Iveta Škodová

Semi-dry grasslands along a climatic gradient across Central Europe: Vegetation classification with validation

Abstract Question: What is the variation in species composition of Central European semi-dry grasslands? Can we apply a training-and-test validation approach for identifying phytosociological associations which are floristically well defined in a broad geographic comparison; can we separate them from earlier described associations with only a local validity? Location: A 1200 km long transect running along a gradient of increasing continentality from central Germany via Czech Republic, Slovakia, NE Austria, Hungary to NW Romania. Methods: Relevés with > 25% cover of Brachypodium pinnatum and/or Bromus erectus were geographically selected from a larger database. They were randomly split into two data sets, TRAINING and TEST, each with 422 relevés. Cluster analysis was performed for each data set on scores from significant principal coordinates. Different partitions of the TRAINING data set were validated on the TEST data set, using a new method based on the comparison of % frequencies of species occurrence in clusters. Clusters were characterized by statistically defined groups of diagnostic species and values of climatic variables. Results: Species composition changed along the NW-SE gradient and valid clusters were geographically well separated. Optimal partition level was at 11 clusters, six being valid: two clusters Germany and the Czech Republic corresponded to the Bromion erecti; two clusters from the Czech Republic and Hungary to the Cirsio-Brachypodion, and two clusters were transitional between these two alliances. Conclusion: The training-and-test validation method used in this paper proved to be efficient for discriminating between robust clusters, which are appropriate candidates for inclusion in the national or regional syntaxonomic overviews, and weak clusters, which are specific to the particular classification of the given data set. Nomenclature: Ehrendorfer (1973).

Ecology and distribution of Tephroseris longifolia subsp. moravica in relation to environmental variation at a micro-scale

Tephroseris longifolia subsp. moravica is an endemic endangered taxon of European importance. Within the nine recently known populations it occurs in very specific site conditions of ecotone habitats. In our contribution, we try to quantify its realized niche with regard to the measured components of its biotic and abiotic environment. The main aim was to assess the importance of spatial environmental variation on taxon occurrence and performance and to relate the obtained ecological information to data on taxon abundance and demography. Possible reasons of taxon rarity are discussed, too. Comparison of plot pairs indicated that plots containing the taxon had deeper soil and higher soil Na and Mg contents than plots without it. They also contained higher number of species, especially forbs. Several soil parameters were positively correlated with taxon size and density while light parameters played minor role. Negative correlations between cover of vascular plants, especially grasses and taxon size and density suggest its reduced competitive ability. Vascular plant-based ecological indicator values were set for light (6), temperature (5), continentality (4), moisture (5), soil reaction (7) and nutrients (5). The studied sites differed in topography, soil characteristics (pH, soil Na, K, Ca, P and NH4) and cover of herb litter. Size of taxon populations was negatively related to their finite rate of increase which varied between 1.25 and 2.04 and was most sensitive to demographic parameters related to growth. We conclude, that the studied taxon is not strictly stenotopic as the ranges of several environmental variables were rather wide. We suppose, that the narrow limits of recent taxon occurrence are consequences of its low competitive ability and demographic processes related to germination and seedling establishment. The differing requirements of its ontogenetic stages (seedlings and generative individuals) may define the final limits of its small-scale distribution.

Phytosociological affiliation of Annex II species Tephroseris longifolia subsp. moravica in comparison with two related Tephroseris species with overlapping distribution

The phytosociological affiliation of Tephroseris longifolia subsp. moravica, species of European importance, was studied in relation to two closely related species of the genus Tephroseris which have overlapping distribution within the Western Carpathian Mts: T. intergrifolia and T. crispa. The main aim was to compare plant communities inhabited by the three taxa, to assess the major environmental gradients responsible for variation in their distribution and to estimate ecological indicator values for Tephroseris longifolia subsp. moravica. T. longifolia subsp. moravica was recorded in nine localities in the Slovakia and Czech Republic where it occurs in very specific site conditions of ecotone habitats. Its phytosociological affiliation is restricted to grasslands of the alliances Bromion erecti and Arrhenatherion elatioris and to the ecotone vegetation between these grasslands and beech forests. T. integrifolia occurs most frequently in the Diantho lumnitzeri-Seslerion, Bromion erecti and Quercion pubescenti-petraeae alliances. T. crispa occurs predominantly in communities of the Calthion palustris alliance and Scheuchzerio-Caricetea fuscae, Mulgedio-Aconitetea and Montio-Cardaminetea classes. The major gradient responsible for variation in species composition of communities inhabited by the studied taxa was associated with moisture and nutrient content. The vascular plant-based ecological indicator values for Tephroseris longifolia subsp. moravica calculated from phytosociological relevés with its occurrence were set for light — 6, temperature — 5, continentality — 4, moisture — 5, soil reaction — 6 and nutrients — 5. We conclude that the studied taxon has intermediate relationship to the most of the studied factors in comparison with two related species, T. crispa and T. integrifolia.

Twin plots – appropriate method to assess the impact of alien tree on understory?

Abstract Replacing native forests by alien tree plantations can lead to changes in the species composition of the understory. However, differences in the understory species spectrum can also be a part of the natural variability of forest stands. We have tested the suitability of the twin plots method for an evaluation of the impact of alien trees on the species composition of the understory. This research was conducted on an alluvial plain (SW Slovakia) that was originally covered by a hardwood floodplain forest. The study was based on 7 twin plots of black locust (Robinia pseudoacacia) and native forest plots, with a maximum distance of 100 meters between the members of the twins. The dissimilarity of the plots within the black locust forest was significantly lower than the dissimilarity between the twin plots. In addition, the dissimilarity of the plots within the hardwood floodplain forest was also significantly lower than the dissimilarity between the twin plots. Under the same environmental conditions, the higher dissimilarity of the twin plots was caused by major edificators and their impact on the understory vegetation. The twin plots method proved to be a suitable tool for analyses of the impact of alien trees on understory vegetation.

Seed bank and seedling recruitment of endangered Tephroseris longifolia subsp. moravica (Asteraceae)

Knowledge of seed-bank dynamics and seedling recruitment is crucial for effective in situ conservation of endangered species. Herein, we studied Tephroseris longifolia subsp. moravica in five of nine existing population sites to determine its spatio-temporal regeneration patterns. Our main aims were: (i) to confirm the existence of a soil seed bank and to determine its type and density, (ii) to assess the rate of natural seedling recruitment and the factors affecting seed germination and seedling survival, and (iii) to assess the potential of artificial disturbance regimes to enhance natural seedling recruitment. We used a series of experiments based on long-term seed burial, seedling emergence, germination and seedling establishment in permanent plots and artificial disturbance regimes. We found that this taxon forms a short-lived persistent seed bank and its seed germinability decreases over time. The average germination in situ was 3.8 %. While the moss and herb layer cover supported seedling survival, tree-litter cover negatively affected in situ germination. Turf removal had the strongest positive effect on germination percentage in our three tested in situ treatments, followed by litter removal and no management procedures. Seedling mortality was very high (60–100 % of seedlings died), with no difference determined between the treatments. Our results suggest that seedling recruitment from seed banks and artificial disturbance regimes might be an extremely beneficial conservation protocol to enhance small populations of this critically endangered taxon.