Calcareous Grassland Research Articles

Non-random association patterns in a plant-mycorrhizal fungal network reveal host-symbiont specificity.

Arbuscular mycorrhizal (AM) fungi are obligate plant symbionts that have important functions in most terrestrial ecosystems, but there remains an incomplete understanding of host-fungus specificity and the relationships between species and functional groups of plants and AM fungi. Here, we aimed to provide a comprehensive description of plant-AM fungal interactions in a biodiverse semi-natural grassland. We sampled all plant species in a 1,000-m2 homogeneous plot of dry calcareous grassland in two seasons (summer and autumn) and identified root-colonizing AM fungi by SSU rDNA sequencing. In the network of 33 plant and 100 AM fungal species, we found a significant effect of both host plant species and host plant functional group on AM fungal richness and community composition. Comparison with network null models revealed a larger-than-random degree of partner selectivity among plants. Grasses harboured a larger number of AM fungal partners and were more generalist in partner selection, compared with forbs. More generalist partner association and lower specialization were apparent among obligately, compared with facultatively, mycorrhizal plant species and among locally more abundant plant species. This study provides the most complete data set of co-occurring plant and AM fungal taxa to date, showing that at this particular site, the interaction network is assembled non-randomly, with moderate selectivity in associations between plant species and functional groups and their fungal symbionts.

Get larger or grow longer wings? Impacts of habitat area and habitat amount on orthopteran assemblages and populations in semi-natural grasslands

Habitat loss and fragmentation are major threats to biodiversity and can change community composition, species traits and intraspecific morphology. Calcareous grasslands are hotspots of diversity for plants and invertebrates in Europe, but habitat area and habitat amount declined strongly over the last century. It is controversially discussed how habitat area and habitat amount independently affect species assemblages, traits and morphology. With variable transects we recorded orthopteran assemblages on 22 calcareous grasslands along independent gradients of habitat area and habitat amount in a 1 km matrix. We measured male body size and wing length of two abundant grasshopper species. Orthopteran assemblages showed positive species–area and abundance–area relationships with habitat area and (extenuated) with habitat amount. We found a stronger effect of habitat area reduction on specialists and endangered species, compared to generalists and non-threatened species. The species Chorthippus biguttulus and Gomphocerippus rufus had a larger body size (fitness-related trait) in landscapes with high habitat area and habitat amount. Grasshoppers had longer wings in relation to body size (dispersal-related trait) in landscapes with a low amount of habitat. Our findings emphasize the value of large patches and landscapes with high habitat amount to (i) enhance species richness and abundances, (ii) protect threatened species, (iii) ensure long term survival of habitat-specialists and (iv) preserve individuals with high fitness traits (large body size). Conservation strategies for Orthoptera should focus on large habitats and areas with a high habitat amount.

Sampling for conservation genetics: how many loci and individuals are needed to determine the genetic diversity of plant populations using AFLP?

Molecular markers such as AFLPs are frequently applied in molecular ecology and conservation genetics to determine the genetic diversity of plant populations. However, despite the extensive utilization there is little consensus about the number of loci and individuals which should be used to estimate genetic diversity. As a consequence, these two parameters strongly vary among investigations. In our study we analysed the impact of loci and individual number on the determined level of genetic diversity of 15 calcareous grassland species using AFLP. We investigated curve progressions of genetic diversity with an increasing number of individuals and computed the appropriate number of loci and plant individuals to reach 90% and 95% of a population’s genetic diversity. According to our results approximately 120 loci are sufficient for a stable estimation of genetic diversity. Regarding the number of analysed individuals on average about 14 samples are needed to cover 90% and about 23 samples are needed to cover 95% of the total genetic diversity. Wind-pollinated species require, however, larger sample sizes than insect-pollinated species. Since funding is often limited, especially in conservation, our results may help to avoid time-consuming and costly surveys and may contribute to a more efficient use of the financial resources available for the determination of genetic variation.

