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Harvard Forest Data Archive

HF215

Canopy Phenology and Greenness Indices at 13 Sites across North America 2003-2012

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Data

Overview

  • Lead: Andrew Richardson, Michael Toomey
  • Investigators: Dennis Baldocchi, Carl Bernacchi, Sebastien Biraud, Gil Bohrer, Edward Brzostek, Sean Burns, Carole Coursolle, Mark Friedl, Steve Frolking, David Hollinger, Koen Hufkens, Stephen Klosterman, Hank Margolis, Harry McCaughey, Russell Monson, William Munger, Stephen Pallardy, Richard Phillips, Oliver Sonnentag, Margaret Torn, Sonia Wharton, Marcelo Zeri
  • Contact: Andrew Richardson
  • Start date: 2003
  • End date: 2012
  • Status: completed
  • Location: North America
  • Latitude: +36.6970 to +49.6924
  • Longitude: -121.9521 to -71.2881
  • Elevation: 80 to 3055 meter
  • Taxa:
  • Release date: 2014
  • Revisions:
  • EML file: knb-lter-hfr.215.3
  • DOI: digital object identifier
  • Related links:
  • Study type: long-term measurement
  • Research topic: ecological informatics and modelling; forest-atmosphere exchange; regional studies
  • LTER core area: primary production
  • Keywords: aboveground production, canopies, imagery, leaves, phenology, remote sensing
  • Abstract:

    This data set contains camera-derived color index data, which serve as a proxy for canopy phenology. The data set spans 13 geographically distinct research sites, including 17 different cameras it total, each of which was mounted on a eddy flux tower for intercomparison of canopy and photosynthesis phenology. Each site was dominated by one of three PFTs: deciduous broadleaf forest, evergreen needleleaf forest, and grassland/crops (see HF215-01 for details). On each eddy covariance tower, a digital camera was installed in a fixed position, with a view across the top of the canopy. Most cameras collected photos, which were saved in 24-bit JPEG format, at 30-60 minute intervals, 12-24 hours a day. Time series were first visually inspected for camera shifts and changes in field of view. Noting these changes, we processed the image archives to extract regions of interest (ROI) that encompassed all portions of the full canopy within the foreground. To quantify canopy greenness, we calculated the green chromatic coordinate (GCC), which is widely used to monitor canopy development and identify phenological phase changes, as follows:

    GCC = DNG / (DNR + DNG + DNB)

    where DN is the digital number and R, G and B denote the red, green and blue channels, respectively. The Excess Green (ExG) index was then calclated as follows:

    ExG = 2 * DNG - (DNR + DNB)

    To characterize canopy coloration in fall, the red chromatic coordinate (RCC) was calculated using the same form as GCC, substituting DNR in the numerator. Indices have been smoothed along a 3-day interval, using a 90th percentile filter (Sonnentag et al. 2012). For each deciduous broadleaf site, there are three files – one each for GCC, ExG and RCC. For the grassland and evergreen needleleaf sites, there are two files, one each for GCC and ExG.

  • Methods:

    This study contains data from the EMS tower at Harvard Forest (HF004, HF158).

    All original camera imagery data are located at http://phenocam.sr.unh.edu. Eddy covariance data for each of the sites can be obtained from the Ameriflux network: http://ameriflux.lbl.gov/.

    For additional details, see: Toomey, M. et al. 2014. Greenness indices from digital cameras predict the timing and seasonal dynamics of canopy-scale photosynthesis. Ecological Applications.

  • Use:

    This dataset is released to the public under Creative Commons license CC BY (Attribution). Please keep the designated contact person informed of any plans to use the dataset. Consultation or collaboration with the original investigators is strongly encouraged. Publications and data products that make use of the dataset must include proper acknowledgement.

  • Citation:

    Richardson A, Toomey M. 2014. Canopy Phenology and Greenness Indices at 13 Sites across North America 2003-2012. Harvard Forest Data Archive: HF215.

Detailed Metadata

hf215-01: site information

  1. site: site name
  2. pft: plant functional type
    • DBF: broadleaf deciduous forest,
    • ENF: evergreen needleleaf forest
    • GRS: grassland/crops
  3. lat: latitude (unit: meter / missing value: NA)
  4. long: longitude (unit: meter / missing value: NA)
  5. alt: altitude (unit: meter / missing value: NA)
  6. loc: site location
  7. start.year: first year of data
  8. end.year: last year of data
  9. camera: camera model
  10. citation: ciation

hf215-02: green chromatic coordinate

  1. site: site name
  2. year: year
  3. doy: day of year (unit: nominalDay )
  4. gcc: green chromatic coordinate (unit: dimensionless / missing value: NA)

hf215-03: red chromatic coordinate

  1. site: site name
  2. year: year
  3. doy: day of year (unit: nominalDay )
  4. rcc: red chromatic coordinate (unit: dimensionless / missing value: NA)

hf215-04: excess green indices

  1. site: site name
  2. year: year
  3. doy: day of year (unit: nominalDay )
  4. exg: excess green indices. Indices have been smoothed along a 3-day interval, using a 90th percentile filter. (unit: dimensionless / missing value: NA)