FORESTRY AND CONSERVATION 363 



year; with shade-enduring, not before the twentieth or twenty-fifth 

 year. The necessary severity of the thinning and the repetition are 

 somewhat interdependent. It is better to thin carefully and repeat 

 the operation oftener than to open up so severely at once as to 

 jeopardize the soil conditions. Especially in younger growths and 

 on poorer soil, it is best never to open a continuous crown cover so 

 that it could not close up again within 3 to 5 years; rather repeat 

 the operation oftener. Later, when the trees have attained heights 

 of 50 to 60 feet and clear boles (which may be in 40 to 50 years, ac- 

 cording to soil and kind) the thinning may be more severe, so as to 

 require repetition only every 6 to 10 years. 



The condition of the crown cover, then, is the criterion which di- 

 rects the ax. As soon as the crowns again touch or interlace, the time 

 has arrived to thin again. In mixed growths it must not be over- 

 looked that light-needing species must be specially protected against 

 shadier neighbors. Shade-enduring trees, such as the spruces, beech, 

 sugar maple, and hickories, bear overtopping for a time and will 

 then grow vigorously when more light is given, while light-needing 

 species, like the pines, larch, oaks, and ash, when once suppressed, 

 may never be able to recover. Particular attention is called to the 

 necessity of leaving a rather denser "wind mantle" all around small 

 groves. In this part of the grove the thinning must be less severe, 

 unless coniferous trees on the outside can be encouraged by severe 

 thinning to hold their branches low down, thus increasing their value 

 as windbreaks. 



The thinnings, then, while giving to the "final harvest" crop all 

 the advantage of light for promoting its rapid development into 

 serviceable timber size, furnish also better material from the subordi- 

 nate crop. At 60 to 70 years of age the latter may have been entirely 

 removed and only the originally selected "superiors" remain on the 

 ground, or as many of them as have not died and been removed ; 250 

 to 400 of these per acre will make a perfect stand of most valuable 

 form and size, ready for the final harvest, which should be made as 

 indicated in the preceding chapter. (Y. B. 1894.) 



THE FARM WOODLOT. 



The woodlot is a part of the farm which in too many cases has 

 been neglected and looked upon as of no real value in its relation to 

 the farm. It has furnished the owner with fuel and building mate- 

 rial and frequently revenue by the sale of a few logs to the local mill. 

 In many cases, however, the woodlot has not been considered as being 

 a permanent resource or a necessary part of the farm economy. 



The following pages take it for granted that the owner desires 

 to make the woodlot a permanent and paying part of the farm. 



Ground Fires as Related to the Woodlot. Fire should never be 

 allowed to run through the woodlot. By burning off the leaf litter 

 and vegetable mould or humus the soil is greatly weakened. The 

 healthy development of the forest tree is dependent upon the humus 

 condition of the soil. 



Ground fires also destroy the seed and young growth and make 

 it much more difficult for seeds to germinate in the future. The 



