Artrikedom i stadsnära hästhagar i Stockholms län

Sammanfattning: Pastures are important due to their high biodiversity. A constant change has taken place in pastures in Sweden where fewer pasture lands are being grazed and more are abandoned. Many cattle farms are converted to horse farms in suburban and urban areas. Furthermore, research has indicated that increased urbanisation can have an negative impact on biodiversity. When pastures are abandoned the land reverts to forest within which the diversity of plant species is reduced. In order to obtain a greater diversity of plant species the Intermediate Disturbance Hypothesis suggests moderate disturbance is required. The purpose of this study is to investigate the effects of three anthropocentric factors on plant species richness at ten different horse farm paddocks in the municipalities Ekerö, Huddinge and Vallentuna, in Stockholm County. Twelve plots of 0.5 meters x 0.5 meters were investigated at each farm. Three factors are tested against plant species richness; The length of time pastures have been claimed by horses, the degree of disruption, the degree of urbanisation. We found that only certain plant species were affected by urbanisation and not all plant species, especially species that thrive in more overgrown habitats. An inverse correlation was found between the number of years of horse grazing and plant species richness. There was no difference in the plant species richness inside and outside the paddock. In these outcomes it appears that horse grazing has a significant impact on plant species. Pasture development and maintenance are important factors that influence the composition of species.