Vegetational changes on two eroding banks of a short‐term regulated river reservoir in northern Sweden

• Published in: Nordic Journal of Botany
• Main Author: Grelsson, Gunnel
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1985
• Subjects: Plant Science; Ecology, Evolution, Behavior and Systematics; Northern Sweden
• Online Access: http://dx.doi.org/10.1111/j.1756-1051.1985.tb01695.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1756-1051.1985.tb01695.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1756-1051.1985.tb01695.x

This study deals with the vegetational changes and the course of erosion on two types of river banks bordering a river reservoir, in northern Sweden. The water‐level has been short‐term regulated since 1961, with an amplitude of about 3 m in the uppermost reaches of the reservoir and about 1 m furthest downstream. The pattern of regulation includes both a weekly and a daily rhythm. The banks of the river reservoir have been cut in fine‐grained sediments. The two sites selected for study were (1) a formerly littoral area (2) a formerly dry‐land area. Percentage cover and number of shoots were determined annually within belt transects subdivided into 10 times 10 cm quadrats, during the period 1977–1981. The course of bank erosion was initiated and mainly continued by water movements. In the formerly littoral area, erosion proceeded only slowly, whereas in the formerly dry‐land area erosion was rapid and the bank was continuously being undercut, leading to the formation of an overhanging mat of vegetation. As erosion progressed, this overhanging mat split up and slumped down into the reservoir. The vegetational changes on the overhang were considerable, while the terrace maintained a more stable vegetation cover. In the long‐term, the composition of the vegetation on the former littoral river‐bank remained more stable than on that cut into the former dry‐land area. The break‐up of the vegetation cover on the overhang also initiated secondary vegetational successions on the exposed soil. Considerable differences in the vegetation cover were also recorded from one year to the next. These differences were considered to be mainly due to differences in the rate and local course of erosion. Annual differences in the rhythm and/or amplitude of the fluctuations in water‐level were considered to be less important in this respect.