Beta-diversity of Central European forests decreases along an elevational gradient due to the variation in local community assembly processes

Beta-diversity has been repeatedly shown to decline with increasing elevation, but the causes of this pattern remain unclear, partly because they are confounded by coincident variation in alpha- and gamma-diversity. We used 8,795 forest vegetation-plot records from the Czech National Phytosociological Database to compare the observed patterns of beta diversity to null-model expectations (beta-deviation) controlling for the effects of alpha- and gamma-diversity. We tested whether \b{eta}-diversity patterns along a 1,200 m elevation gradient exclusively depend on the effect of varying species pool size, or also on the variation of the magnitude of community assembly mechanisms determining the distribution of species across communities (e.g., environmental filtering, dispersal limitation). The null model we used is a novel extension of an existing null-model designed for presence/absence data and was specifically designed to disrupt the effect of community assembly mechanisms, while retaining some key features of observed communities such as average species richness and species abundance distribution. Analyses were replicated in ten subregions with comparable elevation ranges. Beta-diversity declined along the elevation gradient due to a decrease in gamma-diversity, which was steeper than the decrease in alpha-diversity. This pattern persisted after controlling for alpha- and gamma-diversity variation, and the results were robust when different resampling schemes and diversity metrics were used. We conclude that in temperate forests the pattern of decreasing beta-diversity with elevation does not exclusively depend on variation in species pool size, as has been hypothesized, but also on variation in community assembly mechanisms. The results were consistent across resampling schemes and diversity measures, thus supporting the use of vegetation plot databases for understanding...Comment: Accepted version 25 pages, 5 figures, 1 tabl

Panicum virgatum L.

V Brně bylo na dvou místech nalezeno zplanělé severoamerické Panicum virgatum. Je to prní nález tohoto adventivního druhu v České republice. V Brně-Bohunicích je zřejmá spojitost adventivního výskytu s pěstováním na okrasných záhonech v univerzitním kampusu. Doklad je uložen v herbáři BRNU.Panicum virgatum was found as introduced in the city of Brno in southern Moravia (Czech Republic). This is the first record of this North American species in the Czech Republic. In Brno-Bohunice the species was found in a street adjacent to the campus of the Masaryk University university, where it is cultivated as an ornamental. The herbarium voucher is deposited in the herbarium BRNU

Alien plant invasions in Mediterranean habitats: an assessment for Sicily

Levels of plant invasions in different habitat types were assessed in several regional studies, but few of them were from the Mediterranean. Here we compare the levels of vascular plant invasion across habitats and plant communities of Sicily. We used a large dataset of plant species presences/ absences in vegetation plots to analyze the invasion patterns across habitats considering biogeography, life form and phenology of alien plants. Vegetation plots were classified based on the EUNIS classification of European habitats. The invasiveness of each species was expressed in terms of its absolute and percentage frequency. Representation of different life forms and phenological patterns was compared between alien and native species. The fidelity of alien species to individual habitats was calculated using the phi coefficient. Our analysis shows that annual and woody species are the most represented life forms in the alien flora of Sicily and that alien species tend to have a longer flowering period than the native species. The investigated habitats differed strongly in their level of invasion by alien species, ranging from 0 to 15.6% of aliens of all species recorded. Most of the habitats were colonized by very few alien species or completely lacked them, except for sandy coasts, naturally-disturbed riverbeds, and synanthropic habitats. It must be noted, however, that the number of alien species occurring in a given habitat does not relate to the severity of the impact of invasion in that habitat. Some habitats are invaded by few (or single) species, which attain a high cover, transforming the whole ecosystem. The habitat-based approach proved to be suitable for evaluating the habitat specificity and frequency of alien species at a regional scale, improving the capacity for risk assessment in different ecological contexts

A comparative framework for broad-scale plot-based vegetation classification

Aims: Classification of vegetation is an essential tool to describe, understand, predict and manage biodiversity. Given the multiplicity of approaches to classify vegetation, it is important to develop international consensus around a set of general guidelines and purpose-specific standard protocols. Before these goals can be achieved, however, it is necessary to identify and understand the different choices that are made during the process of classifying vegetation. This paper presents a framework to facilitate comparisons between broad-scale plot-based classification approaches. Results: Our framework is based on the distinction of four structural elements (plot record, vegetation type, consistent classification section and classification system) and two procedural elements (classification protocol and classification approach). For each element we describe essential properties that can be used for comparisons. We also review alternative choices regarding critical decisions of classification approaches; with a special focus on the procedures used to define vegetation types from plot records. We illustrate our comparative framework by applying it to different broad-scale classification approaches. Conclusions: Our framework will be useful for understanding and comparing plot-based vegetation classification approaches, as well as for integrating classification systems and their sections. We present a comparison framework for vegetation classification that distinguishes four structural elements (plot record, vegetation type, consistent classification section and classification system) and two procedural elements (classification protocol and classification approach). The framework will be useful for understanding and comparing plot-based vegetation classification approaches, as well as for integrating classification systems and their sections. © 2015 International Association for Vegetation Science

Glacial refugia and mid-Holocene expansion delineate the current distribution of Castanea sativa in Europe

