TAE LARCH AND ITS IMPORTANCE IN SWEDISH FOREST ECONOMY. ESCVII 
After this, on pp. 631-639, the regeneration and culture of the larch is 
treated, in course of which there are given many examples of fine self-sown 
areas in Sweden, but it is also shown, none the less, that the reproduction 
of the larch must mainly be secured by planting. 
On pp. 639—0652 is treated the productivity of the European larch in 
Sweden, first of all in pure woods. In order to obtain a general view of 
the growth of the larch in accordance with valuation results from the sample 
plots, it was first necessary to divide the material into different qualities. 
In the qualitative valuation of the ground it has hitherto been customary to 
use the mean height of the wood as the determining factor. This, however, 
is not very suitable for the purpose because of the strong influence that a 
certain mode of thinning may exercise on it, in that a low thinning may 
raise the mean diameter and a high thinning may lower it. This inconve- 
nience comes out more, it is true, in the case of the real mean height than 
Sek 
in the case of the mean height as calculated according to the formula A= 
(4 
which has hitherto been used for what are called "yield tables”. In or- 
der to prevent the mode of thinning from leaving its mark on the mean 
height, however, it is more appropriate in estimating quality to make use of 
the mean height in the first tree-stratum. In estimating the quality of the 
larch-plots this factor has accordingly been used. 
The larch material which has been collected in the course of only a few 
vears, often from almost unthinned woods or, in any case woods thinned too 
late and too slightly, could not properly be used for the drawing up of a com- 
plete productivity table, as the present writer would rather like to call it. 
It is not until after the plots that are now being thinned by the State Institute 
have been further revised and thinned several times, that trustworthy figures 
can be obtained as regards the yield by thinning and as regards the growth 
of the trees after heavy and well-arranged thinnings. They need, therefore, 
to be followed up for at least 15—20 years. "The intention of the present 
enquiry has been only to make out what the present writer will call a stand- 
survey (Table VII), which gives an approximate view of the amount of 
wood that has been produced, as a rule, by pure larch forest in Sweden, and 
the dimensions which have been developed. In order to make the material 
of more uniform value the valuation figures have been chosen from the plots 
after they had been thinned by the State Institute; which thinning, on the 
whole, has been carried out as a heavy low thinning, but which has given a 
very different thinning yield according to the appearance of the wood 
before the thinning. The nature of the woods and the thinning carried out 
are shown in greater detail in the tabular appendices accompanying this treatise. 
Accordingly the stand-survey gives only a distribution into quality classes with 
the corresponding yield of wood in stands which, as a rule, have long been 
undisturbed or have only recently been thinned, but the present writer does not 
wish to express an opinion as to their more or less normal condition. The 
only survey of larch-stands which has previously been worked out, is that 
made by Jurius HAMM (507) on the basis of material from the regions round 
Lake Constance. HAMM set out seven different classes of ground, as is shown 
in detail in Table VIII. A comparison between HAMM's tables and those of 
the State Institute, shows that they extend over about the same limits of va- 
