EMORY OAK IN SOUTHERN ARIZONA. 



cents a pound, even when the supply is plentiful. Birds, bears, and 

 rodents eat the acorns, and many are spoiled by insect larvae. 



Since most of the stands have not been touched by the ax, the 

 sprouts originate from injury to seedling growth, the principal 

 sources of injury being fire, grazing, drought, or frost. These sprouts 

 have been designated "injury sprouts/' in contrast to the utiliza- 

 tion or stump sprouts. Fire has been the chief source of injury, 

 the fires having been set in the interest of the grazing industry, 

 and rarely extinguished except where they threatened houses. 

 Most of the stools represent many generations of sprouts, and none 

 less than two generations. Since the damage from grazing and from 

 unfavorable climatic conditions is restricted to seedlings or shoots, 

 fire and cutting account for the origin of most of the stands. 



Trees have been cut only near towns and mining camps, and since 

 the stumps persist for at least 35 years, the resulting sprouts clearly 

 show their origin. Stump sprouts, like injury sprouts, spring from 

 the root collar, with but few exceptions. In the valleys only from 

 1 to 6 per cent of the stump sprouts come from the stem, and in all 

 cases these were fewer in number and weaker in growth than those 

 from the root collar. The reason for this lack of sprouting above 

 the roots is found in the dryness of the climate and the consequent 

 shrinking of the wood away from the bark, so that there is but slight 

 chance for the formation of a callus. In the narrow valleys at higher 

 elevations there was a slightly greater proportion of stem sprouts 

 from 2 to 10 per cent due largely to lower stump heights, smaller 

 diameter, and better atmospheric conditions. But even in stumps 

 cut close to the ground most of the growth comes from dormant buds 

 at the root coUar. 



Careful counts showed that there is little if any difference in the 

 sprouting capacity between the north and south sides of the stumps, 

 and the shade of the stump evidently has no protective influence. 



Small stumps are more likely to produce sprouts and sprouts of 

 greater vigor than large stumps. 



As with other broadleaf trees, the season of cutting has a decided 

 influence on the sprouting capacity of the resultant stump, and sum- 

 mer cutting is most likely to result in the death of the stump. When 

 land is to be cleared for cultivation the trees are cut in August or are 

 girdled then and cut the following year. Emory oak is locally con- 

 sidered a tree which it is hard to kill simply by cutting. Nevertheless, 

 on many cut-over slopes in the Pajarito Mountains the sprout growth 

 has failed entirely on areas immediately adjoining thrifty stands of 

 stump coppice. It appears, therefore, that the season, or possibly the 

 method of cutting, or the occurrence of a severe drought have caused 

 the failure. It seems reasonable that the best time for cutting to 

 secure coppice growth is between November and April. 



