The ponderosa pine (Pinus ponderosa Laws.) timber type covers nearly 9 million acres in the Rocky Mountains. The needle litter cast by these trees produces a highly flammable fuel when conditions are dry. The capability for fires to start and spread depends largely on the moisture content of surface fuels and their response to environmental changes. This report summarizes the results of laboratory tests to determine equilibrium moisture contents and absorption-desorption timelags below fiber saturation of ponderosa pine needles. Conducting the tests at conditions below fiber saturation eliminated consideration of the movement of free water and possible leaching of the needles.
United States Department of Agriculture, Forest Service, "Timelag and Equililbrium Moisture Content of Ponderosa Pine Needles" (1978). Forestry. Paper 6.