Forest Layers, Stories, And Stratification

By Vijayalaxmi Kinhal on April 25 2017 in Environment

A rough schematic illustrating forest layer stratification.
A rough schematic illustrating forest layer stratification.

The number of layers of a forest vary, and these layers are as important to every forests distinctive characteristics as the species that make them up. Each forest has a horizontal organization as well as a vertical structure depending on the maximum height of the different trees and other plants. The term layering in forests is used to divide the vertical structure into many sections, and is also called stratification.

10. Many Layers to Every Forest

The number of layers a forest has depends most on its climatic conditions, especially light and temperature, as well as soil type and rainfall. Above-ground starting from the outside is the emergent layer, then the forest canopy, the understory, shrub layer, soil layer, and then underground there is the rhizosphere.

9. Emergent Layer

The emergent layer is the topmost layer, composed of trees, woody climbers, and epiphytes. This strata can have trees reaching 70 to 80 meters high, and is found only in tropical forests. This layer is absent from temperate forests.

8. Forest Canopy

The forest canopy is continuous in a forest and is made of tree crowns. This can be undulating, as not all species, or even all individuals of the same species, have the same height. The forest canopy is always exposed to sunlight, and the flowers and fruits are borne here. However trees have to tolerate high humidity and winds as well . Trees grow tall in their competition to reach light. This layer is found in both tropical and temperate forests. The maximum height in tropical forests can be 60 meters high, though average heights are only 10 to 25 meters. In temperate forests this strata can reach 90 meters.

7. Understory

The forest canopy blocks much of the light from penetrating through it, and consequently the understory is dimly-lit, and calm without much wind due to the overhead shield. So trees found in this layer are those that need less light or are the cohort of young saplings of the canopy trees. This layer is not as densely packed as the canopy, and reaches up to 5 to 10 meters.

6. Shrub Layer

There is even less light here than in the understory. The shrub layer is 1 to 5 meters and is made of very short trees, and seedlings of bigger trees. Shrubs are rarely found in untouched forests, as they usually need a great deal of sunlight, in tropical forests. Some deciduous temperate forests have a rich shrub layer.

5. Non-Woody Herbaceous Ground Cover

Here there are herbaceous plants and some grasses. There are usually few species in this layer compared to the other higher layers in tropical forests. While the tree species can run into a few hundreds, there can be less than 50 species of herbs. In untouched tropical forests this strata is rarely more than 10% of the forest area. In contrast, the temperate forest floor can have more species and covers a larger area.

4. Moss, Cryptogam, and Shallow Soil Layer

This is the zone of the forest with the fallen logs of trees, and the decomposing litter of fallen leaves and twigs. This layer of decomposing organic matter, and cool temperatures are ideal for cryptogams, which are species that use spores and not seeds to propagate, including ferns, mosses, lichens, fungi and algae.

3. Rhizosphere: Realm of the Roots

The rhizosphere is underground, and is made up of roots. Most of the roots are found in shallow soil, which is the first 5 centimeters in tropical forests, and as the soil depth increases the amount of roots decreases.

2. Animals Living in Each Layer

In tropical forests, most of the organisms, including insects, birds, and mammals such as squirrels, primates, and the Australian Ring-Tail Possum pictured hanging out above, are found in the forest canopy. There, they are attracted by the ample supply of flowers, fruits, leaves, and other food sources. Insects and micro-organisms are also found in the soil and litter. In temperate forests most of the animal life is found in the cryptogam and herb layer, with a few of them, such as squirrels, also being found living all the way up to the canopy as. However, the unique niches created in each strata can support different animal life.

1. How the Layers Create and Integrated Forest Ecosystem

The climate and soil of a region can determine the number of layers, which in turn can influence the environmental conditions and characteristic biodiversity of each of the layers. Many tropical species need this interactions, as they can germinate only in the dark, and need shade as seedlings and saplings. Without the stratification, primary forests cannot exist, and would be replaced by secondary common species. In the deciduous nature of temperate forests wild flowers are common and bloom in spring before the trees grow leaves.

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