Land use history and site location are more important for grassland species richness than local soil properties

Lately there has been a shift in Sweden from grazing species-rich semi-natural grasslands towards grazing ex-arable fields in the modern agricultural landscape. Grazing ex-arable fields contain a fraction of the plant species richness confined to semi-natural grasslands. Still, they have been suggested as potential target sites for re-creation of semi-natural grasslands. We asked to what extent does fine-scale variation in soil conditions, management history and site location effect local plant diversity in grazed ex-arable fields. We examined local soil conditions such as texture, pH, organic carbon, nitrogen (N) and extractable phosphate (P) and effects on plant richness in ten pairs of grazed ex-fields and neighbouring semi-natural grasslands in different rural landscapes. Each grassland pair where in the same paddock. A multivariate test showed that site location and land use history explained more of differences in species richness than local soil property variables. Plant species richness was positively associated to grazed ex-fields with low pH, low N and P levels. Sites with high plant richness in semi-natural grasslands also had more species in the adjacent grazed ex-fields, compared to sites neighbouring less species-rich semi-natural grasslands. Although both soil properties and species richness were different in grazed ex-fields compared to semi-natural grassland, the site location within a landscape, and vicinity to species-rich grasslands, can override effects of soil properties. In conclusion, if properly located, ex-arable fields may be an important habitat to maintain plant diversity at larger spatio-temporal scales and should considered as potential sites for grassland restoration.