28 JOURNAL 01'' FORESTRY 



result of differences in the degree of protection from wind or high 

 temperatures. It was finally realized, however, that differences in soil 

 moisture were responsible for the variations in the effect of the drought, 

 and that the soil moisture was, perhaps, more dependent on the depth 

 of water table than on the water-holding capacity of the soil. That the 

 latter condition bad an important bearing on the eft'ect of this hot 

 wave was shown in instances in which the water table was at such a 

 depth that the trees could hardly have obtained much moisture from it. 

 The character of the soil, indicated by the moisture equivalent, in- 

 fluenced the amount of damage to a striking degree. On sandy soils 

 the damage was far greater than any other kind of soil. This was 

 especially noticeable at Fontana. Here the soil is pure sand of great 

 depth, and hundreds of trees, planted for windbreaks about young 

 citrus groves, were killed. There was little difference in the amount 

 or character of injury to trees growing in sand and in clay. However, 

 where the water table lay fairly close to the surface and was. therefore, 

 within easy reach of the root systems, trees on clay soils suffered only 

 slightly if at all. Trees on loamy soils, as a rule, were injured con- 

 siderably less than trees on any other type of soil, apparently being 

 more or less independent of the depth of the water table. This was 

 strikingly seen near Cucamunga, where a long row of gray gums had 

 been planted. The earth in which these trees grew varies from a 

 sandy soil at the foot of the hill, through a loamy soil at the middle 

 elevations, to a heavy adobe at the upper end. Progressively from the 

 foot of the hill to the top, the trees showed, first, almost complete 

 destruction of foliage ; then a heavy though partial defoliation ; at 

 the center, very little injury of any kind ; then, again, a partial leaf 

 injury; and, finally, at the end of the row in the clay type of soil, com- 

 plete loss of all leaves and the death of the trees. Near Azusa there 

 were considerable plantings and these showed the effect of this heat 

 wave. Trees in the lower belt of the hills, where the soil is decidedly 

 gravelly, suffered severely from the loss of their foliage, but the trees 

 farther up the hill, where the soil is heavier, were much more free 

 from injury. At the Del Rosa plantations, two species. Eucalyptus 

 rostrafa and B. tereticornis, are planted on a long slope, ranging from 

 a sandy w-ash to a heavy adobe soil farther up the hill, a distance of 

 about T.J yards. The effect on these trees was similar to the effect on 

 those in the other place. The trees in the sandy wash and those at the 

 top of the hill on the heavy soil lost the major part of their crowns, 

 but those on the loamy soils of the middle elevations lost only a small 



