LXX GUNNAR SCHOTTE. 
strata are found represented in undisturbed larch woods up to the age of 30, 
after which the fourth stratum disappears. 
At the age of 40 or thereabouts some few individuals of the third stratum 
may remain. At the age of 50 only the first and second strata are repre- 
sented. In still older forests, as a rule, the first tree-stratum stands alone; 
but completely undisturbed stands of that age of course have not been found. 
When we consider the great demands of the larch in light, however, it is 
noteworthy that nevertheless so many individuals keep alive in the lower tree- 
strata. When we have further found that it is precisely these individuals 
that suffer from lack of light which are first exposed to the cankerous diseases 
that are dangerous to the larch, we see at once that it is an imperative duty 
to thin larch woods early and often. In larch-woods, therefore, the lowest tree- 
strata must not be left as protection for the ground. ”The fertilizing needle 
refuse, however, keeps the ground in good condition; but in older pure larch 
stands it may certainly be useful to have some undergrowth, preferabiy con- 
sisting of some other kind of tree. 
The tabular appendices give further detailed information (see page 792—3807) 
concerning the thinning yield at the first thinning carried out by the State 
Institute. Thinnings are carried out in larch-stands on the /Zow-thinning 
principle. Accordingly in the first place suppressed and cankerous trees are 
removed. Next crooked individuäåls and trees of marked wolf-type should be 
cleared out. If we have to deal with a stock of larches such as the Tyrolean, 
which has a great tendency to form crooked and spriggy trees, so many 
b. trees may be taken out at the first thinning that the thinning approximates 
to a /zgh-thinning. 
Moreover, the larch is grateful for heavy thinnings. Only then can we fully 
make use of the rapid growth of the larch; and when the larch gets large 
strong crowns it is best able to resist larch-canker. 
In quality I the first thinning may take place at the age of 20, and after 
that the thinning ought to be repeated every fifth year. In qualities II and 
III the first thinning may most suitably take place at the age of 25; and 
in qualities IV and V it may be postponed to ages 25—30. About 20 2 
of the timber falls at the first thinning. If the first thinning does not take 
place till after the ages given, 25—30 2 have to be removed at the first 
thinning. 
As the larch requires large crowns for its development, we ought to endeavour 
to obtain plenty of crown-space. The figures obtained from the sample plots 
with somewhat oppressed trees do not afford the full guidance in that respect, 
but they are given none the less in Table 11. Hence we find that the 
crown-space diminishes with the age. Sample plot 350 shows a wood which 
has been raised in fairly sparse order and has therefore good crowns, though 
they are somewhat squeezed on two sides; and here the crown ratio is 0.34. 
In that place the larches stand at a distance of 8 metres between the rows: 
the German pines that earlier existed between the rows were long since removed. 
In the rows themselves the larches stand at a distance of 4—6 metres. The 
crowns have developed very well towards the empty spaces between the rows. 
By means of heavy thinnings there can here be obtained an ideal larch-stand 
with a high percentage of growth. At the thinning that was carried out in 
the spring of 1916 and is clearly shown in detail by the plan in Fig. 99, 
