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Methods

Down Woody Material is sampled on FIA sample plots using line intersect methods. Line intersect methods for estimating volumes of small fuels involve counting the intersections of downed woody pieces with vertical sampling planes positioned within the fuel complex. Intersected particles are tallied by diameter classes, and volume is calculated from representative diameters for each class. These methods avoid the costly, often impractical task of collecting and weighing large quantities of forest debris. These methodologies have been embraced by foresters as an effective and efficient method of sampling downed woody materials over numerous decades of field application.

The main categories of DWM sampled for estimation by FIA are fine woody debris, coarse woody debris, duff, litter, Fuel bed depth, residue piles, and dead/live shrub/herb biomass.

FIA uses a combination of transect lines, depth samples of duff/litter/Fuel bed depths, and a Micro plot (6.8 ft) for shrub and herb measurement for the estimation of numerous DWM parameters.

The following document, “Woodall, C.W., and M.S. Williams.  2005.  Sampling protocols, estimation procedures, and analytical guidelines for down woody materials indicator of the Forest Inventory and Analysis Program.  USDA Forest Service, Gen. Tech . Rep. 256, North Central Research Station.  47 p.” details numerous aspects of the DWM indicator, especially estimation procedures.  Although released in 2005, the report is already in revision with incorporation of Phase 2 population estimation information.  A revised version is expected to be released in 2007.