490 QUEENSLAND AGRICULTURAL JOURNAL. [1 Noy., 1901. 
Forestry. 
INFLUENCE OF FORESTS ON THE CLIMATIC CONDITIONS OF A 
COUNTRY. 
We have, in the course of many articles on Forestry, frequently pointed 
out that extensive wooded areas exercise a marked influence on the climate of a 
country, and that the destruction of the forests is invariably followed by the 
deterioration of the climate. It is thus that Oskar Peschel teaches in his well- 
known work, ‘Neue Probleme der Vergleichen der Erdkunde.” But he 
entirely omits from his calculation re-evaporation of moisture precipitated on 
the land, and his conclusion cannot consequently be accepted. A well-wooded 
forest area may best be compared to a landlord who spends his income derived 
from the country within it and for the benefit of his neighbours, whereas 
cleared areas resemble absentee proprietors who scatter their revenues in 
foreign parts. It rains; the drops are scattered on the leaves and fall in a 
soft gentle spray or in slow falling big drops, which have collected on the 
foliage, on to the spongy forest ground. 
The water has thus time to percolate slowly into the soil below, whence a 
large quantity is gradually pumped up again through the roots of the forest 
trees, exhaled by their leaves, and again assists in forming rain clouds. Wooded 
areas, no doubt, extract under the same circumstances more moisture out of the 
air than disforested regions, but they serve as a store-house and yield again 
what they take, whereas a great portion of the water precipitated on barren 
soil is only recovered by evaporation from rivers, lakes, and oceans. Forests 
use, therefore, much less moisture than barren areas in the same position and 
under similar conditions, and augment the atmospheric moisture in regard to. 
regions which are separated by such forests from the sea instead. of diminishing 
it. Their action in this respect is not the same thing as that of an intervening 
mountain range. 
In Assam, which is a broad, isolated, well-wooded valley, rain-clouds form: 
in the winter, and it rains when no air-currents reach it from the sea. The 
clouds are home-born, and are to some extent, at least, due to re-evaporation 
from the vast forest areas still in existence. The same laws naturally apply to 
any locality, though they may not be so-strikingly exemplified. It may be 
argued that evaporation from open ground is much more intense than from soil 
covered by forests. No doubt this is the case, and Ebermayer, in his “die 
Physikalisehen Hinwirkungen des Waldes auf Luft und Boden,” gives the 
following data :—‘ The forest alone, without the cover of dead leaves diminishes. 
the evaporations by 62 per cent. as compared with that in the open. Eyapora- 
tion is consequently 2°6 times less in the forests. <A covering of dead leaves 
and vegetable mould diminishes evaporation by a further 22 per cent. J orests. 
with an undisturbed covering of dead leaves and vegetable mould lessen the 
evaporation as compared with that in the open by 84: per ceut. 
These data are based on observations made in Bavaria during the summer 
months. In the Indian climate the difference, which increases in proportion to 
the heat and dryness of the atmosphere, would be even more considerable. 
The above data refer to the evaporation from the soil, which, of course, 
can only take place as long as there is water on the surface, which in the open is 
not the case for long, as it either flows off or gravitates out of reach of the 
influence of evaporation. In a forest the water does not flow off with the same 
rapidity, and much of that which gravitates into the soil is pumped back by the 
long roots of the forest trees, and especially during the period of vegetation is 
exhaled by the leaves in quantities which represent far more than the moisture: 
evaporated from the open ground. ‘There can be no doubt, whatever may be 
said to the contrary, that the widely-spread notion that forests tend to increase 