Comparison of mining spoils to determine the best substrate for rehabilitating limestone quarries by favoring native grassland species over invasive plants

Habitats being restored in Belgian quarries are easily invaded by non-native plant species, which can hamper the germination and development of vegetation deemed to be of high conservation value. Substrates of terraces created when mining limestone quarries could be inhospitable to native plants. However, they can provide opportunities for establishing specific vegetation, such as dry calcareous grasslands. Applying suitable mining spoils could be a cost-effective way to provide growing substrate when restoring limestone terraces. We assessed the efficacy of using mining spoils, collected on-site, as a potential growing substrate (bedding material). We tested gravely limestone (product of on-site mining activities), limestone dust (by-product), and no addition (bare limestone bedrock) to determine which was best for favoring the growth of native, dry calcareous grassland species and discourage the growth of two non-native invasive species that commonly invade altered mining sites: Buddleja davidii Franch and Senecio inaequidens DC. In a field experiment (in two quarries), we studied short-term (2 y) growth response of native and invasive species after sowing three seed mixtures of native grassland species, varying in functional diversity (and one no-sowing control treatment), all treatments subjected to competitive pressure exerted by invasive species. Percent cover of native and invasive species, species abundance and reproductive characteristics of the invasive species were monitored during 2-y. Native grasslands coverage was low on all substrate types, demonstrating how slowly calcareous grasslands species establish in such harsh substrate conditions. However, type of substrate did show a significant relationship with plant abundance, with limestone dust being the most beneficial for native species establishment (coverage). Although limestone dust appeared to be the best option for restoring grassland species to limestone quarries (based on its low cost, wide availability, and potential to support native species), it was also likely to support the two invasive species. Functional diversity of the seed mixture had no consistent effect. Our study shows the importance of identifying the most appropriate substrate to both establish calcareous grasslands and resist invasive species. This approach provides insights into developing strategies to conserve biodiversity in industrial and agricultural landscapes with limestone quarries.

Demography of the endangered butterfly Euphydryas aurinia (Lepidoptera: Nymphalidae): A case study of populations in sub-Mediterranean dry calcareous grasslands

We studied a population of the regionally endangered marsh fritillary butterfly Euphydryas aurinia inhabiting a system of loosely connected dry calcareous grasslands in sub-Mediterranean Slovenia. Our goal was to set the basis for a long-term monitoring of this butterfly in four meadows using mark-release-recapture (MRR). We determined its demographic parameters, dispersal, behaviour and utilization of nectar plants in different quality patches. Total population size was estimated to be approximately 347 males (95% confidence interval: 262-432) and 326 females (95% confidence interval: 250-402), with an unbiased sex ratio. The average lifespans were 6.3 and 8.6 days, respectively. Daily population sizes followed a parabola with marked protandry. Both sexes were relatively highly mobile with both occasionally moving over half a kilometre. The spatial distribution of animals seemed to be associated with patch size, host plant densities and nectar sources, resulting in much higher population densities in the largest patch. Adult behaviour differed between the sexes, with females resting more and flying less than males. Behaviour also changed during daytime and with the progression of the season. Adults were confirmed to be opportunistic feeders, since as many as ten nectar sources were detected. We conclude that demographic parameters differ greatly among regions and habitats, thus conservation aims should be planned accordingly. Although the population studied is apparently in good condition, there are threats that may hamper the long-term persistence of the species in this area: succession, intensification of mowing and overgrazing.

