224 



FORESTRY AND IRRIGATION 



May 



is conservative to place the average 

 annual rainfall for the watershed in 

 question at 25 inches. There is one 

 pronounced rainy season, and this 

 comes in July and August, usually 

 closing in September. At this season 

 the sweltering people of our cities 

 north and east would do well to come 

 to southwestern New Mexico for their 

 summer resort. The mercury finds the 

 midsummer forenoon too short to rise 

 higher than 85 degrees Fahrenheit, 



where the air is quiet and several de- 

 grees warmer than in the neighboring 

 valley. Here is encountered at night 

 a stream of cold air on its way from 

 the mountains to the plain, there to 

 replace the heated atmosphere of the 

 day. The light snows and rains that 

 usually fall during the mild winter 

 suffer comparatively little by evapo- 

 ration and transpiration. When the 

 warmth of spring reappears, this 

 moisture is quickly utilized bv the veg- 



Photo by W. R. Matoon. 



General View of Bull Pine on North Slope in center and along stream. Juniper and 

 Blue Oak Chapparal on other slopes. Streams run dry except at time of floods; 

 and where fed by a few precious springs. 



rarely does it venture above this point. 

 By noon the warm air has ascended to 

 the mountain tops, comes in contact 

 with cooler bodies here and is con- 

 densed, clouds begin to lower and de- 

 scend through the keen atmosphere, 

 and soon to refresh the entire moun- 

 tain side by shade, or gentle shower, 

 or bursting torrent. The nights are 

 always cool. In autumn it is found ad- 

 visable to pitch camp upon a knoll, 



etation, and it makes as quickened 

 growth. As the drouth and parching 

 heat of spring advances, this growth 

 recedes to a minimum, takes on new 

 impulse and fresh color with the be- 

 nignant midsummer showers, only to 

 dwindle and fade a second time with 

 the approach of winter. 



Thus we find in evergreen trees the 

 phenomenon of two annual rings 

 formed within one year. Since many 



