606 FOREST LITTKK. 



these powers, and this is only possible when the indispensable 

 soil-covering of humus and litter is maintained. 



If, however, the removal of litter changes the nature of the 

 soil, the productive energy of its trees is impaired owing to 

 bad nutrition. This is manifested either by a reduction in the 

 wood-increment, or in the resulting impossibility of producing a 

 certain species of tree, so that a change in the standing crop 

 ensues. 



(a) liediiction of ]]\K)d-hicremcnt. 



In all forests from which the litter has been continuously 

 removed, experience shows that the woods become more and 

 more open and the crowns of the trees thin and spreading, 

 whilst their height-growth and the annual wood-increment are 

 reduced ; the life of the trees is thus shortened and long 

 rotations become impossible. 



A chemically rich, moist and deep soil aflbrds sufficient 

 nourishment to trees in a small space ; as soon, however, as the 

 nutriment in the soil has been reduced, the tree requires more 

 room, dominating stems crowd out their weaker neighbours by 

 taking the nutriment formerly obtained by the latter and hence 

 the w^oods become open. This opening of the woods causes other 

 changes. The soil is no longer protected by a dense leaf-canopy, 

 the wind and the sun's rays gain continually more access to 

 the ground, Avhich parts with its moisture and becomes still 

 less nutritious, so that the growth of the trees is further 

 impeded. It is chiefly the growth of the stem in height and 

 thickness which suffers ; thus on a soil weakened by the re- 

 moval of litter the arboreal growth gradually loses its distinctive 

 character and finally sinks to that of mere scrub, the develop- 

 ment of branches gradually predominating over that of the stem. 

 In this way the possibility of obtaining the most valuable forest 

 produce is seriously impaired and the forest revenue conse- 

 quently suffers, the woods yielding chiefly firewood and the 

 proportion of branchwood and faggots continually increasing. 



An organism, the vitality of which has been notably weak- 

 ened, has a shorter life than one possessing full vital vigour ; 

 hence by the removal of litter the rotation of woodland is 

 shortened. In vigorous forests, adapted to long rotations, the 

 annual wood-increment remains steadily at its maximum for a 



