588 FOREST LITTER. 



more rapidly tlian (•onit'crous needles. Mosses are known to 

 decompose very slowly ; but tlieir decomposition once commenced, 

 passes quickly throu<,'h the condition of humus to that of com- 

 plete dissolution. On this account, the living layer of moss 

 rests on the ground with hardly any noticeable intermediate 

 layer and may be removed from it like a carpet. 



(b) Soil. — The most important factors in the soil which expedite 

 decomposition of the soil-covering, are its capacity for heat, its 

 degree of porosity and the amount of moisture it contains. 

 Decomposition is generally slowest on clay or loam, quickest 

 on calcareous soil and sand. It is especially rapid on moist 

 calcareous soil in South Germany ; after two years most of the 

 litter is decomposed, the humus decomposing still more quickly. 



(c) Locality. — It is well-known that decomposition proceeds 

 more slowly on north and east than on south and west aspects ; 

 northerly slopes are damp and cool, and in folds of the hills near 

 the valleys the rate of decomposition is extremely slow : in such 

 places the greatest amount of })artly decomposed humus and 

 litter accumulates. 



(d) Climate. — Southern countries prove strikingly that heat 

 combined with moisture is most eilective in expediting decom- 

 position ; in South Germany, and still more in Hungary, t^-c. 

 decomposition proceeds much more rapidly than in North 

 Germany and the countries bordering on the Baltic. Whilst 

 in the latter case 3 or 4 years are often required to complete 

 the process of decomposition, one or at most two years suffice 

 for the former. [In an Indian forest, except in mountainous 

 districts, it is rare to lind any noticeable layer of humus in 

 forests. — Th.] The contrasting climates of the lowlands and 

 high mountain-regions of Euroiie have opposite effects on de- 

 composition ; the high relative humidity of the air and low mean 

 temperature in mountain tracts cause deep layers of raw humus 

 to accumulate in forests, fallen Avood may there be found which 

 has hardly made any progress in decomposition during a century 

 or more. 



(e) Density of Standing-Crop of Trees. — The denser a wood, 

 other conditions being similar, the slower the decomposition of 

 forest litter. Densely growing poles shelter the soil from air and 

 heat, by their complete cover they hinder evaporation of water 



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