32 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



pine is grown under similar conditions and secures a price as 

 good or better than that of silver fir. Surely such a golden 

 opportunity for securing the introduction of a species whose 

 regeneration is so assured should not be lost sight of owing 

 to the conservative attitude of the forest staff towards 

 exotics. 



The same attitude towards larch is found in the eastern 

 section of the Puy de Dome Department, where, although the 

 few samples of larch appear to have put on quite as good 

 increment as the surrounding silvers and spruces, the species is 

 regarded with distrust because the local traders will not give 

 as much for larch timber as for these others. 



Common spruce is used considerably in the planting or re 

 afforestation of areas which have proved too wet and marshy, 

 and, as may be seen in St Germain d'Herment, it thrives much 

 better than the Scots pine under such conditions. It is also 

 found in most of the silver fir forests, forming a small percentage 

 of the crop ; but it is seldom allowed to oust the more valuable 

 species, for under its shade not even the silver fir can come up. 



Methods of Calculating the Yield. 



These may be taken under the two headings : — 



{a) By area, when replacing Scots pine by Silver fir. 

 {b) By volume, using the 1883 method for Selection 

 forests. 



{a) By Area. — As has already been mentioned, the Scots 

 pine is treated as a conversion crop and the forest is divided 

 into ten equal areas, one of which is cut over each year and 

 a percentage of the crop removed. This appears to be done 

 by the number of stems,— for instance, in the Chez Paris Serie, 

 in the first lo-year period one-third of the stems are removed, 

 in the second 10 years, two-fifths of the remaining stems are 

 cut, and so on, with three-fifths in the third period, and the 

 rest of the stock in the fourth. For the purpose of calculating 

 the financial yield, however, volumes are used. The present 

 volume of 500 m. per hectare, plus the increment on the 

 remaining stock throughout the 40 years, which is taken at 

 200 m., gives a total of 700 m. to be cut in the 40 years ; 

 valued at 30 fr. per cm. this gives a return of 525 fr. per hectare 

 per annum. 



