Vegetation ecologists use a wide range of importance ("abundance") measures for plant species in vegetation plots, including percentage cover, ordinal cover scales, frequency and fractional biomass. Resurvey studies and analyses of heterogenous data from large vegetation-plot databases need to deal with data sampled with different approaches, yet very little is known about how these approaches relate to each other. For the Square Foot Project, in which hundreds of historic grassland plots in Switzerland of 0.09 m2 size were resurveyed after having been originally sampled via biomass harvest, we had the challenge that the historical method was too time-consuming for our study and thus had to resort to careful cover estimation in percent. However, we used both methods to sample 40 such plots representative of the grasslands of Switzerland and compared the results. We found that with biomass-based species determination, an average of 0.9 additional species (4.6%) per plot were found compared to cover-based sampling. Graminoids were three times more likely to be overlooked than forbs. Fractional cover was well related to fractional biomass with an allometric (power-law) function, with an exponent of 0.6 for all species combined, while graminoids and forbs showed clear differences in function parameters when analysed separately. Generally, our overlooking probabilities were much lower than in other comparable studies, which might be due to the very small plot size or to the careful sampling with percentage estimates. Our allometric functions allow reliable transformations between fractional biomass and fractional cover in temperate European grasslands. We recommend the development of further such empirical functions for other regions and ecosystems.

Grasslands host a significant share of Europe's species diversity but are among the most threatened vegetation types of the continent. Resurvey studies can help to understand patterns and drivers of changes in grassland diversity and species composition. However, most resurveys are based on local or regional data, and hardly reach back more than eight decades. Here, we publish and describe the Historic Square Foot Dataset, comprising 580 0.09-m2 and 43 1-m2 vegetation plots carefully sampled between 1884 and 1931, covering a wide range of grassland types across Switzerland. We provide the plots as an open-access data set with coordinates, relocation accuracy and fractional aboveground biomass per vascular plant species. We assigned EUNIS habitat types to most plots. Mean vascular plant species richness in 0.09 m2 was 19.7, with a maximum of 47. This is considerably more than the present-day world record of 43 species for this plot size. Historically, species richness did not vary with elevation, differing from the unimodal relationship found today. The data set provides unique insight into how grasslands in Central Europe looked more than 100 years ago, thus offering manifold options for studies on the development of grassland biodiversity and productivity. The Historic Square Foot Dataset comprises several hundred vegetation plots conducted between 1884 and 1931 in grassland habitats all over Switzerland. These data are unique in providing insights in how grasslands in Central Europe were composed, making them an important source of information for vegetation science and global-change studies. The digitised and georeferenced data are made accessible through this publication.image

The inner-alpine dry valleys of the Swiss Alps are characterized by subcontinental climate, leading to many peculiarities in dry grassland species composition. Despite their well-known uniqueness, comprehensive studies on biodiversity patterns of the dry grasslands in these valleys were still missing. To close this gap, we sampled 161 10-m 2 vegetation plots in the Rhône, Rhine and Inn valleys, recording vascular plants, terricolous bryophyte and lichen species, as well as environmental data. Additionally, we tested the scale-dependence of environmental drivers using 34 nested-plot series with seven grain sizes (0.0001–100 m 2 ). We analysed the effects of environmental drivers related to productivity/stress, disturbance and within-plot heterogeneity on species richness. Mean species richness ranged from 2.3 species in 0.0001 m 2 to 58.8 species in 100 m 2 . For all taxa combined, the most relevant drivers at the grain size of 10 m 2 were southing (negative), litter (negative), mean annual precipitation (unimodal), gravel cover (negative), inclination (unimodal) and mean annual precipitation (unimodal). For vascular plants the pattern was similar, while bryophyte and lichen richness differed by the opposite relationship to mean annual precipitation as well as negative influences of mean herb layer height, grazing and mowing. The explained variance of the multiple regression model increased with grain size, with very low values for the smallest two grain sizes. While southing and litter had high importance for the fiver larger grain sizes, pH and gravel cover were particularly important at the intermediate grain sizes, and inclination and mean annual precipitation for the two largest grain sizes. The findings emphasize the importance of taxonomic group and grain size for patterns and drivers of species richness in vegetation, consistent with ecological theory. Differences in the diversity–environment relationships among the three taxonomic groups can partly be explained by asymmetric competition that leads to low bryophyte and lichen diversity where vascular plants do well and vice versa. The relatively low alpha diversity of vascular plants in dry grasslands in Swiss inner-alpine valleys compared to similar communities in other parts of the Palaearctic remains puzzling, especially because Swiss stands are often large and well-preserved.

