1906 



FORESTRY AND IRRIGATION 



549 



produces but how it grows in the for- 

 est, how well it succeeds in holding its 

 own, unaided, in competition with 

 other, less valuable, rival trees. Upon 

 this knowledge depends our choice or 

 control of species in forest manage- 

 ment, and the details of the manage- 

 ment. Without it, we can make but a 

 sorry showing as technical foresters 

 and can expect only loss in the long 

 run in our account with the forest as 

 business men. No amount of time in- 

 telligently given to silvics can be wast- 

 ed ; the very fullest opportunities 

 should be found, or made, to facilitate 

 the investigation and classification of 

 the forest habits and behavior of our 

 commercial species. It is largely by 

 his superior wisdom in this lore that 

 the forester is able to show the way to 

 the lumberman, who in most of the 

 other branches of practical forestry 

 has the clear advantage which comes 

 of experience learned in the school of 

 necessity. It is the lumberman's busi- 

 ness to know everything about the 

 business side of the forest. As soon 

 as the forester is prepared to show 

 him the business of silvics, lumberman 

 and forester, as wood growers, will 

 stand evenly abreast. 



Without full knowledge of silvics 

 grave mistakes easily occur in forest 

 management. A little misunderstand- 

 ing as to the comparative reproductiv- 

 ity, growth-rate, tolerance, or root- 

 firmness of two species may too surely 

 result in the supremacy of an inferior 

 tree and heavy financial loss in the 

 eventual yield of a vast tract. A little 

 misjudgment in the selection of a di- 

 ameter limit, based on false silvical 

 facts, may, by its effects on the after 

 forest, prove far costlier than clean 

 cutting would have been, with all the 

 expense of planting and the longer 

 wait for the new crop duly counted in. 



Our silvical knowledge, though 

 growing, is still very incomplete. By 

 whatever means may prove most effi- 

 cient and economical, every effort 

 should be made to add to it, to give it 

 due weight, and to draw upon it sys- 

 tematically. In the Forest Service sil- 

 vics has long been eagerly pushed, and 



now that the reserves offer such excel- 

 lent experimental areas, it is hoped 

 that the science will gain added im- 

 petus. 



Our silvics has been first mentioned 

 because it stands first in importance 

 for the science and practice of forestry 

 considered as the means of controlling 

 the production of wood. Quite as im- 

 portant economically is the problem of 

 forests and water supply. In foreign 

 countries this has been studied ex- 

 haustively, and the invaluable function 

 of the forest in impounding and gradu- 

 ating to a useful rate of run-off the 

 rainfall on a given area has been -es- 

 tablished and reduced to conclusive 

 figures. No competent and impartial 

 person doubts for a moment that this 

 function of the forest is as active and 

 vital in our own country. Without 

 reference to the general physical laws 

 on which it is based laws which are, 

 of course, broadly the same every- 

 where and always it has been abun- 

 dantly verified by observers in regions 

 where the forest, once normal, has 

 been depleted or destroyed. But here 

 again the newness of the conditions, 

 differences of topography, climate, 

 soil, and soil-cover, confront the Amer- 

 ican forester virtually with a fresh 

 problem, the details of which in their 

 local significance he must work out 

 for himself. Investigations of rainfall 

 and run-off from well forested and 

 from sparsely covered or denuded 

 slopes, particularly over our western 

 area of scant or unequal precipitation, 

 are much needed as a means of devel- 

 oping to its fullest capacity the ac- 

 knowledged usefulness of the forest 

 as a water conservator. 



Another line of investigation, close- 

 ly allied to the last, is more purely 

 scientific, less directly practical, but of 

 very high universal economic value. 

 This is the relation of the forests to 

 climate. Though it is generally accept- 

 ed by European foresters that climate 

 is not appreciably affected by the pres- 

 ence or absence of forests, it may be 

 that this position is supported only 

 within the area limits covered by the 

 foreign investigations. It is perfectly 



