REGENERATION MEASURES AND THE FORMATION OF SALTPETRE CXI 
is more or less heated, and consequently the changes in the bacterial flora 
brought about by the fire would not seem to be ascribable solely to the intro- 
duction of soluble salts which affect the humus-covering, but seem also to have 
their direct cause in the alterations caused by the heat in the micro-biological 
condition of the ground As regards the formation of saltpetre, it is true 
that in the experiments carried out by RussEL and HUTCHINSON (1909) that 
has been reduced through heating; but other researchers have found that in 
treated soil which has again been infected with saltpetre-forming bacteria the 
formation of saltpetre becomes more active than in the unsterilized soil 
(DEHERAIN and DEMOUSSY, 1896, cf. KOPELOFF etc., 1916). | 
The alterations in the transformation of nitrogen which we can bring about 
through cutting, preparation of the soil or denshiring, represent only a more 
or less temporary condition of the ground. 
They are expressions of the alterations of the soil-forming factors, chiefly 
in the evaporation and temperature of the ground that we bring about through 
our measures of forest regeneration. When the forest once more closes up 
over the ground, so that it becomes exposed to the soil-forming factors that 
prevail in dense coniferous woods, the formation of nitrate gradually ceases. The 
nitrogen of the humus-covering is no longer decomposed beyond the stage of 
ammonia. The conditions normally prevailing in mossy coniferous forests are 
restored. No detailed investigations have yet been made as to how soon the 
normal condition reappears and as to what factors affect this development. 
The more or less desultory observations that I have made have been reported 
in the preceding pages. 
The alterations in the conversion of nitrogen which have been described 
above are thus of a transitory nature, but they are none the less of the very 
greatest importance in the development of the coniferous forests. They play, 
indeed, a very great part in their regeneration, whether that is effected arti- 
ficially or we leave it to nature. 
CHaAP. xt. The connection between the regeneration of coniferous 
"forests and the nitrification of nitrogen. 
It can scarcely” have escaped the attention of any woodsman who is ac- 
quainted with the condition of our forest-regeneration, especially in Norr- 
land, ”thatithiere vs mvyanttestiyrar close parallelism between the 
factors that produce thesmtiviftcatron of the nitrogen ofthe humus 
and otbfoset that fävourtmhetsepeneration of the forest, Om burnt or 
denshired areas (see fig. 21), on road borders and other places where the 
ground has been disturbed (see fig. 22), in wind-caused gaps where the roots 
have disturbed the ground at the fall of the trees, the humus nitrogen is 
nitrified and the forest is regenerated with ease (see fig. 14), and mouldering 
brushwood favour the formation of saltpetre and the regeneration. In those 
parts of central and southern Sweden where the practice of » Femelschlag» first 
made any considerable headway a mere gap cutting produces a nitrification 
(e. g.g. the Jönåker communal forests, the forests under Högsjö and Äs in 
Södermanland and Alkvättern in Värmland). Where fire has passed over the 
