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High nitrogen (N) deposition rates can cause soil eutrophication and acidification causing harmful effects to many plant species. One species that seems to be affected is Juniperus communis, populations of which are declining in Western Europe, due to a lack of regeneration. This is primarily caused by limited seedling recruitment and low viable seed production; factors that have both been attributed to increased levels of N deposition. J. communis sapling performance could be dependant on mycorrhizal fungi (MF) in their roots, but how – and under what conditions – MF contribute to the performance of J. communis has not been studied before. Here we experimentally tested the effect of MF on J. communis cuttings along an acidity gradient in situ. To manipulate the interaction with MF, we used ingrowth cores, effectively allowing for root-MF interactions or strongly reducing these. After six months we measured growth and needle nutrient concentrations of cuttings with a normal or reduced mycelial network. MF had a positive effect on absolute growth of our cuttings. However, this effect was weakened as soil Mg2+, Ca2+ and Na+ concentrations declined. Soil pH itself was not directly associated with the effect of MF on J. communis. MF also decreased needle phosphorous concentrations, most likely because the increased plant growth by MF diluted its concentration in the plants. We conclude that MF stimulate the performance of J. communis, but that leaching of cations, accelerated by N deposition, negatively affects their mutualism and thereby the performance of J. communis saplings. This highlights the potential positive role of MF in effective conservation and restoration efforts of J. communis habitats in Western Europe and the importance of prioritising the reduction of ongoing eutrophication and acidification.

Land abandonment is increasing in recent decades in Europe, usually accompanied by a decline in biodiversity. Whether livestock grazing and mowing can safeguard biodiversity across spatial scales in the long term is unclear.Using a 48-year experiment in a salt marsh, we compared land abandonment (without grazing and mowing) and seven management regimes including cattle grazing, early season mowing, late season mowing, both early and late season mowing, and grazing plus each of the mowing regimes on plant diversity at the local (i.e. plot) and landscape scales (i.e. across plots). Also, we compared their effects on community composition (both in identities and abundances) in time and space.Under land abandonment, plant diversity declined in the local communities and this decline became more apparent at the landscape scale, particularly for graminoids and halophytes. All management regimes, except the late season mowing, maintained plant diversity at these scales.Local plant communities under all treatments underwent different successional trajectories, in the end, diverged from their initial state except for that under grazing (a cyclic succession). Interannual composition change remained stable over time under land abandonment and grazing plus early season mowing. It increased over time under grazing and late season mowing, it increased in the second half of the experiment under other treatments. Vegetation homogenized in the landscape over time under land abandonment while vegetation was heterogeneous under all management regimes.Synthesis. Our experiment suggests that late season mowing may not be sustainable to conserve plant diversity in salt marshes. Other management regimes can maintain plant diversity across scales and vegetation heterogeneity in the landscape in the long term, but local community composition may change over time.

The digestive tract of animals harbors microbiota important for the host’s fitness and performance. The interaction between digestive tract bacteria and soil animal hosts is still poorly explored despite the importance of soil fauna for ecosystem processes. In this study, we investigated the interactions between the bacterial communities from the digestive tract of the litter-feeding, semi-terrestrial crustacean Orchestia gammarellus and those obtained from the environment; these organisms thrive in, i.e., soil and plant litter from salt marshes. We hypothesized that elevation is an important driver of soil and litter bacterial communities, which indirectly (via ingested soil and litter bacteria) influences the bacterial communities in the digestive tract of O. gammarellus. Indeed, our results revealed that elevation modulated soil and litter bacterial community composition along with soil organic matter content and the C:N ratio. Soil and plant litter differed in alpha diversity indexes (richness and diversity), and in the case of plant litter, both indexes increased with elevation. In contrast, elevation did not affect the composition of bacterial communities associated with O. gammarellus’ digestive tract, suggesting selection by the host, despite the fact that a large component of the bacterial community was also detected in external sources. Importantly, Ca. Bacilloplasma and Vibrio were highly prevalent and abundant in the host. The taxonomic comparison of Ca. Bacilloplasma amplicon sequence variants across the host at different elevations suggested a phylogenetic divergence due to host habitat (i.e., marine or semi-terrestrial), thus supporting their potential functional role in the animal physiology. Our study sheds light on the influence of the environment on soil animal–bacteria interactions and provides insights into the resilience of the O. gammarellus–associated bacteria to increased flooding frequency.

