Phenology is the study of plant and animal life cycle events, which are triggered by environmental changes, especially temperature and photoperiod (or daylength). Wide ranges of phenomena are included, from first openings of leaf and flower buds in the spring, to changes in foliar color and eventual leaf fall in the autumn, to insect hatchings and migrations of birds. In addition to being a metric for annual cycles of plants and animals, decadal- or longer-scale changes in these phenomena serve as robust integrators of the effects of climate change on natural systems.
At the Hubbard Brook Experimental Forest in the White Mountains of New Hampshire, the US Forest Service has been making phenology measurements of leaf on and off manually at Hubbard Brook since 1989. These long term records show that, on average, the period between leaf on and leaf off (i.e., green canopy duration) has increased by ~10 days.
Historically, these canopy measurements were made manually by a trained observer on a weekly basis during the spring and fall at individually tagged trees at nine different locations across the Hubbard Brook. Recently, StarDot cameras have been introduced as a more objective and automated method to assess leaf phenology. These webcams serve as multi-channel (red, green and blue color channels) imaging sensors which can continuously track the development, senescence, coloration and abscission of forest canopies.
Click on the image at right to see the unfolding of the canopy in the spring and subsequent senescence in the fall of 2012. These images provide both a powerful framework by which to monitor the timing and extent of critical phonologic events as well as a 'window on the watersheds' available for public viewing and enjoyment.