From flowering to foliage: Accelerometers track tree sway to provide high-resolution insights into tree phenology

• Accelerometers can detect mass changes associated with flower and foliar phenology. measure phenophases not captured by imagery-based analysis. complement data streams such as direct or image-based observations. alleviate cost privacy barriers to monitoring trees (e.g. urban). could facilitate real-time acquisition on tree health services. Trees are bioindicators of global climate change regional urbanization, but available tools ineffective for fine-scale observation many species. Using six accelerometers mounted two urban ash ( Fraxinus americana ), we looked at high-frequency vibrations, in periodicity sway a proxy changes, infer seasonal patterns flowering foliage (phenophases). We compared accelerometer-estimated those derived from digital repeat photography using Green Chromatic Coordinates (GCC) visual defined the USA National Phenology Network (NPN). also drew comparisons between commercial assessed how placement height influenced ability extract transition dates. Most notably, showed greenness signal an environment produced clear time-series peak (PF), marking first observations phenophase accelerometer data. Estimated start spring (SOS) time-lapse GCC were more similar than autumn (SOA); lagged behind camera dates three four days SOS 13 14 SOA each tree. Estimates cameras aligned closely different NPN phenophases. The season onset: difference 2.4 3.8 SOS, 2.1 SOA, 0.5 2.0 PF. placed main crown branch point versus higher canopy 0.2 4.9 -1.5 1.7 Our results suggest present novel opportunity objectively monitor reproductive biology fill gaps phenology Furthermore, widely show promise scaling up individual landscape level aid forest management assessing impacts