Plants & Nature

Lakes, watercourses and bogs

When we are out on a tur and want to take a break, we often head for water; large lakes with open views, small still glittering tarns, surging rivers or trickling streams.

When we are out on a tur and want to take a break, we often head for water; large lakes with open views, small still glittering tarns, surging rivers or trickling streams. There is something alluring about all of them. We like to use the water for activities such as sailing, swimming, canoeing, fishing, windsurfing and other activities. But we also depend on water for our daily tasks and for industry. We are fortunate that here in Norway we have so much fine water that we can enjoy in countless ways. The different types of freshwater have very different qualities.

Contents

Lakes

In Norway we have more than 450,000 lakes, which make up about 5% of the land area. They were formed in connection with the last ice age and are therefore 10,000–12,000 years old (Bjerkely, 2018).

The lakes vary greatly in size and depth, and the definition of what counts as a lake, a pond, a tarn or a puddle can be a little fluid. But what they all have in common is that they are depressions in the surface of the ground that are filled with water. Some have water supplied from larger or smaller rivers, while others only have a supply of rainwater and runoff from the surrounding areas.

We often divide lakes up according to how many nutrients are in the water, since this matters a great deal for the physical and chemical conditions in the water, and for which plants and animals are found there.

Nutrient-poor waters

have little plant growth, both along the shore and out in the water. There are therefore also relatively few animal species. Typically you find brown trout and Arctic charr. The water is very clear because there is little plankton and few dissolved substances in the water. We usually find such waters in the mountains.

Nutrient-rich lakes

usually have lush vegetation along the edge and a lot of plankton in the water. The water here is therefore more turbid. There is plenty of food for animals and therefore usually several different species as well. Here you can find fish species such as roach, common bream, crucian carp and pike. Such waters are usually found in areas with agriculture, industry and high population density. Fertiliser applied to fields in farming, but also discharges from industry and household sewage, seep with surface water down into lakes and watercourses.

When fertiliser is added to a nutrient-poor lake, it may at first seem positive, as the vegetation becomes more lush and more fish appear. But if too much fertiliser is added, the water becomes so murky that plants can no longer grow on the bottom. Less oxygen is therefore supplied. Fewer organisms can then live there, and the water is no longer drinkable for us humans either.

Plants in lakes

Plants grow around the edge of lakes and watercourses that are easy to see. But tiny algae called plankton also float around in the water.

If we go from the bank out into the water, we can see that the plants change a little. Some plants grow with only their roots in water or wet soil furthest from the lake, while others may grow with only the topmost flowers and leaves above the water, and still others may be entirely under the water. Many plants in and by water have their roots in mud where there is very little oxygen. Since the plants need oxygen, many such plants have distinct air channels in their stems. Try cutting through a marsh plant and see if you can find the air channels. Blow through a long piece of stem and watch bubbles form at the other end.

The rooted plants are important in that they provide food and hiding places, dampen the effect of wind and waves, and create the basis for a community of life that cannot exist in the open water masses. Larvae and fish fry can, for example, find shelter from larger fish. But it is plankton that is the most important food source for the animals in the water.

Watercourses

In rivers and streams the water flows along at a fast or calm pace, but always in the same direction. The water is constantly being mixed, and any nutrients supplied flow on with it to the next lake or all the way out to the sea. There is always plenty of oxygen in water that runs quickly. We therefore find different plant and animal communities than in lakes.

The watercourse changes character from start to finish. The uppermost part of the watercourse may be started by a spring or small streams with meltwater from snow and glacier. Here there is little water, low temperature and few plants and animals. The next zone, where the water runs through the mountains, can be quite long and varied. The water runs fast, and there is heavy erosion, so the water carries a fair amount of particles with it. Lower down in the terrain the river becomes larger, carries more water with it at a lower speed, and the water has a higher temperature. The river begins to meander, and there is more both plant and animal life. Finally the river runs out into the sea, and there is a zone where freshwater and saltwater mix together.

Plants in watercourses

In the river you find most plants where the current is not so strong. Here they find it easier to get a foothold on the bottom and not be carried off by the current. Small animals such as insect larvae, on the other hand, can be found even in the most fast-flowing places. They are then found close against the bottom and near stones, where the water is slowed a little because of friction.

