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Understanding whether land use intensification causes regime shifts is of key importance for management, particularly if these shifts are associated with thresholds separating different ecosystem states and with hysteretic dynamics. Here we use a unique, long-term grassland database to identify thresholds in the response of 16 ecosystem functions and the diversities of 21 taxa to land use intensity. We show that aboveground diversity (5 of 10 taxa), shoot biomass and soil N retention showed threshold responses to land use intensity, i.e., abrupt changes between extensively and intensively managed grasslands. Time-series analysis revealed that ecosystem functions showed hysteresis around the threshold, while diversity did not. Shifting back to the functioning seen in extensively managed grasslands may therefore require larger reductions in land use intensity than shifting to the high intensity state. Identifying such thresholds along land use gradients is critical to prevent ecosystem degradation and conserve biodiversity and ecosystem functions.

The dynamics of interactions amongst natural enemies are central to the investigation of insect pest ecology. Ternary and quaternary interactions between parasitoids and predators in the presence of entomophagous organisms are yet to be comprehensively explored. We investigated the performance of a clone of green peach aphid (Myzus persicae(Sulzer); Hemiptera: Aphididae), raised on savoy cabbage (Brassica oleraceaLinnaeus; Brassicaceae), under all possible combinations of: I) the parasitoidAphidius colemaniViereck (Hymenoptera: Braconidae); II) the predatorChrysoperla carnea(Stephens) (Neuroptera: Chrysopidae); III) the predatorAdalia bipunctata(Linnaeus) (Coleoptera: Coccinellidae); and IV) the spiderParasteatoda tepidariorum(Koch) (Araneae: Theridiidae). We demonstrate a considerably differential green peach aphid abundance, polyphenism, and fine-scale spatial distribution in response to the combination, number, and identity of the present enemy species and their interactions. Surprisingly, certain combinations led to thriving green peach aphid populations due to interference between enemies; whereas, other combinations resulted in tangible collective suppression of the population. At the frontier of agroecology and entomology, we provide fresh insights on the effects of conflict and synergy between natural enemies sharing a pest of a cash crop as prey, highlighting the consequences of the presence of a novel synanthropic spider, as a top predator, on pest regulation.

Land-use intensification is a major driver of biodiversity loss. However, understanding how different components of land use drive biodiversity loss requires the investigation of multiple trophic levels across spatial scales. Using data from 150 agricultural grasslands in central Europe, we assess the influence of multiple components of local- and landscape-level land use on more than 4,000 above- and belowground taxa, spanning 20 trophic groups. Plot-level land-use intensity is strongly and negatively associated with aboveground trophic groups, but positively or not associated with belowground trophic groups. Meanwhile, both above- and belowground trophic groups respond to landscape-level land use, but to different drivers: aboveground diversity of grasslands is promoted by diverse surrounding land-cover, while belowground diversity is positively related to a high permanent forest cover in the surrounding landscape. These results highlight a role of landscape-level land use in shaping belowground communities, and suggest that revised agroecosystem management strategies are needed to conserve whole-ecosystem biodiversity., Nature Communications, 12 (1), ISSN:2041-1723

Nitrogen (N) cycling is a critical pathway by which producer, consumer, and decomposer interact with each other and with environmental circumstances simultaneously. The natural abundance composition of 15N/14N in plants and soils (termed as δ15Nplant and δ15Nsoil), as well as the difference between them (δ15Nsoil-to-plant = δ15Nplant −δ15Nsoil), is a useful tool for better understanding ecosystem N cycling. However, the drivers and mechanisms of ecosystem N cycling in alpine grasslands on the Tibetan Plateau are mostly unknown, especially across different grassland types at a regional scale. To fill this knowledge gap, we measured δ15Nplant (200 samples of top-dominant species) and δ15Nsoil (85 samples of top-layer soils, 0–20 cm) at nine sites that represent zonal communities of alpine deserts, steppes, and meadows in North Tibet, and calculated the corresponding δ15Nsoil-to-plant. Our results showed that δ15Nplant, δ15Nsoil, and δ15Nsoil-to-plant were significantly different among the three zonal grassland types (analysis of differences with non-parametric Kruskal Test, P

Summary • Vesicular–arbuscular mycorrhiza (VAM) and earthworms are known to affect plant and herbivore performance. However, surprisingly few studies have investigated their interactions. • In a glasshouse experiment we investigated the effects of earthworms (Aporrectodea caliginosa) and VAM (Glomus intraradices) on the growth and chemistry of Plantago lanceolata and the performance of aphids (Myzus persicae). • Earthworms did not affect VAM root colonization. Earthworms enhanced shoot biomass, and VAM reduced root biomass. VAM increased plant phosphorus content, but reduced the total amount of N in leaves. Earthworms led to a preferential uptake of soil N compared with 15N from the added grass residues in the absence of VAM. Earthworm presence reduced the concentration of catalpol. Earthworms and VAM combined accelerated the development of M. persicae, while the development tended to be delayed when only VAM or earthworms were present. • We suggest that earthworms promote plant growth by enhancing soil N availability and may affect herbivores by influencing concentrations of secondary metabolites. VAM enhances the P uptake of plants, but presumably competes with plant roots for N.

Nutrient enrichment is widespread throughout grassland systems and expected to increase during the Anthropocene. Trophic interactions, like aboveground herbivory, have been shown to mitigate its effect on plant diversity. Belowground herbivory may also impact these habitats’ response to nutrient enrichment, but its influence is much less understood, and likely to depend on factors such as the herbivores’ preference for dominant species and the symmetry of belowground competition. If preferential toward the dominant, fastest growing species, root herbivores may reduce these species’ relative fitness and support diversity during nutrient enrichment. However, as plant competition belowground is commonly considered to be symmetric, root herbivores may be less impactful than shoot herbivores because they do not reduce any competitive asymmetry between the dominant and subordinate plants. To better understand this system, we used an established, two-layer, grassland community model to run a full-factorially designed simulation experiment, crossing the complete removal of aboveground herbivores and belowground herbivores with nutrient enrichment. After 100 yr of simulation, we analyzed communities' diversity, competition on the individual level, as well as their resistance and recovery. The model reproduced both observed general effects of nutrient enrichment in grasslands and the short-term trends of specific experiments. We found that belowground herbivores exacerbate the negative influence of nutrient enrichment on Shannon diversity within our model grasslands, while aboveground herbivores mitigate its effect. Indeed, data on individuals’ above- and belowground resource uptake reveals that root herbivory reduces resource limitation belowground. As with nutrient enrichment, this shifts competition aboveground. Since shoot competition is asymmetric, with larger, taller individuals gathering disproportionate resources compared to their smaller, shorter counterparts, this shift promotes the exclusion of the smallest species. While increasing the root herbivores’ preferences toward dominant species lessens their negative impact, at best they are only mildly advantageous, and they do very little reduce the negative consequences of nutrient enrichment. Because our model’s belowground competition is symmetric, we hypothesize that root herbivores may be beneficial when root competition is asymmetric. Future research into belowground herbivory should account for the nature of competition belowground to better understand the herbivores’ true influence.

