Table 3.--Windspeed ratio U /U. 



: Tolerant species : Intolerant species 



Stocking : Young : Mature : Pacific : Young : Mature : Pacific 

 level : 40' : 100' : 180' : 40' : 100' : 180' 



Dense 0.155 0.113 0.084 0.220 0.196 0.146 



Open 0.293 0.210 0.156 0.332 0.248 0.185 



Three "typical" tree heights are used in this table to represent 

 young stands (40 ft), mature stands (100 ft) and old-growth Pacific 

 Coast stands (180 ft) . For the latter, the crovm ratios of "mature" 

 stands from table 2 were used. 



Since applies (almost) all the way to the ground, it is the "midflame" windspeed. 



Hence the "midflame" windspeed in relation to the windspeed 20 ft over the canopy can 

 be found by using equation (4) and choosing the ratio U^/U^^ from table 3 or calculating 

 it from equation (20) . 



The equation for calculating for stands with arbitrary values of f and H is: 



U^/U2Q+^ = 0.555y 



VfH in ^ 



(20 + 0.36H) /0.13H 



(21 



o o 



50 100 150 200 



HEIGHT OF UNIFORM CANOPY TOP, FT 



Fig. 2. Ratio of windspeed within (and helow) forest canopy to windspeed 20 ft above 

 canopy top . 



9 