We thank J.A. López-Saéz for very useful comments that improved the quality of the manuscript. We also thank two anonymous reviewers for their useful suggestions. JVRD was supported by "Severo Ochoa" PhD Grant (BP 12-093) and by funding through "Ayuda para Estancias Breves" (EB15-12) for a research stay at Masaryk University (Brno, Czech Republic) in 2015. Both grants were provided by the "Plan de Ciencia, Tecnología e Innovación" (PCTI) Government of Principado de Asturias. BJA was supported by the project Employment of Best Young Scientists for International Cooperation Empowerment (CZ.1.07/2.3.00/30.0037) co-financed from the European Social Fund and the state budget of the Czech Republic. MC was supported by the Czech Science Foundation (Centre of Excellence PLADIAS, 14-36079G).Areas of Quaternary refugia for tree species have been mainly delineated based on fossil records and phylogeography, but niche modelling can provide useful complementary information. Here we use palaeodistribution modelling to test the main hypotheses about the distribution of Castanea sativa in the Last Glacial Maximum (LGM) and the mid-Holocene in Europe. We computed distribution models for current climatic conditions using different methods, and projected them onto three climatic scenarios for the LGM and the mid-Holocene. The projections were validated with pollen and charcoal records. LGM refugia were suggested in the north of the Iberian, Italian and Balkan Peninsulas, and in northern Anatolia. The projections for the mid-Holocene indicated high climatic suitability and geographic expansion of the species range across southern Europe, including some areas where the species is nowadays considered as non-native. In general, our models are consistent with the patterns proposed with pollen and charcoal records, and partially also with phylogeographic information inferred from genetic data, suggesting that the most suitable areas for C. sativa were extended significantly during the mid-Holocene, but declined afterwards and lost connectivity. The projected patterns were compatible with existing palaeobotanical records of C. sativa and provide a spatially-explicit picture of the species past distribution

Intercontinental comparison of habitat levels of invasion between temperate North America and Europe

Several studies have demonstrated that floras of the New World contain larger proportions of alien species than those of the Old World; however, the differences in fine-scale invasion patterns are poorly known. We compared the levels of invasion in analogous habitats of two environmentally similar regions in temperate North America and Europe (the Carolinas and the Czech Republic), using comprehensive vegetation-plot databases. Native and alien vascular plant species were identified within 4165 vegetation plots assigned to 12 habitats occurring in both areas. The level of invasion was calculated for each habitat (1) as the proportion of aliens recorded cumulatively across multiple plots (habitat scale) and (2) as the mean proportion of aliens per plot (plot scale), both separately for all alien species and for the subgroup of aliens originating in one region and invading the other. The proportions of species native on one continent and invading the other were also calculated for each habitat to compare the alien species exchange between continents. Habitat levels of invasion showed remarkably similar patterns on the two continents. There were significant positive relationships for the levels of invasion, both for all alien species (habitat-scale R2 = 0.907; plot-scale R2 = 0.676) and for those that originated on the opposite continent (habitat-scale R2 = 0.624; plot-scale R2 = 0.708). In both regions, the most and the least invaded habitats were the same, but on average, North American habitats showed higher habitat-scale levels of invasion than their European counterparts. At the same time, a larger proportion of alien species was provided by European habitats for invasion to North America than vice versa. The consistent intercontinental pattern of habitat levels of invasion suggests that these levels are driven by similar mechanisms in distant regions. Habitat conditions are likely to have stronger effect on the level of invasion than the identity of alien species, as shown by similar levels of invasion in analogous habitats despite different geographical origins of alien species. The higher flux of alien species from Europe to North America is consistent with a generally higher level of invasion of North American habitats

Similarity of introduced plant species to native ones facilitates naturalization, but differences enhance invasion success

The search for traits associated with plant invasiveness has yielded contradictory results, in part because most previous studies have failed to recognize that different traits are important at different stages along the introduction–naturalization–invasion continuum. Here we show that across six different habitat types in temperate Central Europe, naturalized non-invasive species are functionally similar to native species occurring in the same habitat type, but invasive species are different as they occupy the edge of the plant functional trait space represented in each habitat. This pattern was driven mainly by the greater average height of invasive species. These results suggest that the primary determinant of successful establishment of alien species in resident plant communities is environmental filtering, which is expressed in similar trait distributions. However, to become invasive, established alien species need to be different enough to occupy novel niche space, i.e. the edge of trait space

The leaf economic and plant size spectra of European forest understory vegetation

Forest understories play a vital role in ecosystem functioning and the provision of ecosystem services. However, the extent to which environmental conditions drive dominant ecological strategies in forest understories at the continental scale remains understudied. Here, we used ~29 500 forest vegetation plots sampled across Europe and classified into 25 forest types to explore the relative role of macroclimate, soil pH and tree canopy cover in driving abundance-weighted patterns in the leaf economic spectrum (LES) and plant size spectrum (PSS) of forest understories (shrub and herb layers). We calculated LES using specific leaf area (SLA) and leaf dry matter content (LDMC) and PSS using plant height and seed mass of vascular plant species found in the understories. We found that forest understories had more conservative leaf economics in areas with more extreme mean annual temperatures (mainly Fennoscandia and the Mediterranean Basin), more extreme soil pH and under more open canopies. Warm and summer-dry regions around the Mediterranean Basin and areas of Atlantic Europe also had taller understories with heavier seeds than continental temperate or boreal areas. Understories of broadleaved deciduous forests, such as Fagus forests on non-acid soils, or ravine forests, more commonly hosted species with acquisitive leaf economics. In contrast, some coniferous forests, such as Pinus, Larix and Picea mire forests, or Pinus sylvestris light taiga and sclerophyllous forests, more commonly hosted species with conservative leaf economics. Our findings highlight the importance of macroclimate and soil factors in driving trait variation of understory communities at the continental scale and the mediator effect of canopy cover on these relationships. We also provide the first maps and analyses of LES and PSS of forest understories across Europe and give evidence that the understories of European forest types are differently positioned along major axes of trait variation