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THE AGHICULTUKAL NEWS. 



Jii.Y 13, 1918. 



agnculluial lauds, which is ot'ten icuileied apparent by 

 thf reckless ilenudation of mountains and hillsides. 



There an' two ijuestions involved in this aspect ot 

 the matter. First the effect of the forest cover on the 

 conditions within its own boundary, and secondly, its 

 effect on the conditions of the sunounilinc; country. 



The inriueuce upon the conditions under its o\Yn 

 cover which a forest exercises seems to be mainly due 

 to the canopy of foliage interposed between the sun, 

 the rain and the wiu'l, and the soil. Tne e.xclusion of 

 the sun and the wind reduces the evaporation, and 

 therefore both the air ind the soil under the shade of 

 a forest are, as a rule, iiot only cooler, but muister than 

 in an open field. Trees bring up the water also from 

 greater depths, and transpire this water into the air, 

 thus increasing its humidity in their neighboiirhootl. 



It is true that it does not seem likely that an 

 increase of rainfall in their neighbourhood can properly 

 be attributed to the influence of forests, for other condi- 

 tions producing rainfall are so much more powerful, 

 that it is doubtful whether such a forest effect, even if 

 it existed, would be appreciable. 



The moit important eflect of forests upon water 

 and soil conditions is a mechanical one. J t mist be 

 remembered that agricultural crops depend chiefly on 

 water supplied to their roots, whether furnisherl by 

 rain directly, by artificial watering on the surface, or 

 by a natural underground drainage, this latter being 

 the ideal form of supply. 



Now this is e.sactly what a forest covering aids in 

 securing. A forest growth conserves moisture in the 

 air above the soil, and by itsileep-reaching root systein 

 assists the percolation of the tailing rain, and permits 

 thi! .subdrainage of such water, at the same time 

 prexenting its wastage by surface evaporation. The 

 •waters falling on a well forested slope find lower levels 

 undergronml, and furnish constant supplies to fields 

 b(;lo'.s them. 



( '..nsideririg forestry as the art of producing a crop, 

 it must be remembered that the forest crop dithers 

 from all other crops in the fict that it takes such 

 a long period to yield returns. There is no definite 

 period when the crop can be.s»id to be mature, as in 

 the cjise of agricultural products. It consists of 

 armual accumulations which are allowed to continue 

 until the imlividual trees attain eithi-r a useful 

 or a profitable size; and, to attain such si^e 

 ^ long time, and, witH different .species and condition.s, 

 a\ariable time is needed. Thus, for firewood pi.iduc- 



tion a grow ih nt fifteen to twenty-five years might suffice, 

 while for good lumber production not less than seventy- 

 five to one hundreil years and niire are neede<l. In 

 an average of a hundred years the yeirly growth, 

 :w;cording to species, soil, aod climatic conditions, 

 would vary between SO and ISO cubic feet of wooil 

 per acre each year But, unless firewood is the object 

 of foi'cst cropping, it is no c ipiantity of wood merely, 

 but wooil ot given size and of given '|uality, wood fit 

 for the arts, that is to be grown. 



' With regard to the production of timber, then; 

 is a great drawback attaching to tropical forests ia 

 the fact that, although such forests contain valuable 

 woods, these woods are seldom found in groups of trees 

 of the same species in any considerable number. One 

 object of scientific forestry in the improvement of 

 already existing forests in the.se islands might well be 

 the elimination of the less valuable kinds of trees, 

 leaving those of more value, and the planting of seed- 

 lings of the kind desired in thi' room of the trees 

 taken out. In this way. in course of tin.e, existing 

 forests would become more and more valuable as the 

 source of timber supply. 



But a still more practicable .ind profitable aim 

 would seem to be the reatt'orestation of already denuded 

 tiacts of land, especially on hillsides, or on mcky or 

 sandy soils unsuitable for growing ordinary crops. In 

 this connexion the \alue of .scientific forestry \M)uld 

 certainly make itself felt. The mere planting of a 

 few- trees of one species this year, and perhaps next 

 year the planting of a few more of possibly 'juite a 

 different kind, and so on, ;t!though useful in a way, 

 is not likely to obtain the production of any really 

 valuable forest crop. 



In tile first place, the suitability of any species of 

 tree, or the situation in which it is to be grown, oughti 

 to be determined, in order to avoid inevitable disap- 

 pointments which arise from trying to grow any plant 

 in an unsuitable en\iroument in the next place, it 

 has been deuionstrated in countries where forestry is 

 successfully practised, especially in France and (}er- 

 inaiiy, thai afforestation is only really beneficial and 

 profitable when considerable tracts of the area to be 

 aHbrested are planted at oni- lime with seedlings of the 

 same age, in order that there may bi' .i wood crop ui 

 sufficiently laige proportions which uonld arriM- ,it 

 maturit} at th- same tin.e. 



' ' ■ In Trinidad it appears that a considerable extent, 

 of country is being now afforested in thi.s way with rh-." 



