Influence of experimental soil disturbances on the diversity of plants in agricultural grasslands

Aims and Methods Disturbance is supposed to play an important role for biodiversity and ecosystem stability as described by the intermediate disturbance hypothesis (IDH), which predicts highest species richness at intermediate levels of disturbances. In this study, we tested the effects of artificial soil disturbances on diversity of annual and perennial vascular plants and bryophytes in a field experiment in 86 agricultural grasslands differing in land use in two regions of Germany. On each grassland, we implemented four treatments: three treatments differing in application time of soil disturbances and one control. One year after experimental disturbance, we recorded vegetation and measured biomass productivity and bare ground. We analysed the disturbance response taking effects of region and land-use-accompanied disturbance regimes into account.Important Findings Region and land-use type strongly determined plant species richness. Experimental disturbances had small positive effects on the species richness of annuals, but none on perennials or bryophytes. Bare ground was positively related to species richness of bryophytes. However, exceeding the creation of 12% bare ground further disturbance had a detrimental effect on bryophyte species richness, which corresponds to the IDH. As biomass productivity was unaffected by disturbance our results indicate that the disturbance effect on species richness of annuals was not due to decreased overall productivity, but rather due to short-term lowered inter- and intraspecific competition at the newly created microsites.Generally, our results highlight the importance of soil disturbances for species richness of annual plants and bryophytes in agricultural grasslands. However, most grasslands were disturbed naturally or by land-use practices and our additional experimental soil disturbances only had a small short-term effect. Overall, total plant diversity in grasslands seemed to be more limited by the availability of propagules rather than by suitable microsites for germination. Thus, nature conservation efforts to increase grassland diversity should focus on overcoming propagule limitation, for instance by additional sowing of seeds, while the creation of additional open patches by disturbance might only be appropriate where natural disturbances are scarce.

No shift to a deeper water uptake depth in response to summer drought of two lowland and sub-alpine C3-grasslands in Switzerland

Temperate C3-grasslands are of high agricultural and ecological importance in Central Europe. Plant growth and consequently grassland yields depend strongly on water supply during the growing season, which is projected to change in the future. We therefore investigated the effect of summer drought on the water uptake of an intensively managed lowland and an extensively managed sub-alpine grassland in Switzerland. Summer drought was simulated by using transparent shelters. Standing above- and belowground biomass was sampled during three growing seasons. Soil and plant xylem waters were analyzed for oxygen (and hydrogen) stable isotope ratios, and the depths of plant water uptake were estimated by two different approaches: (1) linear interpolation method and (2) Bayesian calibrated mixing model. Relative to the control, aboveground biomass was reduced under drought conditions. In contrast to our expectations, lowland grassland plants subjected to summer drought were more likely (43–68 %) to rely on water in the topsoil (0–10 cm), whereas control plants relied less on the topsoil (4–37 %) and shifted to deeper soil layers (20–35 cm) during the drought period (29–48 %). Sub-alpine grassland plants did not differ significantly in uptake depth between drought and control plots during the drought period. Both approaches yielded similar results and showed that the drought treatment in the two grasslands did not induce a shift to deeper uptake depths, but rather continued or shifted water uptake to even more shallower soil depths. These findings illustrate the importance of shallow soil depths for plant performance under drought conditions.

Experimental evidence for the immediate impact of fertilization and irrigation upon the plant and invertebrate communities of mountain grasslands

