We have created three databases, two CWD and one FWD, that can be combined with woody detritus volume data to calculate the mass of this material (Appendices 2, 3,and 4). For both FWD and CWD we present the density in either absolute or relative terms. In the case of FWD we report the estimates for absolute and relative density for each of three size classes in one database. For CWD we report the estimates for the five decay classes in separate absolute and relative density databases. For each estimate, except undecayed CWD, we present a code for the method of estimation, as described in the methods, that determines the uncertainty of the estimate. While the absolute density values are probably the easiest to use, the relative density values helps one understand how the absolute densities were calculated. In addition to an estimate of the most likely value (i.e., the mean or median value depending on how the estimate was made) we also present an uncertainty value. This is analogous to one standard error of the mean, therefore to approximate the 95% confidence intervals the estimated uncertainty needs to be multiplied by 2 and then added and subtracted from the most likely value.

For both FWD and CWD the majority of species have not been sampled, and therefore the uncertainty is generally high. For CWD, of the 260 species considered by the FIA inventory 53 (20%) have been sampled for at least some decay classes. While sampling more species and genera would improve estimates, it should be noted that many major genera have been sampled. For FWD very few species-size class combinations have been sampled, with only 25 of the possible 1046 combinations with actual data. The low proportion of combinations being sampled (2%) has lead to a very high uncertainty in FWD density estimates.