s Die Grün-Erle (Alnus viridis) befindet sich im Alpenraum aufgrund der Extensivierung der landwirtschaftlichen Nutzung seit einigen Jahrzehnten in Ausbreitung. Dadurch werden artenreichere Lebensräume verdrängt und aufgrund der Symbiose mit

Meso-xeric grasslands have declined sharply in Central Europe during the last century. These species-rich habitats are threatened by intensification or abandonment of agricultural use, eutrophication, climate change and landscape fragmentation. However, different studies in various regions of Central Europe are inconsistent in their findings about degree and direction of changes. We thus resurveyed the historical vegetation plots of the alliance Mesobromion in the Swiss Jura Mts. In 2020, we re-sampled 28 quasi-permanent vegetation plots originally recorded in 1980 to quantify potential vegetation change. Frequency of individual species, species diversity, 11 ecological indicator values and four functional traits, as well as the presence of diagnostic species of phytosociological alliances, were analysed. Further, a habitat classification and detrended correspondence analysis (DCA) were also performed. Species richness, indicator values for light availability and temperature, seed dispersal by animals and seed persistence had significantly decreased by 2020. Conversely, ecological indicator values for nutrient availability and soil moisture as well as community-weighted means for seed mass and canopy height had significantly increased. There were significantly fewer ruderal species, stresstolerators, therophytes and herbaceous chamaephytes in 2020. In contrast, highly competitive species and hemicryptophytes had increased. Together, these findings indicate an increase in productivity over time. There were fewer specialized species in 2020 than in 1980, indicating a homogenization of the vegetation and a shift towards nutrient-rich pastures and meadows. The shift towards a later successional stage might indicate reduced grazing disturbance. Most of these sites are currently not included in an agri-environmental scheme. Partial differences of our findings from those reported elsewhere in Central Europe highlight the importance of regionally adapted conservation strategies in order to stop biodiversity loss in meso-xeric grasslands.

Many studies have demonstrated significant alterations in the species composition of grasslands in Central Europe over the past decades due to multiple drivers of anthropogenic environmental change. Most such studies deal with dry, acidic, wet or alpine grassland types, while little is known about changes in mesic grasslands, particularly in urban areas. To investigate the effects of anthropogenic environmental change on such grasslands, we resurveyed a selection of plots in the city of Zurich (Switzerland) approximately 25 years after their original recording. First, we checked whether 241 extensively used mesic grasslands (belonging to the Arrhenatheretalia elatioris) in the city were still grasslands, and whether their management had changed. Then we resurveyed a representative subset of 30 quasi-permanent plots of 50 m2. We tested whether biodiversity metrics, mean ecological indicator values, community weighted means (CWMs) of functional traits or the presence of individual vascular plant species had changed. We found that 15% of the original grasslands had been lost due to changes in land use during this period. Of the remaining grasslands, most of the former meadows were still mown, while many of the former pastures had been transformed into meadows. Measures of alpha diversity had not changed significantly for the 30 plots. However, species composition now indicated nutrient poorer, less base-rich and less ruderal site conditions, while CWMs of specific leaf area (SLA) had decreased and that of seed mass increased. In stands that were managed by mowing in both periods there was practically no change, while there was a pronounced change in those that had been transformed from grazing to mowing. In general, five species showed a significant increase and 16 species a significant decrease in frequency, with no obvious ecological difference between winners and losers. Alien species were rare in both periods and showed hardly any trend, except Veronica persica, which became rarer. In conclusion, more extensively used grasslands have survived to date than would be anticipated in such a rapidly growing city as Zurich. Their quality has hardly changed during the past Manuscript received 09 May 2021, accepted 07 August 2021 Published online 31 October 2021 Co-ordinating Editor: Valentin Klaus 424 quarter century, and if changes occurred, they are rather attributable to the intentional change of management from grazing to mowing. The relatively good ecological state of these urban grasslands might be due to a lower agricultural land use pressure than outside urban areas, as well as a constant management of many of these grasslands with a conservation focus. By maintaining these grasslands in their current state, they may have the potential to contribute to the conservation of biodiversity in urban areas.