A large part of the plant material found in the watercourse comes from vegetation standing along the edge. Which plants grow along the edge can therefore have great significance for which species of animals can live in the water.

Bogs

A bog is an area where the soil is saturated with water, but the surface is at the same time covered by plant growth, so there is no open water surface. There is a great deal of bog in the large coniferous forest belt found on the land areas south of the Arctic across the entire northern hemisphere. In Norway we reckon that about 10% of the land area is covered by bog (Bjerkely 2018). The oldest bogs in Norway formed after the last ice age and are therefore around 8,000–10,000 years old. Just under a third of the bogs in Norway lie in the bare mountains.

Different types of bog

Bogs can be quite different, since they have formed in different ways and have different access to nutrients.

Rain-fed bog

A rain-fed bog gets its moisture and nutrients through precipitation. The plants get no nutrients other than those that come with rain, snow and wind. It is therefore a relatively nutrient-poor and often quite acidic environment. Such bogs are dominated by bog mosses. You can also find cloudberry, heather, cranberry, hare’s-tail cottongrass and crowberry.

Groundwater-fed bog

Another type of bog is the groundwater-fed bog. Here water and nutrients come from groundwater or seepage water lying near the surface. This type of bog is formed by the overgrowing of ponds. When such bogs receive seepage from lime-rich rocks, they can have very rich vegetation including many orchids. In areas that receive seepage from acidic rocks there are often carnivorous plants, since there are few nutrients in such bogs.

Even though we distinguish between these two main types of bog, many bogs are a mixture of rain-fed bog and groundwater-fed bog. What is common to bog is, as mentioned, that the soil is waterlogged. This means there is little oxygen for the plants’ roots. There are therefore very few trees that grow on bog. The lack of oxygen also means that the breakdown of dead animals and plants takes place very slowly, often more slowly than the new growth. Layer upon layer of old dead plant remains is therefore built up, which is pressed together and turns into peat.

The significance of bogs

Bogs are of great significance for the water balance in the landscape. When it rains heavily, the bogs act like “sponges” that soak up the water and prevent the water from running directly into the watercourses and causing floods. At the same time they act as nature’s treatment plant, because the water passes slowly through the bogs and is cleaned on the way. The bogs are also important grazing and hunting areas for many birds and animals, and breeding grounds for many bird species.

In many places bog has been drained and cultivated since it is easy to convert into good farmland. But once a bog has been destroyed, it is very difficult to recreate what was there. There is a large store of carbon in the world’s bogs. If we destroy bogs, we can therefore affect climate change in an even more negative direction. Over time, many bogs and wetland areas have therefore been protected.

Bogs can tell us about the past

Because the breakdown of all organic material takes place so slowly, bogs can keep secrets from the past. Among other things, you can find old pollen remains that can tell us what kind of vegetation there has been in the area several thousand years ago. Since many plants require particular temperature and precipitation conditions, this can say something about what climate there has been earlier.

Another secret that bogs can keep is human. In Denmark in 1952 the body of a man was found that turned out to be from around 300 BC. Because he has lain in a waterlogged bog without oxygen, he is so well preserved that hair, nails, stubble and fingerprints are all well preserved after around 2,000 years in the bog.

Plants by lakes, watercourses and bogs

  • Moss

    We have over 1,000 moss species in Norway. Mosses do not have roots like trees and other plants. They have some attachment organs that hold them fast to the ground, but they do not draw nutrients and water up through these. They get nutrients and water from the air and take it in through the leaves. Mosses can withstand drying out for a long time, but they must have water and humid air now and then in order to complete their life cycle.

    Mosses are variable in both colour and growth form. They can grow on soil, in trees and on stone. There are mosses in almost all habitat types, but especially in bog and the mountains they can be very dominant and actually make a greater contribution to photosynthesis than other plants. In the forest a great deal of moss often grows too. In a small area there can be many different species of moss.

    In the past, mosses were used to seal roofs, walls and boats. Today mosses are used in environmental monitoring. Mosses are, for example, used in studies of air pollution because different species react differently to different substances. Some moss species have medicinal properties, for example an antibiotic effect.

