Restoration of montane fen meadows by mowing remains possible after 4-35 years of abandonment

Billeter R., Peintinger M. and Diemer M. 2007. Restoration of montane fen meadows by mowing remains possible after 4-35 years of abandonment. Bot. Helv. 117: 1 - 13. The abandonment of management in Swiss fen meadows has reduced their plant species diversity and the fitness of some typical fen species. We examined whether the resumption of mowing can reverse these effects, and if so, which mechanisms are responsible for community change; we also tested whether restoration success depends on the duration since abandonment. Experimental mowing was applied to 15 montane fen meadows of NE Switzerland that had been abandoned for 4-35 years. After two years of mowing, plant species richness was 11% higher in mown plots (2 m2) than in fallow plots, approaching levels of neighbouring continuously managed fen meadows. In particular, experimental mowing significantly increased the number of fen indicator species (+15%) as well as herbs and woody species (seedlings and saplings), while grass, sedge and rush species richness was not affected. Mowing had little effect on aboveground biomass, but strongly reduced litter mass (−50%) and canopy height (−20%). Seedling densities of two common species showed opposite responses to mowing: they increased in Carex davalliana and decreased in Succisa pratensis, approaching values of continuously mown fen meadows. Duration since abandonment had no significant effect on any of the variables. Our results demonstrate a rapid recovery of montane fen plant communities irrespective of the duration since abandonment (up to 35 years). We conclude that the restoration of pre-fallow plant community composition is likely to be successful if site conditions (hydrology, nutrient status) remain intact and if common habitat specialists are still present in the vegetation and/or seed ban

Why only tetraploid Solidago gigantea (Asteraceae) became invasive: a common garden comparison of ploidy levels

Many studies have compared the growth of plants from native and invasive populations, but few have considered the role of ploidy. In its native range in North America, Solidago gigantea Aiton (Asteraceae) occurs as a diploid, tetraploid and hexaploid, with considerable habitat differentiation and geographic separation amongst these ploidy levels. In the introduced range in Europe, however, only tetraploid populations are known. We investigated the growth performance and life history characteristics of plants from 12 European and 24 North American (12 diploid, 12 tetraploid) populations in a common garden experiment involving two nutrient and two calcium treatments. Twelve plants per population were grown in pots for two seasons. We measured 24 traits related to leaf nutrients, plant size, biomass production and phenology as well as sexual and vegetative reproduction. Native diploid plants had a higher specific leaf area and higher leaf nutrient concentrations than native tetraploids, but tetraploids produced many more shoots and rhizomes. Diploids grown with additional calcium produced less biomass, whereas tetraploids were not affected. European plants were less likely to flower and produced smaller capitulescences than North American tetraploids, but biomass production and shoot and rhizome number did not differ. We conclude that a knowledge of ploidy level is essential in comparative studies of invasive and native populations. While clonal growth is important for the invasion success of tetraploid S. gigantea, its potential was not acquired by adaptation after introduction but by evolutionary processes in the native rang

The invasion of plant communities following extreme weather events under ambient and elevated temperature

Erworben im Rahmen der Schweizer Nationallizenzen (http://www.nationallizenzen.ch)Although the problem of plant invasions is expected to increase with climate change, there is as yet little experimental evidence, in particular, for the effects of extreme weather events. We established communities of European meadow species, which were subjected to warming and extreme event (drought and deluge) treatments in a factorial design at an experimental garden in Zurich, Switzerland. Phylogenetically matched pairs of native and alien species (Bromus erectus, B. inermis, Trifolium pratense, T. hybridum, Lactuca serriola, and Conyza canadensis) were introduced into the communities to test if invader performance is favored by warming and extreme events, and if alien invaders perform better than native colonizers. With a warming of on average 0.3°C, a higher cover of native plant communities was observed, while drought decreased cover in the short-term and lowered biomass. Germination, survival, and growth of the introduced species were lower under elevated temperature. Survival of all pairs and growth of Trifolium was greater in drought pots, while deluge had no effect. While the alien species showed a faster rate of increase in the number of leaves, mortality of alien species was greater than of native species. Overall, the performance of the focal species varied much more among taxonomic groups than native/alien provenances. The results suggest that with climate change, different types of extreme events will differ in the severity of their effects on native plant communities. Meanwhile, the effects of climate change on plant invasions are more likely to operate indirectly through the impacts on native vegetation

