REGENERATION MEASURES AND THE FORMATION OF SALTPETRE GRIVi 
forests, no nitrification or saltpetre-formation occurs, or very 
little. The organically bound nitrogen is not transformed further 
than ammonia. This holds good even of our finest and most pro- 
ductive mixed coniferous forests. 
Fellings that bring about a strong access of light have a strong 
influence on the transformation of nitrogen. 
Where the humus-covering is rather thin and loose, chiefly com- 
posed of mosses and fallen needles, felling may bring about a 
very active transformation of the humus nitrogen to nitrate, owing, 
among other things, tor the tact that thecfelling bringsrab on a 
radical alteration in the bacterial flora of the hummus c€0oveting. 
When the humus-covering is very markedly of the nature ofraw 
humus, there appears only a more active transformation ofthe hu- 
mitst nitrogen, but mo nitriftcationt takes: place. The varetrestod 
change undergone by the humus-covering can, to some extent, be 
estimated from the ground-vegetation. Where the humus nitrogen 
is transformed into nitrate, there appear nitratophilous plants 
raspberry, Epilobium angustifolium, Arenaria trinervia, Galeopsis 
bifida, Senecio silvaticus, Rumex acetosella, etc. Where the humus- 
covering moulders without the humus nitrogen being transformed 
into nitrate, ÅAira flexuosa is the predominant clearing-plant. 
Thorough methods of preparing the ground, such as are able 
to mix the humus-covering with the mineral soil, mouldering 
brushwood and timber, and also the burning fof the ground 
produce a formation of saltpetre even in a marked raw humus 
covering. 
There is close parallelism between the mnitrification of the 
humus nitrogen and the regenerative possibilities of the ground. 
The forests where even select cutting produces nitrification are 
comparatively easily regenerated. Road-sides, places where stumps 
have been broken up, and burns, are often distinguished by a fine 
regrowth, and there, too, the humus nitrogen is nitrified. Fallen 
trumks andkothker brushkwocdkt favour the formation of saltpetre 
and regeneration. Raw-humus lands without nitrification, on the 
other Damd ane difficult ONtesSenNeratLon. 
Experiments that have been made and direct observations zz 
natura show that the pine in its youth develops more strongly in 
a humus-covering with nitrification than without nitrification. 
Probabilyrtter same holds good of the spruce also. 
In herbulent-spruce-forests there is usually nitrification ofthe 
ground. In such forests, felling produces an increased formation 
of saltpetre, which may bring about herb and grass vegetation 
troublesome to coniferous plants. In such places, however, the 
spruce grows again in small gaps, such as do not permit any very 
strong development of the ground-vegetation. In such forests it 