The response of montane and subalpine hay meadow plant and arthropod communities to the application of liquid manure and aerial irrigation – two novel, rapidly spreading management practices – remains poorly understood, which hampers the formulation of best practice management recommendations for both hay production and biodiversity preservation. In these nutrient-poor mountain grasslands, a moderate management regime could enhance overall conditions for biodiversity. This study experimentally assessed, at the site scale, among low-input montane and subalpine meadows, the short-term effects (1 year) of a moderate intensification (slurry fertilization: 26.7–53.3 kg N·ha−1·year−1; irrigation with sprinklers: 20 mm·week−1; singly or combined together) on plant species richness, vegetation structure, hay production, and arthropod abundance and biomass in the inner European Alps (Valais, SW Switzerland). Results show that (1) montane and subalpine hay meadow ecological communities respond very rapidly to an intensification of management practices; (2) on a short-term basis, a moderate intensification of very low-input hay meadows has positive effects on plant species richness, vegetation structure, hay production, and arthropod abundance and biomass; (3) vegetation structure is likely to be the key factor limiting arthropod abundance and biomass. Our ongoing experiments will in the longer term identify which level of management intensity achieves an optimal balance between biodiversity and hay production.

Dry grasslands of Central-Eastern and South-Eastern Europe shaped by environmental heterogeneity and human land use – Editorial to the 10th Dry Grassland Special Feature

Der diesjährige 10. Trockenrasen-Sonderteil von Tuexenia beginnt mit einem Bericht über die aktuellen Aktivitäten der European Dry Grassland Group (EDGG). Zunächst geben wir einen Überblick über die Entwicklung der Mitgliederzahl. Dann berichten wir vom letzten European Dry Grassland Meeting in Tula (Russland, 2014) und vom letzten European Dry Grassland Field Workshop in Navarra (Spanien, 2014) und informieren über künftige Veranstaltungen der EDGG. Anschließend erläutern wir die Publikationsaktivitäten der EDGG. Im zweiten Teil des Editorials geben wir eine Einführung zu den fünf Artikeln des diesjährigen Trockenrasen-Sonderteils. Zwei Artikel beschäftigen sich mit der Syntaxonomie von Trockenrasen in Ost- bzw. Südosteuropa: der eine präsentiert erstmalig eine Gesamtklassifikation der Trockenrasengesellschaften Serbiens und des Kosovo während der andere Originalaufnahmen sub-montaner Graslandgesellschaften aus den bislang kaum untersuchten ukrainischen Ostkarpaten analysiert. Zwei weitere Artikel behandeln Trockenrasen-Feuchtwiesen-Komplexe im ungarischen Tiefland: Der eine behandelt den Einfluss der Landnutzung auf die Phytodiversität von Steppen und Feuchtwiesen, der andere den Einfluss von Niederschlagsschwankungen in einem Zeitraum von drei Jahren auf die Ausbildung salzbeeinflusster Steppen-Feuchtwiesen-Komplexe. Der fünfte Artikel analysiert landnutzungsbedingte Veränderungen des Graslands des Tsentralen-Balkan-Nationalparks in Bulgarien über einen Zeitraum von 65 Jahren

Plant diversity drives soil microbial biomass carbon in grasslands irrespective of global environmental change factors

Soil microbial biomass is a key determinant of carbon dynamics in the soil. Several studies have shown that soil microbial biomass significantly increases with plant species diversity, but it remains unclear whether plant species diversity can also stabilize soil microbial biomass in a changing environment. This question is particularly relevant as many global environmental change (GEC) factors, such as drought and nutrient enrichment, have been shown to reduce soil microbial biomass. Experiments with orthogonal manipulations of plant diversity and GEC factors can provide insights whether plant diversity can attenuate such detrimental effects on soil microbial biomass. Here, we present the analysis of 12 different studies with 14 unique orthogonal plant diversity × GEC manipulations in grasslands, where plant diversity and at least one GEC factor (elevated CO2, nutrient enrichment, drought, earthworm presence, or warming) were manipulated. Our results show that higher plant diversity significantly enhances soil microbial biomass with the strongest effects in long-term field experiments. In contrast, GEC factors had inconsistent effects with only drought having a significant negative effect. Importantly, we report consistent non-significant effects for all 14 interactions between plant diversity and GEC factors, which indicates a limited potential of plant diversity to attenuate the effects of GEC factors on soil microbial biomass. We highlight that plant diversity is a major determinant of soil microbial biomass in experimental grasslands that can influence soil carbon dynamics irrespective of GEC.

