Continuity in phenological monitoring: Assessing the performance of an updated PhenoCam

Abstract

Vegetation phenology plays a crucial role in land-atmosphere interactions and ecosystem productivity, necessitating high-quality, long-term datasets. The PhenoCam Network addresses this need by using digital cameras to capture canopy greenness (GCC, the green chromatic coordinate). Since 2008, the StarDot NetCam SC has been the network's backbone, but its discontinuation, particularly exacerbated by supply chain problems and delays during the COVID-19 pandemic, requires the identification of a successor to ensure continuity. This study evaluates the StarDot NetCam Live 2 camera's performance against the SC model. We visually compared imagery from different seasons, evaluated color accuracy using a ColorChecker, and assessed the similarity of seasonal and diurnal GCC patterns. Results show that the Live 2 provides slightly improved GCC accuracy relative to the ColorChecker. Both cameras effectively capture seasonal changes in canopy greenness for three different vegetation types. High R² values (0.87–0.95) between the cameras 3-day GCC, confirm strong agreement in seasonal GCC time series and phenological transition dates, with an average difference of 4.1 ± 1.6 days. Diurnal GCC patterns also showed consistent agreement, strongest on sunny days (R²=0.71). The results of this study support the integration of the Live 2 camera into the PhenoCam Network, thereby facilitating the continuation of long-term phenological monitoring efforts.