Aims Ecological theories predict that assembly processes shape communities so that co-existing species may either be functionally more dissimilar ("divergence") or more similar ("convergence") than expected by chance. Two important factors that are rarely considered in combination are spatial scale and successional stage. Our aim is to identify different functional patterns during succession across spatial scales and to discuss the likely underlying assembly processes. We expect to find convergence due to environmental filtering at early succession, especially at the largest scales, and a tendency towards divergence driven by competitive interactions as succession unfolds and at smaller spatial scales. Location Protected Landscape Area "Bohemian Karst", Czech Republic. Methods We studied three succession stages (two, eight and 55 years after abandonment). Each field was sampled using 40 1-m(2) quadrats containing 100 pins in a regular grid. We analysed trait dispersion at several combinations of grain and extent and characterised trait similarity using phylogeny and four traits: specific leaf area, leaf dry matter content, height, and seed mass analysed individually and combined using Gower distance (multi-trait dissimilarity). Results In the youngest field, three of the traits individually and the multi-trait dissimilarity showed convergence regardless of scale. Phylogeny showed convergence at most spatial scales of the youngest stage. The other two fields showed greater divergence predominantly in the oldest field at the smallest spatial scale. Conclusions The results are mainly congruent with theoretical expectations and provide a valuable example of directional changes from trait convergence to divergence along succession. The scale-invariant convergence in the early stages of succession seems to be the result of environmental filtering and weaker competitive exclusion. At later stages and particularly at smaller scales, divergence becomes more common, likely because competition limits the trait similarity of species. These results highlight the importance of predictable (non-random) changes in ecological succession.

Questions Species-area relationships (SARs) are fundamental for understanding biodiversity patterns and are generally well described by a power law with a constant exponent z. However, z-values sometimes vary across spatial scales. We asked whether there is a general scale dependence of z-values at fine spatial grains and which potential drivers influence it. Location Palaearctic biogeographic realm. Methods We used 6,696 nested-plot series of vascular plants, bryophytes and lichens from the GrassPlot database with two or more grain sizes, ranging from 0.0001 m(2) to 1,024 m(2) and covering diverse open habitats. The plots were recorded with two widespread sampling approaches (rooted presence = species "rooting" inside the plot; shoot presence = species with aerial parts inside). Using Generalized Additive Models, we tested for scale dependence of z-values by evaluating if the z-values differ with gran size and tested for differences between the sampling approaches. The response shapes of z-values to grain were classified by fitting Generalized Linear Models with logit link to each series. We tested whether the grain size where the maximum z-value occurred is driven by taxonomic group, biogeographic or ecological variables. Results For rooted presence, we found a strong monotonous increase of z-values with grain sizes for all grain sizes below 1 m(2). For shoot presence, the scale dependence was much weaker, with hump-shaped curves prevailing. Among the environmental variables studied, latitude, vegetation type, naturalness and land use had strong effects, with z-values of secondary peaking at smaller grain sizes. Conclusions The overall weak scale dependence of z-values underlines that the power function generally is appropriate to describe SARs within the studied grain sizes in continuous open vegetation, if recorded with the shoot presence method. When clear peaks of z-values occur, this can be seen as an expression of granularity of species composition, partly driven by abiotic environment.