Effects of grazing versus mowing on the vegetation of wet grasslands in the northern Pre‐Alps, Switzerland

Question: Wet grasslands are among the most threatened habitats in Central Europe and are subject to loss of their unique species assemblages. Grazing and mowing are important conservation management tools for such semi-natural habitats. The aim of this study was to investigate and compare the influence of grazing and mowing on the diversity and species composition of wet grassland vegetation. Location: Montane wet grasslands in the Gantrisch Nature Park, Switzerland. Methods: We sampled 18 pairs of vegetation plots along land-use borders between grazing and mowing (fence-line contrasts), distributed over six fens, mostly belonging to the phytosociological alliance Calthion palustris. We tested for differences in structural parameters, biodiversity indices, mean ecological indicator values and the frequency of individual species. In addition, a detrended correspondence analysis was carried out. Results: Management type had no influence on species richness, Shannon index or Shannon evenness. Maximum microrelief, vegetation height, mean nutrient indicator value and mean competitive strategy were significantly higher with grazing, whereas the mean aeration indicator value and the mean ruderal strategy were significantly higher with mowing. Cirsium oleraceum, Filipendula ulmaria, Geum rivale and Juncus effusus, species of nutrient-rich wet meadows, were more frequent under grazing, whereas mowing favoured grassland species with wide ecological amplitude, such as Plantago lanceolata and Trifolium pratense. Conclusions: At the plot scale, vascular plant diversity did not differ between these management regimes. Thus, from the conservation point of view, in the study region, there is no clear preference for either management type, and both should be eligible for subsidies. At the landscape scale, it is beneficial to have both management types present to ensure high gamma-diversity, as they favour different species

Optimal site conditions for dry grasslands of high conservation value in the canton of Zurich, Switzerland

Semi-dry semi-natural grasslands such as those of the alliance Mesobromion (Festuco-Brometea) are one of the most-diverse habitat types in Europe with regard to many taxonomic groups, but these remnants of traditional extensive agriculture are currently threatened throughout the continent. It is important to know how and where such valuable vegetation types could be best maintained (or re-established) under current environmental conditions. To address this question, we selected 27 dry grassland sites in the canton of Zurich, Switzerland, half of which had been classified as of “good” and half as of “poor” quality one decade ago. We sampled vegetation, soil and topographical data in three 1-m² plots in each of these sites. We then compared the current environmental conditions and plant species composition of the two original quality levels. Furthermore, we related four metrics of current conservation value (vascular plant species richness, evenness, forb/graminoid ratio and an ad hoc developed conservation score) to measured environmental predictors and mean ecological indicator values. We found that the “good” and “poor” sites differed in only few environmental predictors, such as good sites having higher pH, lower soil nitrogen and steeper slopes, while they had higher numbers and covers of typical semi-dry grassland species and a higher conservation value. The metrics of con-servation value behaved inconsistently when relating them to various environmental predictors. Inter-estingly, species richness decreased with slope inclination, but was also marginally negatively related to soil phosphorus. Conservation score, in contrast, increased with inclination, but also with increasing litter cover and soil nitrogen. While evenness largely showed similar response as conservation score, those of the forb-graminoid ratio were reversed for several environmental predictors. Overall, our results indicate that the conservation value of semi-dry grasslands cannot simply be attributed to one or two main factors. As different metrics of conservation value behaved differently, taking just one as a proxy would not be sufficient. Despite some variation, generally lower nutrient status, higher pH and steeper slopes seem to favour the maintenance of dry grasslands of higher quality. Some of our counter-intuitive results such as the higher litter cover in the plots of higher conservation value may indicate that current conservation management of these grasslands is too extensive to maintain their quality, par-ticularly given the high atmospheric nitrogen input in the region. We thus propose an experiment to test whether earlier and/or more frequent mowing helps in maintaining the quality of semi-dry grasslands

Changes in biodiversity and species composition of temperate beech forests in Switzerland over 26 years

