Search

Floral traits, including floral display and nutritional rewards from pollen and nectar, drive pollinator visitation. Even within a single plant species, environmental factors can influence the quality and quantity of floral resources. Yet, the ecological interactions driving this variation in floral resources, especially those belowground, remain unknown. Here, we investigate how soil microbial community composition and nutrient availability, specifically distinct arbuscular mycorrhizal fungi (AMF) species and phosphorus (P) supply, affect plant growth, AMF traits, floral traits, and how that, in turn, affects bee visitation. We found that increased AMF richness of functional diversity enhanced floral display (flower size and number) and rewards (nectar volume and pollen protein) and increased bee visitation. Using structural equation modeling, we found that AMF associations could boost bee visitation by enhancing flower size. However, trade-offs occur; flower size correlates negatively with root colonization but positively with hyphal length, suggesting that AMF traits drive the effects of AMF on flower growth. Overall, the effect of AMF on floral traits and bee visitation was not homogenous; instead, AMF trait differences interact with P supply, resulting in varying effects on floral traits and subsequently bee foraging dynamics. These results highlight that focusing on beneficial belowground interactions could provide an opportunity to bolster bee visitation.

Positive plant diversity–productivity relationships are known to be driven by complementary resource use via differences in plant functional traits. Moreover, soil properties related to nutrient availability were shown to change with plant diversity over time; however, it is not well‐understood whether and how such plant diversity‐dependent soil changes and associated changes in functional traits contribute to positive diversity–productivity relationships in the long run. To test this, we investigated plant communities of different species richness (1, 2, 6, and 9 species) in a 15‐year‐old grassland biodiversity experiment. We determined community biomass production and biodiversity effects (net biodiversity [NEs], complementarity [CEs], and selection effects [SEs]), as well as community means of plant functional traits and soil properties. First, we tested how these variables changed along the plant diversity gradient and were related to each other. Then, we tested for direct and indirect effects of plant and soil variables influencing community biomass production and biodiversity effects. Community biomass production, NEs, CEs, SEs, plant height, root length density (RLD), and all soil property variables changed with plant diversity and the presence of the dominant grass species Arrhenatherum elatius (increase except for soil pH, which decreased). Plant height and RLD for plant functional traits, and soil pH and organic carbon concentration for soil properties, were the variables with the strongest influence on biomass production and biodiversity effects. Our results suggest that plant species richness and the presence of the dominant species, A. elatius, cause soil organic carbon to increase and soil pH to decrease over time, which increases nutrient availability favoring species with tall growth and dense root systems, resulting in higher biomass production in species‐rich communities. Here, we present an additional process that contributes to the strengthening positive diversity–productivity relationship, which may play a role alongside the widespread plant functional trait‐based explanation. [ABSTRACT FROM AUTHOR]

Summary: Herbivore population dynamics are strongly influenced by the interactions established through their shared host. Such plant‐mediated interactions can occur between different herbivore species and different life developmental stages of the same herbivore. However, whether these interactions occur between leaf‐feeding herbivores and their soil‐dwelling pupae is unknown.We studied whether tomato (Solanum lycopersicum) leaf herbivory by the American serpentine leafminer Liriomyza trifolii affects the performance of conspecific pupae exposed to the soil headspace of the plant. To gain mechanistic insights, we performed insect bioassays with the jasmonate‐deficient tomato mutant def‐1 and its wild‐type, along with phytohormones, gene expression and root volatiles analyses.Belowground volatiles accelerated leafminer metamorphosis when wild‐type plants were attacked aboveground by conspecifics. The opposite pattern was observed for def‐1 plants, in which aboveground herbivory slowed metamorphosis. Leafminer attack induced jasmonate and abscisic acid accumulation and modulated volatile production in tomato roots in a def‐1‐dependent manner.Our results demonstrate that aboveground herbivory triggers changes in root defence signalling and expression, which can directly or indirectly via changes in soil or microbial volatiles, alter pupal development time. This finding expands the repertoire of plant–herbivore interactions to herbivory‐induced modulation of metamorphosis, with potential consequences for plant and herbivore community dynamics. [ABSTRACT FROM AUTHOR]

