EVERGREENS OF COLORADO 69 



cumulated in the shelter of evergreen forests due to shading and dimin- 

 ished air currents. It has been found that those forests which contain 

 numerous open spaces or glades of small area into which the snow readily 

 finds its way, give the maximum protection to the snow, while the 

 densest forest cover, which tends to keep some of the snow from reaching 

 the ground beneath, falls considerably behind. Much of the benefit due 

 to forest growth upon the higher and more exposed levels was found 

 to be in the catching of the 

 snow which would otherwise 

 be blown off to lower levels 

 where earlier melting occurs.* 

 Another condition which is 

 brought about by the presence 

 of forests is that due to the 

 deposits of decaying organic 

 matter from the trees them- 

 selves. This duff or humus, 

 consisting of the cast-off 

 leaves, shreds of bark, twigs 

 and branches, withered flow- 

 ers and fallen cones, accumu- 

 lates very slowly during the 

 years that a forest is growing 

 to maturity. The soil also is 

 completely filled with a net- 

 work of fine rootlets within 

 a fairly dense stand of tim- 

 ber, so that it is held in place 

 and prevented from washing 

 under the impact of heavy 

 rainfalls. Under such condi- 

 tions, the forest floor tends to 

 readily absorb water and to 

 allow it to percolate into the 

 underground channels of 

 springs instead of rushing 

 over the surface to the near- 

 est water course. 



Fig". 



Water and trees 

 spot attractive. 



make this 



A forested mountain slope, therefore, tends to regulate and prolong 

 the stream flow and favors the better utilization of the water during the 

 entire growing season in the valleys below. While the value of a forest 

 cover upon mountain slopes has been a well established fact in the 

 countries of Europe, where forestry has been carried on for many years, 

 it has been particularly emphasized in our own country during the past 



* Recent Studies of Snow in the United States, by J. B. Church, Jr., 

 from the Quarterly Journal of the Royal Meterological Society, Vol XL, 

 No. 169, 1914. 



