The Earth as Modified by Human ActionMarsh, George P. (George Perkins)
History
The Earth as Modified by Human Action
Marsh, George P. (George Perkins)
Conservation of natural resources; Human geography; Nature -- Effect of human beings on; Physical geography
be fit for cultivation without any other artificial drainage than, in
the ordinary course of cultivation, is given to other new soils.
[Footnote: A special dessicative influence has long been ascribed to the
maritime pine, which has been extensively planted on the dunes and
sand-plains of western France, and it is well established that, under
certain conditions, all trees, whether evergreen or deciduous, exercise
this function, but there is no convincing proof that in the cases now
referred to there is any difference in the mode of action of the two
classes of trees. An article by D'Arbois de Jubainville in the Revue des
Eaux et Forets for April, 1869, ascribing the same action to the Pinus
sylvestris, has excited much attention in Europe, and the facts stated
by this writer constitute the strongest evidence known to me in support
of the alleged influence of evergreen trees, as distinguished from the
draining by downward conduction, which is a function exercised by all
trees, under ordinary circumstances, in proportion to their penetration
of a bibulous subsoil by tap or other descending roots. The question has
been ably discussed by Beraud in the Revue des Deux Mondes for April,
1870, the result being that the drying of the soil by pines is due
simply to conduction by the roots, whatever may be the foliage of the
tree. See post: Influence of the Forest on Flow of Springs. It is
however certain, I believe, that evergreens exhale more moisture in
winter than leafless deciduous trees, and consequently some weight is to
be ascribed to this element.]
The Forest in Winter.
The influence of the woods on the flow of springs, and consequently on
the supply for the larger water-courses, naturally connects itself with
the general question of the action of the forest on the humidity of the
ground. But the special condition of the woodlands, as affected by snow
and frost in the winter of excessive climates, like that of the United
States, has not been so much studied as it deserves; and as it has a
most important bearing on the superficial hydrology of the earth, I
shall make some observations upon it before I proceed to the direct
discussion of the influence of the forest on the flow of springs.
Public-domain text, read in full here on John Shaqi.
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