Abstract Plants provide resources and shape the habitat of soil organisms thereby affecting the composition and functioning of soil communities. Effects of plants on soil communities are largely taxon‐dependent, but how different functional groups of herbaceous plants affect trophic niches of individual animal species in soil needs further investigation. Here, we studied the use of basal resources and trophic levels of dominating soil meso‐ and macrofauna using stable isotope ratios of carbon and nitrogen in arable fallow systems 3 and 14–16 years after abandonment. Animals were sampled from the rhizosphere of three plant species of different functional groups: a legume (Medicaco sativa), a nonlegume herb (Taraxacum officinale), and a grass (Bromus sterilis). We found virtually no consistent effects of plant identity on stable isotope composition of soil animals and on thirteen isotopic metrics that reflect general food‐web structure. However, in old fallows, the carbon isotope composition of some predatory macrofauna taxa had shifted closer to that of co‐occurring plants, which was particularly evident for Lasius, an aphid‐associated ant genus. Trophic levels and trophic‐chain lengths in food webs were similar across plant species and fallow ages. Overall, the results suggest that variations in local plant diversity of grassland communities may little affect the basal resources and the trophic level of prey consumed by individual species of meso‐ and macrofauna belowground. By contrast, successional changes in grassland communities are associated with shifts in the trophic niches of certain species, reflecting establishment of trophic interactions with time, which shapes the functioning and stability of soil food webs.

Few restoration studies consider soil invertebrates such as termites although these are present throughout many ecosystems worldwide and provide a range of ecosystem services as soil engineers. The few studies that do consider the recovery of termites after human‐induced disturbance are geographically concentrated in Africa and South America and tropical seasonal savannah ecosystems. These studies suggest that termites can in some cases recover to pre‐disturbance levels after a few years, or take up to 30 years, although with altered community composition. While termites could potentially have negative impacts on restoration efforts by damaging vegetation, their recovery was shown to have benefits on ecosystems which warrants further research into their recovery across a wider range of continents and biomes. [ABSTRACT FROM AUTHOR]

Ecosystems world‐wide experience changes in species composition in response to natural and anthropogenic changes in environmental conditions. Research to date has greatly improved our understanding of how species affect focal ecosystem functions. However, because measurements of multiple ecosystem functions have not been consistently justified for any given trophic group, it is unclear whether interpretations of research syntheses adequately reflect the contributions of consumers to ecosystems. Using model communities assembled in experimental microcosms, we examined the relationship between four numerically dominant detritivore species and six ecosystem functions that underpin fundamental aspects of carbon and nitrogen cycling above‐ and below‐ground. We tested whether ecosystem responses to changes in detritivore identity depended upon species trait dissimilarity, food web compartment (aboveground, belowground, mixed) or number of responses considered (one to six). We found little influence of detritivore species identity on brown (i.e. soil‐based) processes. Only one of four detritivore species uniquely influenced decomposition, and detritivore species did not vary in their influence on soil nitrogen pools (NO3− and NH4+), or root biomass. However, changes in detritivore identity influenced multiple aboveground ecosystem functions. That is, by serving as prey, ecosystem engineers and occasionally also as herbivores as well as detritivores, these species altered the strength of aboveground predator–herbivore interactions and plant–shoot biomass. Yet, dissimilarity of detritivore functional traits was not associated with dissimilarity of ecosystem functioning. These results serve as an important reminder that consumers influence ecosystem processes via multiple energy channels and that food web interactions set important context for consumer‐mediated effects on multiple ecosystem functions. Given that species are being lost, gained and redistributed at unprecedented rates, we can anticipate that changes in species identity will have additional ecosystem consequences beyond those predicted by species' primary functional role. [ABSTRACT FROM AUTHOR]

Summary: Plants often associate with specialized decomposer communities that increase plant litter breakdown, a phenomenon that is known as the 'home‐field advantage' (HFA). Although the concept of HFA has long considered only the role of the soil microbial community, explicit consideration of the role of the microbial community on the foliage before litter fall (i.e. the phyllosphere community) may help us to better understand HFA. We investigated the occurrence of HFA in the presence vs absence of phyllosphere communities and found that HFA effects were smaller when phyllosphere communities were removed. We propose that priority effects and interactions between phyllosphere and soil organisms can help explain the positive effects of the phyllosphere at home, and suggest a path forward for further investigation. [ABSTRACT FROM AUTHOR]

