Mean Ellenberg Indicator Values Research Articles

Invasion of Raised Bogs by the Scots Pine; a Review of Vegetation History and Case Study in Selected Peat-Bogs in Bieszczady Mts. (Eastern Carpathians)

ABSTRACT The objective of this study was to analyse the diversity of pine and spruce bog forests on the domes of Carpathian raised bogs located in the Upper San River Valley. In order to determine the present species composition, 59 phytosociological releves were performed (32 within spruce forests, and 27 in pine forests). For all releves, the Shannon-Wiener index, evenness index and mean Ellenberg indicator values were calculated. Detrended correspondence analysis was conducted in order to determine the degree of similarity between distinct units of vegetation and to identify the main environmental gradients that have an impact on species composition. The results revealed considerable similarities between the ground vegetation of both spruce and pine forests growing on peat substrate. Within pine forests there was a greater proportion of certain plant species characteristic of raised bogs, and plants typical of bog coniferous forests. The ground flora of spruce forests was more diverse. Although spruce ...

Soil disturbance as a grassland restoration measure-effects on plant species composition and plant functional traits.

Soil disturbance is recognized as an important driver of biodiversity in dry grasslands, and can therefore be implemented as a restoration measure. However, because community re-assembly following disturbance includes stochastic processes, a focus only on species richness or establishment success of particular species will not inform on how plant communities respond ecologically to disturbance. We therefore evaluated vegetation development following disturbance by quantifying species richness, species composition and functional trait composition. Degraded calcareous sandy grassland was subjected to experimental disturbance treatments (ploughing or rotavation), and the vegetation was surveyed during four subsequent years of succession. Treated plots were compared with control plots representing untreated grassland, as well as nearby plots characterized by plant communities representing the restoration target.Species richness and functional diversity both increased in response to soil disturbance, and rotavation, but not ploughing, had a persistent positive effect on the occurrence of specialist species of calcareous sandy grassland. However, no type of soil disturbance caused the plant species composition to develop towards the target vegetation. The disturbance had an immediate and large impact on the vegetation, but the vegetation developed rapidly back towards the control sites. Plant functional composition analysis indicated that the treatments created habitats different both from control sites and target sites. Community-weighted mean Ellenberg indicator values suggested that the observed plant community response was at least partially due to an increase in nitrogen and water availability following disturbance. This study shows that a mild type of disturbance, such as rotavation, may be most successful in promoting specialist species in calcareous sandy grassland, but that further treatments are needed to reduce nutrient availability. We conclude that a functional trait based analysis provides additional information of the vegetation response and the abiotic conditions created, complementing the information from the species composition.

Decreasing deer browsing pressure influenced understory vegetation dynamics over 30 years

Thanks to the concomitant recordings of vegetation and deer browsing sampled first in 1976, then resurveyed in 2006, we show that forest plant communities shifted in response to deer population dynamics, stand management and eutrophication. High deer populations alter forest understory dynamics worldwide. However, no study ever attempted to rank the importance of deer herbivory relatively to other environmental drivers. In the Arc-en-Barrois National Forest (France), we investigated whether (i) deer browsing is a critical driver of vegetation composition and dynamics, (ii) the vegetation communities recover after a decrease in deer populations. In 2006, we resurveyed 321 plots from a network of 1027 plots where vegetation composition and browsing pressure was first assessed in 1976. We used coinertia analysis to identify the gradients in vegetation composition in 1976, when abiotic variables were also recorded. We assessed shifts in plant community composition using mean Ellenberg indicator values, analysed plot scores shifts along the axes of the coinertia analysis and correlated these shifts with changes in browsing pressure. Two major gradients determined vegetation composition in 1976: edaphic variables (nitrogen availability and soil moisture) and browsing pressure. Over the next 30 years, we noticed a strong increase in nitrophilous plant species frequency and community composition shifted towards lightly browsed characteristics, accompanying a decrease in browsing pressure. Shifts in community composition were significantly correlated with the intensity of changes in browsing pressure, showing that deer population dynamics were a determinant driver of changes in plant assemblages. Our results provide evidence for a structuring effect of deer browsing on vegetation composition, once forest site variations (soil moisture and nitrogen) were accounted for. We observed an incomplete recovery of the communities 25 years after the reduction of deer densities, suggesting a delayed response to deer population reduction. Long-term monitoring of forest biodiversity should therefore include browsing pressure assessment to control for potential effects of wild ungulates.

