138 MINNESOTA STATE HORTICULTURAL SOCIETY. 



shade of the former and escaped or resisted the destructive agencies will 

 occupy the ground. 



Especially the different requirements in regard to light conditions and 

 the relative rate of height growth, by which the species or individual 

 may or may not escape suppression by its neighbors, influence the tempo- 

 rary local distribution of plants and are of the greatest interest to the 

 forest manager. 



Light is one of the essential factors of tree growth, and alnost the only 

 one which man can regulate. Forest management, then, could be defined 

 in the main as management of light conditions. The leaves functionate 

 under the influence of light and feed the tree by assimilating the carbon 

 of the air. Such thinly foliaged trees as the aspen and some of the birches 

 and others can only exist under a full complement of sunlight; they are, 

 therefore, endowed with a rapid rate of height growth to enable them to 

 grow quickly out of the danger of being overshadowed by their neighbors. 

 Other species, like the firs, and in less degree the spruces, with a dense 

 foliage and a large number of leaves to functionate, can be satisfied with 

 less light and are as a rule slower growers; other kinds again, like the oak, 

 while dependent for their full development on a large amount of light, 

 probably by virtue of specially vigorous root action can persist in the 

 shade for a long time until more favorable light conditions allow thrifty 

 growth. 



Especially the young seedlings of most kinds are very sensitive in regard 

 to light conditions, and some have such a small range of light and shade 

 endurance that, while there may be millions of little seedlings sprouted, 

 they will all perish if some of the mother trees are not removed and more 

 light given; and they will perish equally, if the old growth is removed at 

 once and the delicate leaf structure under the influence of the direct sun- 

 light and heat is made to functionate beyond its powers. 



We can, then, understand that not only the different species, but the 

 same species at different periods of life, make varying demands in regard 

 to light conditions, and the art of the forest manager in securing repro- 

 duction, as well as in other operations, thinning, etc , consists mainly in 

 a proper regulation of light conditions by proper and timely use of the 

 axe. 



The composition of the forest, climatic, soil and moisture conditions 

 modify again the requirements, so that all general rules of management 

 need to be modified according to local conditions, and it will appear at 

 once that a considerable exercise of judgment, born from experience and 

 knowledge, is expected of the forest manager. 



The practice of the forest manager then is to assist the desirable species 

 in the struggle for existence and supremacy, to antagonize the undesirable 

 ones, and to create proper conditions of soil, light and composition of 

 species for a desirable reproduction. 



The practice of thinning is based on similar principles. Eegard to the 

 danger of windfalls, of fires, of frosts to the young plants, etc., will also 

 influence the management. 



So much for the technical part of forest management. 



Before concluding I want to call your attention to the improper clearing 

 of lands for agricultural use; cold, thin, stony and rocky sites and de- 

 clivities are devoted to farming, yielding only a precarious living to the 



