RESEARCH SUMMARY 



Sorption studies of ponderosa pine (Pinus ponderosa Laws.) needles 

 and litter beds of current year cast show a shorter response time and 

 lower equilibrium moisture contents than most other conifer needle data 

 in the literature. For conditions below fiber saturation, the response 

 time is described best by considering the time for 95 percent of the total 

 change in moisture content. Equilibrium moisture content can be esti- 

 mated by an equation based on temperature and humidity, but type of 

 vegetation must be considered. 



Analysis of moisture response at the test conditions indicates that 

 the moisture diffusivity of the needles and beds remains nearly constant 

 for both adsorption and desorption. 