Humans are increasingly acknowledged as apex predators that shape landscapes of fear to which herbivores adapt their behaviour. Here, we investigate how humans modify deer space-use and their effects on vegetation at two spatial scales; zones with different types of human use (largescale risk factor) and, nested within that, trails (fine-scale risk factor). In zones with three contrasting types of human activities: 1) no recreation, no hunting, 2) with recreation, no hunting and 3) with recreation and hunting, we linked deer space-use (dropping counts) to browsing intensity, relative growth and survival of planted saplings. Plots were located at two distances to trails (20 versus 100 m) to test how trails affect deer space-use and sapling performance. Additionally, plots were distributed over forest and heathland as risk effects are habitat-dependent. Deer space-use was highest in the zone without recreation or hunting, resulting in higher browsing levels and lower sapling growth and survival, but only in heathland. In contrast, deer space-use and sapling performance did not differ between zones with recreation only and zones with recreation and hunting. Deer dropping counts were lower near trails used for recreation, but this was not associated with browsing impact or sapling performance. Our results show that recreational use modifies deer space-use which is associated with browsing impact on woody vegetation, while seasonal hunting activities in zones with recreation did not have additive year-round effects. Yet, effects were only observed at the larger scale of recreation zones and not near trails. Furthermore, deer space-use was only associated with sapling performance in open heathland, where high visibility presumably increases avoidance behaviour because it increases detectability and decreases escape possibilities. This suggests that recreation creates behaviourally mediated cascading effects that influence vegetation development, yet these effects are context-dependent. We advocate incorporating human-induced fear effects in conservation, management and research.

The long-term influence of persistent small herbivores on successional plant community configuration is rarely studied. We used a herbivore exclusion experiment along the successional gradient in a salt-marsh system, to investigate the effects of hares and geese, and hares alone, on plant diversity at five successional stages (the earliest, two early, the intermediate and the late successional stages) in the short and long term, i.e. 7 and 22 years, respectively. Plant diversity declined over time at all successional stages except for the earliest one. Small herbivores slowed down species decline, but only at one early successional stage. Small herbivores slowed down species decline via decreasing dominance of preferred grass Festuca rubra in the short term, and less preferred Elytrigia atherica in the long term. The effects of hares and geese were more pronounced than hares alone, indicating an important additive role of geese, especially in the long term. Synthesis. Small herbivores can have a strong and long-lasting impact on plant diversity, but it highly depends on the abundance of small herbivores, which in turn depends on the quality and abundance of forage plants. A diverse herbivore community may have more positive effects on regulating plant communities. Fil: Chen, Qingqing. University Of Groningen; Países Bajos Fil: Howison, Ruth A.. University Of Groningen; Países Bajos Fil: Bakker, Jan P.. University Of Groningen; Países Bajos Fil: Alberti, Juan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Kuijper, Dries P. J.. Mammal Research Institute Of The Polish Academy Of Sciences; Polonia Fil: Olff, Han. University Of Groningen; Países Bajos Fil: Smit, Christian. University Of Groningen; Países Bajos

It is increasingly acknowledged that stresses can resonate across the boundaries between ecosystems. Salt marshes, vast areas shaped by ocean-shore interactions, constitute prime examples of ecosystems where multiple stress factors arising from one ecosystem act on the local community of another ecosystem. Although it is generally recognized that zonation of plant communities on salt marshes is strongly affected by marine stress factors associated with frequent flooding (salinity, anoxia), it is largely unknown what the isolated and interacting effect are of these different stresses. This calls for experiments to disentangle the relative effects of these single and interacting multiple stresses. In this study, we determined the single and interacting effects of two main abiotic stress factors on salt marshes: salinity and anoxia (as a result of flooding) and one biotic stress factor: soil compaction (as a result of livestock grazing) on the growth of the twelve dominant salt marsh plant species, using a full-factorial experiment. To link the experimental work to distributions of natural plant communities along a natural stress gradient, we related our experimental results to observed plant species distributions on a salt marsh that is exposed to all these three stresses. Whereas salinity strongly affected ten species with two high-marsh species not surviving the highest salinity levels whereas anoxia only consistently affected growth of four species. Interestingly, we observed no synergistic effect of anoxia and salinity in salt marsh plants. Moreover, we observed a trade-off between the amount of aerenchyma and mechanical strength, indicating that species vary in their resistance to soil compaction. Overall, our results suggest that salinity is a major determinant of plant species composition on the salt marsh, followed by anoxia. The importance of soil compaction depends on salt marsh elevation: on the low marsh, increased oxygen supply by aerenchyma seems to outweigh resistance against mechanical stress whereas on the anaerobe low marsh, the reverse applies. Using the experimental data to predict cover of plant species in the field, our results suggest that the combination of plant responses to the various stresses may be a powerful predictor for explaining the plant composition on the salt marsh.

