Alder
Alder, scientifically known as Alnus incana (gray alder) and Alnus glutinosa (black alder), are deciduous tree species that are a natural part of the Norwegian flora. These trees belong to temperate forests and are often found in moist areas such as riverbanks and wetlands. Alder is known for its ability to thrive in moist areas and along waterways. It is a pioneer species that quickly colonizes open areas and disturbed soils1 2.
Characteristics
Grey alder can grow up to 20 meters tall and has a slender trunk with smooth, gray bark that becomes more furrowed with age. The leaves are oval, toothed and have a dark green color on the upper side and lighter on the underside. Gray alder has a more open and bushy crown. It has a normal lifespan of around 60-80 years, but can live up to 200 years. The tree species is a natural part of the Norwegian flora, especially widespread in the lowlands and along the coast from Østfold to Troms. Gray alder thrives best in moist, nutrient-rich soil types and tolerates shade and varying climate conditions. It is also known for its nitrogen-fixing root tubers that enrich the soil1 2 3.
Blackthorn can grow up to 30 meters tall and have a trunk diameter of 80 cm. The trunk is dark and has smooth buds. The leaves of the blackthorn are obovate or heart-shaped, rounded or concave at the tip, with rusty brown hair tufts in the nerve angles on the underside. The blackthorn has a broad and round crown1 4. Blackthorn thrives best in deep, clayey, calcareous soil with a high water content. It is light-requiring and can tolerate shade only as a small plant. Blackthorn has a normal lifespan of about 100 years, but can live up to 300 years and grows in a belt along the coast from the Swedish border to Sunnmøre and spread further north.4.
Growth conditions
Alder is common in old-growth Norwegian forests and is not threatened with extinction. Threats to alder include climate change, which can affect its growth conditions, as well as pests and diseases that can weaken the trees. Globally, alder is also exposed to similar threats, but it is generally a robust species.5In old-growth forests, alder plays an important role by contributing to biodiversity through its ability to create habitat for various species.
Ecological significance
Alder plays an important role in forest ecosystems by improving soil fertility through nitrogen fixation. This helps to enrich the soil and support the growth of other plants. The trees also provide habitat and food for a variety of animal species, including birds and insects. Alder's ability to grow rapidly and colonize new areas makes it an important species for biodiversity2. It also helps stabilize the soil on slopes and along riverbanks. Birds such as thrushes and finches eat the alder seeds, while small mammals find shelter among the roots. Alder also attracts a variety of insects, including bees and butterflies, which are important for pollination2.
Climate benefits
Alder helps reduce greenhouse gas emissions by sequestering carbon in its biomass. The trees also improve air quality by absorbing pollutants. Compared to other tree species, alder is particularly effective at improving soil fertility, which indirectly supports carbon storage in the soil. Alder's ability to grow in marginal areas also makes it an important species in restoration projects. The roots of alder help hold the soil together, preventing soil loss and improving water quality2.
Cultural-historical significance and uses
Historically, alder has been used in Norway for building houses, boats and tools because of its light and durable wood. Modern uses include furniture, papermaking and as fuel. Alder wood is easy to work with and has a light color that makes it attractive for various craft projects. In earlier times, alder was also used in rituals and as medicine, especially for its anti-inflammatory properties2.
Alder was also used to make knobs during World War II.1 5. Knots were small pieces of wood, usually from hardwoods such as alder and black alder, that were used as fuel in wood gas generators. Due to the shortage of gasoline, wood gas generators, also known as knob generators, were used to produce gas from wood to power internal combustion engines in cars, buses, trucks, and tractors.1 5.
Due to its light weight and resistance to water, alder was also used to build boats.2. Traditional clinker boat building, which has a history of over a thousand years, often used alder because of the wood's durability and availability. Alder was used to make various utensils and tools, including wooden spoons, wooden shovels, and tool handles. Its fine texture and beautiful reddish color made it an attractive choice for woodcarvers.
