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Harvard Forest Research Project 2024

  • Title: Extended evaluation of near-infrared digital hemispherical photography for estimating leaf and wood area index during leaf-on conditions
  • Principal investigator: Luke Brown (l.a.brown4@salford.ac.uk)
  • Institution: Not Specified
  • Primary contact: Luke Brown (l.a.brown4@salford.ac.uk)
  • Team members: Courtney Meier
  • Abstract:

    The proposed project will provide an extended evaluation of near-infrared digital hemispherical photography (DHP) as a new means of measuring leaf area index (LAI) and wood area index (WAI). Current DHP approaches, (including those used in NEON’s routine sampling) make use of standard cameras with red, green, and blue bands, but they are unable to discriminate between foliage and woody material. As a result, they can only provide an estimate of plant area index (PAI), which represents the sum of LAI and WAI. Although WAI can be determined as the leaf-off PAI for deciduous species, this is not an option for evergreen species. The subtraction of leaf-off PAI may also lead to overcorrection, as a non-trivial proportion of woody material is covered by leaves during leaf-on conditions. Woody material is known to account for up to 35% of total plant area in forests, whilst recent work has demonstrated that uncorrected estimates of PAI may overestimate LAI by up to 61%. In this work, near-infrared DHP was proposed as a means of estimating and correcting for woody material during leaf-on conditions, but the approach was only tested at one deciduous broadleaf forest site in the United Kingdom. Therefore, the objective of the project is to evaluate the potential of near-infrared DHP over a wider range of sites and vegetation types. In doing so, the project will provide representative baseline WAI data that users of PAI from NEON’s routine DHP sampling may apply for a first-order woody material correction.