The Structure of Forest Layers

When studying plants, plant geographers tend to focus on the general plant cover in a space by looking at life-forms.

A life-form is defined as a plant’s function in an ecosystem, which can include how a plant’s size, shape, and physical structure impacts its ecosystem function. Instead of using species identification, a life-form is an alternate way to classify plants.

This blog post will be focusing on the types of life-forms that may be found in the moist forest layer, such as trees, shrubs, herbs, and lianas, and quick overview on how they are structured.

Keep in mind that different groups may classify the structure of a forest in various ways other than the ways I list below.

Forest 

What exactly is a forest? Every group has its own definition of a forest. I’m defining a forest as an area with a group of trees packed in close proximity, that may create an area of shade under their leaves.

Tree Layer

Trees can be described as big standing plants with woody stems and branches arranging into a crown shape on top. Trees make up the uppermost layer in a forest. Getting the most sunlight in the forest, the tops of the trees are called the canopy layer. Just under the canopy layer, you can find the understory layer filled with smaller trees that have thinner trunks.

Shrub Layer

 Similar to trees, shrubs also have an upright position with a woody stem. However, the leaves and branches of shrubs form near the ground, which lead to shrubs being smaller than mature trees. The shrub layer makes up the middle layer of the forest landscape. Young trees may also be also be found in this layer.

Herb Layer

 Herbs are tiny plants that do not have woody stems. They come in a variety of shapes and leaf sizes such as narrow-leaved and broad-leaved such as grasses, ferns, and weeds. The herb layer usually forms the lowest layer in a forest. Sunlight is very limited in this layer.

Liana Layer

Lianas are woody plants shaped like vines that can be found twirling around shrubs and trees. Some examples of lianas include poison ivy and English ivy.

 

Moss Layer 

Some forests may contain a lower layer than the herb layer filled with mosses. A moss is a small plant that lacks roots, seeds, and flowers. Mosses are usually found near the forest floor where the dead matter resides to restore nutrients back into the soil.

 The Importance of Forest Layers

The diversity of the sizes, shapes, and structures found in forest layers are essential to the functioning of forest ecosystems. Through these various life-forms, forests are able to provide a home to a large range of animal and plant species.

(Photo Credit: Above photo from Oliver Henze through the Creative Commons License)