Forested lands in the mid-Atlantic region are invaded by both woody and herbaceous exotic species, many of which are thought to have serious impacts on biodiversity and forest health. However, accurate knowledge of the distributions of these species in large forested tracts is currently unknown, making the development of effective removal actions and forest restoration difficult. We are conducting a joint experiment with a non-governmental organization, the New York-New Jersey Trail Conference, to recruit volunteers and train them to collect semi-quantitative data over large areas of forested state parks and forests. During 2006 and 2007, a total of 92 volunteers were trained to identify a suite of exotic species and collect data on the location and abundance of their occurrence. Each pair of volunteers surveyed a 2 mile section of hiking trail, and also collected data on a common 1-mile ‘validation’ trail; nearly 100 miles of trail in four park areas were sampled. Data were validated by knowledgeable botanists, who repeated the data collection at a subset of data points, and also collected data on transects perpendicular to trails.

Results/Conclusions

In both years, 66-75% of volunteer teams correctly identified all species; exotics that occurred infrequently were less successfully identified. However, in both years, >90% of hiker observations matched those of validators in both species abundance and distance from the trail. Volunteers were more likely to fail to observe a species that was present than to incorrectly report a species presence, and errors were more frequent for uncommon species. In the four regions sampled for the study, Berberis thunbergii  was the most frequently encountered species (23-26% of observations), and Microstegium vimineum was the second most-frequently encountered species (11 – 19% of observations). In the survey areas for 2006, there was no trend of higher exotic species occurrence along trails than off trails, but in 2007, there was a weak trend of higher abundances within 100 m of the trail. These data suggest that 1) for commonly-occurring exotic species, volunteers given brief training in plant identification can collect reliable data over large regions and learn about both data-collection methods and an environmental issue, 2) exotic species are widespread but patchily distributed and 3) plant invasions are not strongly associated with trails, but occur throughout the forested lands, contrary to studies from other forested regions.