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Harvard Forest Symposium Abstract 2011

• Title: Using a Full-Waveform, Ground-Based, Scanning Lidar (Echidna®) To Retrieve Forest Vegetation Structural Parameters In Hardwood and Conifer Stands
• Primary Author: Alan Strahler (Boston University)
• Additional Authors: Darius Culvenor (CSIRO Sustainable Ecosystems, Australia); David Jupp (CSIRO Marine and Atmospheric Research, Australia); Jenny Lovell (CSIRO Marine and Atmospheric Research, Australia); Glenn Newnham (CSIRO Sustainable Ecosystems, Australia); Crystal Schaaf (Boston University); Curtis Woodcock (Boston University); Xiaoyuan Yang (Boston University); Tian Yao (Boston University); Feng Zhao (Boston University)
• Abstract:

  A ground-based, scanning, near-infrared (1064 nm) lidar, the Echidna® validation instrument (EVI), built by CSIRO Australia, retrieves structural parameters of forest stands rapidly and accurately, and by merging multiple scans into a single point cloud, also provides 3-D stand reconstructions.
  
  
  Deployments in New England in 2007 and the southern Sierra Nevada of California in 2008 tested the ability of the instrument to retrieve mean tree diameter, stem count density stems/ha), basal area, and above-ground woody biomass from single scans at points beneath the forest canopy. Parameters retrieved from five-scan averages in six 1-ha stand sites matched manually-measured parameters, R2 = 0.94–0.99 (New England) and 0.92–0.95 (Sierra Nevada). In New England, retrieved leaf area index (LAI) values were not significantly different from those of LAI-2000 and hemispherical photography (ANOVA β <= 0.16); and in the Sierra, R2 = 0.81 and 0.96. New England stand heights, obtained from foliage profiles, were not significantly different (β= 0.91) from LVIS RH100 values in 2003.
  
  
  Three-dimensional stand reconstruction identifies one or more “hits” along the pulse path; hits are classified as trunk, leaf, or ground returns using the shape of the return pulse and its location. Point clouds of hit locations, intensities, and object classes from overlapping scans are merged to produce the 3-D reconstruction, which can be used to measure individual DBH (R2 = 0.97) and tree height (R2 >= 0.98, compared to LVIS RH100 values.
  
  
  At the Harvard Forest, lidar scans and accompanying stem maps and measurements were acquired in 2007, 2009, and 2010. Sites included the hemlock stand south of the hemlock tower (Figure 1); a site south of the EMS tower; and a site in the Lyford plots area. Comparison of scans and measurements at the Lyford plot site shows a reduction in leaf area index related to the ice storm of December, 2008 (Figure 2). Three-dimensional reconstructions have been assembled for most Harvard Forest sites in most years.
  
  
  Supported by NASA grants NNG06GI92G and NNX08AE94A and NSF grant DBI-0923389.
  
  
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  Figure 1. An image of mean apparent reflectance as acquired by the Echidna lidar in the Harvard Forest hemlock stand. The image is shown in a plate carrée projection that displays the data by azimuth angle (x-axis) and zenith angle (y-axis).
  
  
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  Figure 2. 3-D reconstruction of a single tree at the Lyford plot site showing crown damage from the ice storm of December, 2008.

• Research Category: Ecological Informatics and Modelling


• Figures:
HF Hemlock Scan.jpg
Ice Damage Image B-W.jpg