Phenology has been widely used as a bioindicator of potential tree responses to climate change. Additionally, past studies have successfully modeled species distributions based on phenology because plants are unlikely to persist in a location if they are at high risk of freeze damage to leaves, flowers, or fruits. Large citizen science networks such as the USA National Phenology Network have increased the spatial distribution observations for many tree species, but are unable to robustly capture rare or threatened species having restricted or climate-sensitive distributions. Botanic gardens and arboreta help fill this gap by growing diverse arrays of species, often emphasizing preservation of rare species through taxonomically or geographically oriented collections. At The Morton Arboretum, we are combining phenology observations of tree species both in and outside of their natural habitats through volunteer and national citizen science efforts in order to better determine climatic constraints on tree species distributions. In 2017, we began to pilot these concepts through analyses of the genus Quercus (oaks) as one of the most broadly distributed and ecologically important taxa across the globe.
Results/Conclusions
In 2017, we monitored leaf and reproductive phenology for 64 trees from 29 species of Quercus, which was then expanded to 234 trees representing 58 species in 2018. Due to a mild winter in 2017, the onset of budburst was nearly 3 weeks earlier in 2017 than in 2018, although the dates of peak fall color were similar across years. In both years, species showed a narrower range for date of first budburst than for peak fall color, suggesting more consistent cues for start of growing season in temperate deciduous oaks than for the end of season. In the future, we will use the phenological covariance among co-occurring or phylogenetically related species in botanic gardens and the USA National Phenology Network to better assess climate sensitivity and potential vulnerability of species of concern.