FORESTRY AND CONSERVATION 341 



There are, to be sure, different natural types of development, 

 some, like the walnuts, oaks, beeches, and the broad-leafed trees gen- 

 erally, having greater tendency to spread than others, like spruces, 

 firs, and conifers in general, which lengthen their shaft in preference 

 to spreading, even in the open. This tendency to spreading is also 

 influenced by soil conditions and climate, as well as by the age of 

 the tree. When the trees cease to grow in height, their crowns 

 broaden, and this takes place sooner in shallow soils than in deep, 

 moist ones; but the tendency can be checked and all can be made 

 to develop the shaft at the expense of the branches by proper shading 

 from the sides. 



It follows that the forest planter, who desires to produce long 

 and clean shafts and best working quality of timber, must secure 

 and maintain side shade by a close stand, while the landscape gar- 

 dener, who desires characteristic form, must maintain an open 

 stand and full enjoyment of light for his trees. 



Now, as we have seen, different species afford different amounts 

 of shade, and in proportion to the shade which they afford can they 

 endure shade. The beech or sugar maple or spruce, which maintain 

 a large amount of foliage under the dense shade of their own crown, 

 show that their leaves can live and functionate with a small amount 

 of light. They are shade-enduring trees. On the other hand, the 

 black walnut, the locust, the catalpa, the poplars, and the larch 

 show by the manner in which their crowns thin put, the foliage 

 being confined to the ends of the branches, that their leaves require 

 more light they are light-needing trees; so that the scale which 

 arranges the trees according to the amount of shade they exert 

 serves also to measure their shade endurance. In making, there- 

 fore, mixed plantations, the different kinds must be so grouped and 

 managed that the shady trees will not outgrow and overtop the light- 

 needing ; the latter must either have the start of the former or must 

 be quicker growers. 



Rate of Growth. Not only do different species grow more or 

 less rapidly in height and girth, but there is in each species a 

 difference in the rate of growth during different periods of life, and 

 a difference in the persistence of growth. It stands to reason that 

 trees grow differently in different soils and situations, and hence 

 we can not compare different species with respect to their rate of 

 growth except as they grow under the same conditions. 



Thus the black walnut may grow as fast as or faster than the 

 ash on a rich, deep, moist, warm soil, but will soon fall to the 

 rear in a wetter, colder, and shallower soil. 



Given the same conditions, some species will start on a rapid 

 upward growth at once, like the poplars, aspen, locust, and silver 

 maple, making- rapid progress (the most rapid from their tenth 

 to their fifteenth year), but decreasing soon in rate and reaching 

 their maximum height early. Others, like the spruce, beech, and 

 sugar maple, will begin slowly, often occupying several, sometimes 

 as many as 10 to 15 years before they appear to grow at all, their 



