What does your own lawn or the park downtown most likely have in common with the Bothnian Bay? That there is Grass, lots and lots of grass. Strictly speaking only the family Poaceae can be called grasses with around 12.000 different species. However, other families such as Cyperaceae (sedges) and Juncaceae (rushes) have species that resemble grass.
Poaceae is an important plant family for humans and animals alike. For humans it has a economical value as food (wheat, rice, corn), construction material (floormats, weaving, paper) or cultural value like a botanical garden or sports turf. It also has some aesthetic value through the use of grasses in lawns and garden design. For animals, grasses provide food or shelter from weather conditions or predators.
But grasses also have important ecological roles. The roots of grass keep the substrate together and can significantly slow down erosion. The roots also move the substrate around and prevents it from becoming too dense, providing a better habitat for creatures living in the substrate. However, grasses can also have severe negative effects on their surroundings. Grasses are usually not picky about their habitats and can settle quickly in a new habitat. Grasses also grow relatively quick compared to other non-grass species. This results in grasses usually outcompeting the other non-grass species.
Reeds are grass-like plants that grow in wetlands. In the grass family Poaceae, Phragmites australis is the most common reed found in the Bothnian Bay. While blooming it is easy to spot with the dark purple plumage that sits on top of the plant. While P. australis shares the same benefits as other grasses, it is considered a threat to most other native plants in the Bothnian Bay. P. australis forms dense reed-beds that is unsuitable as a habitat for other plants. Due to the length of P. australis, which can reach about 2-3 meters, it blocks light for other smaller plants. Dead reed will also cover up the substrate after a period of time, making it almost impossible for other plants to grow.
Luckily reeds can be kept in check by allowing grazing along the shores. Preventing reeds from growing to big and creating dense reed-beds. This in turn allows other native plants to grow again and creates a higher biodiversity in the area.
Written by Sjef Heijnen, Metsähallitus