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Recognition of species richness spatial patterns is important for nature conservation and theoretical studies. Inventorying species richness, especially at a larger spatial extent is challenging, thus different data sources are joined and harmonized to obtain a comprehensive data set. Here we present a new data set showing vascular plant species richness in Poland based on a grid of 10 × 10 km squares. The data set was created using data from two sources: the Atlas of Distribution of Vascular Plants in Poland and the Polish Vegetation Database. Using this data set, we analysed 2,160 species with taxonomical nomenclature according to the Euro + Med PlantBase checklist in 3,283 squares covering the entire territory of Poland (ca. 312,000 km2). The species were divided into groups according to their status and frequency of distribution, and the statistics for each square were obtained. For purposes of analysis, sampling bias was assessed. The data set promotes theoretical analysis on species richness and reinforces the planning of nature conservations. [ABSTRACT FROM AUTHOR]

The increasing dominance of competitive plant species may reduce species richness of plant communities. Yet, species richness may depend on spatial scale and the alien versus native status of the dominant species. To explore the dominance effects of alien versus native species on species richness, we sampled semi-natural grasslands in southwestern Poland. We established 100 m2 squares at different grassland sites, and in two opposite corners we placed two series of five nested plots (0.001, 0.01, 0.1, 1 and 10 m2), in which we recorded all vascular plant species. Next, we selected squares with a strongly dominant plant in one corner (high-dominance series) and with no strong dominant in the opposite corner (low-dominance series). The number of species per plot and the slopes of the species–area curves fitted to each nested-plot series were used to assess whether the alien vs. native status of the dominant species influences species-richness pattern across scales. We found a significantly lower number of species in the high-dominance series than in the low-dominance series, regardless of the alien versus native status of the dominant species. The slopes of the species–area curves indicated that the rate of species accumulation with increasing area was faster in the high-dominance series than in the low-dominance series; however, this pattern did not depend on the alien vs. native status of the dominants. Our study confirms that increasing dominance is linked to a decline in species richness, but reveals that alien dominants do not have a stronger impact than native dominants. [ABSTRACT FROM AUTHOR]

Intermittently wet meadows of the Molinion alliance, as with many other grasslands of high-nature value, have become increasingly exposed to abandonment due to their low economic value. The potential consequences of land abandonment are the decrease in species diversity and environmental alterations. The issue of land-use induced changes in plant species composition and soil physico-chemical parameters have been rarely studied in species-rich intermittently wet grasslands. In this study we attempt to i) to identify determinants of plant species composition patterns and ii) to investigate the effect of cessation of mowing on vegetation composition and soil properties. The study was conducted in an area of 36 ha covered with Molinion meadows, comprising of mown sites and sites that were left unmown for 10 years. In total, 120 and 80 vegetation plots were sampled from mown and unmown sites, respectively. In these plots we measured plant community composition and soil physico-chemical parameters. The results have shown that the two groups of variables (soil properties and management) differ considerably in their ability to explain variation in plant species data. Soil variables explained four-fold more variation in plant species composition than management did. The content of soil organic matter, moisture, total nitrogen and exchangeable forms of potassium, calcium and magnesium were significantly higher in mown than in unmown grassland systems. The results revealed that soil organic matter was the component of the soil most strongly affected by management, followed by moisture, magnesium, calcium and potassium in that order. Each of these soil parameters was negatively correlated with the abundances of woody plants and invasive species. We concluded that low-intensity, late time of mowing is suitable grassland management practice to ensure high plant species diversity and sustainability of the grassland ecological system while cessation of mowing not only lead to reduced plant species richness and diversity, but also to reduced nutrient levels in grassland soils. [ABSTRACT FROM AUTHOR]

The influence that different sampling methods have on the results and the interpretation of vegetation analysis has been much debated, but little is yet known about how the spatial arrangement of samples affect patterns of species composition and environment-vegetation relationships within the same vegetation type. We compared three data sets of the same sample size obtained by three standard sampling methods: preferential, random and systematic. These different sampling methods were applied to a study area comprising of 36 ha of intermittently wet Molinia meadows. We compared the performance of the three methods under two management categories: managed (extensively mown) and unmanaged (abandoned for 10 years). A total of 285 vegetation-plots were sampled, with 95 plots recorded per sampling method. In preferential sampling, we sampled only patches of vegetation with an abundance of indicator species of the habitat type, while random and systematic plots were positioned independently from the researcher by using GIS. The effect of each sampling method on the patterns of species composition and species-environment relationships was explored by redundancy analysis and the significance of effects was tested by the randomization test. Preferential sampling revealed different patterns of species composition than random and systematic sampling methods. Random and systematic sampling methods have resulted in broader vegetation variability than with preferential sampling method. Preferential sampling revealed different relationship between soil parameters and species composition in contrast to random and systematic sampling methods. Although we have not found significant differences in vegetation-environment relationships between random and systematic sampling methods, random sampling revealed a more robust correlation of species data to soil factors than preferential and systematic sampling methods. Intentional restriction of vegetation variation sampled preferentially may be detrimental to statistical inference in studies of species composition patterns and vegetation-environment relationships. [ABSTRACT FROM AUTHOR]

