CHAP, xii.] Protection of the Soil 261 



intervals, twenty to twenty-five years; while this composite 

 form of crop is in its turn less conservative of the productive 

 capacity than High-Forest timber crops. 



The frequent deterioration of soils under coppice does not 

 arise on account of these kinds of trees making high demands 

 per se for food-supplies, although for young poles, shoots from 

 stools, and stoles of sucker-growth considerably higher demands 

 are continuously being made than would be the case if these 

 were to be allowed to develop into young trees having a larger 

 proportion of ripe wood to the foliage and bark in which the 

 mineral ashes are chiefly deposited ; but it is mainly ascribable 

 to the fact of the soil being laid bare to the exhausting influ- 

 ence of sun and wind every twelve to sixteen years on the hags 

 being cut over for the harvesting of the crops of poles, bark, or 

 small material. 



So far, therefore, as considerations regarding conservation of 

 the productive capacity of the soil are concerned, high-forests 

 in general, and those formed of thickly-foliaged species in 

 particular, or copses of standard trees having a good protective 

 soil-covering of underwood, are certainly the forms of woodland 

 crops most thoroughly satisfying the first fundamental prin- 

 ciple of Sylviculture, viz. that the natural productive capacity 

 of the soil must be carefully conserved, in order that it may satisfy 

 continuously and uninterruptedly all rational demands made on 

 the land with regard to the production of timber or of other 

 forest crops. Both the quantitative yield and the qualitative 

 outturn in timber, or in other forest produce, are dependent 

 on the manner in which this fundamental principle is kept in 

 view. If, on merely average or inferior land, such kinds of 

 crops be formed, or methods of treatment be adopted, as 

 imperil the productivity of the soil, then any extra returns that 

 are promised in the immediate future must be dearly pur- 

 chased at the cost of the inevitable ultimate deterioration of 

 the land for timber-production. It would, in fact, be merely 

 discounting the future productivity of the land. The demands 