Ongoing climate warming affects vegetation in multiple ways, although it is difficult to distinguish its influence from other drivers of vegetation change. We studied how forest vegetation in the Albiskette (canton of Zurich, Switzerland), mainly dominated by European beech (Fagus sylvatica), changed from 1993 to 2019, while the mean temperature rose by 1.5 °C. To investigate how species richness and vegetation composition had changed during these 26 years, we resampled 46 permanently marked nested-plot series (30 m², 200 m² and 500 m²). Using paired t-tests, we analysed changes in biodiversity metrics and mean ecological indicator values and related the quantified changes to poten-tial explanatory variables via linear regressions. Using the z-values from the power law species-area relationships, we analysed potential changes in beta diversity. Both species richness and herb layer cover significantly decreased from 1993 to 2019 across the three grain sizes. The z-values for the transi-tion from 200 m² to 500 m² were significantly higher in 2019. The mean light value in the 500-m2 plots in 2019 was also significantly lower than in 1993. Species richness, Shannon diversity and Shannon evenness decreased with increasing tree layer cover. With increasing herb layer cover, species richness increased in the 30-m2 plots and the relative species loss decreased in the 30-m2 and 200-m2 plots. The relationship between species loss and increased canopy cover confirmed that light availability acts as an important driver for species richness. Whether the loss in both herb cover and species is also related to recent summer drought events such as 2018 can only be clarified through further resurveys. Decreases in z-values indicate lower beta diversity and more homogenous vegetation in 2019. The decrease in species richness was more pronounced in the 500-m2 plots than in the smaller plots. In some cases, explanatory variables had an effect on the change in species diversity only in the 30-m² and 200-m² plots, but not in the 500-m² plots, indicating that other drivers prevail. The change in species diversity and the influencing factors were clearly scale dependent. Further investigation is required to determine whether our findings are merely region-specific or also valid in other biogeographical regions. To ensure that further species loss does not go unnoticed, we recommend the continuation of coordinated resurvey studies and monitoring

Regional typology of spring vegetation in Parc Ela (Grisons, Switzerland)

Aims: The spring habitats of Central Europe are insular biotopes of high ecological value. Although subject to severe exploitation pressures, they do not yet have a comprehensive protection status in Switzerland. Contributing to this challenge is the controversy involved with their syntaxonomic classification. In the context of the development of a regional conservation strategy and the establishment of a national inventory of Swiss springs, we carried out a regional survey of spring vegetation and aimed to translate this into a classification system. Study area: Montane and subalpine zones of Parc Ela (Grisons, Switzerland). Methods: We selected 20 springs to cover different regions, elevations and bedrock types within the park. In each of them we recorded complete vascular plant and bryophyte composition as well as a range of environmental variables in three 1-m² plots that were placed to reflect the heterogeneity within the spring. After running an unsupervised classification with modified TWINSPAN, the distinguished vegetation units were characterized in terms of diagnostic species, species richness and environmental variables and placed within the syntaxonomic system. Results: Species richness was high (total species 264, mean 21.7 species in 1 m2). The two most important environmental gradients of the ordination were elevation/water conductivity and insolation/water pH/soil reaction EIV. We distinguished seven communities within two main groups. Conclusions: All unshaded springs, including those over siliceous bedrock, could be assigned to a broadly defined Cratoneurion. The petrifying springs were not strongly distinguishable floristically from other base-rich springs. The forest springs, although often not clearly differentiated from their unshaded counterparts, could be provisionally divided into the alliances Caricion remotae and Lycopodo europaei-Cratoneurion commutati. As there is a certain threat to these habitats in the park due to anthropogenic influence, protection measures are recommended, most importantly the appropriate management of alpine pastures

Vegetation changes in urban grasslands over 25 years in the city of Zurich, Switzerland

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 ex-tensively 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 trans-formed 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 quarter century, and if changes occurred, they are rather attributable to the intentional change of man-agement from grazing to mowing. The relatively good ecological state of these urban grasslands mightbe due to a lower agricultural land use pressure than outside urban areas, as well as a constant manage-ment 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

Wenn Gämsen Schafe ersetzen : Fallstudie zu den Auswirkungen auf die Diversität von alpinen Rasen

