Integrated analysis of conditions accounting for intersite distribution of grassland plants

The objectives are to relate species distributions among 110 non-fertilized grassland ('dry meadow') sites in southeastern Sweden to soil chemical, physical, exposure and management variables using correlation, stepwise regression and factor (PCA) analysis based on quantitative data. It was suggested that soil acidity variables (pH, base saturation, exchangeable Ca, Al, Mn,and Fe), P, K, Mg, and N conditions, water-retaining properties, soil texture and contents of organic matter, as well as degree of grazing, total cover of the vegetation and exposure (inclination and orientation) of the sites, to a variable extent are able to account for the intersite distribution of vascular plant species. Frequent enough to consider separately were 64 species. A majority of them displayed significant relationships, either positive or negative, to soil acidity. At least 10 species were related to both soil acidity and grazing and/or exposure, and another 10 species mainly (always positively) to grazing and/or exposure. The distribution of 8-10 species was closely positively related to the phosphorus status of the soils, mainly plants which are even more abundant in fertilized pastures or abandoned fields. Magnesium appeared important to the distribution of at least 6 species and K to a few. Many variables tested including those related to water-retaining properties and soil texture, as well as density (total cover) of the vegetation, were only significant in few cases. Nitrogen mineralization rate, as determined by standard incubation technique, was not related to the distribution of any species. Species richness was positively correlated with total cover of the vegetation, negatively with soil acidity and phosphorus status.