Lichen species richness is highest in non-intensively used grasslands promoting suitable microhabitats and low vascular plant competition

Lichens are very sensitive to habitat changes and their species richness is likely to decline under intensive land use. Currently, a comprehensive study analyzing lichen species richness in relation to land-use types, extending over different regions and including information on habitat variables, is missing for temperate grasslands. In three German regions we studied lichen species richness in 490 plots of 16 m2 representing different land-use types, livestock types, and habitat variables. Due to the absence of low-intensity pastures and substrates such as woody plants, deadwood and stones, there were no lichens in the 78 plots in Schorfheide-Chorin. In the two other regions, the richness of lichen species was 45 % higher in pastures than in meadows, and 77 % higher than in mown pastures, respectively. Among the pastures, the richness of all lichen species was on average 10 times higher in sheep-grazed pastures than in the ones grazed by cattle or horses. On average, the richness of all lichen species increased by 3.3 species per additional microhabitat. Furthermore, the richness of corticolous lichens increased by 1.2 species with 10 % higher cover of woody plants, lignicolous lichen species richness increased by 4.8 species with 1 % higher cover of deadwood, and saxicolous lichen species richness increased by 1.0 species with 1 % higher cover of stones. Our findings highlight the importance of low-intensity land use for lichen conservation. In particular, the degradation of grasslands rich in microhabitats and the destruction of lichen substrates by intensification, and conversion of unfertilized pastures formerly grazed at low intensity to meadows should be avoided to maintain lichen diversity.

Plant diversity moderates drought stress in grasslands: Implications from a large real-world study on 13C natural abundances

Land-use change and intensification play a key role in the current biodiversity crisis. The resulting species loss can have severe effects on ecosystem functions and services, thereby increasing ecosystem vulnerability to climate change. We explored whether land-use intensification (i.e. fertilization intensity), plant diversity and other potentially confounding environmental factors may be significantly related to water use (i.e. drought stress) of grassland plants. Drought stress was assessed using δ13C abundances in aboveground plant biomass of 150 grassland plots across a gradient of land-use intensity. Under water shortage, plants are forced to increasingly take up the heavier 13C due to closing stomata leading to an enrichment of 13C in biomass. Plants were sampled at the community level and for single species, which belong to three different functional groups (one grass, one herb, two legumes). Results show that plant diversity was significantly related to the δ13C signal in community, grass and legume biomass indicating that drought stress was lower under higher diversity, although this relation was not significant for the herb species under study. Fertilization, in turn, mostly increased drought stress as indicated by more positive δ13C values. This effect was mostly indirect by decreasing plant diversity. In line with these results, we found similar patterns in the δ13C signal of the organic matter in the topsoil, indicating a long history of these processes. Our study provided strong indication for a positive biodiversity-ecosystem functioning relationship with reduced drought stress at higher plant diversity. However, it also underlined a negative reinforcing situation: as land-use intensification decreases plant diversity in grasslands, this might subsequently increases drought sensitivity. Vice-versa, enhancing plant diversity in species-poor agricultural grasslands may moderate negative effects of future climate change.

Enriching plant diversity in grasslands by large-scale experimental sward disturbance and seed addition along gradients of land-use intensity