    • Bog mosses

      Bog mosses are a genus of mosses that thrive well in wet places. There are around 200 species of bog moss, and we have about 50 species in Norway. The colour can be green, red, brown or golden. They grow in dense carpets.

      Bog mosses have a special growth in which they grow at the top while the lowest part is brown and dead. The dead part of the moss does not break down because bog mosses contain bactericidal substances. Dead bog moss is therefore continually built up at the bottom while the plant grows at the top. The dead parts are pressed together more and more and after many years turn into peat. In this way bog moss can help to create “land” where there was previously open water in the bog. In many places the peat has been dug up by people and used as fuel.

      The leaves of bog mosses are built up of two different types of cell. One type is ordinary plant cells that can carry out photosynthesis. The other type is special cells that can store water. When there is drought, these cells are filled with air, and the moss will look white. When water comes again, the cells fill up and the plant gets its colour back. Because they have these water-storage cells, bog mosses can soak up water equivalent to 20 times their own weight (Bjerkely 2018). This water-storage ability can help to prevent flooding when a lot of rain suddenly comes, because they soak up the water.

      Try taking a bog moss and another moss. Dry both. Weigh them while they are dry. Put them in water for 5–10 min. Let them drip a little and weigh again.

      Since bog mosses contain an antiseptic substance that is bactericidal, they have over time been used for storing fish, vegetables and so on. They have also been used by women as sanitary towels during menstruation and as nappies for children. In this use both the antiseptic effect and the ability to soak up water were exploited. We can also use bog moss as toilet paper when we are out on a tur, and to wash our hands after a toilet trip. And if you get an insect bite, rubbing the spots with damp bog moss can be soothing.

      Peat and bog mosses have over time been harvested in large quantities, both for fuel and now in our times because it is a good soil improver and growing medium. Large quantities of peat soil are therefore sold in garden centres and plant nurseries. The problem is that it takes nature many years to build up layer upon layer of bog mosses, while harvesting it goes very quickly (see the section on the significance of bogs).

  • Carnivorous plants

    Usually it is animals and humans that eat plants. But some plants can also eat animals, and are therefore called carnivorous plants. Carnivorous plants obtain nutrients by eating animals. They therefore do not need so much nutrition from the soil, and can therefore grow on very mineral-poor bogs.

    In Norway we have six different species of carnivorous plant that grow on land, three species of sundew and three species of butterwort. All of these grow on or by bog.

Untitled

Next steps

Learn more

Text LĂŠrke SĂžndergaard Stewart, Snuitide (2022)

  • Sources

    Bakke, H.H.K. (2017). Natur 1. Barn opplever naturen. 2. utgave. Cappelen Damm.

    Bakke, H.H.K. & Munkebye, E. (2016). Økologi for grunnskolelÊrerutdanningen. 1. utgave. Cappelen Damm AS.

    Bevanger, K. & Jonsson, B. (2007). Kysten. Flora og fauna. 2. utgave. Cappelens Forlag AS.

    Bjerkely, H.J. (2018). Norske naturtyper – þkologi og mangfold. 2. utgave. Universitetsforlaget.

    Halleraker, J. H. (2019, 5. desember). naturtyper. https://snl.no/naturtyper

    Hamre, H.B. (2006). Fjellet. Flora, fauna, geologi. 2. utgave. Cappelens Forlag AS.

    Kvammen, P.I., Lie, S., Nyhus, G.C. & Vedum, T.V. 2021, Ødegaard, T. (2021). Oppdag naturen. 2. utgave. Fagbokforlaget.

    Sabima (u.Ă„.). VI SKAL REDDE GAMMELSKOGEN! Hentet 12. juli 2022 fra https://www.sabima.no/reddgammelskogen/

    Store norske leksikon: https://snl.no/

    SĂžmme (1987). Vegetasjonssoner. I Blystad, J.T. (red.) (2010). Turlederboka (s. 172). Oslo. Den Norske Turistforening

    Urtekildens Planteleksikon: https://rolv.no/urtemedisin/medisinplanter.htm