Non-consumptive effect of predation is a well-researched subject of which certain temporal, non-consumptive and predator-mimetic facets are yet to be investigated in plant-parasite systems. Here we focus on the consequences of the exposure of a pest population to predator-associated risk. One clone of the green peach aphid Myzus persicae (Sulzer), raised on a model crop Brassica oleracea (L.), was exposed to different regimes of risks associated with the aphidophagous predator ladybird Coccinella septempunctata (L.). This encompassed consumption, consumption alternated by non-competitive predation risk, presence of isolated predators with and without aphid feed, dead predator, predator dummy, scented (mimed) dummy, treated plants (or soil) with predator-borne cues, and predator removal. Over time, the respective risk regimes led to variable yet conspicuous suppression of the prey population. For example, unlike predator removal, ladybird corpses and dummies had considerable persistent negative effects on aphid reproductive success. Also, by the end of the experiment, polyphenism (winged morph production) varied across the risk regimes and was animated under the presence of a starved isolated predator, but faded when a predator corpse was present, and vanished in the presence of a predator dummy. Using a model aphid-crop system, we provide timely and novel insights on differential impacts of a variety of predator-associated cues on the population growth and phenotypic plasticity of the parthenogenetic pest in question. This work has implications for the rapidly developing area of the ecology of fear and thus merits applications across different eco-agricultural contexts.

Along with the global decline of species richness goes a loss of ecological traits. Associated biotic homogenization of animal communities and narrowing of trait diversity threaten ecosystem functioning and human well-being. High management intensity is regarded as an important ecological filter, eliminating species that lack suitable adaptations. Below-ground arthropods are assumed to be less sensitive to such effects than above-ground arthropods. Here, we compared the impact of management intensity between (grassland vs. forest) and within land-use types (local management intensity) on the trait diversity and composition in below- and above-ground arthropod communities. We used data on 722 arthropod species living above-ground (Auchenorrhyncha and Heteroptera), primarily in soil (Chilopoda and Oribatida) or at the interface (Araneae and Carabidae). Our results show that trait diversity of arthropod communities is not primarily reduced by intense local land use, but is rather affected by differences between land-use types. Communities of Auchenorrhyncha and Chilopoda had significantly lower trait diversity in grassland habitats as compared to forests. Carabidae showed the opposite pattern with higher trait diversity in grasslands. Grasslands had a lower proportion of large Auchenorrhyncha and Carabidae individuals, whereas Chilopoda and Heteroptera individuals were larger in grasslands. Body size decreased with land-use intensity across taxa, but only in grasslands. The proportion of individuals with low mobility declined with land-use intensity in Araneae and Auchenorrhyncha, but increased in Chilopoda and grassland Heteroptera. The proportion of carnivorous individuals increased with land-use intensity in Heteroptera in forests and in Oribatida and Carabidae in grasslands. Our results suggest that gradients in management intensity across land-use types will not generally reduce trait diversity in multiple taxa, but will exert strong trait filtering within individual taxa. The observed patterns for trait filtering in individual taxa are not related to major classifications into above- and below-ground species. Instead, ecologically different taxa resembled each other in their trait diversity and compositional responses to land-use differences. These previously undescribed patterns offer an opportunity to develop management strategies for the conservation of trait diversity across taxonomic groups in permanent grassland and forest habitats.

1AbstractEutrophication is widespread throughout grassland systems and expected to increase during the Anthropocene. Trophic interactions, like aboveground herbivory, have been shown to mitigate its effect on plant diversity. Belowground herbivory may also impact these habitats’ response to eutrophication, but the direction of its influence is much less understood, and likely to depend on factors such as the herbivores’ preference for dominant species and the symmetry of belowground competition. If preferential towards the dominant, fastest growing species, root herbivores may reduce these species’ relative fitness and support diversity during eutrophication. However, as plant competition belowground is commonly considered to be symmetric, root herbivores may be less impactful than shoot herbivores because they do not reduce any competitive asymmetry between the dominant and subordinate plants.To better understand this system, we used an established, two-layer, grassland community model to run a full-factorially designed simulation experiment, crossing the complete removal of aboveground herbivores and belowground herbivores with eutrophication. After 100 years of simulation, we analyzed communities’ diversity, competition on the individual-level, as well as their resistance and recovery. The model reproduced both observed general effects of eutrophication in grasslands and the short-term trends of specific experiments. We found that belowground herbivores exacerbate the negative influence of eutrophication on Shannon diversity within our model grasslands, while aboveground herbivores mitigate its effect. Indeed, data on individuals’ above- and belowground resource uptake reveals that root herbivory reduces resource limitation belowground. As with eutrophication, this shifts competition aboveground. Since shoot competition is asymmetric—with larger, taller individuals gathering disproportionate resources compared to their smaller, shorter counterparts—this shift promotes the exclusion of the smallest species. While increasing the root herbivores’ preferences towards dominant species lessens their negative impact, at best they are only mildly advantageous, and they do very little reduce the negative consequences of eutrophication. Because our model’s belowground competition is symmetric, we hypothesize that root herbivores may be beneficial when root competition is asymmetric. Future research into belowground herbivory should account for the nature of competition belowground to better understand the herbivores’ true influence.

