Down Woody Materials
The Down Woody Materials Indicator is the measurement of fallen trees, dead branches, and large fragments of wood on or near the forest floor. Small branches less than 3 inches in diameter are measured as fine woody debris (FWD), while larger branches and down trees are measured as coarse woody debris (CWD). For coarse woody debris, the DWM inventory records the species, sizes, holes, and stages of decay. In addition to CWD and FWD, this survey measures the depth of the litter/duff layers and fuel bed. The height and cover of standing live and dead shrubs/herbs are also measured to quantify these pools of biomass.
The FIA sampling design consists of three phases, of which DWM constitutes part of the third phase. During the first phase of inventory, sample points are randomly placed within a hexagonal grid across the entire United States. Each sample point is assigned to either non forest, forest/non forest, or forest classes based on remotely sensed imagery.
The second phase involves field crews visiting all forest/non forest and forested sample points to establish permanent sample plots. Each sample plot consists of a cluster of four subplots, each subplot having a fixed-radius of 24 feet. On all these sample plots, individual tree information (e.g., diameter and height) as well as site information (e.g., slope and land use) is collected for the forested portions of the sample plot.
During the third phase, a randomly selected sub sample of field established phase 2 plots are visited to collect forest health information. Critical data are collected pertaining to specific forest health issues such as soils, understory vegetation, and tree damage. These specific forest health issues are referred to as "Indicators of Forest Health."
Why sample Down Woody Material?
Down Woody Material inventories serve as an indicator of forest health. Scientists from many disciplines may use DWM data to quantify numerous aspects of forest ecosystems.
The DWM inventory, coupled with the entire integrated FIA program, can provide
unbiased and empirically derived information about our Nation's forest ecosystems
to policymakers, scientists, States, and concerned citizens as a whole.
DWM inventories provide estimates of fuel loadings by 1-hour, 10-hour, 100-hour, 1000-hour+, duff, and litter classes. Additionally, estimates of Fuel bed depths and Micro plot vegetative structures can provide estimates of the spatial aspects of fuel. Coupled with the entire FIA inventory, the DWM inventory may indicate levels of fire hazard at strategic scales across the United States. This assessment of forest fuels across the country has never been done and can greatly aid efforts to reduce fire hazards faced by our forests and adjacent communities.
The DWM inventory, in combination with the soils and FIA Phase 2 inventory, can aid in estimating carbon pools for the United States. Our Nation, in alliance with the international community, seeks to better quantify carbon pools in our forest ecosystems. This quantification of the carbon budget can aid efforts to better understand climate change and the role of forest carbon dynamics in climate change.
DWM serves as critical habitat for many wildlife species. From "nurse logs" in the Pacific Northwest to hollow oak logs in the Southeast, numerous species find their ecological niche in the shelter that DWM provides. With the possibility of dwindling habitat for many native animal species across our Nation, inventories of DWM will be crucial to any wildlife conservation efforts.
Last Modified: 02/06/2007