Table 3. --Moisture response properties of ponderosa pine needles 

 and litter beds 



Material 



: Density 



: Packing 

 : ratio 



: Thickness : 



Timel ag 



: Diffusivity 





G/crn^ 





Cm 



c 

 o 





Cm^/s 





DESORPTION WITHOUT SOLAR 













Needles 



0.51 



1.0 



0.0695 



15,084 



1. 



oy 





-L U 



Dea 



.005 



.0098 



2.0 



io , DOO 



1 



27 



X 



10-5 



tseci 



. 015 



.0294 



2.0 





.1. 



12 



X 



10-5 



oeu 



.045 



.0882 



2.0 



1 Q QAS 



1. 



18 



X 



10-5 





ADSORPTION WITHOUT SOLAR 













Needles 



.51 



1.0 



.0695 



14,556 



1 



96 



X 



10-8 



Dea 



.005 



.0098 



2.0 



1 Q QRA 

 i y , y oD 



1 



18 



X 



10-5 



KeQ 



.015 



.0294 



2.0 



7 17/1 



1 



02 



X 



10-5 



Bed 



.045 



.0882 



2.0 



18,870 



1 

 1 



25 



X 



10-5 







DESORPTION 



WITH SOLAR 













DcU 



.005 



.0098 



2.0 



1 H , o y o 



1 



62 



X 



10-5 



DfciU 



.015 



.0294 



2.0 



1 9 X7? 

 1 z, , o / ^ 



1 



91 



X 



10-5 



Bed 



. 045 



.0882 



2.0 



9,240 



2 



56 



X 



10-5 







ADSORPTION 



AFTER SOLAR 













Bed 



.005 



.0098 



2.0 



22,974 



1 



03 



X 



10-5 



Bed 



.015 



.0294 



2.0 



24,408 



9 



.68 



X 



10-6 



Bed 



.045 



.0882 



2.0 



24,678 



9 



.57 



X 



10-6 



For the Missoula area, the diffusivity of the free air was calculated to be 0.292 cm^/s. 

 For the voids within the fuel beds, the approach cited by Fosberg (1975) was used. 

 Work by Millington and Shearer (1971) shows the reduction in diffusivity to be a 

 function of bed porosity: 



V /v^ = ())2X (9) 



and the exponent, x , is defined by 



H 1 - (1 - (j))'', tortuosity factor (10) 



where 



free air diffusivity, cm^/s 

 void diffusivity, cm^/s 



bed porosity, fraction of volume, diraensionless . 



18 



