118 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



beech. The quality of the timber must also be considered when 

 thinning. When strong thinnings are made at an early stage, a 

 large quantity of rough timber is produced, while the lighter 

 thinnings, if resulting in less growth at the outset, make up in 

 the long run, so that by the fortieth to the seventieth year the 

 temporary loss is repaid. 



Taking the comparative yields of timber and branchwood on 

 the strong and main crop thinnings respectively, it is found that 

 the former works out at 183 - 8 cubic metres of timber and 335 4 

 cubic metres of branchwood, while the latter gives 200-7 cubic 

 metres timber and 214-0 cubic metres branchwood. Still more 

 favourable to the main-crop thinning is the number of stems, and 

 their sectional area, compared with the strong and moderate 

 thinnings, the advantage being further heightened when one 

 considers that with the moderate thinning the badly-shaped stems 

 are still present, whereas these have been removed in the main- 

 crop thinning. 



Tables are given showing the influence of the three degrees 

 (a, b, and c) of thinning on the different stem classes arranged 

 according to their diameter, from which the following conclusions 

 are arrived at : — (1) By means of heavier thinnings the growth of 

 the remaining stems is increased. (2) This increase is much 

 greater with the transition from the moderate to strong degree 

 than that of the moderate compared with the weak thinning. 

 Sometimes no appreciable difference can be noted between the 

 a and b degrees. (3) The amount of absolute growth rises from 

 the weaker to the stronger stem classes with all degrees of thioning. 

 (4) The increase of growth is in proportion to the age, and in 

 youth and on poor soils is inconsiderable. The effect of the 

 increase of growth (due to thinning) on individual stems is so 

 important that it counterbalances the decrease occasioned by the 

 reduction in the number of stems. (5) The absolute and relative 

 rise in diameter growth is most important in the weakest, and 

 gradually decreases with the stronger stem classes, the reason for 

 this being thai with the latter the conditions are already so favour- 

 able to rapid growth, that any increase caused by further thinning 

 can only take place to a limited extent, and also that those trees 

 which would respond most readily to the improved conditions are 

 chiefly removed in the process of repeated thinnings. 



On two of the main-areas (Frienwalde) the diameter growth of 

 the weakest stem class with moderate is about the double of that 



