Härjedalens fjällängar – en flygbildsstudie över igenväxningen av subalpina ängar

Abstract

Overgrowth in the mountains has become a well-studied topic in recent years. Interest in the issue has become big by global warming, which is expected to change the mountain environments. In this study, I’ve look at an alternative explanation for the regressive succession, namely the cessation of usage. The purpose of this study was to investigate the overgrowth of ten traditional mowed meadows in the mountain birch forest in Härjedalen to see if overgrowth differ and if this can be traced to grassland management. Using historical maps, historical aerial photographs and modern aerial photographs, a quantitative comparative study of overgrowth has been made. The practical approach to process mapping and aerial photography material has been made through the computer-based analysis program ArcGIS 10.1. As a theoretical background, literature on birch forest biodiversity, mountain agriculture history and succession ecology has been studied. The result is that all out of these ten meadows has grown back by a certain percentage, which varies between 16 % and 81 %. Based on the reduction that has occurred, the average speed of overgrowth can be calculated, as well as making a hypothetical calculation of when the meadows have become overgrown by 100 %, assuming that the regressive succession is linear. With these hard data, an interpretation has been made for the future of biodiversity in the mountain birch woods and the meadows. The future scenario for biodiversity is that it decreases. With both habitat loss and fragmentation in the mountain birch forest also reduces the prospects for the extinction debt of species may remain to keep a viable population. This can take place already within a period of 10 years. If the owergrowth of the meadows continue in the future, the diversity of traditionally favored species will reduce.