EFFECTS OF ITS KEMOVAL. 607 



long period, begins to decline only late in life and the woods 

 continue to grow for a long time with a decreasing increment. 

 Fertility and the production of seed are reached only at an 

 advanced age. On the contrary, a wood, the productive power 

 of which has been weakened by the removal of litter, attains only 

 a poor increment, retains its maximum increment for a short 

 period only, whilst its increment* frequently decreases rapidly. 

 The rotation must therefore be reduced from time to time, the 

 more quickly, the more unrestricted the removal of litter. 

 Seed-production occurs much earlier, even when the wood is 

 quite young, and, as in all weakly plants, is often very abundant. 



(/3) Change in Species of Tree. 



A further effect of the removal of litter sometimes consists in 

 the impossibility of producing any longer a species of tree which 

 has hitherto been well-adapted to the locality. As long as 

 local conditions remain unchanged, nature as a rule continues 

 to produce the same species of trees, the existence and well- 

 being of which depend, in any case, essentially on the effects 

 of sylvicultural treatment and the degree of light admitted to 

 a wood. If the productiveness of a soil is no longer sufficient 

 for any particular species of tree, it must be replaced by one less 

 exacting ; the reverse being true where a locality has recovered 

 its former fertility. 



It is well-known that up to the commencement of the 18th 

 century the forests of the lowlands, hilly tracts and central 

 mountain-ranges of Germany were stocked chiefly with beech, 

 oak, ash, sycamore, elms, kc, and only the sandy tracts near 

 the sea, and the high mountains, Avith conifers. A great change 

 has occurred; broad-leaved trees now only form one third of 

 the German forest-crop, and conifers have replaced them in the 

 lowlands. Although not the only cause of this change, the 

 removal of litter from the forests is chiefly responsible for it. 

 In innumerable places the soil has become so poor in nutritive 

 substance and has lost so much of its former moisture, that 

 species like the beech, oak, elm and silver-fir, which make 

 certain demands on both these factors of fertility in soils, must 



* Vide tlie observations of von Krutzsch in the Tharandter Jahrbuch, vol. xv. 

 p. 66. 