Further east: eutrophication as a major threat to the flora of Vladimir Oblast, Russia

Eutrophication remains a major threat to the flora of Western Europe despite measures to reduce nitrogen emissions. Although nutrient enrichment has been recorded for both inland waters and adjacent seas, there is almost no evidence from Russia for large-scale anthropogenic eutrophication of soils and its impact on terrestrial biota. I used the distribution grid data (337 grid squares, ca. 96 km(2)) on 1,384 vascular plants of Vladimir Oblast for two periods (1869-1999 vs. 2000-2012) to estimate the shifts in mean Ellenberg's indicator values for nitrogen and soil reaction. Decadal changes in the flora of acid sandy Meshchera Lowlands were observed directly during two grid surveys of 2002 and 2012 based on a coarser grid (50 squares, ca. 24 km(2)). Despite the spatial correlation of Ellenberg's indicator values for soil reaction and nitrogen, mean grid values for nitrogen are growing in areas with both acid and neutral soils. The changes in mean grid indicator values for nitrogen are caused by either local extinctions of species from nutrient-poor habitats or spread of nitrophilous plants. I found that oligotrophic habitats are declining rapidly within the eutrophic loamy landscapes. In contrast, changes in landscapes with acid sandy soils are caused by increasing number of records of nitrophilous species, both invasive and native. These two processes have different spatial patterns caused by varying levels of geochemical buffer capacity and should be considered separately. Fragmentary historical data on Vladimir Oblast flora agrees with the overall European picture of eutrophication in the twentieth century.

Long-term changes in calcareous grassland vegetation in North-western Germany – No decline in species richness, but a shift in species composition

We aimed to answer the question of whether the species richness and composition of calcareous grasslands in North-western Germany had changed over the last 70years as a result of atmospheric nitrogen (N) deposition. In total, 1186 plots of Festuco-Brometea (alliance Bromion erecti) grasslands from the sub-oceanic regions of the country were compiled (1061 plots from literature sources spanning a time period from 1936 to 1996, 125 new plots from 2008). Environmental descriptors recorded for each plot included geographic coordinates, altitude, heat index (combining slope and aspect), mean Ellenberg indicator values for light, soil moisture, soil pH and soil N, and cumulative N deposition (the latter being highly positively correlated with the year of sampling).In a Detrended Correspondence Analysis, the sample plot scores along axis one were highly correlated with the mean Ellenberg N-values, those along axis two were significantly affected by the year of sampling. In a general linear model, species richness of vascular plants showed a markedly hump-shaped relationship with mean Ellenberg N-value, whereas it was weakly affected by year (cumulative N load). Species with a significant negative trend over time were more often (than expected by chance) habitat specialists of dry grasslands, small, light-demanding and winter-green or evergreen with smaller seeds and scleromorphic leaves. In contrast to what has been found for acidic grasslands, N deposition in calcareous grasslands did not result in a decline in species richness, most likely because calcareous grasslands are water- and phosphorus-limited, and are well-buffered in terms of soil pH. To prevent a further change in species composition towards more mesophytic communities, grassland management by the site managers needs to be intensified.

Variability of Abies alba-dominated forests in Central Europe

Abstract Using vegetation databases from Poland, the Czech Republic, Austria, Slovakia and our own material collected during a field work, we have analysed the variability of species composition of Abies alba-dominated communities in Central Europe. Analysis was performed using a modified TWINSPAN algorithm in the JUICE software. Ecological analysis was performed on the basis of mean Ellenberg indicator values with a MoPeT_v1.0.r script prepared in R software. In general, the findings indicated that there are at least 8 types of Central European silver fir-dominated forests with different patterns in species composition and habitat conditions. These are the oligotrophic subcontinental silver fir forests of the Polish highlands, oligotrophic (sub)montane silver fir forest, hygrophilous silver fir forests, oligo-mesotrophic (sub)montane silver fir forests, mesotrophic (sub)montane silver fir forests, submontane and montane calcicolous silver fir forests of the Alps and the Carpathians, eutrophic silver fir-beech forests and silver fir ravine forests. The main conclusion is that the diversity of species composition of Abies alba-dominated forests in Central Europe is lower than described in current regional synthesis, which was confirmed by ecological analyses.