Coastal ecosystems, such as salt marshes, are threatened by accelerated sea-level rise (SLR). Salt marshes deliver valuable ecosystem services such as coastal protection and the provision of habitat for a unique flora and fauna. Whether salt marshes in the Wadden Sea area are able to survive accelerated SLR depends on sufficient deposition of sediments which add to vertical marsh accretion. Accretion rate is influenced by a number of factors, and livestock grazing was recently included. Livestock grazing is assumed to reduce accretion rates in two ways: (a) directly by increasing soil compaction through trampling, and (b) indirectly by affecting the vegetation structure, which may lower the sediment deposition. For four years, we studied the impact of two livestock species (horse and cattle) at two stocking densities (0.5 and 1.0 animal ha(-1)) on accretion in a large-scale grazing experiment using sedimentation plates. We found lower cumulative accretion rates in high stocking densities, probably because more animals cause more compaction and create a lower canopy. Furthermore, a trend towards lower accretion rates in horse-compared to cattle-grazed treatments was found, most likely because (1) horses are more active and thus cause more compaction, and (2) herbage intake by horses is higher than by cattle, which causes a higher biomass removal and shorter canopy. During summer periods, negative accretion rates were found. When the grazing and non-grazing seasons were separated, the impact of grazing differed among years. In summer, we only found an effect of different treatments if soil moisture (precipitation) was relatively low. In winter, a sufficiently high inundation frequency was necessary to create differences between grazing treatments. We conclude that stocking densities, and to a certain extent also livestock species, affect accretion rates in salt marshes. Both stocking densities and livestock species should thus be taken into account in management decisions of salt marshes. In our study accretion rates were higher than the current SLR. Further research is needed to include grazing effects into sedimentation models, given the importance of grazing management in the Wadden Sea area. (C) 2014 Elsevier Ltd. All rights reserved.

QuestionFor over three decades, low-intensity grazing has been used to maintain or increase plant species richness in European natural areas, but the effects are highly variable. Thus far, good predictors of whether grazing will have positive effects on plant species richness are limited. How does the interplay between low-intensity grazing and topographic heterogeneity affect plant species richness at different spatial scales?LocationLong-term grazed and ungrazed salt marshes of the Dutch Wadden Sea island of Schiermonnikoog.MethodsWe selected ten plots of 2200m(2) in grazed and ungrazed areas of our study sites, and recorded and compared plant species richness in 0.1, 1, 10, 100 and 1000m(2) subplots. Topographic heterogeneity was quantified at the plot scale using the standard deviation of the elevation derived from a high-resolution (5mx5m) digital elevation model. We calculated species-area relationships to analyse our data.ResultsWe found that large-scale topographic heterogeneity (based on the whole plot of 2200m(2)) positively affects plant species richness at all scales (even at the smallest 0.1-m(2) scale), and that grazing has a positive additive effect at the small scales (0.1 and 10m(2)). While grazing also had a positive effect on species richness at larger scales (1000m(2)), the strength of the effect was dependent on the topographic heterogeneity at that scale. The effectiveness of grazing for increased plant species richness was highest at low topographic heterogeneity, and lowest at intermediate topographic heterogeneity. Effects of intermediate heterogeneity were probably counterbalanced by the effects of grazing.ConclusionsOur results suggest that the variation in elevation is an important predictor of whether low-intensity grazing has positive effects on plant species richness or not. Grazing appears most beneficial at low topographic heterogeneity, but whether these findings hold for other grazed ecosystems will depend on several factors, most importantly, the relationship between topographic and abiotic heterogeneity. Results of our study are highly relevant for the application of low-intensity grazing as tool for conservation management in salt marshes and other natural areas.

