CHAP, vii.] Formation of Mixed Woods 143 



would (from a sylvicultural point of view but pasturage would 

 then be out of the question) be much healthier and more 

 vigorous in growth if they had been well thinned and under- 

 planted with Spruces or Silver Firs about their twenty-fifth to 

 thirtieth year. This is apparently anomalous, for Larch forests 

 occur pure in its Alpine home, though only at high elevations, 

 where the atmosphere is humid, where there is a strong tendency 

 to the growth of moss even in such open forests, where the 

 general growth of Larch is much more vigorous, where there is 

 nearer approach to the maintenance of good canopy, and 

 where, finally, the soil is protected by a deep covering of snow 

 for most of the six to seven months of the year during which 

 the tree is bereft of its foliage. 



Rules for the Formation of Mixed Forests. 



In the same way,, general rules for the formation of mixed 

 crops can also be framed in accordance with the laws of nature 

 and the principles of sylviculture. Those tabulated briefly by 

 Gayer * are as follows : 



1. The concrete conditions of soil and situation must be such as 

 are favourable to the normal development of all species of trees 

 intended to be grown in admixture. It would be erroneous to 

 suppose that mixed crops are advisable only on the better 

 classes of soil, although of course the quality of the latter is 

 an important factor in determining the choice of species to be 

 admixed. In fact, it is on some of the poorer kinds of land 

 that the greatest general advantages of mixed woods make 

 themselves most apparent, particularly when the soils are of 

 a sandy nature. 



2. The admixture of species must not be such as ultimately to 

 endanger the productive capacity of the soil. This is practically 

 a repetition of the first principle laid down with regard to the 



1 Der Waldbau, 3rd edit. 1889, pp. 216, 217. 



