PS 11-137 - Invasion by Pyrus calleryana does not affect understory richness or diversity in early successional meadows

Abstract: Trait differences between invasive plants and their recipient communities modulate the impact of invaders on community composition and ecosystem processes. Callery pear (Pyrus calleryana Decne.) is a fast-growing, stress-tolerant tree native to China that has been widely planted for its ornamental value. In recent decades, P. calleryana has naturalized throughout the eastern United States, where it can spread rapidly and achieve high abundance in early-successional environments. Here, we compare the impact of P. calleryana and functionally similar native trees on the understory community diversity and total cover of three early-successional meadows in the midwestern U.S. Despite our prediction that P. calleryana would have greater negative effects on the total biomass and diversity of the understory plant community compared to native trees, we found that the influence of P. calleryana on communities properties did not differ from that of native Liriodendron tulipifera L., Platanus occidentalis L., or non-tree control plots. This was the case for total cover, species richness, and Shannon’s and Simpson’s indices of diversity for the understory community. Likewise, P. calleryana had no significant impact on the native, introduced, woody, or native tree subsets of the understory community. These results indicate that the trait differences between P. calleryana and functionally similar native trees are not of a great enough magnitude to produce changes in community composition in these young, low-density invasions.