A NATIONAL PLAN FOR AMERICAN FORESTRY 705 



rots than did the original stands. For other types of disease it would 

 be altogether unsafe to predict any diminution in damage and it is 

 entirely possible that our new forests will be considerably less healthy 

 in some respects than the old ones. 



RELATION OF FOREST DISEASES TO RECREATIONAL USE AND 

 WATERSHED PROTECTION 



The foregoing discussion of diseases has been limited to forests as 

 sources of wood. Two other uses of forest land of increasing impor- 

 tance are for recreation and for watershed protection. The patholog- 

 ical problems connected with these uses differ in a number of respects 

 from the problems connected with the growing of timber. High 

 elevation forests and forested areas near cities, often low in timber- 

 producing capacity and growing under quite different conditions 

 from those in the best timber stands, are among the most valuable 

 for these other purposes. There is an increasing number of forest 

 areas that are set aside for municipal water supply, or as national, 

 State or local parks entirely for recreation, in which the standards for 

 judging diseases and the practices that influence them are very 

 different from those previously considered. 



The effect of native diseases on watershed protection is apparently 

 slight. So far as our present knowledge goes, native diseases do not 

 materially lower the efficiency of forest cover either in delaying run- 

 off of water or in preventing erosion. It is altogether probable that 

 in some places, particularly in the drier parts of the country, diseases 

 do reduce the production of litter sufficiently to lessen the water- 

 absorbing capacity of the forest floor ; or that they operate to keep the 

 finer roots from occupying and holding the surface soil to the normal 

 extent. Such effects are not conspicuous and careful experiments 

 continued through a period of years, too expensive to be justified 

 under present conditions, would be needed to determine their im- 

 portance. 



The relation of forest pathology to recreational use is not so simple. 

 It is true that there is no obvious way in which ordinary diseases 

 impair the value of the forest for game purposes. In areas used 

 primarily for recreation, tree diseases, generally speaking, are of 

 importance only when they detract from the beauty of the landscape 

 or upset the natural balance of plant associations which should be 

 maintained so far as possible. Heart rots and growth-reducing 

 diseases that might make the difference between profit and loss in a 

 timber-growing project have much less effect on aesthetic values; in 

 fact to some people, hollow trunks and gnarly or irregular crowns 

 make trees more picturesque. However, killing diseases often 

 materially hurt the appearance of the forest. Trunk and butt rots 

 predispose to windbreak and windthrow and such trees are dangerous 

 in the immediate vicinity of roads, trails, and camps. Diseases 

 which cause a conspicuous amount of unsightly yellow and brown 

 dying foliage are sometimes very objectionable. 



Incongruous though it may seem, the genus Homo, for whose 

 pleasure these tracts have been set aside, continues to be the chief 

 menace to their beauty and permanence, and many areas, especially 

 in the vicinity of hotels, camp and picnic grounds, have already been 

 damaged to such an extent as to impair their value for decades, if 

 not for all time. Continual trampling of feet and frequent building 



