8 



EMORY OAK IN SOUTHERN ARIZONA. 



Table 1 shows that the height growth is slow and the diameter 

 growth fairly rapid, and that, at the start, the growth of stump 

 sprouts is better than that of injury sprouts. Yet, at 35 years, 

 the rate of height growth of the injury sprouts is 2.2 feet in 5 years 

 as against only 1.6 feet for those from the stump; and the rate of 

 diameter growth of injury sprouts for the same period is 1.15 inches 

 and only 1 inch for the stump sprouts. This difference is probably 

 attributable to the fact that the injury stools are younger, and 

 therefore more vigorous. At the same time it must be understood 

 that the larger number of sprouts from a stump will more than 

 compensate in actual volume of wood production for a greater 

 growth of the individual injury sprouts. Moreover, the stump 

 sprouts tend to have a greater clear length than the injury sprouts. 



In order to secure an exact idea of the effect of elevation on growth 

 measurements were taken at intervals of 100 feet on a northeast 

 slope, the summit of which was 350 feet above the valley, with an 

 absolute elevation of 5,800 feet. That increase in elevation results in 

 decreased growth is shown in Table 2. The differences in growth 

 may be ascribed primarily to differences in soil depth, soil moisture, 

 and protection from wind, all of these influences being more favorable 

 at the bases of the slopes. 



TABLE 2. Influence of elevation on height and diameter growth in slope stands. 



REPRODUCTION. 



Although Emory oak produces seed abundantly, and much of this 

 seed germinates to furnish the original seedlings from which subse- 

 quent sprouts develop, reproduction is due almost entirely to sprout 

 growth. Coppice growth is evident everywhere, but even where this 

 is only one straight stem, as in the broad valleys, careful examina- 

 tion will reveal its sprout origin. In fact, diligent search for a dis- 

 tinctly seedling growth failed to disclose a single example. While 

 more actual seedling reproduction would ensue if fires and grazing 

 did not kill back the growth, another reason for the comparative 

 lack of seedling growth is the destruction of the acorns themselves. 

 These usually ripen in August and are a staple article of food with 

 the Indians and Mexicans, who collect them in immense quantities, 

 gathering them from the ground. In a good year one man can pick 

 up 50 pounds of acorns in a day, and they sell for not less than 5 



