Print PageThe heterogeneous distribution of vegetation communities in urban ecosystems provides an opportunity to determine how species are adapting to novel community assemblages. Urban fragments harbor new combinations of interacting species, each of which may be encountering conditions outside of what their conspecifics encounter in wildland forest ecosystems, particularly with respect to invasive plant species. Primary soil nutrients, such as Ca, determine the competitive ability of non-native invasive plants as well as the composition of the arthropod community. Changes in soil Ca availability thus can affect the abundance of bird prey directly when invertebrates are Ca limited (e.g., Gastropoda, Crustacea) and indirectly through host plants (e.g. herbivorous Insecta). The impact of calcium availability on wood thrushes or gray catbirds in urban environments is un known: our preliminary data suggest that patterns observed in more intact systems are not maintained in urban fragments. In 2009, we established urban fragment study sites in Newark, Delaware to study the effects of soil chemistry on plant invasion and the response of the invertebrate and bird communities to these novel plant communities.
Results/Conclusions
We found that invertebrate abundance differed in relation to soil Ca availability. Gastropods and crustaceans were positively associated with soil Ca while insects, mostly herbivorous, may be negatively affected by increases in non-native plant cover associated with high soil Ca levels. Sites differed in the extent of invasion by R. multiflora which affected the avian community. Wood thrush had greater nest density in uninvaded sites while gray catbird had greater nest density in invaded sites. At one site, invasion by R. multiflora increased since 1966 and concurrently, wood thrush densities declined while catbird densities increased We also found an interaction between R. multiflora cover, Ca:Al, and snail abundance.
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