The question why the original growth is not reproduced can best be answered by some illustrations.  When a pine forest is burned over, both trees and seeds are destroyed, and as the burned trees cannot sprout from the stump like oaks and many other trees, the land is left in a condition well suited for the germination of tree seeds, but there are no seeds to germinate.  It is an open field for pioneers to enter, and the seeds which arrive there first have the right of possession.  The aspen poplar (Populus tremuloides) has the advantage over all other trees.  It is a native of all our northern forests, from the Atlantic to the Pacific.  Even fires cannot eradicate it, as it grows in moist as well as dry places, and sprouts from any part of the root.  It is a short-lived tree, consequently it seeds when quite young and seeds abundantly; the seeds are light, almost infinitesimal, and are carried on wings of down.  Its seeds ripen in spring, and are carried to great distances at the very time when the ground is in the best condition for them.  Even on the dry mountain sides in Colorado, the snows are just melting and the ground is moist where they fall.

To grow this tree from seed would require the greatest skill of the nurseryman, but the burnt land is its paradise.  Wherever you see it on high, dry land you may rest assured that a fire has been there.  On land slides you will not find its seeds germinating, although they have been deposited there as abundantly as on the burned land.

Next to the aspen and poplars comes the canoe birch, and further north the yellow birch, and such other trees as have provision for scattering their seeds.  I have seen acorns and nuts germinating in clusters on burned lands in a few instances.  They had evidently been buried there by animals and had escaped the fires.  I have seen the red cherry (Prunus Pennsylvanica) coming up in great quantities where they might never have germinated had not the fires destroyed the debris which covered the seed too deeply.

A careful examination around the margin of a burned forest will show the trees of surrounding kinds working in again.  Thus by the time the short-lived aspens (and they are very short-lived on high land) have made a covering on the burned land, the surrounding kinds will be found re-established in the new forest, the seeds of the conifers, carried in by the winds, the berries by the birds, the nuts and acorns by the squirrels, the mixture varying more or less from the kinds which grew there before the fire.

It is wonderful how far the seeds of berries are carried by birds.  The waxwings and cedar birds carry seeds of our tartarean honeysuckles, purple barberries and many other kinds four miles distant, where we see them spring up on the lake shore, where these birds fly in flocks to feed on the juniper berries.  It seems to be the same everywhere.  I found European mountain ash trees last summer in a forest in New Hampshire; the seed must have been carried over two miles as the crow flies.