Part 2
The leading role among the green population of the forest, undoubtedly, belongs to the trees. It is they who create the forest in the first place, without them there can be no forest itself. The leading role of woody plants is manifested in many ways.
Trees have a huge mass of vegetation. In this respect, they are far superior to all other green plants in the forest - shrubs, shrubs, herbs, mosses. Trees account for the vast majority of organic matter. At the same time, trees are the main object of economic use in the forest, because they are the ones that give us wood.
But the leading role of trees is not limited to this. We must not forget that powerful woody plants create a very special forest environment under their roofs. The whole environment under the canopy of the forest is very different from what we find in the open. This is especially good in summer, on a hot sunny day. But the specific forest environment is not suitable for all flora species. Under the thick canopy of the forest, for example, light-loving grasses and shrubs cannot develop. But the shady ones grow quite well. In short, trees determine the possibility of existence of certain plants under their canopy, as if making a kind of selection. In this, too, their dominant role is manifested.
Trees form the uppermost, dominant tier in the forest. It is usually called a tree stand. All the rest of the lower tiers are called subordinates. And it reflects the essence of the case quite rightly. Everything that grows under trees, experiences more or less oppression from the forest giants, occupies a subordinate position in the forest.
Now let's get acquainted with the tree tier in more detail. First of all it is necessary to tell about features of placing of trees on the area. You have probably noticed that in different parts of the mature forest the tree stand has different density: in some places it is relatively dense, closed, in others, on the contrary, quite rare.
What is the reason for such differences? Most often it is the result of partial felling of trees (for example, in the so-called thinning of trees). But the same phenomenon is also observed in the forest, which is not affected by felling. Here, the density of the tree layer can also vary greatly. However, the reason in this case is completely different. Rare stands are usually found where the soil conditions for tree growth are particularly unfavourable. An example is pine forests that grow on sand dunes. The soil here is very dry, the water "ration" is extremely scarce, and the trees are relatively rare. There is not enough water for the development of a dense forest here. Where the forest develops in favorable soil conditions and receives enough moisture, it is usually dense, closed.
The density of trees is most often expressed in the number of trunks per hectare. If you calculate this number in untouched pine and spruce stands of the same age, and growing in fairly favorable conditions, the result will be different: in the pine stands will be somewhat less than in the spruce stands. Therefore, pine forest is by its very nature more rare than spruce forest. This is due to the different attitude to the light of the tree species that make up the forest. The pine is light-loving and cannot grow as densely as the shady spruce. Therefore, the density of trees is determined not only by soil conditions of tree growth, but also by the nature of the trees themselves, their relationship to light.
In a natural forest, trees are never evenly distributed over a small area. In some places they seem to be bored, in others, on the contrary, they are thinned out. In addition, there are almost always larger or smaller gaps in the tree canopy - the so-called "windows". These gaps are particularly characteristic of the old forest, where some large trees die out from time to time for one reason or another. Trees can die in the forest from old age, from wind damage, insect damage, etc. After the extinction of a large tree, there is a large hole in the tree, which is not overgrown for a long time. "Windows" in the tree canopy is the most common, widespread phenomenon.
Let us now turn to the composition of the tree species that make up our forests. In different parts of the country the species composition of trees in the forest is not the same. The number of tree species also varies. If we go through the northern coniferous forest, we can rarely count more than 2-3 tree species. Our Central Russian oak groves are richer in this respect. Here you can find up to ten different trees (oak, linden, ash, several species of maple, elm, silt, etc.). All this has its reasons. The number of tree species in the forest depends directly on how favorable the natural conditions of the area are - climatic and soil. The better these conditions, the richer the species composition of trees. Northern coniferous forests have few tree species, because they develop in harsh natural conditions - in cold climate and on relatively poor soils. In contrast, oak groves are common in areas with a fairly warm climate an
The continuation should be...