CHAP, xii.] Protection of the Soil 265 



by the ploughing operations that are carried out annually. In 

 sylviculture similar operations are out of the question, except in 

 osier-holts, in nurseries, and in the preparation of patches or 

 strips of soil during natural regeneration or artificial reproduction 

 by means of sowing or planting. Nor are they required when 

 once the young seedlings have firmly established themselves 

 within the soil ; for the latter is not only aerated and mechani- 

 cally loosened by the humification of the dead foliage and the 

 cleaving and fissuring action of the roots, but is likewise pro- 

 tected from the soddening and setting action of rain by means 

 of the leaf-canopy overhead. 



Actual experience shows that, except at the time of the 

 germination of seed, and the initial development of young 

 seedlings, so long as good canopy is maintained throughout 

 the crop no danger is run of the soil becoming set or hardened 

 on the surface by rainfall, as is so apt to be the case in fields 

 that lie fallow for any length of time. The humification of the 

 dead leaves and twigs, and of the roots of individual seedlings, 

 poles, or trees removed during the periodical processes of weed- 

 ing, clearing, or thinning, not only serves to improve the other 

 factors of influence as regards productivity, but most directly 

 acts on the cohesiveness of the soil-particles, by tending to 

 loosen binding soils, and to render more cohesive those which 

 are of a light sandy nature. This natural process is of course 

 aided by the action of the various organisms that are always 

 to be found more numerously in soils in which humification 

 is going on, such as Cladosporium humifaciens, Rostr., and 

 other fungi, insects, earth-worms, &c. 



If the thorough aeration of the upper layer of woodland soil 

 could be periodically undertaken, there can be no doubt that 

 the productive effect of this measure would be speedily notice- 

 able in the more vigorous development and greater increment 

 of the crops. But, except on a small scale in osier-holts, this 

 is, for financial reasons, out of the question ; and besides this, 

 it is open to considerable doubt if the quality of the timber 