Many experiments have shown that loss of biodiversity reduces the capacity of ecosystems to provide the multiple services on which humans depend. However, experiments necessarily simplify the complexity of natural ecosystems and will normally control for other important drivers of ecosystem functioning, such as the environment or land use. In addition, existing studies typically focus on the diversity of single trophic groups, neglecting the fact that biodiversity loss occurs across many taxa and that the functional effects of any trophic group may depend on the abundance and diversity of others. Here we report analysis of the relationships between the species richness and abundance of nine trophic groups, including 4,600 above- and below-ground taxa, and 14 ecosystem services and functions and with their simultaneous provision (or multifunctionality) in 150 grasslands. We show that high species richness in multiple trophic groups (multitrophic richness) had stronger positive effects on ecosystem services than richness in any individual trophic group; this includes plant species richness, the most widely used measure of biodiversity. On average, three trophic groups influenced each ecosystem service, with each trophic group influencing at least one service. Multitrophic richness was particularly beneficial for 'regulating' and 'cultural' services, and for multifunctionality, whereas a change in the total abundance of species or biomass in multiple trophic groups (the multitrophic abundance) positively affected supporting services. Multitrophic richness and abundance drove ecosystem functioning as strongly as abiotic conditions and land-use intensity, extending previous experimental results to real-world ecosystems. Primary producers, herbivorous insects and microbial decomposers seem to be particularly important drivers of ecosystem functioning, as shown by the strong and frequent positive associations of their richness or abundance with multiple ecosystem services. Our results show that multitrophic richness and abundance support ecosystem functioning, and demonstrate that a focus on single groups has led to researchers to greatly underestimate the functional importance of biodiversity.

Plant diversity and soil organisms are both widely studied for their contributions to ecosystem functions. It has been recently shown that soil biota may drive the plant species diversity-function relationship in grasslands, while so far studies on plant intraspecific diversity are lacking. To improve the understanding of how ecosystem functions may be influenced by plant intraspecific diversity, soil organisms, and their interactions, we used a field setting to examine the effects of plant intraspecific diversity and functionally dissimilar soil organisms (manipulated by the addition of northern root-knot nematodes, earthworms, and arbuscular mycorrhizal fungi) on aboveground primary production, pollination and shoot herbivory. Plant intraspecific diversity was manipulated by sowing different seed mixtures of Trifolium pratense L. and Lolium perenne L. cultivars. We found a positive effect of plant intraspecific diversity on total aboveground primary production, contributed mostly by T. pratense. The plant intraspecific diversity-productivity effect on T. pratense was mediated by the nematodes, i.e. aboveground biomass was increased by intraspecific diversity only in the nematode treatment. Further, the average floral visitation length was decreased by earthworm addition, while the abundance of pollinators tended to be increased by high plant intraspecific diversity. Leaf damage of T. pratense were not influenced by the treatments. We conclude that plant intraspecific diversity and soil organisms can interactively or independently modify functions such as aboveground primary production and pollination of T. pratense in the field. Specifically, the positive plant intraspecific diversity effect appears to only emerge under conditions of stress (high nematode abundance). This result indicates that plant intraspecific diversity may be important for the maintenance of ecosystem functions, especially in an agricultural context, where pest pressure can be high and can have large detrimental consequences.

Root herbivory can influence plant interactions with other organisms by systemically affecting plant morphology and chemistry. Strength and direction of this influence may depend on environmental factors such as land use intensity in managed systems. We established local Plantago lanceolata plants with and without root feeding Agriotes spp. larvae (Coleoptera, Elateridae) in their root system in grasslands of different management intensity. We then determined root herbivore impacts on plant interactions with invertebrate shoot herbivores and root fungi. Root herbivory reduced length and biomass of P. lanceolata roots independent of land use intensity. Root colonization by non-mycorrhizal fungi increased with increasing cattle grazing intensity, but was unaffected by root herbivory. The root herbivore impact on root colonization by arbuscular mycorrhizal fungi depended on cattle grazing intensity. Root herbivores increased colonization under low but reduced colonization under high grazing intensities. Root herbivory affected P. lanceolata interactions with shoot herbivores, as indicated by increased leaf damage in the presence of root herbivores. The increase, however, declined with increasing mowing frequency. We conclude that land use intensity may determine the net effect of root herbivory on plant performance in managed systems.

Soil macro-invertebrates, the so-called soil macrofauna, belong to different functional groups such as ecosystem engineers, detritivores, root herbivores, and predators. They have often profound impacts on physical, chemical, and biological soil characteristics. Effects of soil macrofauna on plants are mediated by direct (trophic) and indirect interactions with roots. The objective of this chapter is to summarize the knowledge and identify knowledge gaps on the connection between soil macrofauna, plants, and aboveground arthropod communities. Above–belowground interaction studies involving soil macrofauna mainly focused on insect root herbivores or earthworms, while other taxa of the soil macrofauna have been widely neglected. Root feeding insect larvae can induce defense mechanisms in the whole plant, while earthworms affect plant performance mainly indirectly by changing resource availability, soil structure, and/or impacting other soil biota. The resulting systemic changes in plant traits can further affect aboveground plant interactions with herbivores and higher trophic levels. Other, little studied aspects are legacy effects of soil macrofauna that may alter future plant performance and interactions mediated by changes in soil characteristics and plant traits. Global change factors, such as climatic or land use changes, have also been shown to alter the strength of interactions between soil macrofauna and aboveground organisms. We conclude that more realistic insights in the role of soil macrofauna on plant performance and ecosystem functions could be achieved by more encompassing multispecies interactions under different climatic conditions and at different temporal and spatial scales.

This final chapter briefly summarizes main points clarified by the preceding chapters to capture what we have learned and then highlight key issues for new challenges for the research field of aboveground–belowground community ecology. The reviews and syntheses covered in this book highlight several key issues for exciting challenges in promoting future research in this field. Specifically, these challenges involve (1) strengthening the evolutionary perspective, (2) scaling-up to community and ecosystem level, and (3) developing applied solutions for global problems. These critical issues, which previous studies have little considered, will undoubtedly enhance the perspectives for further development of the research field of aboveground–belowground community ecology.

