1883.] LEAF CANOPY AND PBUNING. 87 



in the impenetrable red moorpan, which gives so much trouble. 

 This is, perhaps, hardly the place for dwelling on the difficulties of 

 renewing a covert where grass and weeds have once got the upper 

 hand, and threaten to overgrow and stifle the young wood plants. 

 The rapid growth of weeds on an extensive bare clearing, with the 

 expense involved in cutting them out and strewing branches to check 

 their growth on the interspaces, affords a powerful argument in favour 

 of renewing coverts under shade of leaf canopy, or in favour of 

 making bare clearings in narrow strips with all possible shade from 

 the side. When a continental forester observes an alarming quantity 

 of weeds on the floor of an advanced covert, he often plants what he 

 calls soil-sheltering wood under the defective canopy. This under- 

 covert can hardly be expected to attain any great intrinsic value, but 

 it protects the continued fertility of the ground, and helps the growth 

 of the over-covert. 



The sixth of the advantages claimed for complete canopy and close 

 order of trees was the protection thereby afforded against the winds. 

 The very essential continuance of the fallen leaves where they have 

 dropped is thus effected, and the useful gases evolved in their decom- 

 position are less liable to be wafted away. At very windy points 

 e\''en the close order of the trees may not be efficacious in retainino- 

 leaf deposits. Here assistance may be rendered by strewing branches 

 in autumn, and even planting low screens in the form of a hedge. 

 Close order will generally, in an extensive and compact wood, inter- 

 pose sufficient barriers against wind. Exclusion of cold winds will 

 have the further advantage of maintaining the temperature higher 

 and more equable. 



Increase of depth in the top soil will be an extremely gradual process. 

 If, however, leaf canopy effects a hardly perceptible improvement, it 

 is at any rate a great protection against loss. Where the top soil is 

 very shallow it would be dangerous to make a large bare clearing ; 

 but renewal of wood can be safely accomplished, though slowly and 

 gradually, under shade. 



Looseness or porosity of consistency, allowing tis for the penetration of 

 air through the soil, is a most desirable and valuable quality in soil 

 which is to produce wood. Leaf canopy preserves and promotes this 

 condition of the ground which it shades. The friable black mould 

 formed each year under the deposit of fallen leaves of hardwoods in 

 close order, must improve the consistency of the surface soil and 

 render it more porous. In general, wherever there is close canopy 

 and no removal of fallen leaves or needles, the ground, besides 

 receiving a powdery addition of vegetable mould, will not be 

 compressed by the direct beating and washing of rain and showers, 

 nor hardened and caked under a hot sun. 



