- Richardson, Andrew
Phenology is the study of recurring lifecycle events influenced by seasonal environmental changes. For deciduous forests, critical phenological events are spring development and autumn senescence of the canopy, as these effectively mark the beginning and end, respectively, of the growing season. Phenology thus exerts a strong control on both spatial and temporal patterns of primary productivity and is therefore critical to carbon sequestration of terrestrial ecosystems. Beyond carbon, however, phenology also influences hydrologic processes, as spring leaf-out is accompanied by a marked increase in evapotranspiration, and nutrient cycling processes as autumn senescence results in fresh litter (nutrient) inputs to the forest floor. Phenology has been shown to be a robust integrator of the effects of climate change (e.g., recent warming trends) on natural systems, and it is now recognized that improved monitoring of phenology on local-to-continental scales is needed. These data will contribute to reducing uncertainties about the effects of climate change and variability on ecosystem processes and forest health.
We initiated a research network that would provide automated “near surface” remote sensing of canopy phenology across the Northern Forest region. We installed commercial-grade digital webcams at 10 established research sites within this area, from Ontario and New York across to Maine at a latitude of roughly 45°N. We are using images from these cameras to track both spring green-up and autumn senescence based on changes in red, green, and blue (RGB) color channel brightnesses of each image. At five of the proposed research sites, ongoing measurements of carbon and water fluxes are being made with the eddy covariance method, and we are directly linking phenology to ecosystem processes. Images from the camera network are presented at the PhenoCam project web page, http:// phenocam.sr.unh.edu.
This cooperative effort involved researchers active in five states and two Canadian provinces, and thus contributes to the NERC objective of cross-border collaboration. Our project will provide valuable information to forest managers (monitoring of forest health) and the tourism industry (targeting optimal “leaf peeping” conditions).