REGENERATION MEASURES AND THE FORMATION OF SALTPETRE CXXIII 
the humus-covering and natural regrowth (see WAGNER, 1912, page 111). It 
seems to me from the observations I have made, however, as if this means 
would be less effective in upper Norrland than further to the south, inasmuch 
as in Norrland, especially in its upper parts, the brushwood moulders con- 
siderably more slowly than in the climatically more favoured parts of the 
country. The spread brushwood can, of course, sometimes serve another pur- 
pose, namely to counteract the injurious trampling of grazing cattle and there- 
by protect the plants that already exist. 
Another means of promoting the conversion of humus nitrogen is to be 
found in different methods of preparing the ground. These have hitherto had 
far too small a place in our forest economy, though interest in them has been 
shown in certain quarters. As is well known, there are ground-preparing 
implements of different types, for instance the Finnish plough, and WIDÉN'S 
cultivating plough; but this is not the place to enter into a description of 
them. It would certainly be of great service to the forest management of 
this country if the types of implement now existing were subjected to expert 
examination in order to test their powers on different kinds of lands. An im- 
portant condition seems to me to be that the mineral soil and the humus 
should be mixed together as thoroughly as possible: that would increase the 
possibility of the favourable transformation of the humus-covering. The ex- 
periments in ground-preparation carried out by GRINNDAL in Södermanland 
show, too, that in Sweden by means of preparation of the soil with the Fin- 
nish plough extremely fine results can be obtained: the regrowth of pine under 
the thick array of seed-trees was extremely fine, and it was only where 
Aira flexuosa had got the upper hand that there was a dearth of plants 
(seeltng: 15 fand detailed description, page 1044)-.It 15 true; that the pre- 
paration of the soil produces a development of grasses and herbs; but these 
do not appear greatly to hinder the development of the plants. Under an 
overshading stand, at any rate, they do not attain any very great lux- 
uriance. 
Another way of bringing about a preparation of the soil: favourable to re- 
growth is to be found in the breaking up of the stumps. With the increased 
demand for wood that has been brought about by the world war, and that 
will probably continue to prevail for a considerable time after the conclusion 
of peace, this will probably play a far greater part than before in the economy 
of our forest management. It has long been known that very bad raw humus 
can be brought into a state of active transformation by means of breaking 
up the stumps, and that this favours regrowth. 
As appears from this account, I am by no means inimical to burning: 
on the contrary, I hold the opinion that fire is of great importance in check- 
ing that formation of raw humus which easily takes place in our climate and 
which becomes especially active in old thin woods. But as fire has not only 
done good but also has many times done great harm, even slight burning 
should be employed with very great diserimination. It is im place 
only where the raw humus covering is very strong, so that a re- 
generation. cutting or the making of a completereléaningiispnmot 
sufifieten tior comverut torra really good humus, that, $:torsdy 
a nitrifying humus. Where the clearing-vegetation wholly, or for the 
most part, consists of berry-shrubs or a thick carpet of Ara flexuosa, 
