(1) Most conifers have no power of sprouting. The chief exceptions are pitch pine and, to a remarkable degree, the redwood, Fig. 67. This power, however, is common in broad-leaved trees, as may be seen after a fire has swept thru second growth, hardwood timber. Altho all the young trees are killed down to the ground, the young sprouts spring up from the still living roots. This may happen repeatedly. Coppice woods, as of chestnut and oak, which sprout with great freedom, are the result of this ability. The wood is poor so that it is chiefly used for fuel.
Fig. 67. Sprouting Redwood Stumps. Glen Blair, Calif. U. S. Forest Service.
(2) Most trees, however, are reproduced by seeds. Trees yield these in great abundance, to provide for waste,—nature's method. Many seeds never ripen, many perish, many are eaten by animals, many fall on barren ground or rocks, and many sprout, only to die. The weight of seeds has much to do with their distribution. Heavy seeds like acorns, chestnuts, hickory and other nuts, grow where they fall, unless carried down hill by gravity or by water, or scattered by birds and squirrels.
Trees with winged seeds, however, Fig. 68, as bass, maple and pine, or with light seeds, as poplar, often have their seeds carried by the wind to great distances.
Fig. 68. Winged Seeds. 1, Basswood; 2, Box-elder; 3, Elm; 4, Fir; 5, 6, 7, 8, Pines. U. S. Forest Service.
Again some trees, as spruce, are very fertile, while others, like beech, have only occasional seed-bearing seasons, once in three or four years. Willow seeds lose their power of germination in a few days, and hence, unless they soon reach ground where there is plenty of moisture, they die. This is why they grow mostly along water courses. On the other hand, black locust pods and the cones of some pines keep their seeds perfect for many years, often until a fire bursts them open, and so they live at the expense of their competitors.
It is such facts as these that help to account for some of the acts of forest composition,—why in one place at one time there is a growth of aspens, at another time pines, at still another oaks; and why beeches spring up one year and not another. That red cedars grow in avenues along fences, is explained by the fact that the seeds are dropped there by birds, Fig. 69.