Distinctive distributions and migrations of 239+240Pu and 241Am in Chinese forest, grassland and desert soils

The vertical distributions and downward migrations of the global fallout derived 239+240Pu and 241Am in diverse types of Chinese soils (forest, grassland and desert) were studied. The mean 239+240Pu and 241Am activity concentrations in the investigated soil cores were 0.28–0.69 mBq/g and 0.13–0.37 mBq/g, respectively, while the accumulative inventories were 61.53–138.99 Bq/m2 for 239+240Pu and 28.29–61.05 Bq/m2 for 241Am. The convection-dispersion equation (CDE) was used to calculate the migration parameters of 239+240Pu and higher apparent dispersion coefficients (D) were observed for the acidic forest soils compared with the alkaline grassland and desert soils; meanwhile a compartment model was employed to compare the migration of 239+240Pu and 241Am in successive soil layers which showed that the migration behaviors of 239+240Pu and 241Am were rather similar; both velocities were less than 0.3 cm/y in diverse types of soils and these findings were compatible with those of short-term laboratory simulation experiments in China.

Past and potential future effects of habitat fragmentation on structure and stability of plant-pollinator and host-parasitoid networks.

Habitat fragmentation is a primary threat to biodiversity, but how it affects the structure and stability of ecological networks is poorly understood. Here, we studied plant-pollinator and host-parasitoid networks on 32 calcareous grassland fragments covering a size gradient of several orders of magnitude and with amounts of additional habitat availability in the surrounding landscape that varied independent of fragment size. We find that additive and interactive effects of habitat fragmentation at local (fragment size) and landscape scales (1,750 m radius) directly shape species communities by altering the number of interacting species and, indirectly, their body size composition. These, in turn, affect plant-pollinator, but not host-parasitoid, network structure: the nestedness and modularity of plant-pollinator networks increase with pollinator body size. Moreover, pollinator richness increases modularity. In contrast, the modularity of host-parasitoid networks decreases with host richness, whereas neither parasitoid richness nor body size affects network structure. Simulating species coextinctions also reveals that the structure-stability relationship depends on species' sensitivity to coextinctions and their capacity for adaptive partner switches, which differ between mutualistic and antagonistic interaction partners. While plant-pollinator communities may cope with future habitat fragmentation by responding to species loss with opportunistic partner switches, past effects of fragmentation on the current structure of host-parasitoid networks may strongly affect their robustness to coextinctions under future habitat fragmentation.

Patch occupancy of grassland specialists: Habitat quality matters more than habitat connectivity

Land-use change has caused degradation, loss and fragmentation of semi-natural habitats, especially in grassland ecosystems. Today, the remaining habitats are often situated in a matrix of intensively used agricultural land and are therefore more or less isolated from each other. Connectivity, area and quality of habitat patches have been identified as the most important drivers for the persistence of grassland specialists living in metapopulations. However, the relative importance of these factors is still under debate. We used a large-scale, multi-taxon approach to obtain a general pattern which would facilitate conservationists to promote many, instead of one, species. We studied the patch occupancy of 13 grassland specialists belonging to three different insect orders within a Central European landscape with 89 fragments of calcareous grasslands. To disentangle the relative importance of the three metapopulation parameters, generalized linear models (GLM) and variation-partitioning techniques were used. Our study revealed that habitat quality was the most important factor determining the occurrence of specialized species, followed by habitat area. In comparison to habitat connectivity, the variance explained by habitat quality was significantly higher across the studied species. Nevertheless, the persistence of at least six model organisms depended on the degree of habitat connectivity. We conclude that maintaining a high habitat quality on large patches should be the first choice for the conservation of habitat specialist insects in fragmented landscapes. As a secondary measure, conservationists should concentrate on the restoration of relict sites. This increases not only the habitat area, but also contributes to better habitat connectivity.

