by DE Pataki, HR McCarthy, T Gillespie, GD Jenerette, S Pincetl
As climate change continues to pose a threat to urban forests globally, there is an increased desire to understand the biodiversity of natural ecosystems. This paper proposes that plant functional trait classifications can be employed for assessment of urban biodiversity in human planted and human dominated land cover. The authors measured leaf functional traits of 24 tree species in Los Angeles, California, to determine whether these traits were able to be predicted based on the biogeographic region of origin; and if these traits could be linked to urban plant performance and ecosystem-services based traits. The specific area, nitrogen, and carbon isotopes of each leaf was measured, and actual urban tree performance was evaluated based on stem growth and leaf water potential. In addition, a novel classification of urban ecosystem services-based traits was established using household surveys which vetted the preferences of Los Angeles residents for specific plant attributes. The relationships among these traits, as well as between each plant’s functional trait and species’ continent, climate, and biogeographic origin was analyzed. The results showed that leaf functional traits were related to biogeographic region of origin. The authors also found that the biogeographic region of origin was related to urban performance and ecosystem services-based traits, with native species showing decreased growth rates and fewer desirable aesthetic attributes. Overall, ecosystem services-based traits were better predicted by biogeographical region of origin than by leaf functional traits. This research demonstrates the usefulness of trait-based ecology for urban forest community assembly studies, in which species composition is greatly influenced by decision-making that is based on the preferences of urban residents and stakeholders. Classic ecological theory, including plant functional traits and fundamental versus realized niches, can provide a useful baseline for furthering knowledge regarding biodiversity for planted urban forests.