86 



Studies in Forestry 



B. CONIFEROUS TREES. 



[CHAP. IV. 



From these tables it appears that none of the conifers 

 make anything like such large demands as the broad-leaved 

 genera of trees per unit of foliage ; for the most exacting 

 of the former makes considerably less demand than the least 

 exacting of the latter. But the amount of nutrients annually 

 withdrawn depends on the total quantity of foliage and of 

 timber formed annually; and, as yet, no exact data of this 

 description have been collected and tabulated. As a matter 

 of actual experience, however, we know that soil improves 

 greatly under coniferous crops, so long as a good canopy of 

 foliage is maintained ; hence there is good reason for believing 

 that, in making very moderate annual demands, they enable 

 the capital in nutrients to be increased within the soil year 

 by year. But the very favourable physical influences exerted 

 simultaneously on the soil by means of the canopy of ever- 

 green foliage overhead must not be left out of the reckoning 

 when this matter is being considered. 



It will be noted, by a comparison of the above table with 

 that previously given for requirements as to water, that, 

 in a general way, the trees transpiring most freely, also with- 

 draw the largest mineral food-supplies from the soil. And 

 these results correspond very fairly with actual sylvicultural 

 experience. Where discrepancies seem apparent, a study of 

 all the circumstances connected with the growth of the tree 