Home-field advantage of litter decomposition differs between leaves and fine roots Keywords: aboveground-belowground; home-field advantage; litter decomposition; local adaptation; plant-soil interactions EN aboveground-belowground home-field advantage litter decomposition local adaptation plant-soil interactions 995 1000 6 07/16/20 20200815 NES 200815 Introduction Litter decomposition is a fundamental process influencing carbon dynamics and nutrient cycling in terrestrial ecosystems. Because leaves and roots of the same species commonly differ substantially in their chemical compositions (Freschet I et al. i , 2012b; Ma I et al. i , 2016; Sun I et al. i , 2018), different substrate qualities may stimulate contrasting microbial communities characterized by varying metabolic requirements and catabolic capacities (Sauvadet I et al. i , 2019). In line with these results, previous microcosm incubation and field studies have also reported that root litter decomposition did not exhibit significant HFA effects (Jacobs I et al. i , 2018; Minerovic I et al. i , 2018). [Extracted from the article]

Plants provide resources and shape the habitat of soil organisms thereby affecting the composition and functioning of soil communities. Effects of plants on soil communities are largely taxon‐dependent, but how different functional groups of herbaceous plants affect trophic niches of individual animal species in soil needs further investigation. Here, we studied the use of basal resources and trophic levels of dominating soil meso‐ and macrofauna using stable isotope ratios of carbon and nitrogen in arable fallow systems 3 and 14–16 years after abandonment. Animals were sampled from the rhizosphere of three plant species of different functional groups: a legume (Medicaco sativa), a nonlegume herb (Taraxacum officinale), and a grass (Bromus sterilis). We found virtually no consistent effects of plant identity on stable isotope composition of soil animals and on thirteen isotopic metrics that reflect general food‐web structure. However, in old fallows, the carbon isotope composition of some predatory macrofauna taxa had shifted closer to that of co‐occurring plants, which was particularly evident for Lasius, an aphid‐associated ant genus. Trophic levels and trophic‐chain lengths in food webs were similar across plant species and fallow ages. Overall, the results suggest that variations in local plant diversity of grassland communities may little affect the basal resources and the trophic level of prey consumed by individual species of meso‐ and macrofauna belowground. By contrast, successional changes in grassland communities are associated with shifts in the trophic niches of certain species, reflecting establishment of trophic interactions with time, which shapes the functioning and stability of soil food webs. [ABSTRACT FROM AUTHOR]

Human activities are accelerating global biodiversity change and have resulted in severely threatened ecosystem services. A large proportion of terrestrial biodiversity is harbored by soil, but soil biodiversity has been omitted from many global biodiversity assessments and conservation actions, and understanding of global patterns of soil biodiversity remains limited. In particular, the extent to which hotspots and coldspots of aboveground and soil biodiversity overlap is not clear. We examined global patterns of these overlaps by mapping indices of aboveground (mammals, birds, amphibians, vascular plants) and soil (bacteria, fungi, macrofauna) biodiversity that we created using previously published data on species richness. Areas of mismatch between aboveground and soil biodiversity covered 27% of Earth's terrestrial surface. The temperate broadleaf and mixed forests biome had the highest proportion of grid cells with high aboveground biodiversity but low soil biodiversity, whereas the boreal and tundra biomes had intermediate soil biodiversity but low aboveground biodiversity. While more data on soil biodiversity are needed, both to cover geographic gaps and to include additional taxa, our results suggest that protecting aboveground biodiversity may not sufficiently reduce threats to soil biodiversity. Given the functional importance of soil biodiversity and the role of soils in human well‐being, soil biodiversity should be considered further in policy agendas and conservation actions by adapting management practices to sustain soil biodiversity and considering soil biodiversity when designing protected areas. Article impact statement: Given the importance of soil biodiversity for human well‐being, it should be considered in conservation policy and actions. [ABSTRACT FROM AUTHOR]

