I 



At the Forest Service I was shovm a cross-section of a tree, such as 

 you cajn see on the end of a log or the top of a stujap in the wood-'lot. 

 It was explained to mo that this natter of weight and strength in any 

 particule,r wood is largely a question of the development of the tree rings. 

 These annual growth rings in the tree arc formed in tvo partsj a layer 

 produced in the spring, and the denser tougher layer laid down in the summer. 

 The more wood a hardwood tree can produce in a year, that is, the faster 

 it grows, the stronger the wood is as a whole. This is because the faster 

 it grows the greater the proportion of the stronger wood fibre cells that 

 is formed. 



In the case of hardwoods such as ash, and hickory, and walnut and 

 elm and the like, our foresters find that when conditions are unfavorable 

 to growth in the later part of the growing season the proportion of these 

 strong wood cells is less so the wood is lighter and weaker. Hov/evdr, 

 hardwood trees crowded too close together ordinarily do not produce as 

 strong timber as trees further apart. Hickory or oak grcrm under the 

 crowded conditions of the original virgin forest are therefore not as 

 strong as second-growth hickory or oak. 



Yet, as you know, we need to grow the trees close enough together 

 so they v/ill shed their lower limbs. So if we want to grow wood both free 

 from defects and sttfong, we have to grow the trees with a close spacing 

 while they are youag and then thin them out later so they will have room 

 enough to get the nourishment they need to make rapid increases of nevr 

 growth. Strength in hardwoods 'oes v;ith a fairly fast but even rate of 

 growth. 



In the case of cone-bearing trees, such as the redwoods ?jid south- 

 ern ;oines, the spacing has a little different effect. Redwoods and ")ines 

 grow faster with more open spacing than when crowded; but the open-grov/n 

 trees produce more of the lighter-weight, weaker spring wood thain they do 

 strong summer wood. In conifers, cells different from those of hardwoods 

 make up the bulk of the wood. In order to grow stronger wood, pines and 

 redwoods must be grown fairly close togetl^er. The pinesand redwoods pro- 

 ducing the stronger wood, don't grow quite as fast as those producing 

 weaker wood. The softwoods having the stronger wood have a goodly pro- 

 portion of dense sunmer wood. 



As we said, second-growth hickory is stronger than virgin-growth 

 hickory. Second-grdAh pine, however, is weaker than the wood from pines 

 which originated imder the fairly crowded virgin forest. 



By wide spacing of trees, we can produce light wood in second- 

 growth fcouthem pines and redwood. The individual trees will have bigger 

 tops, more knots, and will produce less clear lumber; but they vdll grow 

 to a certain size in a much shorter time. 



So you see, by spacing and thinning we can now have quite a say-so 

 as to the quantity and quality of the wood produced in our woods. 



