MOISTURE AND TREE GROWTH 75 



Poplars, Sitka Spruce, or Norway Spruce ; though, as already 

 stated, it is usually very difficult to get trees established on 

 wet localities on account of the increased danger from 

 frosts. 



To a great extent, a damp soil will afford conditions 

 suitable for growing trees which on drier soils will only 

 thrive if the air be moist. And vice versa, a moist air will 

 make good the deficiencies of a dry soil ; 1 for the relative 

 humidity of the atmosphere will determine, to a great extent, 

 the degree of transpiration effected by any tree. 



Thus imported trees which are naturally found in high 

 mountainous regions in their native country, where perhaps 

 the soil is thin and not capable of holding much water, but 

 where they are constantly shrouded in mist, will succeed, 

 here in Britain, only on moist soils at low altitudes, or 

 where the air is moist, such as in the neighbourhood of large 

 sheets of water the sea, or inland lakes. 



Such trees as Norway Spruce, and, to a less extent, Silver 

 Fir, will usually succeed far better in high mountainous 

 regions in their own country than they will in Great Britain. 

 For though in this country they may be planted on moist 

 soil, and though the summer rainfall may be far greater than 

 is the case in their native home, yet the growing season is 

 longer in this country and transpiration continuously more 

 active. Whereas, in their native home the growing season is 

 very short, and excessive transpiration is so often checked by 

 mists and fogs, and on account of the short growing season, 

 the total amount of moisture required is less than in this 

 country. Norway Spruce is more suited for growth in 

 Scotland than in England ; whereas, for Silver Fir, England 

 is more suitable, on account of the warmer summers. 



From the foregoing, it will be evident that on southern 

 aspects, where the air is dry and, in most cases, the soil also, 

 care should be taken to plant only such trees as make slight 

 demands for moisture. Though at high elevations, owing to 

 the growing season being shorter and owing to active 



, 1 Thus on dry soils a far greater choice of trees is possible on 

 northern aspects than on southern aspects. 



