An ecosystem can be subdivided by the layers of its vegetation.
Stratification is determined especially by the sizes and kinds of plants present.
The canopy is the primary site of energy fixation. It influences the amount of sunlight that penetrates deeper into the forest. The understory typically includes tall shrubs and smaller trees. These must be shade-tolerant since they're growing under the canopy trees. The shrub layer varies depending on the kind of and location of the forest.