Small-scale spatial structure in a remnant calcareous grassland

I investigated the relative importance of abiotic factors in species assemblage distribution in remnant calcareous grassland heavily grazed by sheep. A TWINSPAN classification recognized seven vegetation types. Direct gradient analysis (using CCA) revealed that the prevalent pattern in this grassland was represented by species-poor patches (grassland with Carduus pycnocephalus), versus species-rich patches (grassland with Cerastium ligusticum and grassland with Eryngium campestre). Species exclusive to dry grasslands and pastures, such as Carlina corymbosa, Anthemis tinctoria and Xeranthemum inapertum, were positively correlated with low nutrient availability, while species common to disturbed habitats, such as Hordeum murinum, Dasypyrum villosum and Bromus sterilis, were correlated with high nutrient availability and with deposition of dung and urine by grazing animals. The variations in environmental factors is only partially responsible for the spatial patterns in the species data. Open grassland in general agreed with the classification based on species data when considering environmental variables, while Prunus spinosa scrubland showed 65% of the samples misclassified and shrubby grassland with Cerastium arvense, as well as Juniperus communis scrubland did not show any sample classified in their own vegetation type. The results of the present study are discussed in the context of the conservation and restoration of this vegetation type