EMORY OAK IN SOUTHERN ARIZONA. 



Emory oak (Quercus emoryi) forms one of the most important 

 types of the open woodland forest of the Southwest, and is the most 

 common oak in the mountains of southern New Mexico and Arizona. 

 It affords protection to watersheds, and has high value for fuel in 

 a region where wood is scarce. Also, there is a possibility that 

 its bark, which is fairly rich in tannin, may become a source of tannic 

 acid for the Southwest. 



RANGE AND OCCURRENCE. 



The east and west range of Emory oak is from western Texas to 

 the western slopes of the Pajarito Mountains, Ariz.; from north 

 to south it occurs from the south-central portion of Arizona (south 

 of the Colorado Plateau) to the south-central part of the Province 

 of Chihuahua, Mexico. In Texas it grows on most of the mountain 

 ranges west of the Pecos River, and is especially abundant in the 

 canyons and on the southern slopes of the Limpio and Chisos Moun- 

 tains. Its best development in the United States is probably in 

 the Garces National Forest, in southern Arizona, where it furnishes 

 at least half of the timber supply. Here it is valued for fuel more 

 than any other native oak. 



CLIMATE. 



The climate typical of the region within which Emory oak grows 

 is that of the mountains along the Mexican border, where the two 

 rainy seasons are from November to March, inclusive, and from 

 July to September. At the base of the foothills the average annual 

 precipitation is approximately from 11 to 12 inches; but in the 

 mountains it may be as much as 25 inches for a series of years, or 

 even more in exceptional years. 



The winter rains, which are very irregular, originate on the Pacific 

 coast, and are usually preceded by easterly winds. They are not 

 as torrential as the summer rains, which originate in the Tropics. 

 From these the precipitation comes mainly during the afternoon or 

 evening in the form of heavy local thunderstorms, which occur 



3 