Predators can disproportionately impact the structure and function of ecosystems relative to their biomass. These effects may be exacerbated under warming in ecosystems like the Arctic, where the number and diversity of predators are low and small shifts in community interactions can alter carbon cycle feedbacks. Here, we show that warming alters the effects of wolf spiders, a dominant tundra predator, on belowground litter decomposition. Specifically, while high densities of wolf spiders result in faster litter decomposition under ambient temperatures, they result, instead, in slower decomposition under warming. Higher spider densities are also associated with elevated levels of available soil nitrogen, potentially benefiting plant production. Changes in decomposition rates under increased wolf spider densities are accompanied by trends toward fewer fungivorous Collembola under ambient temperatures and more Collembola under warming, suggesting that Collembola mediate the indirect effects of wolf spiders on decomposition. The unexpected reversal of wolf spider effects on Collembola and decomposition suggest that in some cases, warming does not simply alter the strength of top-down effects but, instead, induces a different trophic cascade altogether. Our results indicate that climate change-induced effects on predators can cascade through other trophic levels, alter critical ecosystem functions, and potentially lead to climate feedbacks with important global implications. Moreover, given the expected increase in wolf spider densities with climate change, our findings suggest that the observed cascading effects of this common predator on detrital processes could potentially buffer concurrent changes in decomposition rates. [ABSTRACT FROM AUTHOR]

The rhizosphere microbial community is a complex of organisms interconnecting in multifold ways, acting upon each other and reacting to the surrounding environment. In the present research, we evaluated the influence of dual inoculation with arbuscular mycorrhizal fungi (AMF) and microalgae (Scenedesmus incrassatulus R83 and Synechocystis sp. R10) on basil plants performance. Different modes of basil inoculation (AMF, microalgae and a combination of both) were analyzed. We characterized AMF function (colonization and glomalin-related soil proteins), acid phosphatase activity (in root and soil), plant growth, photosynthetic parameters, secondary metabolites (fluorescence indices of leaf chlorophyll content; flavonols contents; nitrogen balance index), and the activity of plant enzymes linking nitrogen and carbon metabolism (glutamate synthase, aspartate aminotransferase and NADP-malic enzyme). The highest values of biometrical data were as a result of mycorrhiza application alone and in the mixed treatments with both microalgae strains. Dual inoculation with both microalgae and AMF, stimulated mycorrhizal function (concentration of glomalin-related proteins). Indexes of secondary metabolites (flavonols and anthocyanins) increased after treatment with Scenedesmus (Al1 and AM + Al1) compared to control plants. The addition of Synechocystis alone and in combination with fungi positively influenced nitrogen balance index. Different modes of inoculation increased gas-exchange parameters in all variations of inoculations compare to control plants. The results for activities of nitrogen-carbon metabolizing enzymes demonstrated close relationships with the plant growth. The mycorrhizal root colonization of basil may bear considerable economic importance. Thus, the addition of suitable AMF to the rhizosphere would significantly improve the growth and productivity of commercial Ocimum spp. cultivation. [ABSTRACT FROM AUTHOR]

Rhizosphere-enriched microbes induced by foliar phytopathogen infection can be assembled into a functional community to enhance plant defense mechanisms. However, the functions of stably-colonizing rhizosphere microbiota are rarely investigated. In this study, Botrytis cinerea infection changed rhizosphere bacterial communities in tomato plants. The phytopathogen-infected plants recruited specific rhizosphere bacterial taxa, while several bacterial taxa stably colonized the rhizosphere, regardless of phytopathogen infection. Through the analysis of the rhizosphere bacterial community, we established a synthetic community harboring 8 phytopathogen-inducible and 30 stably-colonizing bacteria species. Furthermore, the 38-species community was simplified into a three-species community, consisting of one phytopathogen-inducible (Asticcacaulis sp.) and two stably-colonizing species (Arachidicoccus sp. And Phenylobacterium sp.). The simplified community provided a durable protection for the host plants by synergistic effects, with the phytopathogen-inducible species triggering plant defense responses and the stably-colonizing species promoting biofilm formation. The simplified community exhibited similar protective effects as the 38-species community. Moreover, the activation of oxylipin pathways in the phytopathogen-infected leaves was significantly intensified by the simplified community. However, the inhibited biosynthesis of antimicrobial divinyl ethers, including colneleic and colnelenic acid, fully abolished the community-induced plant disease resistance. In contrast, transgenic plants overexpressing SlLOX5 and SlDES1 , with higher levels of divinyl ethers, displayed stronger resistance against B. cinerea compared to wild-type plants. Collectively, these findings provided insights into the utilization of the simplified community for preventing gray mold disease. • Botrytis cinerea -infected tomato reshaped rhizosphere microbiome. • A simplified synthetic community activated plant oxylipin pathways. • Overexpression of SlLOX5 and SlDES1 increased disease resistance in tomato. [ABSTRACT FROM AUTHOR]

