"How is that?" asked Wilbur, anxious to divert the stream of Rifle-Eye's criticism from the cowboy, who had got himself into trouble defending him. "I didn't know there was any difference between a tree on the outside of a forest and one on the inside."
"Wa'al, then, I guess you're due to learn right now. If there's a tree of any size, standin' out by itself on a mountain side, with plenty of leaves, an' a big wind comes along, you c'n see easy enough that she presents a heap of surface to the wind. An' when a mountain gale gets up and blows fer fair, there's a pressure of air on that tree amountin' to several tons."
"Tons?" queried Bob-Cat incredulously.
"Tons," answered the old Banger. "A tree needs to have some strength in order to hold up its end. There's three ways o' doin' it. One is by havin' a lot more give in the fibers, more elastic like, so that the tree'll bend in the wind an' not get snapped off; another is by puttin' out a lot o' roots an' shovin' 'em in deep an' at the same time havin' a trunk that's plenty stout; an' the third is the thickenin' o' the trunk, right near the ground, where the greatest part o' the strain comes. An' all the various kinds o' trees works this out in different ways. But nothin's ever wasted, an'—"
"Oh, I see now," broke in Wilbur. "You're going to say that the trees which don't grow on the outside of a forest don't have to waste vitality into these forms of resistance."
"That's right. A tree that grows in a ravine, where there is little chance of a high wind, an' where light is scarce an' hard to get, such a tree will have a shallow root system an' a spindlin' trunk, all the growth havin' gone to height, an' a tree in the center of a forest is often the same way. The wind can't git through the forest, an' so the trees don't need ter prop themselves against it."
"Talk about yer eddicated trees!" ejaculated the cowboy, "which colleges is a fool to them."
"It's true enough, Bob-Cat, just the same. But supposin' a belt on the outside o' the forest is cut down, then the inner trees, thus exposed, haven't any proper weapons to fight the wind, an' they go down."
"Doesn't it take a very high wind to blow down some of these big trees?" asked Wilbur.
"Some kinds it does," said the Ranger, "but there's others that go down pretty easy, lodge-pole pine, fer instance. But a tree doesn't have to be blown down to be ruined. Even if a branch is blown off—an' you know how often that happens—insects and fungi get into the wound of the tree and decay follows."