Continuity of forest habitats is evaluated by using the indicator value of plants considered as ancient forest species or closed forest species. This is a subjectively defined group, which includes species that prefer old-growth forests. Until now, the fidelity between ancient forest species and its relation to species richness has not been assessed. Analyses were performed using resources of the Polish Vegetation Database, from which we selected relevés containing at least one species from the group of ancient forest species. Subsequently, we examined whether these species demonstrate a tendency to coexist. We established these relations using the phi coefficient of fidelity. We have distinguished eleven groups of coexisting ancient forest species (CAFS groups). Fairly common taxa in the data set constituted the majority of species forming these groups (frequency of >10%). Only one CAFS group found in the dataset was strongly localised geographically. The other groups did not demonstrate specific patterns of distribution and were recorded in relevés throughout the country. The average species richness of forests, in which at least one CAFS group was present, was significantly higher than the average in the forests, where there were no groups of CAFS found. These forests also differed significantly in the total number of ancient forest species and the number of closed forest species. We found that the coexistence of ancient forest species was an indicator of forest communities characterized by a high diversity. In all types of forests identified in the data set, at least one group of coexisting ancient forest species was identified. However, the occurrence of the CAFS groups was not equally frequent in all types of forests. CAFS groups occurred most often in the oak-hornbeam forests, species-rich beech forests and ravine forests, which are zonal types of vegetation. On the other hand, the CAFS groups were rarely found in bog Scots pine woodlands, acidophilous spruce forests, alder carrs and willow-poplar forests of lowland rivers, and these are mostly azonal vegetation types with a limited range. CAFS groups can be used as a trans-regional indicators of forests with a high diversity of species, however, their usefulness may be limited in relation to forests found in oligotrophic habitats or azonal forest systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • Species-specific biomass and community structure in grasslands was studied. • Nearly half of the total aboveground biomass was dependent on non-dominant species. • Infrequent and non-dominant species were the core of the diversity seen in grasslands. • Biomass inequality among species decreased with increasing functional diversity. • Species-specific biomass was mostly influenced by soil pH and management. Semi-natural grasslands are known to provide numerous ecosystem services, of which one of the most important is production of biomass. However, the contribution of individual plant species to the total biomass is much less well understood. This study addressed questions concerning community structure and responses of species-specific biomass (s-AGB) to gradients in soil acidity and fertility, topographical and climatic features, and disturbance regimes in mown and abandoned grasslands in the Sudetes Mountains (Central Europe). It identified pH as the most significant environmental gradient affecting turnover in s-AGB, and mowing cessation, temperature, and precipitation also had significant effects. Further, it showed high inequality in biomass among co-occurring plant species. It also showed that biomass inequality (measured by the Gini coefficient) among interacting species decreases with increasing functional diversity (Rao's index). This study highlights that common plant species (in terms of frequency) play a major role in contributing to the total aboveground biomass (t -AGB). However, less frequent species are also significant contributors to the t -AGB. Thus, the combined contribution of infrequent species to the t -AGB should not be neglected. Our findings support the mass ratio hypothesis stating that ecosystem functions such as biomass production depend on dominant species. On the other hand, high niche differentiation ensures the coexistence of less competitive species with the dominants by the variety and complementarity of functional traits. Infrequent and non-dominant species were the core of the diversity seen in the studied grasslands. The maintenance of species diversity in grasslands should be prioritized in nature conservation policies to ensure the sustainability of ecosystem services. [ABSTRACT FROM AUTHOR]

Corrigendum to "Effect of environmental gradients, habitat continuity and spatial structure on vascular plant species richness in semi-natural grasslands" [Agric. Ecosyst. [Extracted from the article]

• Effect of the spatial structure was stronger than the environment and habitat continuity. • Proxies of anthropogenic pressure were among the most important environmental drivers. • Effects of different drivers depend on spatial scale and regional ecological context. European semi-natural grasslands host numerous and diverse living organisms within a relatively small area; therefore, conservation of these habitats is crucial to maintain high biodiversity in agricultural areas. The aim of this study was to examine the effects of environment, habitat continuity and spatial structure on semi-natural grassland species richness (SR) at the regional extent. SR and characteristic SR (CHSR) were calculated in 709 georeferenced vegetation plots obtained from the Polish Vegetation Database. For each vegetation plot, (1) environmental variables representing climate, topography, soil characteristics (e.g. pH and physical soil properties), landscape and anthropogenic pressure; (2) habitat continuity in time and (3) variables reflecting the spatial structure of vegetation plots using principal coordinates of neighbour matrices were measured. Environmental data were measured at four different spatial scales (buffers of 0.05-, 0.5-, 2.5- and 5-km radii surrounding each vegetation plot). Boosted regression trees were generated to explore the relationships of SR and CHSR with predictors. Variables associated with anthropogenic pressure, landscape structure and soil characteristics operating in the 0.5- and 5-km buffers significantly improved SR and CHSR model. However, effects of individual predictors on SR and CHSR were not predominant. Habitat continuity and topographic heterogeneity operating in the 0.05-km buffer exclusively improved CHSR model. The results suggest that neutral processes (dispersion limitation, local management history and/or stochastic events) reflected by spatial variables are strongly related to SR and CHSR. Patterns observed herein may also exist in other agriculture-dominated regions in temperate Europe. This knowledge will contribute to effective conservation of valuable habitats over large spatial areas. [ABSTRACT FROM AUTHOR]