442 



PRACTICAL BOTANY 



much of the humus of the forest soils (Fig. 344), the surface 

 water, which is no longer retarded and absorbed by humus, 

 flows with increased rapidity. In so doing it carries away large 

 quantities of soil, sometimes uncovering the burned roots until 

 the trees are easily overturned by winds. An area once for- 

 ested may soon be cut into trenches and ridges until the only 



FIG. 343. Erosion of the soil following removal of the forest 



This land was covered with a heavy pine forest, and had a good soil, which was 



held upon the forest floor. When the timber was removed, erosion soon cut 



ditches through the pasture land 



remaining evidence, if any, of its previously forested condition 

 is seen in the presence of a few plants such as young trees 

 that are trying to grow in the poor soil that is left (Fig. 346). 

 There are several means of preventing much of this loss of 

 soil by erosion. In wooded regions judiciously cutting part of 

 the timber each year rather than cutting all of it at once gives 

 opportunity for new plants to occupy and hold the soil. There 



