454 ATTENTIONS TO GIVE TO THE SOIL. 



by scattering seeds of grasses and hardy gregariotis weeds and un- 

 dershrubs. Ultimately when all this precedent vegetation has ren- 

 dered the place suitable for tree-growth, this last should be intro- 

 duced by sowing or planting at points where soil has collected or 

 has been brought together for the purpose. 



The protection of unstable soil on slopes and the fixing of drift- 

 ing sands are subjects that have already been adequately treated, 

 the former at pp. 233-9, the latter at pp. 228-33. 



Compactness . 



A certain degree of freeness of the soil, sufficient for unimpaired 

 root-aeration and exposure of its interior to fertilising atmospheric 

 action, is a most important factor of productiveness. To prove 

 this we have only to observe the vast difference in development of 

 plants of one and the same species and age grown in thoroughly 

 loosened soil and in one that has been subjected to no kind of cul- 

 tivation at all. 



Soil constantly under a leaf-canopy and covered with dead leaves 

 and low vegetation cannot, like bare-exposed land, be hardened by 

 the pelting action of rain or by the sinking of water through it ; 

 while the decaying and decayed leaves at the surface and the root 

 fibres and hairs in the interior have a direct effect in loosening it 

 very appreciably throughout its mass. 



Very stiff soils should never be exposed and regeneration thereon 

 should hence be effected under cover. 



Amount of moisture. 



The moisture in a soil is the most important factor of its pro- 

 ductiveness. Without sufficient moisture, the richest soil will be 

 sterile, and with a constant supply of it the poorest soil will grow 

 magnificent forests. 



We have already, at pp. 235-6, shown how energetically the soil 

 on forest-clad slopes holds water in store for the benefit of the 

 vegetation on it. This is still truer of level land under forest To 

 enable the soil to retain as much moisture as it can contain we re- 

 quire the presence of a constant leaf-canopy, a form of crop suited 

 to local conditions, avoidance of large clearances, and, whenever 

 possible, regeneration under cover and preservation of the entire 

 covering of humus, dead leaves and grass on it. When it is not 

 possible to maintain a complete leaf-canopy, the requisite protection 

 should be afforded by utilising, wherever the leaf-canopy is inter- 

 rupted, advance growth, stool-shoots and suckers of tree-species, 