Intensive land use is a major cause of biodiversity loss, but most studies comparing the response of multiple taxa rely on simple diversity measures while analyses of other community attributes are only recently gaining attention. Species-abundance distributions (SADs) are a community attribute that can be used to study changes in the overall abundance structure of species groups, and whether these changes are driven by abundant or rare species. We evaluated the effect of grassland management intensity for three land-use modes (fertilization, mowing, grazing) and their combination on species richness and SADs for three belowground (arbuscular mycorrhizal fungi, prokaryotes and insect larvae) and seven aboveground groups (vascular plants, bryophytes and lichens; arthropod herbivores; arthropod pollinators; bats and birds). Three descriptors of SADs were evaluated: general shape (abundance decay rate), proportion of rare species (rarity) and proportional abundance of the commonest species (dominance). Across groups, taxonomic richness was largely unaffected by land-use intensity and only decreased with increasing mowing intensity. Of the three SAD descriptors, abundance decay rate became steeper with increasing combined land-use intensity across groups. This reflected a decrease in rarity among plants, herbivores and vertebrates. Effects of fertilization on the three descriptors were similar to the combined land-use intensity effects. Mowing intensity only affected the SAD descriptors of insect larvae and vertebrates, while grazing intensity produced a range of effects on different descriptors in distinct groups. Overall, belowground groups had more even abundance distributions than aboveground groups. Strong differences among aboveground groups and between above- and belowground groups indicate that no single taxonomic group can serve as an indicator for effects in other groups. In the past, the use of SADs has been hampered by concerns over theoretical models underlying specific forms of SADs. Our study shows that SAD descriptors that are not connected to a particular model are suitable to assess the effect of land use on community structure.

Root herbivory incurs fitness costs, but herbivory by nematodes can additionally increase nutrient availability mediated by enhanced root exudation and soil microbial activity and change plant susceptibility to aboveground herbivores due to systemic changes in plant defence. We hypothesized that such positive indirect effects may outweigh the negative direct effects of root herbivory by nematodes on plant performance. We tested the effects of transient (3 weeks) and continuous (11 weeks) belowground herbivory by root-knot nematodes (Meloidogyne incognita) on the biomass, nitrogen levels, and reproductive output of Nicotiana attenuata, and its interaction with a specialist aboveground herbivore (Manduca sexta) in a greenhouse study. Continuous nematode herbivory caused an increase in shoot biomass and enhanced nitrogen levels in roots, shoots and seeds, but reduced the reproductive output of N. attenuata. Short-term, transient nematode herbivory had no effects. Feeding by the aboveground herbivore reduced reproductive output and increased seed nitrogen content. Nicotine levels in leaves and the plant interaction with M. sexta were not influenced by nematode herbivory. In summary, only continuous nematode herbivory indirectly increased nitrogen availability and caused resource sequestration to the shoots; however, this effect was not strong enough to outweigh the direct fitness costs of nematode herbivory.

A B S T R A C T Plant diversity and different groups of belowground organisms have been shown to influence the characteristics of plant communities and their associated aboveground organisms; however, little is known about the interactions and combined effects of these biotic factors. Furthermore, while plant species richness has received a lot of attention, intraspecific diversity has only recently come into the focus of community ecology. The objective of this study was to determine whether the addition of beneficial soil organisms (arbuscular mycorrhizal fungi (AMF) and anecic earthworms (Lumbricus terrestris L.) and different levels of plant cultivar diversity interactively influence productivity, weed establishment, leaf damage by herbivores and pathogens, and the diversity of aboveground herbivores in legume-grass communities. Our results indicated that the addition of AMF increased aboveground plant productivity and tended to decrease the diversity of aboveground herbivores. Earthworms attenuated the effect of AMF addition on AMF root colonization, but had no effect on plant productivity or herbivore diversity. Weed biomass was significantly lower in plant communities with high cultivar diversity compared to low cultivar diversity. We did not find interactive effects of the two soil organism groups and plant cultivar diversity. Our results demonstrate the independent roles and additive positive effects of AMF and plant cultivar diversity on functions such as productivity and resistance against weeds in the field. We suggest that AMF and plant cultivar diversity manipulations may be applied more frequently in agriculture management programs that aim for sustainable yield enhancement and biocontrol of herbivores and weeds.

Experience and memory of environmental stimuli that indicate future stress can prepare (prime) organismic stress responses even in species lacking a nervous system. The process through which such organisms prepare their phenotype for an improved response to future stress has been termed 'priming'. However, other terms are also used for this phenomenon, especially when considering priming in different types of organisms and when referring to different stressors. Here we propose a conceptual framework for priming of stress responses in bacteria, fungi and plants which allows comparison of priming with other terms, e.g. adaptation, acclimation, induction, acquired resistance and cross protection. We address spatial and temporal aspects of priming and highlight current knowledge about the mechanisms necessary for information storage which range from epigenetic marks to the accumulation of (dormant) signalling molecules. Furthermore, we outline possible patterns of primed stress responses. Finally, we link the ability of organisms to become primed for stress responses (their 'primability') with evolutionary ecology aspects and discuss which properties of an organism and its environment may favour the evolution of priming of stress responses.

Negative plant–soil feedbacks can impair seedling survival near conspecific trees and may enhance forest diversity. However, the reciprocal aspect of this relationship, the influence of tree diversity on the strengths of plant–soil feedbacks is unknown. We examined whether tree diversity can affect plant–soil feedbacks of two common temperate tree species, beech (Fagus sylvatica) and sessile oak (Quercus petraea). Soils were collected from adjacent to beech and oak trees growing in a manipulative tree diversity field experiment and used as inocula in a greenhouse experiment to determine whether increasing tree diversity could moderate the strengths of plant–soil feedbacks. We also compared plant–soil feedback responses between Q. petraea and F. sylvatica to test the hypothesis that stronger negative feedbacks contribute to the relative rarity of Q. petraea. Negative plant–soil feedbacks on seedling emergence were observed for both tree species. Emergence increased with increasing distance of the soil inoc...

Summary Biotic interactions of plants can have legacy effects mediated by changes in plant traits and soil characteristics. Legacy effects are defined as effects that persist after the causal biotic interaction ceases, because plant traits and soil characteristics are plastic and modifications may be maintained for long time periods. To date, studies on biotic interactions of plants with above- and below-ground organisms and their plant-mediated interactions have mainly focused on short-term effects in the continuous presence of interacting organisms. Little is known about how long the changes in plant traits and soil characteristics persist after the biotic interaction ceases and indirectly affect future biotic interactions and community assembly. Further, since some organisms switch between above- and below-ground compartments during ontogeny, impacts on soil-dwelling larval stages can have direct legacy effects on their above-ground adult stages and vice versa. Elucidating legacy effects of biotic interactions above and below the ground will provide a deeper insight into a better understanding of the importance of plant trait- and soil characteristic-mediated indirect interactions in shaping community assembly, biodiversity and ecosystem function.