Nutrient limitation and site-related growth potential of Norway spruce (Picea abies [L.] Karst) in the Bavarian Alps

The hypothesis that soil chemistry is a main constraint for the vigour of Norway spruce trees on calcareous soils is scrutinised based on data from 60 existing and new intensive study sites in the Bavarian Alps, where comprehensive information on soils, climate, foliar nutrient concentration, ground vegetation, and tree growth is available. We characterised ecological gradients of the response variables site index (SI), foliar nutrient level and needle weight by constrained ordination, identified nutrient limitations based on regression trees and modelled SI based on vegetation-based mean Ellenberg indicator values. Our study confirms the assumption that soil development and concurrent acidification are key determinants for the vitality and growth of spruce in the Bavarian Alps, which surpass the importance of climate on nutrition and growth. Pools and availability of P and N are limiting nutrition and growth of spruce in this region. We hypothesize that N-limitation persists despite considerable deposition inputs because N tends to be locked up in organic horizons with low biological activity. K and trace elements, especially Fe, can also be deficient in some cases but do not appear as major limiting factors. High foliar Mn concentrations are a reliable indicator of mature soils and favourable site conditions in the Bavarian Alps, but Mn itself is usually not limiting. P must be regarded as the most critical macronutrient in the Bavarian Alps, particularly in the face of biomass harvesting. Consequently, at sites with shallow soils forest, management should focus on sustaining or restoring humus stocks. SI of spruce can be predicted from composition of ground vegetation and Ellenberg indicator values with remarkable precision (R 2 = 0.75).

Do vascular plants and bryophytes respond differently to coniferous invasion of coastal heathlands?

Invasion by non-native conifers may pose a threat to local biodiversity, but knowledge about introduced conifer effects on Northern Hemisphere ecosystems is scarce. The coastal heathlands of north-west Europe are threatened by invasion of native and introduced tree species. We assess how spread of the introduced conifer Sitka spruce (Picea sitchensis (Bong.) Carr.) into European coastal heathlands affect two major functional groups; vascular plants and bryophytes, and how these effects relate to the environmental changes imposed by the developing tree canopies. We compared the impact of introduced Sitka spruce and native Scots pine (Pinus sylvestris L.) by analysing effects on species richness and turnover of vascular plants and bryophytes along fine-scale transects from individual tree stems into open heathland vegetation. Environmental impacts were assessed by measured environmental variables, and the responses of the two species groups were assessed by calculating changes in their respective mean Ellenberg indicator values. Species richness decreased beneath both conifers, related to decreased light and increased nitrogen and pH. Whereas vascular plants responded negatively to poor light conditions beneath dense and low Sitka spruce canopies, bryophytes were more negatively affected by the warmer and drier microclimates beneath Scots pine. Introduced Sitka spruce impacts the sub-canopy environment differently from the native Scots pine, and the two functional plant groups responded differently to these impacts. This suggests that future forests are likely to differ in species richness and composition, depending on whether succession is based on native or introduced coniferous trees.

Vegetation change and homogenization of species composition in temperate nutrient deficient Scots pine forests after 45 yr

AbstractQuestionDoes eutrophication drive vegetation change in pine forests on nutrient deficient sites and thus lead to the homogenization of understorey species composition?LocationForest area (1600 ha) in the Lower Spreewald, Brandenburg, Germany.MethodsResurvey of 77 semi‐permanent plots after 45 yr, including vascular plants, bryophytes and ground lichens. We applied multidimensional ordination of species composition, dissimilarity indices, mean Ellenberg indicator values and the concept of winner/loser species to identify vegetation change between years. Differential responses along a gradient of nutrient availability were analysed on the basis of initial vegetation type, reflecting topsoil N availability of plots.ResultsSpecies composition changed strongly and overall shifted towards higher N and slightly lower light availability. Differences in vegetation change were related to initial vegetation type, with strongest compositional changes in the oligotrophic forest type, but strongest increase of nitrophilous species in the mesotrophic forest type. Despite an overall increase in species number, species composition was homogenized between study years due to the loss of species (mainly ground lichens) on the most oligotrophic sites.ConclusionsThe response to N enrichment is confounded by canopy closure on the N‐richest sites and probably by water limitation on N‐poorest sites. The relative importance of atmospheric N deposition in the eutrophication effect is difficult to disentangle from natural humus accumulation after historical litter raking. However, the profound differences in species composition between study years across all forest types suggest that atmospheric N deposition contributes to the eutrophication, which drives understorey vegetation change and biotic homogenization in Central European Scots pine forests on nutrient deficient sites.