Um den Einfluss der Aufgabe der sommerlichen Schafbeweidung in alpinen Gebieten (Schafsömmerung) und die Einwanderung von Gämsen (Rupicapra rupicapra) auf die floristische und zoologische Vielfalt zu untersuchen, wurden im Gebiet Graue Hörner (Kanton St. Gallen, Schweiz) drei Gebiete einer Chronosequenz (Raum-für-Zeit-Ersatz) verglichen: 1. eine jährlich kurz, aber intensiv genutzte Schafweide (ca. 81 bzw. 195 Schafe ha-1) (SB0), 2. eine seit fünf Jahren aufgegebene Schafweide, die heute von ca. 1 Gämse ha-1 genutzt wird (SB5), 3. eine seit 19 Jahren aufgegebene Schafweide, die von ca. 5 Gämsen und 1 Steinbock ha-1 genutzt wird (SB19). In den zwei am häufigsten vertretenen Vegetationstypen Poion alpinae und Nardion wurde die Vegetation auf zwei Flächengrössen (10 m2 und 200 m2) erhoben und die floristische Diversität und Ähnlichkeiten zwischen den Gebieten verglichen. Auf insgesamt dreizehn Flächen wurden zudem die Tagfalter und Heuschrecken aufgenommen. Im Gebiet SB0 war das Nardion am häufigsten, in den Gebieten SB5 und SB19 das Poion alpinae. Die Unterschiede der mittleren Artenzahl in den drei Gebieten auf 10 bzw. 200 m2 waren weder beim Poion alpinae noch beim Nardion signifikant. Die Poion alpinae-Aufnahmen auf 200 m² wiesen im Gebiet SB19 mit einem Mittel von 46,8 jedoch 6 Arten mehr auf als im Gebiet SB0. Die Gebiete SB0 und SB19 waren sowohl bei den Poion alpinae- als auch den Nardion-Aufnahmen floristisch am unähnlichsten. Im beweideten Gebiet SB0 konnten insgesamt mehr Tagfalter- und Heuschreckenarten erfasst werden als in den nicht mehr mit Schafen beweideten Gebieten, wobei der Unterschied nur bei den Heuschrecken signifikant war. Dass in den Gebieten, die seit fünf bzw. 19 Jahren nicht mehr mit Schafen beweidet werden, die Artenzahl bei den Gefässpflanzen nicht signifikant anders war als in dem mit Schafen beweideten Gebiet, zeigt, dass die floristische Diversität von alpinen Rasen innerhalb von rund 20 Jahren auf die Ablösung von Schafen durch Gämsen nur wenig reagiert hat. Es lässt sich kein stark negativer Effekt der Schafbeweidung nachweisen, obwohl ein Trend besteht, dass die Diversität ohne Schafbeweidung grossflächig (200 m2) höher ist. Die Unterschiede in der floristischen Zusammensetzung und den Mengenanteilen der Arten deuten darauf hin, dass die Schafbeweidung einen anderen Einfluss auf die Vegetation hat als die extensivere Beweidung durch wildlebende Herbivoren. Auch der hohe Anteil des Nardion im Gebiet SB0 kann wahrscheinlich auf die Schafbeweidung zurückgeführt werden

Patterns of habitat occupancy, genetic variation and predicted movement of a flightless bush cricket, Pholidoptera griseoaptera , in an agricultural mosaic landscape

Habitat fragmentation has been generally regarded detrimental to the persistence of many species, especially those with limited dispersal abilities. Yet, when exactly habitat elements become functionally disconnected very much depends on the dispersal ability of a species in combination with the landscape's composition in which it occurs. Surprisingly, for many small and ground-walking generalists knowledge at what spatial scale and to what extent landscape structure affects dispersal is very scarce. Because it is flightless, the bush cricket Pholidoptera griseoaptera may be regarded susceptible to fragmentation. We applied habitat occupancy surveys, population genetic analyses and movement modelling to investigate the performance of P. griseoaptera in an agricultural mosaic landscape with suitable habitat patches of varying size and isolation. Despite its presumed dispersal limitation we could show that P. griseoaptera occupied the majority of suitable habitats, including small and isolated patches, showed a very low and non-significant genetic differentiation (F ST=0.0072) and, in the model, managed to colonize around 73% of all suitable habitat patches within one generation under weak and strong landscape-effect scenarios. We conclude that P. griseoaptera possesses the behavioural attributes (frequent inter-patch dispersal) necessary to persist in this landscape characterized by a patchy distribution of habitat elements. Yet, sound recommendations to landscape planning and conservation require more research to determine whether this represents a general behaviour of the species or a behavioural adaptation to this particular landscap