Resilience is an important aspect of the non-linear restoration of disturbed ecosystems. Fenced grassland patches on the northern Tibetan Plateau can be used to examine the resistance and resilience of degraded alpine grasslands to grazing and to a changing climate. To examine the non-linearity of restoration, we used moderate resolution imaging spectroradiometer (MODIS) normalized difference vegetation index (NDVI) as a proxy for productivity during a ten-year restoration by fencing. Degraded alpine grasslands exhibited three restoration trajectories: an equilibrium in meadows, a non-linear increase across steppes, and an abrupt impulse in desert-steppes following a slight increase in productivity. Combined with weather conditions, the ten-year grazing exclusion has successfully enhanced the NDVI on the most degraded steppes, but did not do so efficiently on either meadows or desert-steppes. Warming favors the NDVI enhancement of degraded meadows, but higher temperatures limited the restoration of degraded steppes and desert-steppes. Precipitation is necessary to restore degraded alpine grasslands, but more precipitation might be useless for meadows due to lower temperatures and for desert-steppes due to limitations caused by the small species pool. We suggest that detailed field observations of community compositional changes are necessary to better understand the mechanisms behind such non-linear ecological restorations.

Plants are challenged by both above- and belowground herbivores which may indirectly interact with each other via herbivore-induced changes in plant traits, however, little is known about how genetic variation of the host plant shapes such interactions. We used two genotypes (M4 and E9) of Solanum dulcamara (Solanaceae) with or without previous experience of aboveground herbivory by Spodoptera exigua (Noctuidae) to quantify its effects on subsequent root herbivory by Agriotes spp. (Elateridae). In the genotype M4, due to the aboveground herbivory, shoot and root biomass was significantly decreased, roots had a lower C/N ratio and contained significantly higher levels of proteins, while the genotype E9 was not affected. However, aboveground herbivory had no effects on weight gain or mortality of the belowground herbivores. Root herbivory by Agriotes increased the nitrogen concentration in the roots of M4 plants leading to a higher weight gain of conspecific larvae. Also, in feeding bioassays, Agriotes larvae tended to prefer roots of M4 over E9, irrespective of the aboveground herbivore treatment. Fourier-Transform Infrared Spectroscopy (FT-IR) documented differences in metabolic profiles of the two plant genotypes and of the roots of M4 plants after aboveground herbivory. Together, these results demonstrate that previous aboveground herbivory can have genotype-specific effects on quantitative and qualitative root traits. This may have consequences for belowground interactions, although generalist root herbivores might not be affected when the root biomass offered is still sufficient for growth and survival.

Moringa is a mycorrhizal crop cultivated in the tropics and subtropics and appreciated for its nutritive and health-promoting value. As well as improving plant mineral nutrition, arbuscular mycorrhizal fungi (AMF) can affect plant synthesis of compounds bioactive against chronic diseases in humans. Rhizophagus intraradices and Funneliformis mosseae were used in a full factorial experiment to investigate the impact of AMF on the accumulation of glucosinolates, flavonoids, phenolic acids, carotenoids, and mineral elements in moringa leaves. Levels of glucosinolates were enhanced, flavonoids and phenolic acids were not affected, levels of carotenoids (including provitamin A) were species-specifically reduced, and mineral elements were affected differently, with only Cu and Zn being increased by the AMF. This study presents novel results on AMF effects on glucosinolates in leaves and supports conclusions that the impacts of these fungi on microelement concentrations in edible plants are species dependent. The nonspecific positive effects on glucosinolates and the species-specific negative effects on carotenoids encourage research on other AMF species to achieve general benefits on bioactive compounds in moringa.

It is generally thought that soil animals face specific foraging conditions because movement through soil is highly energy consuming. The hypothesis tested here is that root-feeding click beetle larvae (wireworms, Agriotes spp.; Coleoptera: Elateridae), to minimize energy loss, only migrate horizontally through soil when located in food-depleted surroundings. Larvae were placed at either end of a root density gradient created by the grass Holcus lanatus L. (Poaceae), and their position in the gradient was recorded after 12 days of migration. Larval migration depended on the food situation at the starting point, with larvae moving from food-depleted to food-rich areas, but not leaving food-rich areas. Larvae spread further around food-rich areas when together with conspecifics than when being alone, presumably to avoid cannibalism. Food density-dependent migration may have to be taken into account when using trap-crops to control Agriotes larvae. Success may depend on the timing of trap-crop establishment relative to the target crop to generate an effective food gradient.

Plant-soil feedback responses for native and invasive plant species are well documented, but little is known about how feedback effects from the soil biota community affect plant interactions with herbivores. Here we examine whether changes of the soil biota community by the successful invader Solidago canadensis influence growth and herbivore susceptibility of two coexisting native plant species (Tanacetum vulgare, Melilotus albus). Root zone soil from two different habitat types (‘urban’ and ‘suburban’) was collected and used as inocula in a plant-soil feedback study. Each plant species was grown either in its own soil biota community or with the community with a history from the competitive invasive or native plant species. To identify potential drivers of responses to the different soil biota communities, we analyzed root colonization by arbuscular mycorrhizal fungi and dark-septate endophytes (DSE), and the community composition of soil inhabiting nematodes at the end of our experiment. Results show that S. canadensis and M. albus were not affected by soil history. In contrast, T. vulgare showed increased plant growth in ‘foreign’ soil derived from S. canadensis root zone compared with its ‘home’ soil suggesting a growth promotion by the soil biota community of S. canadensis. From the examined drivers, the abundance of DSE explained the growth response of T. vulgare to the S. canadensis soil biota community best. However, shoot herbivory by banded snails (Cepaea nemoralis, C. hortensis) was not affected by soil history, but by the habitat type where the soil inocula originated. Our study shows that a native plant species may profit from the presence of an invasive competitor mediated by changes in the soil biota community.

