276 FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AURICULTURE. 



while in the fortieth year the number would be reduced to l,liO(), and in the hundredth year to 

 280. Hence the rate of growth of any single tree gives no idea of what the acre of forest will do. 



Thus, while a single good white pine might grow the fastest in volume when about one hun- 

 dred years old, then making wood at the rate of, say, 1.5 cubic feet per year, an acre of pine on 

 good soil, containing about 1,000 trees, may make the most wood in the thirtieth year, then 

 growing at the rate of 170 cubic feet per acre, while in the hundredth year the rate would not 

 exceed 70 cubic feet; and an acre of pine in a poorer location, with about 1,400 trees, may make 

 the most wood in the fortieth year, at the rate of 100 cubic feet per acre. 



From the consideration of the relation of light conditions to soil conditions, to form develop- 

 ment, and to rate of growth, we may make the following deductions of interest to the forest 

 planter: 



In order to secure the best results in wood production, in quantity and quality, at the same 

 time preserving favorable soil conditions, the forest should be composed of various species, a 

 mixture of light-needing and shade enduring kinds. The light needing ones should be of quicker 

 growth; the shady ones, in larger numbers, should be slower growers. For the first fifteen to 

 twenty-five years the plantation should be kept as dense as possible, to secure clear shafts and 

 good growth in height; then it should be thinned, to increase crown development and diameter 

 growth; the thinning, however, is not to be so severe tlia the crowns can not close up again in 

 two or three years; the thinning is to be repeated again and again, always favoring the best 

 developed trees. 



KATE OF GROWTH. 



The more commonly cultivated trees may be classified with reference to their rate of growth, 

 as follows : 



Rapid growers to maturity: Oottouwood, aspen, tulip, loblolly pine, white pine, white elm, 

 box elder, silver maple, jack pine. 



liapid growing in youth, but much slower in age: Black cherry, long-leal pine, short-leaf 

 pine, catalpa, black walnut, black locust, honey locust, the birches. 



Slow but persistent growers: White ash, sugar maple, the oaks, the hickories, the spruces, 

 and hemlock. 



REPRODUCTION. 



All trees reproduce themselves naturally from seed. Man can secure their reproduction also 

 from cuttings or layers; and some kinds can reproduce themselves by shoots from the slum]) 

 when the parent tree has been cut. This latter capacity is possessed in a varying degree by 

 different species; chestnuts, oaks, elms, maples, poplars, and willows are most excellent sprouters; 

 most conifers do not sprout at all, and the shoots of those that do sprout-soon die (Sequoia or 

 California redwood seems to be an exception). Sprouts of broad-leafed trees develop differently 

 from seedlings, growing very rapidly at first, but soon lessening in the rate of growth and never 

 attaining the height and perhaps not the diameter of trees grown from the seed; they are also 

 shorter lived. With age the stumps lose their capacity for sprouting. To secure best results, the 

 parent tree should be cut close to the ground in early spring, avoiding severe frost, and a sharp 

 cut should be made which will not sever the bark from the trunk. 



Not all trees bear seed every year, and plentiful seed production, especially in a forest, occurs, 

 as a rule, periodically. The periods differ with species, climate, and season. 



Not all seeds can germinate, and in some/species the number of seeds that can germinate is 

 very small, and they loose their power of germination when kept a few hours, like the willows. 

 Others, if kept till they have become dry, will "lie over" in the soil a year or more before germi- 

 nating. The same thing will occur if they are covered too deep in the soil, provided they 

 germinate at all under such conditions. 



In order to germinate, seeds must have warmth, air, and moisture. The preparation of a seed 

 bed is, therefore, necessary in order to supply these conditions in most favorable combination. 

 In the natural forest millions of seeds rot or dry without sprouting, and millions of seedlings 

 sprout, but soon perish under the too dense shade of the mother trees. 



Man, desiring to reproduce a valuable wood crop, can not afford to be as lavish as nature, and 

 must therefore improve upon nature's methods, making more careful preparation for the production 