Diversity of soil mite communities in different habitats of Saskhori quarries, Georgia

Faunal diversity of the oribatid and mesostigmatid mites was investigated in four habitats (woodland, hemy-xerophiticshrubs, degraded steppe and perennial calcareous and oligotrophic grassland) of Saskhori limestone quarry. Mining processes are not yet started and semi-natural ecosystems are still preserved. Fifty one species of oribatidmites and nine morphospecies of mesostigmatid mites were identified. Two species of mesostigmatid mites Zerconmonigenus Blaszak, 1972and Trachytesstammeni HirschmannetZirngiebl-Nicol, 1969are new records for Caucasian fauna and two more - Proprioseiopsismessor (Wainstein, 1960) and Neoseiulus montanus (Wainstein, 1962a)(both Gamasina) are new for Georgia. Highest number of species was recorded on perennial calcareous and oligotrophic grasslands (43), which were followed by forests (37) and shrubs (25). Degraded steppes were extremely poor by soil mite species – only three oribatid species and no mesostigmatans were recorded there. Overall faunal composition indicateshabitat specific anthropogenic disturbance in studied habitats and less disturbed harboring important rare and sensitive species of mites.

Distribution of Plant Species and Dispersal Traits along Environmental Gradients in Central Mediterranean Summits

High-mountain ecosystems are spots of plant diversity in which species composition and traits depict a long evolutionary history of species adaptation to steep environmental gradients. We investigated the main trends in plant species composition and reproductive and dispersal traits (pollen vector, diaspore appendages, dispersal of diaspores and fruit type) in central Mediterranean summits in relation to environmental factors (altitude, aspect, debris cover and slope). Based on 114 plots, with floristic and environmental data collected in the year 2016 on alpine calcareous grasslands in the central Apennines, we explored how species composition varies in relation to environmental factors using CCA (canonical correspondence analysis). Then, we analyzed the relationships among species presence, the occurrence of reproductive and dispersal traits and environmental variables. We used for this analysis the fourth-corner model approach. Our results highlight a consistent response of floristic composition and of structural and ecological characteristics to environmental gradients, with elevation and debris cover being the most important ones. The environmental characteristics of the analyzed ecosystems (e.g., steep slopes and harsh environments) combined with the persistence of perennial plant species already present in each stand, the high precision of pollination and the prevalence of short-distance dissemination strategies should allow the calcareous endemic plant communities of the analyzed Mediterranean summits to be conserved at least for a mid-term period slowing down the expansion of the warm-adapted species, less adapted to the local environmental constrains.

The invasion of Bromus erectus alters species diversity of vascular plants and leafhoppers in calcareous grasslands

Abstract The most common mechanism of biological invasions is an increase in competition, which usually results in the loss of biodiversity. The invasion of Bromus erectus (Syn. Bromopsis erecta) in calcareous grasslands of western and central Europe is well‐documented. Although, it is largely unknown to what extent this development affects biodiversity. In this study, we analysed the effects of B. erectus invasion on vascular plant and leafhopper assemblages of calcareous grasslands. At each of the 15 randomly selected sites, we compared one plot with stands of Bromus (presence) and one without (absence) (paired sampling design). The invasion of B. erectus affected vegetation structure as well as vascular plant and leafhopper assemblages. Despite similar abiotic site characteristics, Bromus plots had a higher turf height, vegetation density, and litter cover. Additionally, we recorded a much lower species richness in Bromus plots than in absence plots in all analysed groups of vascular plants. A similar pattern was found for leafhoppers. Absence plots exhibited a higher species richness of habitat and diet specialists than Bromus plots. The overall abundance of all leafhopper species was highest in presence plots, whereas that of diet specialists peaked in absence plots. We conclude that the ongoing invasion of B. erectus will lead to a strong structural homogenisation with negative effects on plant and insect diversity. One possible management tool might be a goal‐driven rough grazing with sheep – especially in spring when B. erectus is much more palatable than in summer and autumn.