Aims: Understanding fine- grain diversity patterns across large spatial extents is fundamental for macroecological research and biodiversity conservation. Using the GrassPlot database, we provide benchmarks of fine- grain richness values of Palaearctic open habitats for vascular plants, bryophytes, lichens and complete vegetation (i.e., the sum of the former three groups). Location: Palaearctic biogeographic realm. Methods: We used 126,524 plots of eight standard grain sizes from the GrassPlot database: 0.0001, 0.001, 0.01, 0.1, 1, 10, 100 and 1,000 m 2 and calculated the mean richness and standard deviations, as well as maximum, minimum, median, and first and third quartiles for each combination of grain size, taxonomic group, biome, region, vegetation type and phytosociological class. Results: Patterns of plant diversity in vegetation types and biomes differ across grain sizes and taxonomic groups. Overall, secondary (mostly semi- natural) grasslands and natural grasslands are the richest vegetation type. The open- access file ”GrassPlot Diversity Benchmarks” and the web tool “GrassPlot Diversity Explorer” are now available online (https://edgg.org/datab ases/Grass landD ivers ityEx plorer) and provide more insights into species richness patterns in the Palaearctic open habitats. Conclusions: The GrassPlot Diversity Benchmarks provide high- quality data on species richness in open habitat types across the Palaearctic. These benchmark data can be used in vegetation ecology, macroecology, biodiversity conservation and data quality checking. While the amount of data in the underlying GrassPlot database and their spatial coverage are smaller than in other extensive vegetation- plot databases, species recordings in GrassPlot

Nuphar pumila is a glacial relict, which is nowadays rare throughout Europe and red-listed in most European regions. In Switzerland only three autochthonous populations and one population of the hybrid with N. lutea (N. xspenneriana) have survived to date, one of them in the canton of Zurich. To protect this species regionally, the canton of Zurich has commissioned the ex situ propagation of specimens, which then had been introduced to 37 water bodies in protected areas, including one known former site. Since only about 10% of these introductions had been successful, there was a wish to identify causes of this lack of success. To this end, we compared the vegetation and physical-chemical parameters of the four natural sites in Switzerland with the successful and unsuccessful introduction sites. Additionally, for a subset of sites, we assessed diatom genus composition as a proxy of water quality. Moreover, we derived vegetation plots of N. pumila and N. lutea from across Europe from the European Vegetation Archive (EVA) to compare their site conditions, using mean ecological indicator values and bioclimatic variables of the localities. We found that inside Switzerland the main differences were between the natural sites and all introduction sites, while successful and unsuccessful introduction sites hardly differed in the determined parameters. Natural sites had cooler water with lower magnesium content, and according to mean ecological indicator values, also lower nutrient status. The diatom data, though limited in amount, point into the same direction. The EVA data demonstrate that stands of N. pumila are mainly more oligotrophic, but also cooler and more acidic than those of N. lutea. We could not find any factor that explains the success vs. lack of success of plantations of N. pumila in multiple sites in the canton of Zurich, but our results rather indicate that due to the relatively warm climate, the high atmogenic nitrogen input and the predominantly base-rich bedrock, the sites in the canton are generally not particularly well suited for N. pumila. We consider it therefore more promising to protect and possibly (re-) introduce N. pumila in other cantons with higher elevation, base-poor bedrock and lower atmogenic nitrogen input.

To study how the cessation of transhumant sheep grazing in alpine areas influences biodiversity, three study sites along a chronosequence (space-for-time substitution) were studied in the Canton of St. Gallen (Switzerland): (i) an intensively used sheep pasture (approx. 81 and 195 sheep ha(-1)) (SB0), (ii) a sheep pasture abandoned since five years and now used by approx. 1 chamois ha(-1) (SB5), and (iii) a sheep pasture abandoned since 19 years and now used by about 5 chamois and 1 ibex ha(-1) (SB19). Focussing on the two most frequent vegetation types, Poion alpinae and Nardion, we compared vascular plant diversity and floristic similarity among the three study sites at two grain sizes (10 m(2) and 200 m(2)). In addition, butterfly and orthopteran species were mapped. In SB0, Nardion was the most frequent vegetation type, whereas in SB5 and SB19 Poion alpinae prevailed. Mean plant species richness on 10 m(2) and 200 m(2) did not differ significantly between the three sites of the chronosequence for either Poion alpinae or Nardion. Only for the 200-m(2) plots of the Poion alpinae, we found a substantial but non-significant increase in plant species richness (46.8 vs. 40.8 species). The two extreme points of the chronosequence, SB0 and SB19, were most dissimilar in their floristic composition. In SB0, more butterfly and orthopteran species were recorded than in the areas no longer grazed by sheep, but the difference was significant only for the latter. The fact that the vascular plant species richness at the studied grain sizes did not differ significantly along the 19-year chronosequence suggests, that alpine grasslands respond very slowly to changes such as the replacement of sheep by chamois and ibex. However, it also suggests, that sheep have no major adverse effects on alpine grasslands, even though there seems to be a trend towards increased large-scale diversity when sheep are replaced by wild ungulates. In contrast, sheep grazing clearly influenced vegetation composition. For example, the higher frequency of Nardion grasslands and typical Nardion species in SB0 might be attributed to the effects of relatively intense sheep grazing.

