Callery pear (Pyrus calleryana) invasion is predicted by forest edge not plant species richness in grasslands

Fallow agricultural fields are target landscapes for ecosystem restoration; however, they are degraded and susceptible to plant invasion, requiring extensive management. Pyrus calleryana is an invasive tree in Eastern USA that escaped cultivation and became a prominent invader. The ecology of this tree is relatively unknow, but it grows in dense monocultures, outcompeting native counterparts, and is challenging to remove. Identifying landscapes that are vulnerable to invasion may allow for targeted management and could inform land manager decision making. Here, we assessed the level of invasion in restored prairies as well as their surrounding land use, plant communities and soil chemistry, to determine if these metrics could predict the invasion of P. calleryana. We selected two invaded and two uninvaded sites, sampled 25 quadrats in each and measured distance of quadrat to roads, forests or residences, P. calleryana presence/absence and abundance, plant species richness and cover, and soil moisture, pH and nutrients. We found higher species richness in uninvaded sites than invaded sites, contradicting the biotic resistance hypothesis. Invaded sites had more P. calleryana where grasses and forbs covered less area, indicating open niche space for invasion. Soils in uninvaded sites had higher pH, organic matter and ammonia availability, but lower phosphorus, nitrate and micronutrient content, aligning with our hypothesis that increased organic matter may alter nutrient ratios to promote native species. Finally, P. calleryana was more abundant near forest edges, but was not invasion was not related to roads or residences. Forest edges harbor bird perches which may facilitate dispersal of P. calleryana. Taken together, P. calleryana is more likely to invade on forest edges, suggesting targeted restoration in those areas; however, plant species richness and soil nutrient content may not be an appropriate indicator for determining the suitability of target landscapes.https://ecommons.udayton.edu/stander_posters/3628/thumbnail.jp