Trophic effects of Rosa multiflora in urban forests

Background/Question/Methods

The FRAME program (Forest Fragments in Managed Ecosystems) is long-term study of forest fragments along a gradient of urbanization. One of the main goals of the FRAME is to explore multitrophic interactions in the novel ecosystems created by nonnative plant invasion. To facilitate this research we established 30 sites and quantified soil macro- and micronutrients, vegetation structure and composition, , invertebrate biomass, , herptofauna occupancy, and avian density and reproductive success . The most commonly-occurring invasive plant in our Mid-Atlantic FRAME sites is Rosa multiflora, an Asiatic species once widely planted as a refuge for wildlife. Preliminary data from other sites in DE showed significant differences between Ca-rich invertebrates such as snails and isopods, soil pH, and soil Ca:Al beneath R. multiflora shrubs and those at locations with native plants or leaf litter. We attempted to verify these results with an expanded study in the FRAME including a number of key species in various trophic strata.

Results/Conclusions

The presence of R. multiflora in the 30 Mid-Atlantic FRAME sites was positively and significantly correlated with higher levels of soil calcium, greater numbers of catbird (Dumetella carolinensis) territories, and greater numbers of Ca-rich prey. Over 40% of catbird nests found in our sites were in R. multiflora, and 46% of catbird nests in rose successfully fledged young. Historical data from one of our sites (from the 1960s) shows that invasion by R. multiflora has occurred over the past 50 years. It also reveals a suggestive change between territories numbers for wood thrush (Hylocichla mustelina) - a urban avoider that does not nest in R. multiflora - and catbird territories. Other interactions seen, such as those between leaf litter volume and nonnative plant invasion, beg future research on interactions between nonnative earthworms and invasive plants.