A decisive set of steps in the terrestrial carbon (C) cycle is the fixation of atmospheric C by plants and the subsequent C-transfer to rhizosphere microorganisms. With climate change winters are expected to become milder in temperate ecosystems. Although the rate and pathways of rhizosphere C input to soil could be impacted by milder winters, the responses remain unknown. To address this knowledge-gap, a winter-warming experiment was established in a seminatural temperate grassland to follow the C flow from atmosphere, via the plants, to different groups of soil microorganisms. In situ 13 CO2 pulse labelling was used to track C into signature fatty acids of microorganisms. The winter warming did not result in any changes in biomass of any of the groups of microorganisms. However, the C flow from plants to arbuscular mycorrhizal ( AM) fungi, increased substantially by winter warming. Saprotrophic fungi also received large amounts of plant-derived C-indicating a higher importance for the turnover of rhizosphere C than biomass estimates would suggest-still, this C flow was unaffected by winter warming. AM fungi was the only microbial group positively affected by winter warming-the group with the closest connection to plants. Winter warming resulted in higher plant productivity earlier in the season, and this aboveground change likely induced plant nutrient limitation in warmed plots, thus stimulating the plant dependence on, and C allocation to, belowground nutrient acquisition. The preferential C allocation to AM fungi was at the expense of C flow to other microbial groups, which were unaffected by warming. Our findings imply that warmer winters may shift rhizosphere C-fluxes to become more AM fungal-dominated. Surprisingly, the stimulated rhizosphere C flow was matched by increased microbial turnover, leading to no accumulation of soil microbial biomass. [ABSTRACT FROM AUTHOR]

The present study discusses physiological and biochemical nature of relationships between below- and aboveground processes affected by three different lights spectra. Our objective was to characterize the effect of light quality on Solanum lycopersicum L. by determination of the mycorrhizal function, soil enzyme activities and plant performance (growth, photosynthesis, secondary metabolites and the enzymes linking nitrogen and carbon metabolism). A growth chamber experiment was conducted with young tomato plants and the light was provided by fluorescent tubes (white light, WL) and computer controlled light system that combines four lamps with 4 cm 2 arrays of red, green, blue, amber LEDs. The combinations were RB (Red 66%, Blue 33%) and RG (Red 66%, Green 33%). Under WL mycorrhizal fungi promoted soil fertility increasing enzyme activities and this was linked to the higher plant biomass accumulation. Also, we found the same upward trend between the values of root and soil alkaline phosphatase together with acid root phosphatase activity and accumulation of flavonoids in leaves. RB light stimulated shoot biomass production and gas-exchange parameters in inoculated tomatoes. The enhancement of soil urease activity, mycorrhizal development and nitrogen content in the leaves in parallel with nitrate reductase activity were as a consequence of RG lightening. Plant responses to the light quality and quantity precise manipulation and inoculation with beneficial soil microorganisms could be perspective in extending the production economic efficiency and nutrition potential of vegetables grown in controlled environments. [ABSTRACT FROM AUTHOR]

Aims Climate change is predicted to cause both increased temperatures and changes in precipitation, leading to more severe droughts in some areas. How these changes will affect plant growth may depend in part on biotic context. Most vascular plants form symbiotic relationships with arbuscular mycorrhizal fungi (AMF), root symbionts that provide soil nutrients to plants in exchange for carbohydrates, which may reduce the effects of environmental stresses on plants. We investigated if AMF modified temperature and drought effects on plant growth, fitness and defenses against herbivory. Methods We manipulated AMF presence, temperature and water availability on bell pepper plants (Capsicum annuum L.) in a field setting to measure plant growth and fitness responses. In a growth chamber experiment, we also investigated if AMF influenced insect herbivores feeding on plants at elevated temperatures. Important findings Drought consistently reduced plant growth, and AMF did not change drought impacts. However, with sufficient water, AMF tended to benefit plant growth and flower production (but not fruit production) compared to non-mycorrhizal plants. In the growth chamber, temperature and AMF influenced plant protein and phosphorus contents, but not defensive chemistry or herbivore performance. Thus, AMF may ameliorate the effects of temperature stress due to climate change on plants by increasing growth and nutrient content, but these effects do not extend to the constitutive herbivory defenses examined here. [ABSTRACT FROM AUTHOR]

