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Harvard Forest Symposium Abstract 2012

  • Title: Comparison of phenology dates in deciduous forests from near-surface and remote sensing
  • Primary Author: Stephen Klosterman (Harvard University Herbaria)
  • Additional Authors: Mark Friedl (Boston University); Steve Frolking (University of New Hampshire - Main Campus); Koen Hufkens (Harvard University); Andrew Richardson (Northern Arizona University); Oliver Sonnentag (Harvard College (Harvard University))
  • Abstract:

    Deciduous forest phenology regulates physical processes affecting the lower atmosphere, including the timing and amount of carbon uptake and the partitioning of surface energy fluxes into sensible and latent heat. In order to understand the relation between forest phenology, climate, and associated feedbacks, observations from the scale of individual trees and forest stands must be related to broader scale global data from satellite borne radiometers. This project will produce a comparison of spring onset and fall dormancy dates determined from the MODIS EVI and NDVI products to corresponding metrics obtained with digital repeat photography at 17 deciduous forest sites, over 78 site-years.



    An identical methodology for estimating phenology dates will be applied to satellite data and greenness time series extracted from digital repeat photography of forest canopies. Preliminary results indicate that while determination of phenology dates using these two data sources generally compare well, there is a mean bias across all site years of approximately 11 days toward an earlier spring onset when satellite data is used. Possible causes for this bias will be explored on a site by site basis. Human observations, including determination of phenology dates from series of digital repeat photography and direct observation of trees, will be used to evaluate the comparison of satellite and near-surface phenology detection.



    This project draws two of its components from work done at Harvard Forest. First, Harvard Forest is a core site of the Phenocam network (http://phenocam.unh.edu/webcam/), used to produce the digital repeat photography archives used here. Additionally, participants in the 2011 Summer Research Program in Ecology made observations of phenology dates from series of repeat photography, which form part of a growing set of observations.

  • Research Category: Ecological Informatics and Modelling
    Group Projects
    Physiological Ecology, Population Dynamics, and Species Interactions