Spatial associations of tree saplings with spiny or toxic plants in grazed woodlands are generally explained by associational resistance, i.e., protection against grazing via a well-defended neighbor. In this study, we tested whether directed seed dispersal and post-dispersal seed removal by wood mice are additional explanations for the observed spatial association between thorny shrubs and trees, hence before associational resistance. We performed three studies in grazed woodlands in the Netherlands to test this idea. Our first seed dispersal experiment with tagged acorns showed indeed that wood mice disperse acorns directed towards shrubs. The majority of these dispersed acorns were, however, consumed. Our second experiment revealed that post-dispersal removal of cached acorns was higher under shrubs than in grassland and under trees, but also indicated the importance of within-shrub position: shrub centers were faster depleted than shrub edges. Also the number of freshly emerged seedlings and older saplings differed between micro-habitats, being higher under trees and at shrub inner-edges than at shrub outer-edges, shrub centers, and in grassland. The spatial associations with shrubs got stronger with the age of saplings, which probably reflect accumulated grazing effects over time, being higher in the open than in shrubs. We conclude that directed acorn dispersal and post-dispersal acorn removal by wood mice are two additional explaining mechanisms for the spatial associations between thorny shrubs and trees in grazed woodlands, before associational resistance. Our findings change the view that large herbivores are the sole main drivers behind tree recruitment patterns in grazed woodlands.

The stress gradient hypothesis (SGH) predicts a shift from net negative interactions in benign environments towards net positive in harsh environments in ecological communities. While several studies found support for the SGH, others found evidence against it, leading to a debate on how nature and strength of species interactions change along stress gradients, and to calls for new empirical and theoretical work.In the latest attempt in this journal, it is successfully argued how the SGH should be expanded by considering different life strategies of species (stress tolerance versus competitive ability) and characteristics of abiotic stress (resource versus non-resource based) over wider stress gradients (opposed to low-high contrasts), but the crucial role of biotic stress by consumers is largely ignored in this refinement.We point out that consumers strongly alter the outcome of species interactions in benign and harsh environments, and show how inclusion of consumer-incurred biotic stress alters the predicted outcome of interactions along resource- and non-resource-based stress gradients for stress-tolerant and competitive benefactors and beneficiaries.Synthesis. New studies should include stress gradients consisting of both abiotic and biotic components to disentangle their impacts, and to improve our understanding of how species interactions change along environmental gradients.

In their comment (1) on our review and perspective on trophic rewilding science (2), Rubenstein and Rubenstein launch a critique not so much directed at our study as at trophic rewilding as a conservation approach. They first lament that Pleistocene rewilding has not been scientifically studied since the term was introduced. This is much in line with our study, where we conclude that empirical research on trophic rewilding is rare, fragmented, and geographically biased, with the literature dominated by essays and opinion pieces, and follow this up by providing recommendations for research opportunities and priorities. Rubenstein and Rubenstein (1) then claim … [↵][1]1To whom correspondence should be addressed. Email: svenning{at}bios.au.dk. [1]: #xref-corresp-1-1

Het minimale-interventiebeleid in de Oostvaardersplassen heeft geleid tot indrukwekkende kuddes grazers. Dit beheer wordt echter in verband gebracht met gebrek aan verjonging van bomen en struiken en een daling van de biodiversiteit. Onder welke omstandigheden is verjonging van bomen en struiken mogelijk en welke gevolgen heeft dit voor de biodiversiteit van planten en ongewervelden?

The Amazing European Bison Journey prototype clip shows an extract of the timeline of this species coming back from their near disappearance. It starts in the Białowieża Forest in Poland in 1919, when they went extinct in the wild. And runs up to 2013 in Zuid-Kennemerland in the Nether-lands, where an initial herd of 6 European bison, translocated in 2007 from Poland, had quadrupled to 24 individuals living in the Dutch dunes. The process of production of this animated documentary is de-scribed starting with the ecological research required. Review of literature, contact with specialist scientists and visitation of Poland and the Netherlands are some of the starting points of the process. Subsequently, the preparation for the animation is described. The initial storyboard was constructed out of the preceding ecological research. Afterwards, the development of the script and its respective narration was recorded. The construction of the sets, props and characters is described; specific emphasis is given to the construction of the European bison. Finally, the assemblage of all the elements is explained and the final results of the animation prototype are revealed. This animation forms part of a broader project, which has research into the effectiveness of a set of visual communication formats at its core, and uses rewilding as its ecological platform. A range of animations, infographics and virtual reality pieces will be eventually compared for their effectiveness using several communication research tools.

In het Stroomdallandschap Drentsche Aa was het in het begin van de zeventiger jaren de bedoeling van Staatsbosbeheer de graslanden uit landbouwkundig gebruik te halen en weer te verschralen (Bakker, 1989).Hierbij bestond het beheer uit maaien en afvoeren van het gewas (hooien). In dit artikel vergelijken we het proces van verschralen met mulchen (het gewas niet afvoeren) of bemesten(kunstmest toedienen om de afvoer van voedingsstoffen te compenseren) over een periode van 37 jaar.