FANR5640/7640: Lab 10 – CWD Volume


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Lab 10: Coarse woody debris volume remaining after harvest

[Excerpt from Brian Davis’ 2017 thesis,”REFINEMENT OF A DRONE-BASED METHOD FOR ESTIMATING COARSE WOODY DEBRIS AND BIOMASS RESIDUE FOLLOWING FOREST HARVEST”]

"… Pine forests of the southern US are a major source of woody debris residues used for bioenergy (Milbrandt 2005). “In 2012, approximately 40% of the world’s biomass fuel, in the form of wood pellets created from CWD harvest, was exported from the United State to Europe (REN21 2013), most from the southern US. Estimates are that 60% of the world renewable energy could be in the form of biomass fuel by 2030 (IRENA 2014). With such a large and growing market for the biomass fuel, the need for accurate, quick estimation of CWD residue has never been greater. From an operational standpoint, contractors need means of estimating biomass to plan harvests and schedule equipment. From a regulatory standpoint, estimates of retained biomass are needed to ensure compliance with biomass retention guidelines…"

Current methods of determining the volume of coarse woody debris (CWD) remaining after harvest are time-consuming and not very accurate. In this lab, you will use the orthophoto output from a drone flight to estimate the volume of residual CWD on a recently harvested site.

LAB DATA

Download the lab data HERE. This zipped file contains a Rimes tract data set and an ExhibitB tract dataset. Each site has an orthophoto and a plot boundary. All of the data use the UTM/Zone 17N/NAD1983/METERS coordinate system.

SCATTERED COARSE WOODY DEBRIS

Use the Rimes data set to determine the m3 volume of residual scattered coarse woody debris remaining after harvest on this site (really only within the 10m x 10m plot).

Workflow:

  • Digitize a line over any piece of CWD within the 10mx10m plot
    • Limit yourself to pieces of CWD that are greater than 7.5 cm in diameter
  • Use your GIS’ length calculation capabilities to calculate length of each line segment
  • Determine each stem’s volume
    • Assume each stem is a cylinder; volume = PI*r^2*Length
  • Sum the volumes

Digitizing a line in ArcMap:

  • Start a new instance of ArcMap; save your project in the same folder as your data
  • Create a new line shapefile in the Catalog (right-click on home folder > New > Shapefile); data are in UTM/Zone17/NAD1983/Meters
  • Start Editing your new layer (right-click on layer > Edit Features > Start Editing)
  • Digitize CWD stems that are larger than 7.5cm in diameter
  • Stop Editing (Editor > Stop Editing; Save Edits? YES)
  • Add myLength and myVolume fields
    • Open attribute table; click on the table options button in the upper left > New Field
      • New field should be a FLOAT type
  • Calculate length of each stem (right-click on the myLength field > Calculate Geometry > …)
  • Calculate volume of each stem using the Field Calculator
    • I recommend measuring the diameter of the large stems and
    • Use an average diameter for small stems (use the measuring tool to determine this)
  • Use the Summarize command (attribute table > right-click on myVolume field > Summarize) to determine total volume of each stem

ORIENTED COARSE WOODY DEBRIS

Repeat the above process to determine the volume of pile #6 on the ExhibitB site (this time use the ExhibitB data).

Lab 10 deliverables

Upload to our Lab 10 ELC assignment dropbox:

  • Report the cubic-meter volume of CWD (>7.5cm in diameter) remaining in the Rimes 10mx10m plot.  (+5 points if within 100% of my estimate, +4 if within 150%)
  • Report the cubic-meter volume of pile #6 on the ExhibitB tract.  (+5 points if within 100% of my estimate, +4 if within 150%)