A syntaxonomical synthesis of calcicolous forests dominated by Fagus sylvatica (Cephalanthero-Fagenion suballiance) in the Czech Republic was carried out using the Braun-Blanquet approach. Relevés included in the analyses were selected following formalized approach by using an expert-delimited group of 38 calcicolous and/or xerothermophilous species. Only one association Cephalanthero-Fagetum was distinguished, which usually occurs on limestone, calcareous sandstone and calcareous sandy marlite; however, can be found also on base-rich siliceous bedrock (e.g. basalt, phonolite). Based on TWINSPAN analysis, three subassociations were recognized within the Cephalanthero-Fagetum: (i) Cephalanthero-Fagetum seslerietosum caeruleae on shallow rocky soils with frequent dominance of Sesleria caerulea and presence of petrophytes, (ii) Cephalanthero-Fagetum typicum on dry, shallow soils with a significant presence of light-demanding, thermophilous, and calcicolous species, and (iii) Cephalanthero-Fagetum actaeetosum spicatae on deeper, sufficiently moist soils with an abundance of mesophilous, nitrophilous and acidophilous species. The name Cephalanthero-Fagetum actaeetosum spicatae is a new nomenclatural combination. The relationships between Cephalanthero-Fagetum and similar forest vegetation types containing xerothermophilous and/or calcicolous species in the Czech Republic are discussed. The main gradients in species composition of Cephalanthero-Fagetum subassociations were revealed by gradient analysis. The Ellenberg indicator values, altitude, slope, and ‘southness’ were used to interpret these gradients. Using unconstrained ordination analysis (DCA) the syntaxonomical interpretation indicated three relatively distinct groups. Moreover, further DCA analysis revealed the well-defined position of Cephalanthero-Fagetum within Czech beech forests. The results of the above delimitation of Cephalanthero-Fagetum were compared with the results based on Cocktail-defined species groups improved by similarity-based assignment of relevés (using frequency-positive fidelity index). When the Cocktail-based formulas for beech forests were applied to the relevés selected by our 38-species diagnostic group, the correspondence between these two approaches was only 36%. However, at the lower subassociation level, the highest correspondence occurred for Cephalanthero-Fagetum seslerietosum (84%). The reason for this high correspondence is that the species composition includes many specialists (i.e. good diagnostic species) and it occurs at the end of an ecological gradient. To sum up, it is possible to define vegetation units accurately using strict formulas, as opposed to the less rigorous ‘soft’ traditional approach. However, both approaches fail when defining central units.
A syntaxonomical revision of dry grasslands of the alliances Bromo pannonici-Festucion pallentis, Festucion valesiacae and Koelerio-Phleion phleoidis (class Festuco-Brometea) in the natural biogeographical region of the Western Carpathians and northern Pannonian Basin is presented. A geographically stratified data set of 2686 relevés from the south-eastern Czech Republic, northeastern Austria, Slovakia and northern Hungary was divided into 25 clusters using a modified TWINSPAN algorithm. The proposed classification simplifies and unifies the previous syntaxonomical systems, which differ in these four countries. Main environmental gradients responsible for variation in species composition of theses grasslands were revealed by detrended correspondence analysis and interpreted using indicator values. The major pattern of variation reflects soil nutrient availability and moisture, which are negatively correlated with soil reaction.
The Hydraenidae and Elmidae assemblages living in the Órbigo River Basin (NW Spain) were studied during one year. The aim of the research was to determine which factors were best related to species composition. This knowledge is the first step towards the definition of indicator species or assemblages.
Canonical Correspondence Analysis (CCA) showed that altitudinal gradient was the factor most correlated with beetle distribution. However, some other variables, such as water mineralization and eutrophication, were also important.
Using TWINSPAN program, groups of sites were defined and, afterwards, represented on the CCA diagram. Several species assemblages were defined on the basis of their frequencies of occurrence in these site groups. The environmental features of site groups and beetle assemblages were assessed with the aid of CCA. In this way, assemblages typical of high reaches could be separated from those of low stretches of the rivers. Similarly, communities from non-polluted waters could also be defined. Although several species are present in polluted sites, no assemblage exclusive to these sites has been found.
The aim of our study was to identify the most important ecological factors influencing the breeding density of chukar partridges (Alectoris chukar) in Southeastern Bulgaria. Identified habitats were divided into two categories:1) natural habitats with an extant population of the species, and 2) habitats in which it was absent. In each habitat, annual precipitation, lowest elevation in the habitat, Paliurus cover, grazing livestock per 100 ha, shrub height, shrub density, bedrock type, percentage of pastures, percentage of agriculture, percentage of wetlands, percentage of rocks, presence/absence of buildings, presence/absence of highways, plant
species composition, plant layer coverage, and chukar breeding pairs were measured. We have found several habitat variables that probably affect the density of nesting chukar partridge. These are: 1) grazing intensity, 2) percentage of rock outcrops, 3) percentage of grasslands, 4) shrub cover, and 5) elevation. Grazing intensity and rock outcrop presence, together with the elevation gradient, influence the breeding pair distribution and abundance most significantly. Our study has confirmed only three types of habitats that the chukar currently prefers to nest in. Unknown factors probably changed the other sites in a way that they are no longer suitable for the species’
existence and reproduction.