7. Bogs
Contents
7.1 Finland is full of bogs
Finland is a relatively flat country with a wet and cold climate. The amount of rainfall exceeds the amount of water that is evaporated back into the atmosphere. This water can accumulate in pools and depressions that were created during the last ice age. This explains why bogs are so common in Finland. They comprise almost one third of the nation's land surface area. This makes Finland the most boggy nation on the planet.
The number of bogs differs between various regions of Finland. Bogs are the most common in Northern Ostrobothnia, Kainuu, Koillismaa and Southern Lapland. In contrast, bogs are more rare in Southern Finland.
A pine swamp is a type of bog characterized by the presence of pine trees.
7.2 Bogs are formed from plants
Finnish bogs have formed in three different ways. When a lake or a pond overgrows, bog vegetation will slowly spread from the edges of the lake towards its center. In clear-water lakes, this process can begin from the bottom, where the increasing amount of lake vegetation slowly takes over the lake and before being taken over by bog vegetation. In dark-water lakes, there are fewer bottom-dwelling plants because of the low amount of sunlight available. However, these lakes can still overgrow from the top, when bog plants such as peat moss take over the lake by growing on top of it.
When a lake overgrows, bog vegetation slowly takes over the body of water, spreading from its edges towards the center.
Sometimes, forests can also turn into bogs. In wet depressions where groundwater is partially visible on the ground, haircap moss and other bog plants will slowly take over the forest floor. Over time, they produce peat that makes the growth of non-bog plants impossible.
The third way in which a bog can form is via post-glacial rebound. This can happen near the seashore when previously submerged areas of land rise above the water's surface. Bog plants often take over these new, wet habitats.
7.3 Bogs as habitats
Bogs accomodate relatively few plants. Because peat is an acidic and wet soil type that is low in both oxygen and important nutrients such as nitrogen, only certain plant species such as peat moss and sprigs thrive in it. Bogs can be divided into open bogs, spruce bogs and pine swamps depending on the tree species most prominent in them. Open bogs are completely free of trees.
Because bogs are not rich in nutrients, their plant life is relatively unvaried. This has a direct effect on the number of herbivores and predators found in bogs. Although bog ecosystems accommodate only a handful of plant and animal species, at times the populations of these species can be very abundant. For example, large numbers of mosquitoes can be found in bogs during the summer.
Because the number of bog-dwelling animal species is relatively small, the food chains of the bog often remain quite short. Likewise, the food webs of bog ecosystems are often much simpler than those of forest ecosystems.
The sundew is a carnivorous bog plant.
7.4 Peatland complex types
All bogs share some common characteristics. All bogs produce peat and accommodate bog vegetation. However, despite these similarities, bogs come in a number of different types.
Depending on their topographical features, boggy regions can be divided into three peatland complex types.
Raised bogs are common to Southern Finland. The middle part of a raised bog is higher than its edges, which makes water to flow away from the center of the bog. The raised bog receives nutrients only from rainwater, so the central parts of the bog tend to be low in them.
Aapa fens have high edges and low centers. This makes water and nutrients flow from the edges of the bog towards its center. Aapa fens are common to Northern Finland, where they can cover large areas of land.
Palsa bogs can be found in Northern Lapland. They are peat mounds, and their lowest parts are frozen throughout the year. As the amount of permafrost peat increases, the bog steadily grows higher. Sometimes, the edges of the peat mound can crumble away, making the frozen parts melt. This can cause the whole palsa pog to sink down.
| Type | Features | Species | Where? |
|---|---|---|---|
| raised bog | middle part higher than the edges | few species | Southern Finland, e.g. Torronsuo in Tammela. |
| aapa fens | middle part lower than the edges | rich in species | Northern Finland, e.g. Ilmakkiaapa in Sodankylä. |
| palsa bog | permafrost peat mound | rich in species | Northern Laplend, e.g. Iitto in Enontekiö. |
The Torronsuo bog in Tammela is an example of a raised bog.
7.5 Forest-like bogs
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.
7.6 Gallery: Forest-like bogs
7.7 Open bog types
In addition to forest-like bogs, there are also open bog types. No trees usually grow on these kinds of bogs.
Open bogs are low in nutrients. If any trees can be found, they are usually short pines. Different sedges grow on the ground, above dense mats of peat moss. Some pine swamp species can be found growing on dry tufts of land. Some open bogs are wet and sludgy, whereas others are more dry.
Open bogs are low on nutrients.
Fens are treeless bogs that are rich in nutrients. They can be found only in places where lime can be found in the soil. Fens can accommodate some tree growth, but some are completely treeless. Fens accommodate a number of plant species that thrive only in their nutrient-rich soil type, such as various orchids, heather and wild angelica.
Fens are a relatively rare bog type. They are almost completely nonexistent in Southern Finland, whereas only approximately 2 % percent of the bogs in Northern Finland are fens. This is because lime-rich soil is not usually found on top of the Finnish bedrock. In addition, some fens have been dried and converted into farmland.
Fens are open bogs that are high in nutrients.
The edges of many lakes and ponds have grown boggy. Such areas are called water meadows. Their vegetation is often a mixture of shoreland species and bog plants.
| Type | Characteristics | Other |
|---|---|---|
| spruce bog | A forest-like bog type with pine as the most prominent species. | Small spruce bogs can be found growing near small brooks. |
| pine swamp | A forest-like bog type with spruce as the most prominent species. | Many pine swamps have been ditched and are used in forestry. |
| open bog | An open bog that is low in nutrients. | The centers of aapa fens and raised bogs are usually open bogs. |
| fen | An open bog that is low in nutrients. | A rare bog type found in Lapland |
| water meadow | A type of marshland located near the shores of lakes and ponds. | A lot of water and shore plants. |
7.8 Gallery: Open bog types
7.9 Bogs as natural resources
Many fields in Ostrobothnia used to be bogs.
Bogs have also been converted to be used in forestry. Bogs were dried at a great rate after World War II. Nowadays, approximately one fifth of the nation's forest are former bogs.Peat can be used as a growth medium for many garden and house plants. Peat is also an important energy source when burnt. Approximately 6-7 % of Finland's total energy production is achieved by burning peat. This energy is mainly used in heating and electricity production. Peat is gathered from dried and cleared peat bogs, of which there are approximately 60 000 hectares worth in Finland today.
Peat is a domestic Finnish energy source that is found in great quantities in Finnish bogs. However, extensive peat collection damages bogs and causes many other kinds of environmental damages.
7.10 Bogs and ecosystem services
Bogs are economically important due to the peat and trees they produce. Bogs also provide us with various immaterial benefits, which is why they are worth preserving.Bogs are long-lived carbon sinks that use carbon dioxide accumulated in the atmosphere to produce energy. Because bogs decompose slowly, large amounts of atmospheric carbon can be stored stored in their peat layers.
Bogs are also places where water is stored. The moss and peat layers of bogs absorb water and decrease the risk of flooding.
Bogs also produce a number of healthy and economically important berries, such as cloudberries and cranberries.
Because Finland is the boggiest nation on the planet, bogs are part of our natural heritage.