Aims The relationship between biodiversity and ecosystem functioning is among the most active areas of ecological research. Furthermore, enhancing the diversity of degraded ecosystems is a major goal in applied restoration ecology. In grasslands, many species may be locally absent due to dispersal or microsite limitation and may therefore profit from mechanical disturbance of the resident vegetation. We established a seed addition and disturbance experiment across several grassland sites of different land use to test whether plant diversity can be increased in these grasslands. Additionally, the experiment will allow us testing the consequences of increased plant diversity for ecosystem processes and for the diversity of other taxa in real-world ecosystems. Here we present details of the experimental design and report results from the first vegetation survey one year after disturbance and seed addition. Moreover, we tested whether the effects of seed addition and disturbance varied among grassland depending on their land use or pre-disturbance plant diversity. Methods A full-factorial experiment was installed in 73 grasslands in three regions across Germany. Grasslands were under regular agricultural use, but varied in the type and the intensity of management, thereby representing the range of management typical for large parts of Central Europe. The disturbance treatment consisted of disturbing the top 10 cm of the sward using a rotavator or rotary harrow. Seed addition consisted of sowing a high-diversity seed mixture of regional plant species. These species were all regionally present, but often locally absent, depending on the resident vegetation composition and richness of each grassland. Important findings One year after sward disturbance it had significantly increased cover of bare soil, seedling species richness and numbers of seedlings. Seed addition had increased plant species richness, but only in combination with sward disturbance. The increase in species richness, when both seed addition and disturbance was applied, was higher at high land-use intensity and low resident diversity. Thus, we show that at least the early recruitment of many species is possible also at high land-use intensity, indicating the potential to restore and enhance biodiversity of species-poor agricultural grasslands. Our newly established experiment provides a unique platform for broad-scale research on the land-use dependence of future trajectories of vegetation diversity and composition and their effects on ecosystem functioning.

L'expérience de Iéna démontre les avantages de la diversité végétale pour les prairies

A number of studies suggest that there could be a positive relationship between the productivity of a plant community and its floristic diversity. Besides, for grasslands, productivity is not the only desirable advantage. The Jena trials, constituting a large-scale and long-duration experiment, were set up to tackle these questions. In the plots of the Jena trials, the number of species varies from 1 to 60. Various sub-trials deal with the effects of the composition and the diversity of a pasture sward on its productivity, the diversity of certain organisms, and several ecological processes. The results from the first 6 years show clearly that there exist positive relationships between the number of species, the presence of legumes and/or the functional diversity on the one hand, and on the other the productivity, the resistance to encroachment by plants and to pathogenic fungi, and the cycles of nutrients. The positive effects of the floristic diversity on the processes at the scale of the eco-system are of importance to the agricultural production and to the general environmental impact.

Agricultural land use and biodiversity in the Alps - How cultural tradition and socioeconomically motivated changes are shaping grassland biodiversity in the Swiss Alps

Alpine grasslands are ecosystems with a great diversity of plant species. However, little is known about other levels of biodiversity, such as landscape diversity, diversity of biological interactions of plants with herbivores or fungal pathogens, and genetic diversity. We therefore explored natural and anthropogenic determinants of grassland biodiversity at several levels of biological integration, from the genetic to the landscape level in the Swiss Alps. Differences between cultural traditions (Romanic, Germanic, and Walser) turned out to still affect land use diversity and thus landscape diversity. Increasing land use diversity, in turn, increased plant species diversity per village. However, recent land use changes have reduced this diversity. Within grassland parcels, plant species diversity was higher on unfertilized mown grasslands than on fertilized or grazed ones. Most individual plants were affected by herbivores and fungal leaf pathogens, reflecting that parcels harbored a great diversity of herbivores and pathogens. However, as plant damage by herbivores and pathogens was not severe, conserving these biological interactions among plants is hardly compromising agricultural goals. A common-garden experiment revealed genetic differentiation of the important fodder grass Poa alpina between mown and grazed sites, suggesting adaptation. Per-village genetic diversity of Poa alpina was greater in villages with higher land use diversity, analogous to the higher plant species diversity there. Overall, landscape diversity and biodiversity within grassland parcels are currently declining. As this contradicts the intention of Swiss law and international agreements, financial incentives need to be re-allocated and should focus on promoting high biodiversity at the local and the landscape level. At the same time, this will benefit landscape attractiveness for tourists and help preserve a precious cultural heritage in the Swiss Alps.