Hydrothermal carbonization (HTC) is a method to produce carbonized material at relatively low temperatures (180–250 °C) under pressure and aqueous conditions. The product is called hydrochar and can be used as a soil amendment. However, applied in high dosages it may have detrimental effects on plants or soil biota. The potential impact of hydrochar amendment on beneficial soil organisms such as arbuscular mycorrhizal fungi (AMF) and earthworms and their interactions are not well understood. The goal of the present study was to determine effects of hydrochar on plant growth and soil biota and to evaluate interactions of earthworms and hydrochar on plant and AMF performance and to identify underlying mechanisms. In a greenhouse experiment, we investigated the effect of hydrochar at different addition rates (control, 1% and 10%, v/v) with or without the earthworm Aporrectodea caliginosa on the growth of Plantago lanceolata L. and the performance of its AMF. We observed a positive interaction between earthworms and 10% hydrochar on shoot and root biomass: added as a single treatment hydrochar had a negative effect on plant growth at this dosage, but plant biomass increased significantly when hydrochar was added together with earthworms. Root colonization by AMF increased significantly with increasing concentration of hydrochar, but was not affected by earthworms. Contrastingly, extraradical hyphal length of AMF was reduced by earthworms, but not affected by hydrochar. Thus, hydrochar and earthworms affected the performance of AMF, albeit of different AMF structures and in different directions. Our results indicate that earthworms may play an important role in alleviating the negative impacts of high dosages of hydrochar on plant growth; such interactions should move into focus of future research on potential effects of HTC materials.

Question Does a reduction in size class of soil biota aggravate the impacts of soil compaction on plant communities? Location Controlled mesocosm study with a European ruderal plant community exposed to soil compaction and soil biota communities of different size classes. Methods We evaluated the individual and combined effects of soil compaction and soil biota communities of different size classes (

Arbuscular mycorrhizal fungi (AMF) and rhizobacteria (Pseudomonas fluorescens) have been targeted for plant growth promotion in order to reduce agrochemical inputs. However, the effects of their interaction on root morphology under different nutrient levels are unknown. Moreover, both soil microorganisms can alter the levels of plant hormonal regulators but no in vivo evidence is available for their interplay with cytokinin (CK) on root morphology. In a full-factorial greenhouse experiment we investigated the effects of interaction between Rhizophagus intraradices, P. fluorescens 8569r, phosphorus (P) amendment and plant CK deficiency on tobacco root morphology, shoot yield and quality. Our results suggest that reduced CK levels may be involved in plant signaling to stimulate AMF hyphal growth in the roots. In addition, we document that a bacteria isolated from the rhizosphere of a non-mycorrhizal plant can function as mycorrhizal helper bacteria, most likely via interplay with phytohormones. The two soil microorganisms, depending on the inoculum combination, P amendment and plant CK levels, modified tobacco root morphology. Our results suggest that the positive interactions between P. fluorescens and AMF depend on soil nutrient status and root hormonal balance. Both microorganism modified shoot yield and these effects seem to result from altered root morphology. Overall, our study support early conclusions that the classification of a soil microorganism as detrimental or beneficial should be based upon their net effects on the plant growth according to circumstances. We suggest this consideration to be extended to the effects of interaction between soil microorganisms on root morphology.

The biodiversity-productivity relationship is still under debate for alpine grasslands on the Tibetan Plateau. We know little about direct and indirect effects of biotic and abiotic drivers on this relationship, especially in regard to plant functional trait diversity. Here, we examine how aboveground net primary productivity (ANPP) and precipitation use efficiency (PUE) respond to climate, soil and community structure across alpine grasslands on the Northern Tibetan Plateau. We found that both ANPP and PUE showed nonlinear patterns along water availability and site altitude variation, which together accounted for 80.3% and 68.8% of variation in ANPP and PUE, respectively, by optimal generalized additive models. Functional trait divergence (FTD) and community weighted mean (CWM) of plant functional traits were as important as plant species diversity (PSD) for explaining the nonlinear productivity-climate relationship. These findings were confirmed by results from principal component analyses and structural equation models. We also found that FTD was negatively correlated with PSD across different alpine grasslands. Our results implicate: first, the combinatorial influences of temperature and precipitation gradients are important for predicting alpine grassland dynamics; second, the convergence and divergence of plant functional traits may have the potential to elucidate the effect of plant diversity on ecosystem functionality.

Land-use intensification is a major driver of biodiversity loss(1,2). Alongside reductions in local species diversity, biotic homogenization at larger spatial scales is of great concern for conservation. Biotic homogenization means a decrease in beta-diversity (the compositional dissimilarity between sites). Most studies have investigated losses in local (alpha)-diversity(1,3) and neglected biodiversity loss at larger spatial scales. Studies addressing beta-diversity have focused on single or a few organism groups (for example, ref. 4), and it is thus unknown whether land-use intensification homogenizes communities at different trophic levels, above-and belowground. Here we show that even moderate increases in local land-use intensity (LUI) cause biotic homogenization across microbial, plant and animal groups, both above- and belowground, and that this is largely independent of changes in alpha-diversity. We analysed a unique grassland biodiversity dataset, with abundances of more than 4,000 species belonging to 12 trophic groups. LUI, and, in particular, high mowing intensity, had consistent effects on beta-diversity across groups, causing a homogenization of soil microbial, fungal pathogen, plant and arthropod communities. These effects were nonlinear and the strongest declines in beta-diversity occurred in the transition from extensively managed to intermediate intensity grassland. LUI tended to reduce local alpha-diversity in aboveground groups, whereas the alpha-diversity increased in belowground groups. Correlations between the alpha-diversity of different groups, particularly between plants and their consumers, became weaker at high LUI. This suggests a loss of specialist species and is further evidence for biotic homogenization. The consistently negative effects of LUI on landscape-scale biodiversity underscore the high value of extensively managed grasslands for conserving multitrophic biodiversity and ecosystem service provision. Indeed, biotic homogenization rather than local diversity loss could prove to be the most substantial consequence of land-use intensification.

Summary Plant–microbe mutualisms can improve plant defense, but the impact of root endophytes on below‐ground herbivore interactions remains unknown. We investigated the effects of the root endophyte Piriformospora indica on interactions between rice (Oryza sativa) plants and its root herbivore rice water weevil (RWW; Lissorhoptrus oryzophilus), and how plant jasmonic acid (JA) and GA regulate this tripartite interaction.Glasshouse experiments with wild‐type rice and coi1‐18 and Eui1‐OX mutants combined with nutrient, jasmonate and gene expression analyses were used to test: whether RWW adult herbivory above ground influences subsequent damage caused by larval herbivory below ground; whether P. indica protects plants against RWW; and whether GA and JA signaling mediate these interactions.The endophyte induced plant tolerance to root herbivory. RWW adults and larvae acted synergistically via JA signaling to reduce root growth, while endophyte‐elicited GA biosynthesis suppressed the herbivore‐induced JA in roots and recovered plant growth.Our study shows for the first time the impact of a root endophyte on plant defense against below‐ground herbivores, adds to growing evidence that induced tolerance may be an important root defense, and implicates GA as a signal component of inducible plant tolerance against biotic stress.

