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Classification of higher level vegetation units (orders and alliances) based on numerical methods often yields different results than traditional plant community classification concepts. We performed a numerical cluster analysis of phytosociological relevés from the class Festuco-Brometea in Slovakia with the aim of identifying areas of overlap between the two classification approaches. The research was carried out using a database of approximately 1500 phytosociological relevés sampled in the period between 1927 and 2004. The outputs of the numerical classification form six clusters. Diagnostic taxa of individual clusters were determined using species constancy and fidelity. The cluster analysis enabled us to differentiate the alliances Seslerio-Festucion pallentis, Diantho lumnitzeri-Seslerion albicantis, Festucion valesiacae, Cirsio-Brachypodion pinnati and Asplenio septentrionalis-Festucion pallentis (inch Festucenion pseudodalmaticae). However, it did not permit the differentiation of the alliances Koelerio-Phleion phleoidis and Bromion erecti. It also did not allow us to differentiate the orders Brometalia erecti and Festucetalia valesiacae. The reason for this may be the peripheral occurrence of plant communities of Brometalia erecti in Slovakia.
Between 1996 and 2006 the vegetation succession in drift sands and in blown-out gravel-rich depressions, located in the nature reserve Hulshorsterzand in the central Netherlands, was studied. Within this Natura 2000 habitat (type 2330: inland dunes with open Corynephorus and Agrostis grasslands) so-called lichen steppes are included, famous for their biodiversity, both in flora (cryptogams), and in fauna. With multivariate analysis, the relation between the primary succession, the species composition of the vegetation and the soil quality was studied in three different biotopes i.e. 1. drift sand, 2. blownout gravel-rich depressions and 3. drift sand after management. With a total of up to 34 species, lichen diversity in the study area appeared to be high. Biotope 1, i.e. the pioneer vegetation with Corynephorus canescens on blowing sand, is rather scarce in lichens. Between 1996 and 2006 green algae, C. canescens and Polytrichum piliferum appeared, with the result that much of the former open drift sand area was covered by pioneer stages of the Spergulo-Corynephoretum. If sand stopped blowing in, a combination of P. piliferum with the neophyte Campylopus introflexus occurred. The terminal stages of lichen succession on drift sand, a vegetation with mainly Festuca ovina s.l., Deschampsia flexuosa and reindeer lichens (Cladonia subgen. Cladina), proved to be rather stable. Since 1996 the lichen steppes occurring in biotope 2 were increasingly grass-encroached. Where some sand was still blowing in, lichen diversity did not change much, but gradually C. introflexus increased. However, without sand blowingin, a decreasing lichen cover and loss of some Red List lichens occurred. In general, in this grass-rich vegetation Calluna vulgaris will germinate and gradually a dry heath might develop. However, where dynamics had stopped and Pinus sylvestris seedlings established, succession to a young forest started. Vegetation change from open sand to lichen-rich vegetation is clearly related to a decrease in pH, an increase in organic matter, in % total N and in % total P. The lichen composition is clearly related to this gradient. The applied restoration measures on steep sand dunes in the eastern area, both of cutting pine trees and removing topsoil down to the mineral soil layer, proved to be successful. The sand kept drifting and the pioneer community thriving, including the lichen Stereocaulon condensatum characteristic of pioneer conditions, while the neophytic moss hardly increased between 1996 and 2006.