Impact of land-use intensity and productivity on bryophyte diversity in agricultural grasslands.

While bryophytes greatly contribute to plant diversity of semi-natural grasslands, little is known about the relationships between land-use intensity, productivity, and bryophyte diversity in these habitats. We recorded vascular plant and bryophyte vegetation in 85 agricultural used grasslands in two regions in northern and central Germany and gathered information on land-use intensity. To assess grassland productivity, we harvested aboveground vascular plant biomass and analyzed nutrient concentrations of N, P, K, Ca and Mg. Further we calculated mean Ellenberg indicator values of vascular plant vegetation. We tested for effects of land-use intensity and productivity on total bryophyte species richness and on the species richness of acrocarpous (small & erect) and pleurocarpous (creeping, including liverworts) growth forms separately. Bryophyte species were found in almost all studied grasslands, but species richness differed considerably between study regions in northern Germany (2.8 species per 16 m2) and central Germany (6.4 species per 16 m2) due environmental differences as well as land-use history. Increased fertilizer application, coinciding with high mowing frequency, reduced bryophyte species richness significantly. Accordingly, productivity estimates such as plant biomass and nitrogen concentration were strongly negatively related to bryophyte species richness, although productivity decreased only pleurocarpous species. Ellenberg indicator values for nutrients proved to be useful indicators of species richness and productivity. In conclusion, bryophyte composition was strongly dependent on productivity, with smaller bryophytes that were likely negatively affected by greater competition for light. Intensive land-use, however, can also indirectly decrease bryophyte species richness by promoting grassland productivity. Thus, increasing productivity is likely to cause a loss of bryophyte species and a decrease in species diversity.

Too good to be true: pitfalls of using mean Ellenberg indicator values in vegetation analyses

AbstractQuestionMean Ellenberg indicator values (EIVs) inherit information about compositional similarity, because during their calculation species abundances (or presence–absences) are used as weights. Can this similarity issue actually be demonstrated, does it bias results of vegetation analyses correlating mean EIVs with other aspects of species composition and how often are biased studies published?MethodsIn order to separate information on compositional similarity possibly present in mean EIVs, a new variable was introduced, calculated as a weighted average of randomized species EIVs. The performance of these mean randomized EIVs was compared with that of the mean real EIVs on the one hand and random values (randomized mean EIVs) on the other. To demonstrate the similarity issue, differences between samples were correlated with dissimilarity matrices based on various indices. Next, the three mean EIV variables were tested in canonical correspondence analysis (CCA), detrended correspondence analysis (DCA), analysis of variance (ANOVA) between vegetation clusters, and in regression on species richness. Subsequently, a modified permutation test of significance was proposed, taking the similarity issue into account. In addition, an inventory was made of studies published in the Journal of Vegetation Science and Applied Vegetation Science between 2000 and 2010 likely reporting biased results due to the similarity issue.ResultsUsing mean randomized EIVs, it is shown that compositional similarity is inherited into mean EIVs and most resembles the inter‐sample distances in correspondence analysis, which itself is based on iterative weighted averaging. The use of mean EIVs produced biased results in all four analysis types examined: unrealistic (too high) explained variances in CCA, too many significant correlations with ordination axes in DCA, too many significant differences between cluster analysis groups and too high coefficients of determination in regressions on species richness. Modified permutation tests provided ecologically better interpretable results. From 95 studies using Ellenberg indicator values, 36 reported potentially biased results.ConclusionsNo statistical inferences should be made in analyses relating mean EIVs with other variables derived from the species composition as this can produce highly biased results, leading to misinterpretation. Alternatively, a modified permutation test using mean randomized EIVs can sometimes be used.

