Semi-dry grasslands are of high nature conservation interest both at national and European scales due to their high biodiversity and species richness. For effective conservation, however, the variation in floristic composition and distribution of these grasslands need first to be described. In Hungary, there is currently no comprehensive survey and classification of semi-dry grasslands. Therefore, the aim of this study was to (i) describe the variation in species composition of Hungarian semi-dry grasslands by a country-scale cluster analysis based on a large database; (ii) describe the types (clusters) and compare these descriptions with those in the phytosociological literature, and finally (iii) formulate a new syntaxonomical system for Hungarian semi-dry grasslands. For this analysis 699 relevés were selected in which the percentage cover of at least one of the grasses Brachypodium pinnatum, Bromus erectus, Danthonia alpina, Avenula adsurgens, A. pubescens or A. compressa reached >10%. A geographical stratification of the dataset was performed and then it was split randomly into two equal parts (training and test datasets). Following outlier exclusion and noise elimination, clustering was performed separately for both datasets. The optimal number of clusters was determined by validation. The number of valid clusters was the highest at the level of ten clusters, where seven clusters appeared to be valid. The valid clusters are separated geographically; however, there are considerable overlaps in the species compositions. According to our results, all the grasslands belong to the Cirsio-Brachypodion alliance. The seven valid clusters are assigned to five main groups of semi-dry grasslands in Hungary: 1. Brachypodium pinnatum (and partly Bromus erectus) dominated, species rich meadow-steppe-like grasslands occurring on deep loess in central Pannonia, identified as Euphorbio pannonicae-Brachypodietum Horváth 2009; 2. Brachypodium pinnatum dominated mountain grasslands restricted to the Bükk Mountains; identified as Polygalo majoris-Brachypodietum Wagner 1941; 3. mostly Bromus erectus dominated grasslands on shallow, calcium/rich soils of the Dunántúl region, proposed as a new association Sanguisorbo minoris-Brometum erecti Illyés, Bauer & Botta-Dukát 2009; 4. Brachypodium pinnatum and Danthonia alpina dominated stands occurring mainly in the Északi-középhegység Mts, characterized by species of nutrient poor soils, proposed as a new association Trifolio medii-Brachypodietum pinnati Illyés, Bauer & Botta-Dukát 2009; 5. transition towards meadows and successional stands dominated mainly by Brachypodium pinnatum.
Ambrosia artemisiifolia is the most noxious invasive species of weed in Hungary. The aim of this study was to quantify the environmental and land-use factors that explain the variance in its abundance in arable fields. A survey of 243 arable fields was carried out across Hungary, and 19 environmental and 12 land-use factors were measured. These were used as explanatory variables in classification and regression tree models. The abundance of A. artemisiifolia was significantly higher at the edges than at the centres of fields. The most important land-use variables explaining the variance in abundance of A. artemisiifolia were crop type and crop cover, with the highest abundance recorded in sunflower fields and fields with low crop cover. The following explanatory environmental variables were associated with significantly higher A. artemisiifolia abundance: sandy or acidic soils, mean April precipitation > 39 mm, mean annual precipitation > 592 mm and mean May temperature < 15.5 °C. Ambrosia artemisiifolia was significantly less abundant in fields with soils containing high concentrations of Na, K and Mn. Both farmers and nature conservationists should be made aware of the conditions and practices that favour ragweed so that they can develop effective and selective ragweed control practices, particularly in arable habitats with a high diversity of weeds.
Central European lowland wet meadows are habitats of great conservation interest, however, their phytosociological status has been to a large extent dependent on specific phytosociological traditions in different countries. In order to bridge the gaps between different national schemes of vegetation classification, a statistical analysis of variation in species composition of these meadows in the Czech Republic, E Austria, Slovakia, Hungary and NE Croatia was performed, using a data set of 387 geographically stratified vegetation relevés sampled at altitudes < 350 m. Principal coordinates analysiswas used to identify and partial out the noise component in the variation in this data set. The relevés were classified by cluster analysis. A new method for identifying the optimal number of clusters was developed, based on species fidelity to particular clusters. This method suggested the optimum level of classification with three clusters and secondary optimum levels with five and nine clusters. Classification based on three clusters separated the traditional phytosociological alliances of Calthion palustris and Molinion caeruleae, both with a suboceanic phytogeographical affinity, and a group of flooded meadows of large river alluvia, with a continental affinity. The latter group included the traditional alliances of Agrostion albae, Alopecurion pratensis, Cnidion venosi, Deschampsion cespitosae and Veronico longifoliae-Lysimachion vulgaris; however, the internal heterogeneity of this group did not reflect putative boundaries between these alliances as proposed in the phytosociological literature. Therefore we suggest to unite these alliances in a single alliance Deschampsion cespitosae Horvatić 1930 (the oldest valid name). Classification with nine clusters was interpreted at the level of broad phytosociological associations. Particular clusters were characterized by statistically defined groups of diagnostic species and related to macroclimatic variables.