Calcareous grassland restoration at a coarse quarry waste dump in the Italian Alps

Establishing semi-natural grasslands by using seeds from wild harvesting is an effective method to restore vegetation with high natural value. However, studies implementing this strategy for the revegetation of coarse soils are scarce. In this study, different types of propagation material (green hay, dry hay, and hay-flower from seed stripping) harvested at a species-rich European vegetation typical for calcareous soils (Mesobromion) were used at different sowing densities (range, 450–3000 seeds per m2) to restore a very unfertile soil consisting of coarse wastes from a calcareous quarry. The experiment, organised in a randomised block design with three replicates, was established in 2009, and the species composition and structure were surveyed over five years. The threshold of 70% vegetation cover effective against erosion was achieved within two years after sowing. Neither the type of propagation material nor the sowing density influenced the number of species transferred or the final vegetation cover. However, seed density affected the time of achieving the 70% threshold of plant cover important for erosion control (two or three years after sowing depending on the seed density). Of the seventy-three donor site species, fifty-nine were recorded at least during one year on the restored site (absolute transfer rate of 81%), but only forty-six were recorded in the last year (final transfer rate of 63%). Vegetation development was characterised by loss or decrease of donor site species not well adapted to grow in nutrient-poor soils and increase by species typical for coarse textured soils. The very low soil nitrogen content caused an abundance of nitrogen-fixing species (legumes) compared with that at the donor site. Restoring very coarse calcareous quarry wastes, even without soil improvement, is possible provided the climatic conditions are favourable and seeds of good quality are available.

Drought reduces floral resources for pollinators.

Climate change is predicted to result in increased occurrence and intensity of drought in many regions worldwide. By increasing plant physiological stress, drought is likely to affect the floral resources (flowers, nectar and pollen) that are available to pollinators. However, little is known about impacts of drought at the community level, nor whether plant community functional composition influences these impacts. To address these knowledge gaps, we investigated the impacts of drought on floral resources in calcareous grassland. Drought was simulated using rain shelters and the impacts were explored at multiple scales and on four different experimental plant communities varying in functional trait composition. First, we investigated the effects of drought on nectar production of three common wildflower species (Lathyrus pratensis, Onobrychis viciifolia and Prunella vulgaris). In the drought treatment, L.pratensis and P.vulgaris had a lower proportion of flowers containing nectar and O.viciifolia had fewer flowers per raceme. Second, we measured the effects of drought on the diversity and abundance of floral resources across plant communities. Drought reduced the abundance of floral units for all plant communities, irrespective of functional composition, and reduced floral species richness for two of the communities. Functional diversity did not confer greater resistance to drought in terms of maintaining floral resources, probably because the effects of drought were ubiquitous across component plant communities. The findings indicate that drought has a substantial impact on the availability of floral resources in calcareous grassland, which will have consequences for pollinator behaviour and populations.

Fragmentation in calcareous grasslands: species specialization matters

Habitat fragmentation resulting from anthropogenic land-use change may negatively affect both biodiversity and ecosystem structure and function. However, susceptibility to fragmentation varies between species and may be influenced by for instance specialization, functional traits and trophic level. We examined how total and specialist species richness, species composition and functional trait composition at two trophic levels (vascular plants and sap-feeding hoppers) vary with habitat fragmentation (patch size and connectivity) in dry calcareous grasslands in southeast Norway. We found that fragmentation affected plant and hopper species composition both totally and of habitat specialists, but with a net species loss only for the specialists, indicating greater susceptibility of specialized species. Reductions in patch size and increasing isolation negatively affected plant specialists with different sets of traits, effectively reducing the number of species with trait combinations suitable to persist in small and isolated patches. Fragmentation influenced trait composition of the total hopper community, but not of habitat specialists. A lesser degree of habitat association could explain why hoppers, despite belonging to a higher tropic level, seemed to be less susceptible to fragmentation than plants. Nonetheless, our study shows that habitat fragmentation affects both species richness, species composition and trait composition of plants and hoppers, indicating that fragmentation leads not only to a loss of species, but also alters dominance hierarchies and the functionality of grassland communities.