Habitat fragmentation and adaptation: a reciprocal replant-transplant experiment among 15 populations of Lychnis flos-cuculi

1. Habitat fragmentation and variation in habitat quality can both affect plant performance, but their effects have rarely been studied in combination. We thus examined plant performance in response to differences in habitat quality for a species subject to habitat fragmentation, the common but declining perennial herb Lychnis flos-cuculi. 2. We reciprocally transplanted plants between 15 fen grasslands in north-east Switzerland and recorded plant performance for 4 years. 3. Variation between the 15 target sites was the most important factor and affected all measures of plant performance in all years. This demonstrates the importance of plastic responses to habitat quality for plant performance. 4. Plants from smaller populations produced fewer rosettes than plants from larger populations in the first year of the replant-transplant experiment. 5. Plant performance decreased with increasing ecological difference between grassland of origin and target grassland, indicating adaptation to ecological conditions. In contrast, plant performance was not influenced by microsatellite distance and hardly by geographic distance between grassland of origin and target grassland. 6. Plants originating from larger populations were better able to cope with larger ecological differences between transplantation site and site of origin. 7. Synthesis: In addition to the direct effects of target grasslands, both habitat fragmentation, through reduced population size, and adaptation to habitats of different quality, contributed to the performance of L. flos-cuculi. This underlines that habitat fragmentation also affects species that are still common. Moreover, it suggests that restoration projects involving L. flos-cuculi should use plant material from large populations living in habitats similar to the restoration site. Finally, our results bring into question whether plants in small habitat remnants will be able to cope with future environmental change.

The role of landuse and natural determinants for grassland vegetation composition in the Swiss Alps

The Alps provide a high habitat diversity for plant species, structured by broad- and fine-scale abiotic site conditions. In man-made grasslands, vegetation composition is additionally affected by the type of landuse. We recorded vegetation composition in 216 parcels of grassland in 12 municipalities representing an area of 170 x 70 km in the south-eastern part of the Swiss Alps. Each parcel was characterized by a combination of altitudinal level (valley, intermediate, alp). traditional landuse (mown. grazed), current management (mown, grazed, abandoned). and Fertilization (unfertilized, fertilized). For each parcel we also assessed the abiotic factors aspect, slope, pH value, and geographic coordinates, and for each municipality annual precipitation and its cultural tradition. We analysed vegetation composition using (i) variation partitioning in RDA. (ii) cover of graminoids. non-legume forbs, and legumes, and (iii) dominance and frequency of species. Species composition was determined by, in decreasing order of variation explained. landuse, broad-scale abiotic factors, fine-scale abiotic factors. and cultural tradition. Current socio-economically motivated landuse changes, such as grazing of unfertilized former meadows or their abandonment, strongly affect vegetation composition. In our study, the frequency of characteristic meadow species was significantly smaller in grazed and even smaller in abandoned parcels than in still mown ones, suggesting less severe consequences of grazing for vegetation composition than of abandonment. Therefore. low-intensity grazing and mowing every few years should be considered valuable conservation alternatives to abandonment. Furthermore. because each landuse type was characterized by different species. a high variety of landuse types should be promoted to preserve plant species diversity in Alpine grasslands. (C) 2007 Gesellschaft fur Okologie. Published by Elsevier GmbH. All rights reserved.

Changes in species composition in alpine snowbeds with climate change inferred from small-scale spatial patterns

