicate that invasive species are a persistent and, in some cases, increasing stressor in forest communities of Cumberland Piedmont Network parks. They also reinforce a central management challenge: once invasive species become established, control is difficult, costly, and rarely successful without repeated follow-up. Management priorities include monitoring disturbed areas, documenting control treatments and evaluating outcomes, maintaining early detection and rapid response for newly detected species, and developing long-term plans that match priority species and locations with available staffing and resources. The presence of 110 exotic taxa highlights the importance of continued monitoring to track the distribution and potential expansion of non-native species across park units. Continued monitoring will provide park managers with science-based information for prioritizing invasive species control efforts and protecting native forest composition, tree regeneration, and ecological function.

Invasive Species Monitoring in Select National Park Units in the Cumberland Piedmont Network: Data Summary 2011–2024

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