Small-scale species patterns and associations in an alvar limestone grassland on Oland, Sweden

This paper reports on the results of a transect analysis carried out in order to detect small-scare patterns of Avenetum species in a limestone grassland on the Great Alvar on the Baltic island of Oland, Sweden. Three transects consisting of 500 10 x 10 cm quadrats were used. The cover and number of flowering stalks (if any) of the 21 most common species were recorded. In addition the total cover of vascular plants, cover of mosses and lichens, cover of cow dung and soil depth in each quadrat were recorded. EIlenberg indicator values for light, moisture, reaction and nitrogen were calculated for each quadrat as weighted averages of the values for the species included in the analysis. Patch size frequency analysis, PASFRAN, a new method for detecting patches and their sizes, revealed that 42% of all significant species patches detected had mean patch sizes (diameter) in the range of 26-50 cm, which matched the size of dung patches - 49 cm in transect 1 and 30 cm in transect 2. Results of association analysis revealed correlations for several species pairs and between species and environmental factors with similar patch sizes. Combination of PASFRAN and association analysis is recommended as an effective method for pattern detection.