Urban Trees in Sync with Urban Climate – Phenology and Microclimate Monitoring using Geocommunication and Citizen Science

In this paper, we demonstrate environmental monitoring in a young citizen science project. The dynamics of urban tree phenology and microclimate regulation throughout the growing season is measured in a cross-city approach, along intraand inter-urban gradients and for a set of the most common urban tree species. We equipped urban trees in five European cities with beacons that connect via Bluetooth to a tailor-made app. The app is used for phenological monitoring, to display microclimate measurements, and to broadcast information on the trees' microclimate-regulating ecosystem services. The approach and setting are scalable to other citizen-engagement and VGI projects. It fosters an understanding of how urban trees are in sync with urban climate, and deepens our understanding of systemic feedback, which is key for implementing urban tree management. Results show inter-species differences in the length of the growing season as measures of the delivery of regulatory ecosystem services and as responses to urban heat island intensity.