364 HORTICULTURE, FORESTRY, FLORICULTURE 



natural seedbed of humus soil covered with the leaves gives a pro- 

 tected, natural seedbed which is necessary for reproduction. 



Ground fires frequently pass through the woods in spring and 

 by the middle of the summer the woods seem to have recovered. This 

 is not the case, for usually large trees, which seem to have bark thick 

 enough to withstand the small amount of heat of a ground fire, are 

 injured in a manner not at once visible to the observer. The heat 

 from a ground fire, which it seems is too small to injure a tree with 

 heavy bark, frequently affects the tree very seriously. The injury 

 is of two kinds. 



By burning off the humus and litter the soil is left unprotected 

 so that it lacks moisture during the dry season, as well as weakening 

 the soil in regard to food supply for the trees. Frequently the burn- 

 ing kills the shallow roots or leaves them unprotected. 



The living tissue beneath the bark of the tree close to the ground 

 becomes so heated that it is either killed or partly destroyed. The 

 first visible effect may be seen in the form of a fungus growth about 

 the base of the tree. This parasitic fungus gradually weakens the 

 tree, making it subject to insect pests, and finally causing its death, 

 but the real and first cause was the innocent looking ground fire. 



Probably one of the most serious hindrances to the proper 

 growth and development in the woodlot has been caused by grazing. 

 There were many, a few years ago, who claimed that grazing did not 

 injure the woodlot. 



Experience has shown, however, that grazing must always be in- 

 jurious. Many examples may be seen where the comparison of 

 grazed and ungrazed woodlots show the result. While the injury is 

 admitted by many, there are those who claim that the woodlot is of 

 more value in protecting the cattle during the heat of the day and 

 giving them pasturage than for wood producing purposes. It is very 

 difficult to compare the rental value of the woodlot used for purposes 

 of pasturage and that of the woodlot used exclusively for wood pro- 

 duction. One thing is certain, that to have a permanent woodlot 

 where conditions are favorable for tree growth the stock must be 

 excluded. 



Domestic animals are frequently classed as to the amount of in- 

 jury they inflict on the woodlot. From the standpoint of browsing 

 the degree of injury may be placed in the following order: Goats 

 and sheep, horses, cattle, swine, the first mentioned being the most 

 injurious and the last being least. Injurious effects of allowing stock 

 to run in the woodlot may be discussed in its relation to the soil, the 

 reproduction of young growth and the older trees. 



While the effects of grazing on the soil may be least noticeable, 

 it is very important. Destruction of young growth soon opens the 

 woodlot to drying winds which carry off the humus-forming leaves 

 and greatly lessen the moisture content of the soil. Light begins to 

 enter and reach the ground, causing grass and weeds to start which 

 soon develop a stiff sod. Trampling of the soil causes it to become 

 impervious, thus allowing the water to run off rapidly instead of 

 being held in the soil as is the case in normal conditions. After 