NIRS meets Ellenberg's indicator values: Prediction of moisture and nitrogen values of agricultural grassland vegetation by means of near-infrared spectral characteristics

Ellenberg indicator values are widely used ecological tools to elucidate relationships between vegetation and environment in ecological research and environmental planning. However, they are mainly deduced from expert knowledge on plant species and are thus subject of ongoing discussion. We researched if Ellenberg indicator values can be directly extracted from the vegetation biomass itself. Mean Ellenberg “moisture” (mF) and “nitrogen” (mN) values of 141 grassland plots were related to nutrient concentrations, fibre fractions and spectral information of the aboveground biomass. We developed calibration models for the prediction of mF and mN using spectral characteristics of biomass samples with near-infrared reflectance spectroscopy (NIRS). Prediction goodness was evaluated with internal cross-validations and with an external validation data set. NIRS could accurately predict Ellenberg mN, and with less accuracy Ellenberg mF. Predictions were not more precise for cover-weighted Ellenberg values compared with un-weighted values. Both Ellenberg mN and mF showed significant and strong correlations with some of the nutrient and fibre concentrations in the biomass. Against expectations, Ellenberg mN was more closely related to phosphorus than to nitrogen concentrations, suggesting that this value rather indicates productivity than solely nitrogen. To our knowledge we showed for the first time that mean Ellenberg indicator values could be directly predicted from the aboveground biomass, which underlines the usefulness of the NIRS technology for ecological studies, especially in grasslands ecosystems.

Temporal changes in the island flora at different scales in the archipelago of SW Finland

AbstractQuestion: How have species richness and vegetation patterns changed in a group of islands in the northern Baltic Sea over a 58‐yr period of changing land use and increasing eutrophication?Location: A group of 116 islands, the Brunskär sub‐archipelago, in SW Finland.Methods: A complete survey of vascular plant species performed in 1947–1949 by Skult was repeated by our group using the same methodology in 2005–2007 (historical versus contemporary, respectively). DCAs were performed and total number of species, extinction–colonization rates, species frequency changes and mean Ellenberg indicator values for light, moisture and nitrogen and Eklund indicator values for dependence of human cultural influence were obtained for each island and relevé.Results: Species richness has declined on large islands and increased on small islands. The increase in number of species on small islands is driven by a strong increase in frequency of shore species, which in turn is induced by more productive shores. The decrease in species richness on large islands is related to overgrowth of open semi‐natural habitats after cessation of grazing and other agricultural practices.Conclusions: After the late 1940s, open habitats, which were created and maintained by cattle grazing and other traditional agricultural activities, have declined in favour of woody shrub and forest land. Shores have been stabilized and influenced by the eutrophication of the Baltic Sea, and the vegetation has become more homogeneous. This development, resulting in lower species diversity, poses a challenge for the preservation of biodiversity both on a local and on a landscape level.

Changes in vegetation types and Ellenberg indicator values after 65 years of fertilizer application in the Rengen Grassland Experiment, Germany

AbstractQuestion: How does semi‐natural grassland diversify after 65 years of differential application of Ca, N, P, and K fertilizers? Is fertilizer application adequately reflected by the Ellenberg indicator values (EIVs)?Location: Eifel Mountains, West Germany.Methods: The Rengen Grassland Experiment (RGE) was established in an oligotrophic grassland in 1941. Six fertilizer treatments (Ca, CaN, CaNP, CaNP‐KCl, CaNP‐K2SO4, and unfertilized control) were applied annually in five complete randomized blocks. Species composition of experimental plots was sampled in 2006 and compared with constancy tables representing grassland types in a phytosociological monograph of a wider area. Each plot was matched to the most similar community type using the Associa method. Mean EIVs were calculated for each treatment.Results: The control plots supported oligotrophic Nardus grassland of the Polygalo‐Nardetum association (Violion caninae alliance). Vegetation in the Ca and CaN treatments mostly resembled montane meadow of Geranio‐Trisetetum (Polygono‐Trisetion). Transitional types between Poo‐Trisetetum and Arrhenatheretum (both from the Arrhenatherion alliance) developed in the CaNP treatment. In the CaNP‐KCl and CaNP‐K2SO4 treatments, vegetation corresponded to the mesotrophic Arrhenatheretum meadow. Major discontinuity in species composition was found between control, Ca, and CaN treatments, and all treatments with P application. EIVs for both nutrients and soil reaction were considerably higher in P treatments than in Ca and CaN treatments. Surprisingly, the control plots had the lowest EIVs for continentality and moisture, although these factors had not been manipulated in the experiment.Conclusions: Long‐term fertilizer application can create different plant communities belonging to different phytosociological alliances and classes, even within a distance of a few meters. Due to their correlated nature, EIVs can erroneously indicate changes in factors that actually did not change, but co‐varied with factors that did change. In P‐limited ecosystems, EIVs for nutrients may indicate availability of P rather than N.

