EFFECTS ON TKEE-GROWTH. 759 



(a) Dry fallen leaves or needles, which are shed by the 

 trees forming the standing-crop of the forest ; and to some 

 extent, by shrubs in the underwood. 



(b) Moss and grass, partly living and partly dead. 



(c) Forest weeds, such as broom, bilberry-plants (and other 

 species of Vaccinium), heather, ferns, reeds, rushes, etc. 



Branch-litter, young needle-bearing twigs of conifers, have 

 been described already (p. 694). 



SECTION II. IMPORTANCE OF FOREST-LITTER FOR WOOD- 

 PRODUCTION.* 



It is not the business of " Forest Utilization " to deal 

 thoroughly with the question of the importance of litter for 

 soil-formation, climate, productivity, for forest trees individu- 

 ally, or for the whole forest, any more than in dealing with 

 the utilization of wood, the effects of soil and climate and the 

 methods of starting and tending trees, are discussed. Here 

 only the most essential points will be explained. The works 

 noted below may be consulted for further details. 



1. 7>Vm'//rM/ Htj\-ctx of Litter <ul Humus on (lie (ir<nrth 



of Trees. 



(a) Preservation of Moisture in the Soil. 



The humus which covers the mineral subsoil and is only 

 to a slight extent mixed with it, and the coating of litter above 

 the humus, are the most effectual means of securing and 

 maintaining in the soil the requisite amount of moisture. 

 The action of humus and litter is in this respect threefold, viz. : 

 The mechanical impediment it affords on slopes to rapid 

 drainage of surface-water from atmospheric precipitations, and 

 the time thus allowed for the water to sink into the soil- 

 covering and the soil ; the sponge-like action possessed by dead 



* Kbrnnavcr, "Die gesamintc Lehre der Waldstreu," Berlin, 1H7<>. Wollny, 

 translated into French by K. Henry, " La decomposition des mat ieres organiques 

 et les formes d'huimis," 1'aris, Berger Levrault, 1902. Ramatm, "Forstliche 

 . Stand. alslrhnj,'' 1^1)3. Muller, (- Die natiirlichen Hunmsformon." 



