PhenoCam Images and Canopy Phenology at Harvard Forest since 2008

A collaborative research network (“PhenoCam”) to provide automated "near" remote sensing of canopy phenology across the northeastern US and adjacent Canada has been initiated. A pilot study (2006-2007) at the Bartlett Experimental Forest previously demonstrated the viability of tracking both spring green-up and autumn senescence based on relative changes in red, green, and blue (RGB) color channel brightness values extracted from networked digital camera (“webcam”) images. In 2008, we installed commercial-grade digital webcams at a dozen established research sites across the northeast, from Ontario and New York across to Maine, with most sites concentrated within a few degrees of 45 deg N. Two additional Midwestern sites were subsequently added to the network. At seven camera sites (Bartlett, Howland, Harvard Forest, Groundhog River, Chibougamau, University of Michigan Biological Station, and Morgan Monroe State Forest), ongoing measurements of carbon and water fluxes are being made with the eddy covariance method, which will enable us to directly link phenology to seasonal variation in ecosystem processes. The seasonal trajectory of a “greenness index” for Harvard Forest shows a rapid rise in greenness in spring (coinciding with ground observations of budburst), a gentle decline over the course of the summer, and then a rapid decline with autumn senescence. This network is providing a very rich (and unique) dataset on spatial and temporal patterns of canopy phenology in the across this region. Half hourly images are uploaded to a project web page (http://phenocam.sr.unh.edu), which also features additional information about the project, including a protocol for camera deployment, download tools (so that the imagery is available to a wider community), site locations and contact information, etc. Image processing routines are under development. Time series of greenness will be added to the archive when this is complete; at present, only images are being made available.