Land-use history and abiotic gradients drive abundance of non-native shrubs in Appalachian second-growth forests with histories of mining, agriculture, and logging

Hiking trailheads, but not trailsides, associated with higher cover of non‐native plants’ trail impact on non‐native plant cover

“…Reserve Recreation Maps, 2022) after the forest had been invaded by the most common invasive shrubs in the reserve, Rosa multiflora and Berberis thunbergii (Calinger et al, 2015, Holmes et al, 2021. Both these shrubs have dense, sharp thorns along their stems and thus trail builders may have rerouted trails away from dense patches of thorny shrubs during trail construction or removed shrubs along the new trail.…”

“…This is not consistent with other studies that found non‐native cover was highest along trailsides and lowest further from the trail (Dickens et al, 2005). We suspect that the lack of higher non‐native cover at the trailside relative to the forest interior is because the trails were constructed in 2005 and 2016 (Powdermill Nature Reserve Recreation Maps, 2022) after the forest had been invaded by the most common invasive shrubs in the reserve, Rosa multiflora and Berberis thunbergii (Calinger et al, 2015, Holmes et al, 2021, Powdermill Nature Reserve Trail Map). Both these shrubs have dense, sharp thorns along their stems and thus trail builders may have rerouted trails away from dense patches of thorny shrubs during trail construction or removed shrubs along the new trail.…”

“…Our study was conducted at Powdermill Nature Reserve (PNR), a preserve and field station in southwestern Pennsylvania managed by the Carnegie Museum of Natural History (1999, https://carnegiemnh.org/visit-powdermill/). The reserve has a regularly used trail network beginning at the visitor center and contains abundant non‐native species that are well documented by previous studies (Holmes et al, 2021, 2022; Calinger et al, 2015). Notably, previous plant surveys found non‐native species planted near buildings and trailheads (Utech, 1999), which have the potential to spread and invade into the surrounding forest via the trail networks.…”

“…Here we define non‐native as plants whose presence in the region is attributable to human actions that enabled the species to expand their range beyond their natural dispersal ability (Richardson et al, 2011). The most common and invasive of these non‐native species are Rosa multiflora and Berberis thunbergii , while Lonicera morrowii , Alliaria petiolata , and Celastrus orbiculatus account for a small percent of non‐native cover (Calinger et al, 2015; Holmes et al, 2021). Previous surveys of PNR's flora have found multiple additional non‐native species that were planted near buildings in or near the reserve (Utech, 1999).…”

“…Additionally, the trails in PNR are proximate to areas in the reserve with multiple different land‐use histories, including agriculture and timber harvesting (Calinger et al, 2015; Murphy et al, 2015). These historical disturbances allowed for the extensive invasion of the land prior to trail construction (Calinger et al, 2015; Holmes et al, 2021, 2022). An extensive review of the Carnegie Museum of Natural History's herbarium records for PNR found a total of 297 non‐native species recorded as present in the reserve — including in planted garden areas as well as unplanted forested areas — out of a total 851 recorded species (Utech, 1999).…”