138 
EFFECTS OF BURNING FOREST. 
Effects of Fire on Forest Soil. 
Aside from tlie mechanical and chemical effects of the dis¬ 
turbance of the soil by agricultural operations, and of the freer 
admission of sun, rain, and air to the ground, the fire of itself 
exerts an important influence on its texture and condition. It 
consumes a portion of the half-decayed vegetable mould which 
served to hold its mineral particles together, and to retain the 
water of precipitation, and thus loosens, pulverizes, and dries 
the earth; it destroys reptiles, insects, and worms, with their 
eggs, and the seeds of trees and of smaller plants ; it supplies, 
in the ashes which it deposits on the surface, important ele¬ 
ments for the growth of a new forest clothing, as well as of the 
usual objects of agricultural industry ; and by the changes thus 
produced, it fits the ground for the reception of a vegetation 
different in character from that which had spontaneously cov¬ 
ered it. These new conditions help to explain the natural 
succession of forest crops, so generally observed in all woods 
cleared by fire and then abandoned. There is no doubt, how¬ 
ever, that other influences contribute to the same result, 
because effects more or less analogous follow when the trees 
are destroyed by other causes, as by high winds, by the wood¬ 
man’s axe, and even by natural decay.* 
* The remarkable mounds and other earthworks constructed in the valley 
of the Ohio and elsewhere in the territory of the United States, by a people 
apparently more advanced in culture than the modern Indian, were over¬ 
grown with a dense clothing of forest when first discovered by the whites. 
But though the ground where they were erected must have been occupied 
by a large population for a considerable length of time, and therefore en¬ 
tirely cleared, the trees which grew upon the ancient fortresses and the 
adjacent lands were not distinguishable in species, or even in dimensions and 
character of growth, from the neighboring forests, where the soil seemed 
never to have been disturbed. This apparent exception to the law of change 
of crop in natural forest growth was ingeniously explained by General Har¬ 
rison’s suggestion, that the lapse of time since the era of the mound 
builders was so great as to have embraced several successive generations of 
trees, and occasioned, by their rotation, a return to the original vegetation. 
The successive changes in the spontaneous growth of the forest, as 
