34 SEEDING AND PLANTING 



21. JUDGING THE AMOUNT OF SOIL MOISTURE. The best 

 measure of water content is that expressed in the vegetation itself 

 and in the depth of the soil and the fineness of its particles, con- 

 sidered with the amount and distribution of the precipitation. 

 A deep and relatively fine soil contains much more water during 

 periods of drought than shallower and coarser soils of the same 

 locality. 



As more or less extended intervals of time separate periods of 

 precipitation, the power of a soil to retain water is of great im- 

 portance. The rapidity with which the moisture escapes from 

 the surface layers or, conversely stated, the power that a soil has 

 for retaining water in its surface layers, very often determines the 

 species to use in seeding and planting. Shallow-rooted trees like 

 beech and hard maple are chiefly confined to clay and calcareous 

 upland soils. Because of the much less variation in soil moisture 

 in the deeper layers, upland trees that occur on gravelly or sandy 

 soils are usually deep rooted, as is the case with chestnut, white 

 oak, and shagbark hickory. Where shallow soils are underlaid 

 with an open, porous subsoil or with vertically stratified or much 

 fractured rocks, the available moisture often approaches that of 

 deep soils. Oaks, hickories, chestnut, and many conifers thrive on 

 such soils. On the other hand, where shallow soils are underlaid 

 with an impervious subsoil or where the underlying rock is with- 

 out fractures or in horizontal strata, but few trees make successful 

 growth because the soil is too wet immediately following precipi- 

 tation and too dry during periods of drought. Such soils, how- 

 ever, often sustain a good crop of spruce and occasionally other 

 conifers in regions of abundant precipitation and high humidity. 



22. AVAILABLE MOISTURE IN THE SURFACE SOIL. The avail- 

 able water in the surface soil is of particular importance in repro- 

 duction. After germination starts the roots must be constantly 

 in contact with sufficient moisture to meet the demands of the 

 particular species for transpiration and growth. They must 

 quickly penetrate the soil to a depth beyond that where it be- 

 comes dry during periods of drought. As trees vary greatly in the 

 rapidity and depth of root penetration in their early life, the loss 

 from seeding and planting due to the drying of the surface soil is 

 largely dependent upon the species. Species like the oak, chest- 

 nut, and hickory, which immediately after germination send their 

 roots to a depth of a foot or more, are easily established by 



