Agriculture Reference
In-Depth Information
16
T HE S TRUGGLE BETWEEN
L IGHT AND S HADE
Next in importance to the divine profusion of water, light and air, may be reckoned the universal beneficence of grass.
J J Ingalls
The best friend on earth of man is the tree.
Frank Lloyd Wright
A strong argument for having fewer cattle and sheep in Britain is that there would be
more trees. This is because ruminants compete with trees by forging an alliance with grass.
Our natural environment is the field of a perpetual struggle between light and shade, in
which livestock are one of the principal mediators. The other main mediators are fire (which
favours grass) and water (which favours trees).
Trees compete by outgrowing grass and starving it of sunlight. In order to gain their height
advantage they have to invest a proportion of their energy in the necessary infrastructure -
the trunk, boughs, branches and twigs that allow them to spread their leaves over everything
else.
Whereas trees compete vertically by shading out other species, grass in temperate climes
competes horizontally by crowding out other species; but to be able to do this it enlists the
service of ruminants and other herbivores. These animals assist in two ways: they eat young
tree saplings before they become fully established, and they eat the grass. It is counter-in-
tuitive that by eating both kinds of plant, they should help the one and hinder the other, but
there is a reason. The saplings, in order to grow high, have to develop vulnerable infrastruc-
ture above ground, whereas the grass, which has no need of a trunk, can keep all its essential
parts, namely its roots, safe beneath the soil, in the 'impregnable fortress of its subterranean
vitality' as J J Ingalls put it. 1 When a sapling is bitten off, it has to grow its main stem all
over again, and may not succeed. When grass in temperate regions is eaten, it can put on
more leaf growth immediately, and tends to throw out additional shoots, a process known as
tillering. The more grass is eaten, within reason, the more it tillers, the denser the sward be-
 
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