Determining the long-term habitat preferences of the Duke of Burgundy butterfly, Hamearis lucina, on a chalk grassland reserve in the UK

The Duke of Burgundy butterfly has undergone considerable range contractions across Europe and since the 1970s has lost around 84% of its former distribution in the UK. Despite its endangered status, the butterfly is understudied, with few papers directly investigating its habitat requirements. This limited research effort focusses on the larval life stage, with relatively little being known about the adults of the species. In this study, we investigated the habitat usage of both adults and larvae of the Duke of Burgundy. Fieldwork was carried out in association with the Bedfordshire, Cambridgeshire and Northamptonshire (BCN) Wildlife Trust on their Totternhoe Quarry Reserve in Bedfordshire. Using data collected over the course of a decade, we performed the first long term distribution analysis of the species and we identified habitat attributes associated with long-standing abundance hotspots of both adults and larvae on the reserve. We found both life stages to be conserved in their range, remaining in the same small areas of Totternhoe Quarry year on year, with adults often being more restricted in their distribution than larvae. Sheltered locations were important for both life stages, but small differences in habitat preference, such as slope and aspect, were also identified. These results emphasise the need to target management towards both life stages of the Duke of Burgundy, as supporting the larvae alone may not result in suitable environmental conditions for the adults.

Drought stress inducing intraspecific variability in Potentilla tabernaemontani (Rosaceae), a calcareous grassland species

Background and aims – Calcareous grasslands are among the most species-rich habitats in Western Europe. Populations of plant species characterizing these ecosystems are naturally submitted to high variability in environmental conditions at the very local scale, resulting in pronounced variation in functional traits. Individuals located on xeric parts of calcareous grasslands are characterized by plant traits that potentially ensure more successful performance under stressful conditions. In the context of increased frequency of summer heat waves based on climate change, our aim was to determine a possible intraspecific variability in drought response among individuals of one calcareous grassland plant species.Methods – A greenhouse experiment was set up to follow survival of Potentilla tabernaemontani Asch. individuals according to their habitat of origin (xeric or mesic parts of Belgian calcareous grasslands) and the treatment applied (low or high drought stress).Key results – The results demonstrated that individuals originating from xeric parts survived drought stress better than individuals from mesic parts of calcareous grasslands. Specific leaf area (SLA) of all individuals was very low in the experiment, allowing them to decrease water loss during drought stress. Leaf production was lower for individuals exposed to high drought stress while flower production was higher. That potentially expressed a trade-off between tolerance to water stress, individual growth and reproduction. Conclusions – Local scale environmental heterogeneity deserves to be considered in conservation and restoration plans as it induces intraspecific functional variability between individuals and impacts individuals’ ability to survive drought stress.

Naturally recruited herbaceous vegetation in abandoned Belgian limestone quarries: towards habitats of conservation interest analogues?

We examined if naturally recruited herbaceous vegetation in abandoned Belgian limestone quarries tend towards plant communities analogous to semi-natural habitats of conservation interest. We studied taxon-based assemblages (using two-dimensional non-metric multidimensional scaling ordination) and functional patterns (relative to Grime’s competitor, stress tolerator and ruderal plant strategies (CSR) classification) of plant communities (n = 360 plots) among three different time periods after quarry abandonment ( 20 y). We compared those successional assemblages with those of habitat of conservation interest plant communities (n = 53 plots): lowland hay meadows and rupicolous, xerophilous and mesophilous calcareous grasslands. Our results indicate that naturally recruited herbaceous vegetation compositionally resembled mesophilous grassland, even though initial substrate conditions were more similar to rupicolous or xerophilous grasslands. The specific successional pathway we found in CSR state-space differs from Grime's predictions because there was a functional shift in plant assemblages from dominance by ruderals to dominance by stress-tolerant species. The differences in successional trajectories we found on different types of rock substrate suggest that conservation management should adopt a site-specific approach, recognizing that the highest probabilities of success on hard limestone will be restoration to calcareous grassland analogues.

