Artrikedom av kärlväxter i övergivna och restaurerade hagmarker : betydelsen av igenväxningsgrad och tid sedan igenväxning började

Abstract: Continuously grazed grasslands have remarkably high plant species diversity. In Sweden this type of habitat has declined for the last two centuries. Changed land use has caused habitat fragmentation and loss of habitat quality. This has caused a great number of plant species to end up on the verge of extinction. To try to save this unique habitat and the species that are tied to it, lots of resources are laid on restoration of abandoned grasslands. In this study, plant species richness of continuously grazed, abandoned and restored grasslands were related to degree of overgrowth, time since overgrowth started and rate of overgrowth. To get an approximation of how much trees and bushes that needs to be removed during restoration, species richness in relation to degree of overgrowth was used as a measurement of necessary restoration effort. To get an approximation of the success of restoration, species richness was related to time since overgrowth started and restoration took place. To get an approximation of the success of a restoration for abandoned grasslands, species richness was related to time since overgrowth started. Three hypotheses were tested: 1. The proportion of area covered with trees and bushes will affect specialist species richness negatively. 2. Total species richness and specialist species richness will be higher for grasslands that have been abandoned for a shorter time, while generalist species richness will be higher for grasslands that have been abandoned for a longer period of time. 3. The rate of overgrowth affects plant species richness negatively, the faster grasslands becomes overgrown the lower plant species richness they have. The result showed that high proportion of overgrowth has negative effect on specialist species richness. There is no clear difference in effect of proportion of overgrowth on species richness between restored and abandoned grasslands. Time since overgrowth started has positive effects on generalist species richness and could possibly be used as approximation of how successful a restoration might be. The qualities of grazed grasslands are not only dependent on whether they are restored or abandoned; the quality can be affected by other factors. The most effective way to keep high species richness is to make sure that grazed grasslands are kept relatively open. As long as grazed grasslands are not allowed to be completely covered in trees and bushes high species richness can be kept even if the grasslands are not grazed for a number of years.