Alpine snowbeds are characterised by a very short growing season. However, the length of the snow-free period is increasingly prolonged due to climate change, so that snowbeds become susceptible to invasions from neighbouring alpine meadow communities. We hypothesised that spatial distribution of species generated by plant interactions may indicate whether snowbed species will coexist with or will be out-competed by invading alpine species – spatial aggregation or segregation will point to coexistence or competitive exclusion, respectively. We tested this hypothesis in snowbeds of the Swiss Alps using the variance ratio statistics. We focused on the relationships between dominant snowbed species, subordinate snowbed species, and potentially invading alpine grassland species. Subordinate snowbed species were generally spatially aggregated with each other, but were segregated from alpine grassland species. Competition between alpine grassland and subordinate snowbed species may have caused this segregation. Segregation between these species groups increased with earlier snowmelt, suggesting an increasing importance of competition with climate change. Further, a dominant snowbed species (Alchemilla pentaphyllea) was spatially aggregated with subordinate snowbed species, while two other dominants (Gnaphalium supinum and Salix herbacea) showed aggregated patterns with alpine grassland species. These dominant species are known to show distinct microhabitat preferences suggesting the existence of hidden microhabitats with different susceptibility to invaders. These results allow us to suggest that alpine snowbed areas are likely to be reduced as a consequence of climate change and that invading species from nearby alpine grasslands could outcompete subordinate snowbed species. On the other hand, microhabitats dominated by Gnaphalium or Salix seem to be particularly prone to invasions by non-snowbed species.

An economic assessment of drought effects on three grassland systems in Switzerland

This paper analyzes the economic impacts of summer drought on Swiss grassland production. We combine field trial data from drought experiments in three different grasslands in Switzerland with site-specific information on economic costs and benefits. The analysis focuses on the economic implications of drought effects on grassland yields as well as grassland composition. In agreement with earlier studies, we found rather heterogeneous yield effects of drought on Swiss grassland systems, with significantly reduced yields as a response to drought at the lowland and sub-alpine sites, but increased yields at the wetter pre-alpine site. Relative yield losses were highest at the sub-alpine site (with annual yield losses of up to 37 %). However, because income from grassland production at extensive sites relies to a large extent on ecological direct payments, even large yield losses had only limited implications in terms of relative profit reductions. In contrast, negative drought impacts at the most productive, intensively managed lowland site were dominant, with average annual drought-induced profit margin reductions of about 28 %. This is furthermore emphasized if analyzing the farm level perspective of drought impacts. Combining site-specific effects at the farm level, we found that in particular farms with high shares of lowland grassland sites suffer from summer droughts in terms of farm-level fodder production and profit margins. Moreover, our results showed that the higher competitiveness of weeds (broad-leaved dock) under drought conditions will require increasing attention on weed control measures in future grassland production systems. Taking into account that the risk of drought occurrence is expected to increase in the coming years, additional instruments to cope with drought risks in fodder production and finally farmers’ income have to be developed.

Seed availability in hay meadows: Land-use intensification promotes seed rain but not the persistent seed bank

Intensification of land use in semi-natural hay meadows has resulted in a decrease in species diversity. This is often thought to be caused by the reduced establishment of plant species due to high competition for light under conditions of increased productivity. Sowing experiments in grasslands have found reliable evidence that diversity can also be constrained by seed availability, implying that processes influencing the production and persistence of seeds may be important for the functioning of ecosystems. So far, the effects of land-use intensification on the seed rain and the persistence of seeds in the soil have been unclear. We selected six pairs of extensively managed (Festuco-Brometea) and intensively managed (Arrhenatheretalia) grassland with traditional late cutting regimes across Switzerland and covering an annual productivity gradient in the range 176–1211 gm−2. In each grassland community, we estimated seed rain and seed bank using eight pooled seed-trap or topsoil samples of 89 cm2 in each of six plots representing an area of c. 150 m2. The seed traps were established in spring 2010 and collected simultaneously with soil cores after an exposure of c. three months. We applied the emergence method in a cold frame over eight months to estimate density of viable seeds. With community productivity reflecting land-use intensification, the density and species richness in the seed rain increased, while mean seed size diminished and the proportions of persistent seeds and of species with persistent seeds in the topsoil declined. Stronger limitation of seeds in extensively managed semi-natural grasslands can explain the fact that such grasslands are not always richer in species than more intensively managed ones.