Faktorer som påverkar Vänerns öppna sandstränder och möjligheterna för hög biologisk mångfald – med mossor som indikatorer på igenväxning

Sammanfattning: The sandy beaches of Vänern are threatened by overgrowth and thereby the biodiversity is at high risk to decline. This study is based on an inventory of vegetation of overgrowth character and mosses. The frequency and spread of mosses is perceived as an indication of initial or present overgrowth. External factors that have been taken into consideration are wind-, wave- and ice erosion, the slope of the beach, wear and grade of exposure. The purpose of the investigation is to control the beaches grade of overgrowth and find out which external factor is of most importance for the maintenance of the biotope.   The results show that the beaches environment is affected by the slope of the beach, grade of exposure, size, wear and overgrowth. A high frequency of mosses represents initial or present overgrowth and all beaches were categorized in some faze of overgrowth. The vegetation of overgrowth character is most likely spread from areas with a high slope to areas with low slope. Thereby it is the upper beach zone that is in most danger of overgrowth and because this area is not affected by fluctuation of water level, wear should be the most crucial external factor leading to overgrowth.