Plant-plant facilitation is a crucial ecological process, as many plant species (facilitated) require the presence of an established individual (nurse) to recruit. Some plant facilitative interactions disappear during the ontogenetic development of the facilitated plant but others persist, even when the two plants are adults. We test whether the persistence of plant facilitative interactions is explained by the phylogenetic diversity of mutualistic and non-mutualistic fungi that the nurse and the facilitated species add to the shared rhizosphere. We classify plant facilitative interactions as persistent and non-persistent interactions and quantify the phylogenetic diversity of mutualistic and non-mutualistic fungi added by the plant species to the shared rhizosphere. Our results show that the facilitated species add less phylogenetic diversity of non-mutualistic fungi when plant facilitative interactions persist than when they do not persist. However, persistent and non-persistent facilitative interactions did not differ in the phylogenetic diversity of mutualistic fungi added by the facilitated species to the shared rhizosphere. Finally, the fungal phylogenetic diversity added by the nurse to the shared rhizosphere did not differ between persistent and non-persistent interactions. This study suggests that considering the fungal associates of the plant species involved in facilitative interactions can shed light on the mechanisms of persistence for plant-plant interactions. [ABSTRACT FROM AUTHOR]

In addition to the effect of litter quality ( LQ) on decomposition, increasing evidence is demonstrating that carbon mineralization can be influenced by the past resource history, mainly through following two processes: (1) decomposer communities from recalcitrant litter environments may have a wider functional ability to decompose a wide range of litter species than those originating from richer environments, i.e., the functional breadth ( FB) hypothesis; and/or (2) decomposer communities may be specialized towards the litter they most frequently encounter, i.e., the home-field advantage ( HFA) hypothesis. Nevertheless, the functional dissimilarities among contrasting microbial communities, which are generated by the FB and the HFA, have rarely been simultaneously quantified in the same experiment, and their relative contributions over time have never been assessed. To test these hypotheses, we conducted a reciprocal transplant decomposition experiment under controlled conditions using litter and soil originating from four ecosystems along a land-use gradient (forest, plantation, grassland, and cropland) and one additional treatment using 13C-labelled flax litter allowing us to assess the priming effect ( PE) in each ecosystem. We found substantial effects of LQ on carbon mineralization (more than two-thirds of the explained variance), whereas the contribution of the soil type was fairly low (less than one-tenth), suggesting that the contrasting soil microbial communities play only a minor role in regulating decomposition rates. Although the results on PE showed that we overestimated litter-derived CO2 fluxes, litter-microbe interactions contributed significantly to the unexplained variance observed in carbon mineralization models. The magnitudes of FB and HFA were relatively similar, but the directions of these mechanisms were sometimes opposite depending on the litter and soil types. FB and HFA estimates calculated on parietal sugar mass loss were positively correlated with those calculated on enzymatic activity, confirming the idea that the interaction between litter quality and microbial community structure may modify the trajectory of carbon mineralization via enzymatic synthesis. We conclude that although litter quality was the predominant factor controlling litter mineralization, the local microbial communities and interactions with their substrates can explain a small (<5%) but noticeable portion of carbon fluxes. [ABSTRACT FROM AUTHOR]