A comparison of methods for estimating plant population size

Assessing local population size is one of the most common tasks in biodiversity monitoring. Population size estimates are not only important for conservation management and population threat assessment; they also enter many other analyses in landscape ecology and conservation. It is therefore concerning that methods for estimating plant population sizes are not standardized. We surveyed the literature and found that the most commonly used methods are counting either all or only flowering individuals on a site, as well as counting individuals in random plots or plots on transects. Sometimes, these methods are combined in the same study, without assurance that they produce comparable results. We therefore conducted a field study, in which we obtained population size estimates from all four methods for six different calcareous grassland species at 18 study sites. Our results demonstrate not only substantial differences between overall count rates generated by the different methods, but methods that surveyed the whole population also systematically yielded lower counts when species were less visible and when the area was larger, suggesting that these methods suffer from biases that could distort species and site comparisons. We conclude that estimates from different methods should not be mixed, and that plot or transect based surveys have likely smaller biases for large areas or poorly visible individuals, and are therefore preferable.

Micronutrient metal speciation is controlled by competitive organic chelation in grassland soils

Many elements are scarcely soluble in aqueous conditions found in high pH environments, such as calcareous grassland soils, unless complexed to strong binding organic ligands. To overcome this limitation, some plants and microbes produce chelators that solubilize micronutrient metals such as Fe, Ni, Cu, and Zn from mineral phases. These complexes are taken up by organisms via specific membrane receptors, thereby differentially impacting the bioavailability of these metals to the plant and microbial community. Although the importance of these chelation strategies for individual organisms has been well established, little is known about which pathways coexist within rhizosphere microbiomes or how they interact and compete for metal binding. Identifying these metallophores within natural ecosystems has remained a formidable analytical challenge due to the vast diversity of compounds and poorly defined metabolic processes in complex soil matrices. Herein, we employed recently developed liquid chromatography (LC) mass spectrometry (MS) methods to characterize the speciation of water-soluble dissolved trace elements (Fe, Ni, Cu, and Zn) of soils from native tallgrass prairies in Kansas and Iowa. Both plant and fungal metallophores were identified, revealing compound-specific patterns of chelation to biologically essential metals. Numerous metabolites typically implicated in plant Fe acquisition and homeostasis, including mugineic acids, deoxymugineic acid, nicotianamine, and hydroxynicotianamines, dominated the speciation of divalent metals such as Ni, Cu, and Zn (2–90 pmol/g soil). In contrast, the fungal siderophore ferricrocin was specific for trivalent Fe (7–32 pmol/g soil). These results define biochemical pathways that underpin the regulation of metals in the grassland rhizosphere. They also raise new questions about the competition of these compounds for metal binding and their bioavailability to different members of the rhizosphere population. Small structural modifications result in significant differences in metal ligand selectivity, and likely impact metal uptake within the rhizosphere of grassland soils.

Beneficial effects of restoration practices can be thwarted by climate extremes

The impacts of climate extremes on species, communities and ecosystems have become critical concerns to science and society. Under a changing climate, how restoration outcomes are affected by extreme climate variables is a largely unknown topic. We analyzed the effects of experimental factors (grazing and sowing of native species), extreme climate events (intense precipitation and extreme temperatures indexes) and their combination on the restoration progress of a dry, calcareous grassland in Tuscany (Italy) with a 1 year before/15 years continuous annual monitoring after, control/impact (BACI) experiment. Grazing had a beneficial effect on the diversity of the grassland, while sowing had a limited impact. The climatic index that most affected the entire plant community composition was the number of very heavy precipitation days. The interaction of grazing and extreme climatic indexes had a significant detrimental effect on restoration outcomes, increasing the cover of synanthropic and Cosmopolitan-Subcosmopolitan generalist species and decreasing the cover of more valuable species such endemic species. In the richest grazed plots, species richness showed a lower sensitivity to the average precipitation per wet day but in grazed site, restoration outcomes can be negatively influenced by the intensification of precipitation and temperature extremes. In a context of progressive tropicalization of the Mediterranean area, to assist managers setting achievable restoration goals, restoration practitioners should consider that climate extremes might interfere with the beneficial effects of restoration practices.