Insect root herbivores can alter plant community structure by affecting the competitive ability of single plants. Our study aims at increasing knowledge on the impact of click beetle larvae (Elateridae, genus Agriotes) on grassland plant communities, by determining biomass responses as well as responses of the arbuscular mycorrhizal fungi (AMF) symbiosis to this widespread generalist root herbivore for eight common grassland plant species (Festuca rubra, Holcus lanatus, Poa pratensis, Achillea millefolium, Plantago lanceolata, Veronica arvensis, Medicago lupulina, Trifolium repens), belonging to three functional groups (grasses, herbs, legumes). The presence of larvae in the rhizosphere of individual plants had an overall negative effect on root biomass, which varied in degree between plant species, with more root biomass being removed from larger root systems. The effect of larvae on shoot biomass, total plant biomass and shoot/root ratio also differed in strength between plant species. Relative changes in root and total plant biomass ranged from a 71% and 55% loss, respectively, in V. arvensis to an 11% and 1% increase in T. repens, but were not related to root- or plant size. Root colonization by AMF and the length of extraradical AMF hyphae were not affected by larvae. The plant's functional group did not determine the response of the plant to feeding by larvae. Growth of larvae was positively correlated with root biomass, but did not depend on plant species or group identity. The results confirm the generalist nature of Agriotes spp. larvae, which depend on sufficient root quantity and are likely to feed most on those plant species whose roots are most abundant in their habitat. Their effect on the plant community may be generated through the ability of the respective plant species to cope with the herbivore damage, with tolerances being plant species rather than plant group specific.

Earthworms and arbuscular mycorrhizal fungi (AMF) have profound impacts on plant performance. However, it is largely unknown if and how earthworms and AMF may affect plant succession. We planted mesocosms with an early-mid successional and a mid-late successional grassland plant community and added endogeic earthworms and commercial AMF in a full-factorial way to natural background soil. Earthworms had a positive effect on the total root and shoot biomass of both plant communities, with the effect on the shoots being slightly enhanced by co-inoculation with AMF. Surprisingly, the earthworm effect on the mid successional plant species depended on the successional stage of the plant community. Earthworms had a positive effect on the mid successional plant species when they were growing in the mid-late successional plant community, but no effect when the same plant species were growing in the early-mid successional plant community. Addition of AMF alone tended to reduce the shoot biomass of the early successional plant species, while the addition of earthworms in the presence or absence of AMF increased their shoot biomass. We conclude that the impacts of earthworms on plant species may depend on the successional stage of the plant community, while the effect of AMF addition depends on the successional stage of the plant community and may be changed by the presence of earthworms. Earthworms and AMF addition affect plants and plant communities of different successional stages differently with potential effects on plant succession.

Questions: How do arbuscular mycorrhiza and earthworms affect the structure and diversity of a ruderal plant community? Is the establishment success of newcomer plants enhanced by these soil organisms and their interactions? Methods: We grew a native ruderal plant community composed of different functional groups (grasses, legumes and forbs) in the presence and absence of arbuscular mycorrhizal fungi (AMF) and endogeic earthworms in mesocosms. We introduced seeds of five, mainly exotic, plant species from the same functional groups after a disturbance simulating mowing. The effects of the soil organisms on the native ruderal plant community and seedling establishment of the newcomer plants were assessed. Results: After disturbance, the total above-ground regrowth of the native plant community was not affected by the soil organisms. However, AMF increased plant diversity and shoot biomass of forbs, but decreased shoot biomass of grasses of the native plant community. Earthworms led to a reduction in total root biomass. Establishment of the introduced newcomer plants increased in the presence of AMF and earthworms. Especially, seedling establishment of the introduced non-native legume Lupinus polyphyllus and the native forb Plantago lanceolata was promoted in the presence of AMF and earthworms, respectively. The endogeic earthworms gained more weight in the presence of AMF and led to increased extraradical AMF hyphal length in soil. However, earthworms did not seem to modify the effect of AMF on the plant community. Conclusion: The present study shows the importance of mutualistic soil organisms in mediating the establishment success of newcomer plants in a native plant community. Mutualistic soil organisms lead to changes in the structure and diversity of the native plant community and might promote newcomer plants, including exotic species.

Root-feeding insects are important drivers in ecosystems, and links between aboveground oviposition preference and belowground larval performance have been suggested. The root-colonizing arbuscular mycorrhizal fungi (AMF) play a central role in plant nutrition and are known to change host quality for root-feeding insects. However, it is not known if and how AMF affect the aboveground oviposition of insects whose offspring feed on roots. According to the preference-performance hypothesis, insect herbivores oviposit on plants that will maximize offspring performance. In a greenhouse experiment with rice (Oryza sativa), we investigated the effects of AMF (Glomus intraradices) on aboveground oviposition of rice water weevil (Lissorhoptrus oryzophilus), the larvae of which feed belowground on the roots. Oviposition (i.e., the numbers of eggs laid by weevil females in leaf sheaths) was enhanced when the plants were colonized by AMF. However, the leaf area consumed by adult weevils was not affected. Although AMF reduced plant biomass, it increased nitrogen (N) and phosphorus concentrations in leaves and N in roots. The results suggest that rice water weevil females are able to discriminate plants for oviposition depending on their mycorrhizal status. The discrimination is probably related to AMF-mediated changes in plant quality, i.e., the females choose to oviposit more on plants with higher nutrient concentrations to potentially optimize offspring performance. AMF-mediated change in plant host choice for chewing insect oviposition is a novel aspect of below- and aboveground interactions.

Aims In nature, plant communities are affected simultaneously by a variety of functionally dissimilar organisms both above and below the ground. However, there is a gap of knowledge on interactive effects of functionally dissimilar organisms on plant communities that is needed to be filled to better understand and predict the general impact of biotic factors on plant communities. Methods We conducted a full-factorial mesocosm study to investigate the individual and combined impacts of above- and belowground functionally dissimilar organisms on a grassland plant community. We studied the effects of aboveground herbivores (Helix aspersa, Gastropoda), arbuscular mycorrhizal fungi (AMF; Glomus spp., Glomeromycota) and endogeic earthworms (Aporrectodea spp., Lumbricidae) on the diversity, structure and productivity of an experimental grassland plant community and each other. Important Findings Aboveground herbivory by snails decreased, AMF increased and earthworms had no effects on the diversity of the grassland plant community, while their combined effects were additive. The biomass of the plant community was negatively affected by snails and AMF, while no effects of earthworms or interaction effects were found. The plant species were differently affected by snails and AMF. No effects of the above- and belowground organisms on each other’s performance were detected. Since the effects of the functionally dissimilar organisms on the grassland plant community were mainly independent, the results indicate that their combined effects may be predicted by knowing the individual effects, at least under the conditions used in the present mesocosm study.

