Changes in grassland vegetation on the island of Plavnik (Croatia) over 100 years

Abstract

The changes in the grassland vegetation that have occurred over the last almost 100 years on the northeastern Adriatic island of Plavnik (Croatia) were studied. For this purpose, 29 phytosociological relevés of standard plot size were collected using the Braun-Blanquet phytosociological approach and compared with those of 100 years ago. With the aim of defining the differences among the communities and identifying the main environmental gradients, cluster analysis (Ward's method on a Chord distance matrix) and non-metric multidimensional scaling ordination were applied. Taxa score-weighted means of the Ellenberg-type indicator values of main environmental variables were used to assess ecological differences among communities, and disturbance-related indicator values were calculated to assess the disturbance regime in shaping plant communities. According to the syntaxonomic framework for the grassland associations, three associations and two subassociations were found. Among them the Festuco valesiacae-Poetum bulbosae (Poetalia bulbosae, Poetea bulbosae), the Helichrysetum italici salvietosum officinalis (Scorzoneretalia villosae, Festuco-Brometea), and the Hedypnoido rhagadioloidis-Asphodeletum ramosi were proposed as new. The Festuco valesiacae-Poetum bulbosae documents for the first time, based on phytosociological data, the occurrence of the Poetea bulbosae in Croatia. Three associations were considered extinct, possibly as a result of changes in grazing pressure and type.