1857. 



NEW ENGLAND FARMER. 



603 



and practice ssoiling. It makes hens laj', chickens 

 live, and prevents swine from rooting up meadows. 

 Progressive agriculture keeps on hand plenty of 

 dry fuel, and brings in the oven-wood for the women. 

 It plows deeply, sows plentifully, harrows evenly, 

 and prays for the blessing of Heaven. Finally, it 

 subscribes for good religious, agricultural, and fam- 

 ily journals, and pays for them in advance, advo- 

 cates free schools, and always takes something be- 

 sides the family to the county fair. 



For the Neto England Farmer. 



RELATION OF TREES TO THE SOIL. 



BY WILSON FL\GG. 



It is admitted by all, that the prosperity of agri- 

 culture depends greatly on preserving the general 

 sources of spontaneous fertilization, and that ade- 

 quate supply of moisture to the uplands which are 

 exposed to drought. The surface of the earth is 

 very uneven. I will not dilate upon this point, as 

 the forms of these inequalities are very well known. 

 I believe this arrangement to be one of the most 

 beneficent provisions in the economy of nature, and 

 one which is necessary, to keep up that constant 

 action on which the life of all things is dependent. 

 Suppose the ocean to be the original source of all 

 the vapors of the atmosphere, the return of this 

 moisture to its original source can be effected only 

 by these inequalities. If the whole earth's surface 

 were a dead level, it could only be returned by 

 percolating through the earth, till it arrived at the 

 bed of the ocean. Hence we find that extensive 

 plains, if they are not sandy or elevated, are un- 

 wholesome morasses, and unfavorable to the pur- 

 poses of agriculture. The soil cannot receive the 

 chemical action of the atmosphere, on account of 

 the water that rests upon it, and it can be reduced 

 to tillage only by the laborious operations of drain- 

 ing by the hand of man. 



One of the points which I wish to establish is 

 that if trees were of no value at all to mankind, as 

 timber or fuel, it would still be necessary to keep a 

 large proportion of the country covered with them, 

 on account of their serviceability to agriculture. 

 Trees are useful and indispensable agents, in the 

 economy of nature, for preserving the humidity of 

 the soil in dry and upland situations. All vegeta- 

 tion, in its growing state, tends to fill the atmos- 

 phere with moisture, by drawing it up through the 

 roots, and exhaling it into the air. Trees are more 

 useful than other plants in this respect, because 

 they draw up moisture from greater depths and in 

 larger quantities. The question now arises whether 

 any given amount of surface would evaporate its 

 moisture faster when covered with trees, or when 

 bare of vegetation. I am prepared to show that a giv- 

 en space of land would exhale more moisture when 

 covered with trees, than without them; but that at 

 the same time, the earth would be better supplied 

 ■with moisture, with the trees than without them. 

 With a covering of trees, every leaf is an exhalant, 

 ■which, through the roots, is drawing up the moisture 

 of the earth and pouring it out into the atmosphere. 

 The outer surface of the soil will exhale less mois- 

 ture than if it was bare; but the roots of the trees 

 penetrating to a considerable depth, and perme- 

 ating every inch of the whole substance, make the 

 case equivalent to one in which the surface is con- 

 stantly turned over by plowing, and exposed to the 



action of the sun and air. Hence, if in both cases 

 there was an equal supply of moisture returned to 

 the earth, the land when covered with trees would 

 tie drier than if it were a bare surface. But this 

 is not the fact. The fact is that a much larger 

 quantity of moisture is returned to the earth when 

 it is covered with trees, especially on a very wide 

 tract of country ; for the larger and the more ex- 

 tensive the tract the more determinate and sure is 

 the operation of the principle. We will speak, 

 therefore, with reference to a whole country, say a 

 thousand miles square. If this whole surface is 

 bare of trees, whenever a rain falls upon it, the ■wa- 

 ter runs down from the hills, and floods the val- 

 leys, and fills up the rivers which rapidly return it 

 to the sea. A few days of sunshine dries up the sur- 

 face, and the water has got back to the ocean, be- 

 fore it has pei formed its destination. If the same 

 country be entirely covered with trees, they arrest 

 the progress of the water in its journey down the 

 hills ; less of it escapes by direct evaporation from 

 the surface, and more by absorption from the roots 

 of trees and by exhalation from their foliage. 

 Showers are more abundant over a whole country 

 which is saturated with water. The rivers and 

 lakes are comparatively full of water, and the whole 

 atmosphere is in a state of excessive humidity. 



The same principle may be traced where the 

 earth is partially covered. But another question 

 arises in this place — whether trees are equally use- 

 ful with respect to their influence upon the mois- 

 ture of the earth and atmosphere in all places ? 

 I would contend that it is only on dry and elevated 

 places that trees can act beneficially upon the soil. 

 Here they act by retaining the moisture which 

 would otherwise rapidly run down into the lakes, 

 rivers and valleys ; by the obstacles interposed by 

 their roots, and the substances always collected 

 around them, they cause it to percolate dowo the 

 slopes by slow degrees, affording constant irriga- 

 tion to the surfaces below, without inundating 

 them by the rapid flow of the waters. 



We could easily explain the operation of this 

 process. Here is a hemispherical hill, of the su- 

 perfices of one square mile. If it stood upon a 

 level plain, the whole surface of this hill might be 

 covered with trees, greatly to the advantage of the 

 tract lying immediately around its base ; for when- 

 ever a shower fell upon the earth, the plain would 

 not be immediately inundated by the water from 

 the hill, as it would be if the hill was bare of trees. 

 Not only would the earth be more porous on ac- 

 count of the roots of the trees, and consequently 

 absorb more of the rain as it falls, but the trunks 

 and elevated roots of the trees, the shrubbery that 

 forms their undergrowth, and the decaying foliage, 

 the mosses, lichens and other cryptogamous plants 

 upon the surface, are all so many obstacles to pre- 

 vent the free passage of the water from the hill to 

 the plain. This water, which would otherwise have 

 escaped in a few hours, continues trickling down 

 from the hill for several weeks, a source of con- 

 stant irrigation to the plain. Hence the plain 

 would suffer less from drought and less from in- 

 undation, on account of the forest that covers the 

 hill. This action would be still more favorable to 

 an arable strip of land all round the bottom of the 

 hill, above its base, suppose half the area of the 

 hill, from the summit half way down to its base, to 

 be covered with forest. The rains that fell on the 

 summit which is covered with ■wood, would be in a 



