Effects of urbanization on flowering phenology in the metropolitan phoenix region of USA: Findings from herbarium records

Phenological studies have become more prominent recently because of rising interests in understanding how plants, communities, and ecosystems respond to global climate change and urban climate modifications. Herbarium records of plants can be a particularly useful source of information for studying historical trends in phenology in areas where long-term phenological records do not exist. In this study, we used herbarium records to examine the historical patterns of flowering phenology of 87 shrubs and ephemerals in the Phoenix metropolitan region in the southwestern United States from 1902 through 2006. We found that 19% of plant species examined either advanced or delayed their flowering. Also, the flowering responses of 28% of the species examined showed significant differences between urban and non-urban areas: 24% advanced in urban areas and 5% delayed. Our study indicates that urbanization may have a significant effect on the flowering phenology of a small but substantial proportion of plants, which will likely affect native biological diversity and ecosystem services due to potential changes in population and community dynamics.