1883.] LEAF CANOPY AND PBUNING. 85 



7. Leaf canopy gradually increases the depth of the top-soil by the 

 deposit of vegetable mould, or humus, under the fallen leaves. 



8. Leaf canopy has a favourable effect on the looseness and porosity 

 of the soil. 



9. With leaf canopy there is less necessity for artificial pruning, 

 and the shafts of the trees grow straight. 



Close order of trees, with the consequent leaf canopy and shade, 

 seems, then, to be enjoined on the forester, in the first place, in order 

 that he may utilize to the utmost the area at disposal. On the given 

 ground — unless there are some cogent reasons for a contrary proceed- 

 ing — there should be raised as many trees as it will well support. 



The second argument, which in many parts of the world would be 

 the most important, seems in our humid climate not to have the 

 same imperative force. On the continent of Europe, and in most 

 climates of the world, the preservation and equalization of moisture in 

 the soil is perhaps the most important function of leaf canopy. In 

 England, especially after the cold wet summers of late years, it may 

 seem of only secondary importance. But would it not be premature 

 to assume that our climate had permanently changed ; and to neglect 

 all precautions against warm and dry summers, like that of 186(S^ 

 wdiich in the natural course of events we may expect to recur ? 



The increase and even distribution of fallen leaves and tree 

 droppings is most beneficial to the soil. These form the only manure 

 which, in the present state of science as applied to forestry, can be 

 bestowed on the forest soil. The under layers of fallen leaves rot 

 slowly under the shade, and form a rich black vegetable mould, or 

 liuiuus, which improves the contents, the consistency, and eventually 

 the depth of the top soil. In some rare instances, under very dense 

 canopy, cases have occurred, particularly in Beech-woods, where the 

 deposit of leaves almost knee-deep was so excessive as to become 

 injurious. This would easily be corrected by bolder thinnings. 

 Lettim? a little light in on the leaves would soon rot them and stimu- 

 late the stagnant growth of the Beeches. The beneficial effects of 

 leaves and tree droppings decomposing under a complete, but not too 

 dense, canopy cannot easily be overrated. 



Complete leaf canopy has thus a great influence on the decaying 

 leaves which it has itself shed and supplied. If the leaves w'ere 

 allowed to rot very quickly they would not add so much to the soil ; 

 but under complete shade they decay slowly, forming rich black 

 humus and useful gases. 



With reference to weeds, attention must first be given to some 

 questions raised by ]\Ir. D. M'Corquodale last month. The 

 deterioration of soil which has been overrun by weeds is manifested 

 in a retarded growth of the trees, and sometimes by the spontaneous 