Plant communities with Helianthus tuberosus L. in the towns of the Upper Silesian Industrial Region (southern Poland)

The aims of the research were: to show the floristic composition of patches with participation of Helianthus tuberosus, to find the major environmental gradients in species composition of these patches and to compare plant communities with this species from Poland with those recorded in neighbouring European countries. Fifty four phytosociological relevés, made in a variety of ruderal habitats in the towns of the Upper Silesian Industrial Region (Poland), were analysed using the Correspondence Analysis (CA). To identify the main environmental gradients in the floristic composition of relevés the CA site scores were correlated, using the Kendall correlation coefficient, with the following explanatory variables: Shannon H’ index of species diversity, the number of species from the Convolvuletalia sepium order, the Calystegion sepium alliance, the Onopordetalia acanthii order, the Molinio-Arrhenatheretea class, the Stellarietea mediae class; mean Ellenberg indicator values for light, moisture, temperature, soil reaction and nitrogen. Two major gradients in species data were detected: (i) from plant communities of abandoned meadows of the Molinio-Arrhenatheretea class to nitrophilous communities of the Convolvuletalia sepium order and (ii) a gradient related to the number of species of the Stellarietea mediae class and to the indicator value for light. Helianthus tuberosus stands recorded in European countries can be divided into two separate groups. The first group is differentiated by species of the Onopordetalia acanthii order and higher participation of meadow species from the Molinio-Arrhenatheretea and Stellarietea mediae classes. The second group is characterized by a high frequency of nitrophilous species from the Convolvuletalia sepium order.

Long‐term impacts of nitrogen and sulphur deposition on forest floor vegetation in the Northern limestone Alps, Austria

Abstract.Question: Are there effects of long‐term deposition of airborne nitrogen and sulphur on the forest floor vegetation from permanent plots collected in 1993 compared to 2005.Location: Northern limestone Alps in Austria.Methods: Single species responses were analysed by correlating trends in cover‐abundance values, as derived from marginal models, with Ellenberg indicator values. Changes in the species composition of plots were analysed by correlating changes in mean Ellenberg indicator values with the displacement of plots within a multidimensional scaling ordination.Results: Trends in single species abundance were positively correlated with indicator values of soil pH but were independent of nutrient availability. A general trend towards the homogenisation of vegetation, due to convergent time vectors of the relevés, became obvious. Oligotrophic sites previously situated at the distal ends of ordination axes shifted towards the centre since they were enriched by species preferring mesotrophic conditions. The bulk of plots with intermediate site conditions hardly showed any trends. A concomitant analysis demonstrated that temporal changes in species composition exceed the variation in cover abundance estimates among different field botanists.Conclusions: N deposition can lead to a homogenisation of forest floor vegetation. Larger limestone areas with diverse soil conditions, such as the Northern limestone Alps in Austria, as a whole are thus negatively affected by airborne N deposition. Nevertheless, the vegetation was at least as strongly affected by an increase of basiphilous species as a result of decreasing S deposition.

Using species‐environmental amplitudes to predict pH values from vegetation

AbstractQuestion: Species optima or indicator values are frequently used to predict environmental variables from species composition. The present study focuses on the question whether predictions can be improved by using species environmental amplitudes instead of single values representing species optima.Location: Semi‐natural, deciduous hardwood forests of northwestern Germany.Methods: Based on a data set of 558 relevés, species responses (presence/absence) to pH were modelled with Huisman‐Olff‐Fresco (HOF) regression models. Species amplitudes were derived from response curves using three different methods. To predict the pH from vegetation, a maximum amplitude overlap method was applied. For comparison, predictions resulting from several established methods, i. e. maximum likelihood/present and absent species, maximum likelihood/present species only, mean weighted averages and mean Ellenberg indicator values were calculated. The predictive success (squared Pearson's r and root mean square error of prediction) was evaluated using an independent data set of 151 relevés.Results: Predictions based upon amplitudes defined by maximum Cohen's x probability threshold yield the best results of all amplitude definitions (R2= 0.75, RMSEP = 0.52). Provided there is an even distribution of the environmental variable, amplitudes defined by predicted probability exceeding prevalence are also suitable (R2= 0.76, RMSEP = 0.55). The prediction success is comparable to maximum likelihood (present species only) and – after rescaling – to mean weighted averages. Predicted values show a good linearity to observed pH values as opposed to a curvilinear relationship of mean Ellenberg indicator values. Transformation or rescaling of the predicted values is not required.Conclusions: Species amplitudes given by a minimum and maximum boundary for each species can be used to efficiently predict environmental variables from species composition. The predictive success is superior to mean Ellenberg indicator values and comparable to mean indicator values based on species weighted averages.

