In addition to the three peatland complex types, bogs can also be divided in terms of their site factors such as the amount of nutrients, the water level and the thickness of the peat layer. These site factors are often reflected in the bog's vegetation. Spruce bogs and pine swamps are forest-like bog types.

Spruce bogs are forest-like bogs with a thin peat layer. They are dominated by spruce trees, but birches and willows can also be found in them. The field layer of a spruce bog is characterized by species from wet taiga forests, such as blueberry and chickweed wintergreen. The ground layer of a spruce bog consists of various mosses, such as peat moss and fork moss.

Because the peat layer of a spruce bog is thin, the plants of the bog have access to nutrient-rich soil below it. This makes it possible for spruce trees and various shrubs to grow in the bog.

A spruce bog. The presence of peat moss in the forest floor reveals that the forest is actually a bog.

If a forest-like bog consists mainly of pine trees, the bog is called a pine swamp. The peat layer of a pine swamp is thicker than that of a spruce bog. This means that the plants do not have access to many nutrients. As a result, pine swamps accommodate only a few plant species. The field layer of a pine swamp is characterized by large shrubs, such as dwarf birches and wild rosemaries. The ground layer of a pine swamp is covered entirely in peat moss.

​A pine swamp.