Floristic heterogeneity of Festuca airoides-dominated grasslands in the Romanian Carpathians

Abstract

We numerically analysed 154 relevés of Potentillo chrysocraspedae–Festucetum airoidis in order to review the compositional variability of these grasslands, the main eco-floristic gradients and the representativeness of the lectotype. Apart from 30 small-sized clusters composed of singular or transitional relevés (outliers), three distinctive groups of 77, 19 and 12 communities were finally retained and denominated as typical (TP), closed (CL) and open (OP) facies, as they were significantly different in terms of total species cover. The three facies are well separated but do not form distinctive clusters in the non-metric multidimensional scaling (NMDS) ordination space. Juncus trifidus and Agrostis rupestris are the best differential species of OP and TP, respectively, whereas the best discriminator of CL is the higher cover of F. airoides. There are no significant differences between the three facies regarding altitude. The floristic structure of CL indicates poorer but moister soils compared with the other facies. CL may represent either a post-disturbance, recovery phase following sheep overgrazing and intensive trampling, or a late seral stage. OP gathers communities that are little disturbed and mainly occur on ridges and upper, sunny slopes. Although well distinguished floristically, TP is weakly defined in terms of homotoneity and complexity of the core species assemblage. The most representative relevé of TP is poorer in character species than the relevé lectotype (5 versus 12), the latter being classified as an outlier in terms of normal specific assemblage. Such patterns may reflect the spatio-temporal heterogeneity in alpine grasslands due to uncontrolled, intensive grazing and stochastic natural disturbances.