ROLE OF FIRE IN CALIFORNIA PINE FORESTS 89 
A curve drawn through the plotting of these generalized figures in- 
dicates that 50 per cent stocking or better appeared on only 22 per 
cent stock of the area. Nearly a third of the area is entirely de- 
nuded, while two-thirds show only 334 per cent stocking. Only one- 
twentieth of the entire area boasts more than 83 per cent of normal 
density of young growth. | 
It has already been shown that in many places repeated fires ulti- 
mately either deteriorate the site to a point where timber will no longer 
erow, or change the type from a desirable to a very inferior one. 
Fires on cut-over lands often duplicate at a single stroke these pro- 
found changes of site and type that in the virgin forest may require 
decades. An example of site deterioration is illustrated in Plate VII, 
Figure 1, by aphotograph taken seven years after logging opera- 
tions that were followed the next summer by a severe slash fire. A 
cruise line on the cut-over area showed in 14 miles only two living 
seedlings and no seed trees. In addition, the rabbit brush (Chryso- 
thamnus) that has occupied the area is indicative of reversion to a non- 
timber site and it is certain that the forest will not return naturally 
to this area for many tree generations. 
Sometimes the change is from commercial timber to an inferior type. 
One area, originally a western yellow-pine white-fir type, was logged 
in 1913 and a slash fire followed the logging. A large amount of 
lodgepole pine reproduction has come in, and it seems evident that 
the future forest on the area. will be composed principally of this less 
desirable species. 
FIRE IN BRUSH FIELDS 
SITE DETERIORATION 
The cumulative effects of repeated fires in forming brush fields and 
reducing the yield of timber are but different phases and stages of 
the general process of attrition. The end of this process is destruc- 
tion of all merchantable timber. The history of forests throughout 
the world teaches this one lesson of outstanding significance: Con- 
tinued abuse of the forest, through either excessive cutting, burning, 
grazing, or other agency, results in the final obliteration of the forest 
cover and such deterioration of the site that timber will no longer grow 
there. In extreme cases, no cover at all will grow. One of the princi- 
pal results of continued burning in parts of the California pine region 
has been the repetition of this process of site retrogression. The forest 
has been more susceptible in the lower limits of the timber belt, 
since at best it must struggle severely to maintain itself along this tran- 
sition zone in competition with the more drought-resisting plants. 
The same climatic factors which make reproduction of the forest more 
difficult also create critical fire conditions, so that fires are not only 
more frequent, but burn with greater intensity and destructiveness. 
It is therefore not surprising to find that at these lower limits the 
forest itself has been pushed back and the potentiality of the land to 
sustain timber has been destroyed, for many years at least. The 
ravages of successive fires, followed by erosion and leaching, have 
here critically reduced the fertility and the amount of the soil. (Pl. 
Ei efe 2%) 
