rock, or ground water) the water not only can penetrate but also can 

 readily be reached and taken up by the roots. 



The moisture of the soil being the most important element in 

 it for tree growth, the greatest attention must be given to its con- 

 servation and most advantageous distribution through the soil. No 

 trees grow to the best advantage in very dry or very wet soil, al- 

 though some can live and almost thrive in such unfavorable situa- 

 tions. A moderately but evenly moist soil, porous and deep enough 

 or fissured enough to be well drained, and yet of such a structure 

 that the water supplies from the depths can readily be drawn up and 

 become available to the roots that is the soil on which all trees 

 grow most thriftily. The agriculturist procures this condition of 

 the soil as far as possible by plowing, drainage, and irrigation, and 

 he tries by cultivating to keep the soil from compacting again, as it 

 does under the influence of the beating rain and of the drying out 

 of the upper layers by sun and wind. 



The forest grower can not rely upon such methods, because 

 they are either too expensive or entirely impracticable. He may, 

 indeed, plow for his first planting, and cultivate the young trees, but 

 in a few years this last operation will become impossible and the 

 effects of the first operation will be lost. He must, therefore, attain 

 his object in another manner, namely, by shading and mulching 

 the soil. The shading is done at first by planting very closely, so 

 that the ground may be protected as soon as possible from sun and 

 wind, and by maintaining the shade well throughout the period of 

 growth. This shade is maintained, if necessary, by more planting, 

 and in case the main crop in later life thins out inordinately in the 

 crowns or tops, or by the accidental death of trees, it may even 

 become desirable to introduce an underbrush. 



The mulching is done by allowing the fallen leaves and twigs 

 to remain and decay, and form a cover of rich mold or humus. This 

 protective cover permits the rain and snow waters to penetrate with- 

 out at the same time compacting the soil, keeping it granular and 

 in best condition for conducting water, and at the same time pre- 

 venting evaporation at the surface. The soil moisture, therefore, is 

 best maintained by proper soil cover, which, however, is needful 

 only in naturally dry soils. Wet soils, although supporting tree 

 growth, do not, if constantly wet, produce satisfactory wood crops, 

 the growth being very slow. Hence they must be drained and their 

 water level sunk below the depth of the root system. 



Irrigation is generally too expensive to be applied to wood 

 crops, except perhaps in the arid regions, where the benefit of the 

 shelter belt may warrant the expense. Attention to favorable mois- 

 ture conditions in the soil requires the selection of such kinds of 

 trees as shade well for a long time, to plant closely, to protect the 

 woody undergrowth (but not weeds) , and to leave the litter on the 

 ground as a mulch. Different species, to be sure, adapt themselves 

 to different degrees of soil moisture, and the crop should therefore 

 foe selected with reference to its adaptation to available moisture 

 supplies 