The role of soil and microclimatic variables in the distribution patterns of urban wasteland flora in Brussels, Belgium

Despite increased recognition of the importance of urban vegetation research, few attempts have been made to assess the relative influence of ecological variables on the species composition of urban wastelands. The main aim of this paper is to assess the relative importance of soil and microclimatic variables in structuring plant species richness and diversity in this habitat. Field investigations were carried out in 22 wasteland sites situated within the city of Brussels. The vegetation has been recorded in 38 4 m 2-plots according to the Braun–Blanquet-method. A total of 19 environmental variables were taken into consideration, among others the presence of different kinds of anthropogenic substrates and microclimatic variables. Results indicate that plant species composition in urban wastelands is mainly driven by soil nutrient content, soil moisture, soil pH and light intensity (as inferred by the mean Ellenberg's indicator values). Various types of anthropogenic substrates such as concrete, pebbles, sand and rubble had different effects on the species composition, the proportion of neophytes, hemeroby and urbanity level. Air temperature and humidity did show a significant influence on the presence of some species. The contribution of these environmental variables to the species composition and diversity of urban wastelands is discussed.

Bias in Ellenberg indicator values — problems with detection of the effect of vegetation type

AbstractA recent analysis published in this journal found different relationships between mean Ellenberg indicator values and environmental measurements in different vegetation types. The cause was stated as bias in mean Ellenberg values between relevés which in turn suggested to reflect a bias in individual Ellenberg values. We discuss two phenomena that could explain these results without the need to invoke bias in either individual or mean Ellenberg values. Firstly, slopes of linear regression lines underestimate true relationships when analyses involve explanatory variables measured with error. Secondly, syntaxon‐specific distributions of Ellenberg values follow from the floristic definition of phytosociological units. Mean Ellenberg values per relevé therefore carry the stamp of their associated syntaxon even though associated abiotic conditions may vary between relevés. This will lead to variation in slopes and intercepts between vegetation types not because of bias in individual Ellenberg values but because of prescribed bias in the distribution of Ellenberg values between syntaxa. The residual variation in calibrations carried out across vegetation types is undoubtedly reduced by introducing vegetation type as a factor. However users should note that this is unlikely to reflect bias in individual Ellenberg values but is more likely to reflect error in environmental measurements as well the constraint imposed by phytosociological classification.

Trends in species diversity and composition of urban vegetation over three decades

AbstractQuestion: What was the change in diversity of urban synantropic vegetation in a medium‐sized Central European city during the period of increasing urbanization (1960s‐1990s)?Location: The city of Plzeň, an industrial centre of the western part of the Czech Republic.Methods: Sampling of various types of synanthropic vegetation, conducted in the 1960s, was repeated by using the same methods in the 1990s. This yielded 959 relevés, of which 623 were made in the 1960s and 336 in the 1990s. The relevés were assigned to the following phytosociological classes: Chenopodietea, Artemisietea vulgaris, Galio‐Urticetea, Agropyretea repentis and Plantaginetea majoris. Total number of vascular plant species, evenness index J, number of alien species (classified into archaeophytes and neophytes), and mean Ellenberg indicator values for light, temperature, continentality, moisture, soil reaction, and nutrients were obtained for each relevé.Results: From 1960s to 1990s, there was a significant decrease of species richness and diversity in synanthropic vegetation. The proportion of archaeophytes decreased in most vegetation types, indicating the contribution of this group of species, often confined to specific rural‐like habitats, to the observed impoverishment of ruderal vegetation. The proportion of neophytes did not change between the two periods. Comparison between 1960s and 1990s indicated a decrease in light, temperature, moisture, soil reaction and nutrient indicator values in some vegetation types. In both periods, Artemisieta, Galio‐Urticetea and Chenopodietea formed a distinct group harbouring more species than Agropyretea and Plantaginetea. Neophytes, i.e. recently introduced species, were most represented in the early successional annual vegetation of Chenopodietea, rather than in perennial vegetation of the other classes.Conclusions: Synanthropic vegetation of Plzeň exhibited a general trend of decrease in species diversity.