CLIMATE AND SOIL 27 



for a woodman to thoroughly understand the effect of light 

 and shade on the growth of the different species. A tree 

 which does not receive enough light languishes and eventually 

 dies. Moreover, any individual branch which is too much 

 shaded will die. This fact is taken advantage of by the 

 woodman to make his trees grow into the desired form. If, 

 for instance, an oak wood is planted closely, say at 2 feet 

 apart ; after a few years it will enter into the thicket stage, 

 and become densely crowded. In this state a struggle for 

 existence is set up in which each tree is striving to outgrow 

 its neighbour in order to obtain light. This causes the trees 

 to grow rapidly in height, while at the same time the branches 

 are killed off by the heavy shade of the surrounding trees, 

 and we thus get trees which are tall and clear of branches. 

 If, on the other hand, we plant the oaks far apart there is no 

 struggle for existence, as each tree has plenty of light, and it 

 develops a large crown and large side branches. 



The woodman, as explained in Chapter VI, regulates the 

 amount of light given to any tree by making thinnings, and 

 causes that tree to grow into the shape desired. 



The actual amount of light which must be given to a tree 

 depends on the species. Some must have their heads fully 

 out to the light, and will not stand any overhead shade at all. 

 Such species are called light- dcmanders. Others will bear 

 a considerable amount of shade and are called shade-bearers. 

 Others occupy an intermediate position, demanding light on 

 poor soils and situations, but bearing a fair amount of shade 

 under favourable conditions. These trees may be termed 

 in ode rate shade-bearers. 



The following list shows the species in the order in which 

 they demand light : 



L ight-demanders. 



1. Larch, birch. 



2. Scotch pine, poplars, willows, false acacia, Corsican pine. 



3. Oak, ash, sweet chestnut. 



