AOL. QUEENSLAND AGRICULTURAL JOURNAL. [lL Nor., 1899. 
From these figures it will be obvious that the destruction of forests situated 
.on considerable elevations is fraught with injurious consequences to the under- 
ground water supply at the lower levels. The balance of water in the soil, after 
allowing for evaporation, sinks below the surface and acts as a feeder of water- 
courses and springs, besides preserving the moisture of the soil by capillary 
attraction. Doubtless, in addition to evaporation, the forest trees absorb a 
certain amount of that balance, but not in such excess as to sensibly affect the 
supply to the springs at lower levels. 
EFFECT OF FORESTS ON THE SOIL. 
Certain species of trees exercise a beneficial effect upon the soil. This 
.can easily be shown by a consideration of our open forest and scrub lands. In 
an open forest, say of Stringy Bark (Zucalyptus eugentoides, and #. Batleyana), 
an examination of the soil will almost invariably disclose its rocky or gravelly 
nature, its general aridity, and the sparseness of undergrowth and of grass.. 
‘Such a forest, where no other or few other trees are to be found, demands 
certain plant food for its crop, and this the trees constantly take from the soil, 
so that there is an absolute yearly diminution of some particular element of 
the latter, and, owing to there being no canopy of broad-leafed crowns to restore 
the absorbed element, by the decomposition ot fallen leaves, &c , these Lucalyptt 
are unable to keep up and preserve for their own use the productive capacity 
of the soil. It is the same with all forests consisting of only one species, which 
are known as pure forests. Nor can the productiveness of the soil of these 
pure forests be improved without the expense of planting trees and shrubs 
suitable for forming an undergrowth. I need not illustrate this further than 
to point to those portions of the colony where the ridges are clothed with the 
Silver-leafed Ironbark (2. melanophloia), and to the fringes of some of our 
inland scrubs, covered with a stunted growth of wattle, oak, and other narrow- 
seated timber. 
Tf, on the other hand, we examine into the conditions which obtain in the 
.dense coastal and riverine scrubs, a very different picture presents itself. 
Here we find a marvellous diversity of species, not only forming a dense 
jungle, but matted together by gigantic lianas, which, climbing to the tops of 
the trees which support them, spread out into myriads of leafy tendrils, thus 
assisting to form a dense canopy of shade overhead. It requires no great 
intelligence to realise what must be the inevitable effect of such a canopy on 
the soil beneath. Evaporation has scarcely any appreciable effect on the rich 
humus formed by the decomposition of masses of fallen leaves, rotting trunks, 
and branches of soft-wooded trees. A warm atmosphere highly conducive to 
the forcing of growth, and a constant moisture in and below the surface, are 
amongst the beneficial functions of the shade overhead. ‘The soil is constantly 
kept up to a high standard of productive capacity, as is evidenced by the 
gigantic growth of many of the scrub trees. Amongst the most important of 
these, for the purposes above mentioned, are the Gigantic Stinging-tree 
(Laportea gigas) with its congener, the Shiny-leafed Stinging-tree (L. 
photoniphylla). The former often attains a height of from 60 to 100 feet, 
with a diameter of from 4 feet to 7 feet, whilst its leaves are a foot in diameter. 
‘The latter also attains a great altitude and diameter, but its leaves are much 
smaller, being only about t inches long and about 4 inches in width. 
Tn both these species the wood and bark are soft, the former of a spongy, 
fibrous nature. When they are felled, or have reached the ground by natural 
means, they decay in an incredibly short space of time, and so add to the 
richness of the soil. , 
The Bottle trees of the scrubs (Sterculie) occur in most of the southern 
scrubs, but usually some distance from the coast. They often attain a diameter 
cof 7 feet and even more, and a height towering far above the scrub timber. 
The bark is hard and brittle, and forms, as it were, a casing surrounding a 
succulent, watery, mass of fibrous matter. When these trees fall, their decom- 
position is even more speedily accomplished than that of the Stinging-trees, and 
it has a very marked effect upon the soil on which the trees have fatten. 