International audience; The productivity and diversity of plant communities are affected by soil organisms such as arbuscular mycorrhizal fungi (AMF), root herbivores and decomposers. However, it is unknown how interactions between such functionally dissimilar soil organisms affect plant communities and whether the combined effects are additive or interactive. In a greenhouse experiment we investigated the individual and combined effects of AMF (five Glomus species), root herbivores (wireworms and nematodes) and decomposers (collembolans and enchytraeids) on the productivity and nutrient content of a model grassland plant community as well as on soil microbial biomass and community structure. The effects of the soil organisms on productivity (total plant biomass), total root biomass, grass and forb biomass, and nutrient uptake of the plant community were additive. AMF decreased, decomposers increased and root herbivores had no effect on productivity, but in combination the additive effects canceled each other out. AMF reduced total root biomass by 18%, but decomposers increased it by 25%, leading to no net effect on total root biomass in the combined treatments. Total shoot biomass was reduced by 14% by root herbivores and affected by an interaction between AMF and decomposers where decomposers had a positive impact on shoot growth only in presence of AMF. AMF increased the shoot biomass of forbs, but reduced the shoot biomass of grasses, while root herbivores only reduced the shoot biomass of grasses. Interactive effects of the soil organisms were detected on the shoot biomasses of Lotus corniculatus, Plantago lanceolata, and Agrostis capillaris. The C/N ratio of the plant community was affected by AMF. In soil, AMF promoted abundances of bacterial, actinomycete, saprophytic and AMF fatty acid markers. Decomposers alone decreased bacterial and actinomycete fatty acids abundances but when decomposers were interacting with herbivores those abundances were increased. Our results suggests that at higher resolutions, i.e. on the levels of individual plant species and the microbial community, interactive effects are common but do not affect the overall productivity and nutrient uptake of a grassland plant community, which is mainly affected by additive effects of functionally dissimilar soil organisms. (c) 2010 Elsevier Ltd. All rights reserved.

Soil organisms affect plant growth and chemistry and have subsequent effects on aboveground herbivore performance. However, whether herbivores discriminate between plants exposed to different soil organisms when colonizing their host plants is largely unexplored. In a greenhouse study, Tanacetum vulgare L. (Asteraceae) growing in a ruderal plant community in the presence and absence of arbuscular mycorrhizal fungi (AMF) and earthworms [Aporrectodea spp. (Haplotaxida: Lumbricidae)] was colonized by aphids [Myzus persicae Sulzer (Hemiptera: Aphididae)]. The aphids preferred to colonize plants without earthworms in the soil, and the numbers of aphids remained lower on the plants with earthworms, irrespective of the presence of AMF. Although the N, C, and P concentrations of the shoots were not affected by the soil organisms, AMF increased total aboveground biomass, total N, C, and P content, and photosynthetic activity (measured as electron transport rate) in the leaves under high light intensity. These results suggest that earthworms affect chemical cues that are used by aphids to judge host quality prior to feeding. Discrimination between plants with and without exposure to earthworms by aboveground herbivores is a novel aspect of plant-mediated interactions between below- and aboveground organisms.

Earthworms affect plant performance and can influence plant–herbivore interactions. Both primary and secondary metabolites and the expression of stress-responsive genes of plants can be affected by earthworms. Plant-mediated effects of earthworms on aboveground herbivore performance range between positive and negative. These indirect, plant-mediated effects likely depend on the altered resource uptake of plants or changes in the soil microbial community composition in presence of earthworms. Studies on belowground interactions between earthworms and root herbivores focussed almost exclusively on root-feeding nematodes. These interactions can be either direct (e.g. ingesting of nematodes) or indirect, mediated by changes in host plant performance or biotic and abiotic soil characteristics. Earthworms were documented to counteract the negative effects of root-feeding nematodes on plants. Consistently, earthworm-worked soils (vermicompost) have been reported to reduce numbers of root-feeding nematodes and plant damage by aboveground herbivores. The results suggest context dependent impacts of earthworms on herbivore performance and an alleviation of herbivore damage of plants by earthworms, besides their well-known effects on plant growth. This knowledge is crucial for understanding the impact of earthworms on plants in natural environments, and may be applied as alternative plant protection in sustainable agriculture.

Activated carbon (AC) is widely used in ecological studies to elucidate the role of allelopathic substances in interspecific plant competition. However, by adsorbing chemical signalling compounds AC may also have negative effects on plants with symbiosis partners such as arbuscular mycorrhizal fungi and rhizobia. Here we test whether addition of AC has detrimental effects on the mycorrhizal root colonization of the native forb Plantago lanceolata and the exotic legume Lupinus polyphyllus, the nodulation of L. polyphyllus, and the nutrient uptake and growth of the plants growing in intra- and interspecific competition. Allelopathic effects probably occurred in the germination and seedling establishment phase when P. lanceolata suffered from the presence of L. polyphyllus. However, this negative effect of L. polyphyllus on P. lanceolata was not ameliorated by AC addition. AC negatively affected L. polyphyllus root biomass in week 4, and root and shoot biomass of P. lanceolata in week 9 of the experiment; both effects were independent of the presence and absence of the competing plant species. Mycorrhizal root colonization of both plant species was reduced in the presence of AC, although the effect tended to be stronger for L. polyphyllus. No significant effect of AC on the nodulation of L. polyphyllus was detected. P. lanceolata was the superior competitor and led to reduced biomasses of L. polyphyllus in interspecific competition. We conclude that AC can reduce the mycorrhization and performance of plants which may lead to changes in interspecific competition without the involvement of allelopathy. Contrary to former studies the AC used in our study did not enhance the nutrient availability for the plants, but reduced plant growth and mycorrhization. We suggest that the nutrient properties of the used AC are of crucial importance for the direction and the mechanisms of the effects and should always be reported.