INFLUENCE OF DIFFERENT DEGREES OF THINNING ON BEECH. 121 



to crown development, the growth of stem classes, other than 

 the predominant and suppressed, increases with the degree of 

 thinning. 



2. At an early age (up to the fiftieth or sixtieth year) the 

 favourable effect of heavy thinning is not so marked, especially 

 on poor localities, as later on. The beech has the capacity for 

 responding to improved conditions of growth up to a late period, 

 so long as it is not actually crippled by crowding. 



3. With the ordinary methods of light and moderate thinning, 

 no great increase of growth takes place, and only when stronger 

 thinnings are instituted does this occur, and more especially when 

 the predominant broad-crowned trees are removed to the advan- 

 tage of middle stem classes. 



4. Only with severe thinning is an increase of growth in all 

 stem classes observable. With thinnings confined to the sup- 

 pressed and half-suppressed trees, the relative increase of growth 

 is most important in the weakest remaining stems. With thin- 

 nings which chiefly remove the broad-crowned predominant 

 stems, the conditions are so far altered that the relative 

 increase is much about the same in all stem classes. 



5. By the increase of growth on single stems with sharper 

 thinnings, the loss caused by diminution of stems is not only 

 made up, but exceeded, and only sinks with very thin stocking. 

 In early age (up to the sixtieth year) the difference in favour of 

 relatively stronger light-fellings is small, but rises after that 

 even on poor soil, quickly. Only with a light-felling, which 

 exceeds 60 per cent, of the strong thinning, does the increase 

 sink again. From the point of view of increased growth, about 

 30 to 40 per cent, in excess of the strong thinning should be 

 aimed at. 



6. Upon comparing the yields of different methods of thinning 

 woods under sixty years of age, the main-crop thinning gives 

 the best results. 



7. A light-felling of 20 per cent, over the strong thinning in 

 woods over sixty years of age gives an increased yield of at least 

 10 to 15 per cent. 



So far as the different methods of thinning are concerned, the 

 weak thinning cannot be considered a cultural measure, as it 

 produces not only less growth than severe thinnings, but, by 

 leaving badly formed and broad-crowned trees, lowers the quality 

 of the timber produced. At an early age, however, these badly- 



VOL. XVI. PART I. I 