The upper Rhone valley in the Swiss canton of Valais is one of the driest and most continental of the inner-alpine valleys and harbours a rich xerothermic flora. We studied syntaxonomy and ecology of dry grasslands and their species richness patterns. In 2018 we recorded 28 vegetation plots (10 m(2)) and three nested-plot series of 0.0001 to 100 m(2) on the south-facing slopes above the village of Ausserberg. Mean richness of all species ranged from 1.7 on 1 cm(2) to 47.3 on 100 m(2), with little contribution of bryophytes and lichens. The species-area relationship for total richness closely followed a power function. Modified TWINSPAN yielded a three-cluster solution, which could easily be matched with three orders of the class Festuco-Brometea: Stipo pulcherrimae-Festucetalia pallentis (xeric, rocky), Festucetalia valesiacae (xeric, non-rocky) and Brachypodietalia pinnati (meso-xeric). The subdivision of the xeric types into two orders is new for Swiss dry grasslands, where these types up to now had been joined in a single alliance Stipo-Poion within the Festucetalia valesiacae.

Low-Intensive control of bracken promotes floristic diversity. In Switzerland, the native bracken (Pteridium aquilinum) is threatening local species diversity. In the present study, we investigated the impact of low-intensity bracken control treatments on the floristic diversity of a protected Mesobromion-Type grassland near Chur (Grisons, Switzerland). In 2008, we started a long-term bracken control experiment where bracken was removed once a year by uprooting and mowing, respectively. In 2015, i.e. 8 years after the start of the experiment, bracken was significantly less vital on the treatment plots as compared to the adjacent control plots. Uprooting in early June proved to damage bracken significantly more effectively than mowing. On the treatment plots, the number of vascular plant species per m2 was significantly greater than on the control plots, and also plant species composition differed significantly between treated and untreated plots. In conclusion, even low-intensity treatments such as uprooting or mowing once a year in early June does both effectively harm bracken and foster species richness in the herb layer. Uprooting is particularly recommended if other vascular plant species should be preserved.

Upgrading of forest edges: impacts of orientation and site fertility Wide, species-rich forest edges are rare in Switzerland. For some years now, the ecological improvement of forest edges has therefore been encouraged by the federal government. In order to make optimal use of the limited resources, we need a good knowledge of the site factors that influence the success of upgrading treatments. We studied 48 improved forest edges in Canton Aargau to understand the impacts of orientation and site fertility on the success of the improvement measures. The results showed that both orientation and site fertility had a significant impact on the quality of the enhanced forest edges. On south-facing and nutrient-poor sites, the ecological quality of the improved forest edges was significantly better than on nutrient-rich sites oriented towads other directions. On sites which were not south-facing fertility had no significant effect on the ecological quality of the improved forest edges. On nutrient-poor sites, the risk that problematic or invasive plant species become dominant after upgrading treatments was much smaller than on nutrient- rich sites. The orientation of the forest edge, on the other hand, had no significant effect on that risk. In the future, therefore, forest edge enhancement projects should preferably be carried out on south-facing and nutrient-poor sites. On sites with other expositions or with high fertility, successful upgradings are less likely but not impossible.