Aims The majority of angiosperms are pollinated by animals, and this interaction is of enormous importance in both agricultural and natural systems. Pollinator behavior is influenced by plants’ floral traits, and these traits may be modified by interactions with other community members. In recent years, knowledge of ecological linkages between above- and belowground organisms has grown tremendously. Soil communities are extremely diverse, and when their interactions with plants influence floral characteristics, they have the potential to alter pollinator attraction and visitation, but plant–pollinator interactions have been neglected in studies of the direct and indirect effects of soil organism–root interactions. Here, we review these belowground interactions, focusing on the effects of nitrogen-fixing bacteria, arbuscular mycorrhizal fungi and root-feeding herbivores, and their effects on floral traits and pollinators. Further, we identify gaps in our knowledge of these indirect effects and recommend promising directions and topics that should be addressed by future research. Important Findings Belowground organisms can influence a wide variety of floral traits that are important mediators of pollinator attraction, including the number and size of flowers and nectar and pollen production. Other traits that are known to influence pollinators in some plant species, such as floral volatiles, color and nectar composition, have rarely or never been examined in the context of belowground plant interactions. Despite clear effects on flowers, relatively few studies have measured pollinator responses to belowground interactions. When these indirect effects have been studied, both arbuscular mycorrhizal fungi and root herbivores were found to shift pollinator visitation patterns. Depending on the interaction, these changes may either increase or decrease pollinator attraction. Finally, we discuss future directions for ecological studies that will more fully integrate belowground ecology with pollination biology. We advocate a multilevel approach to these questions to not only document indirect effect pathways between soil interactions and pollination but also identify the mechanisms driving changes in pollinator impacts and the resultant effects on plant fitness. A more thorough understanding of these indirect interactions will advance ecological theory and may inform management strategies in agriculture and conservation biology. [ABSTRACT FROM AUTHOR]

Plants interact with a variety of other community members that have the potential to indirectly influence each other through a shared host plant. Arbuscular mycorrhizal fungi (AMF) are generally considered plant mutualists because of their generally positive effects on plant nutrient status and growth. AMF may also have important indirect effects on plants by altering interactions with other community members. By influencing plant traits, AMF can modify aboveground interactions with both mutualists, such as pollinators, and antagonists, such as herbivores. Because herbivory and pollination can dramatically influence plant fitness, comprehensive assessment of plant-AMF interactions should include these indirect effects. To determine how AMF affect plant-insect interactions, we grew Cucumis sativus (Cucurbitaceae) under five AMF inoculum treatments and control. We measured plant growth, floral production, flower size, and foliar nutrient content of half the plants, and transferred the other half to a field setting to measure pollinator and herbivore preference of wild insects. Mycorrhizal treatment had no effect on plant biomass or floral traits but significantly affected leaf nutrients, pollinator behavior, and herbivore attack. Although total pollinator visitation did not vary with AMF treatment, pollinators exhibited taxon-specific responses, with honey bees, bumble bees, and Lepidoptera all responding differently to AMF treatments. Flower number and size were unaffected by treatments, suggesting that differences in pollinator preference were driven by other floral traits. Mycorrhizae influenced leaf K and Na, but these differences in leaf nutrients did not correspond to variation in herbivore attack. Overall, we found that AMF indirectly influence both antagonistic and mutualistic insects, but impacts depend on the identity of both the fungal partner and the interacting insect, underscoring the context dependency of plant-AMF interactions.

Plants interact with a variety of other community members that have the potential to indirectly influence each other through a shared host plant. Arbuscular mycorrhizal fungi (AMF) are generally considered plant mutualists because of their generally positive effects on plant nutrient status and growth. AMF may also have important indirect effects on plants by altering interactions with other community members. By influencing plant traits, AMF can modify aboveground interactions with both mutualists, such as pollinators, and antagonists, such as herbivores. Because herbivory and pollination can dramatically influence plant fitness, comprehensive assessment of plant-AMF interactions should include these indirect effects. To determine how AMF affect plant-insect interactions, we grew Cucumis sativus (Cucurbitaceae) under five AMF inoculum treatments and control. We measured plant growth, floral production, flower size, and foliar nutrient content of half the plants, and transferred the other half to a field setting to measure pollinator and herbivore preference of wild insects. Mycorrhizal treatment had no effect on plant biomass or floral traits but significantly affected leaf nutrients, pollinator behavior, and herbivore attack. Although total pollinator visitation did not vary with AMF treatment, pollinators exhibited taxon-specific responses, with honey bees, bumble bees, and Lepidoptera all responding differently to AMF treatments. Flower number and size were unaffected by treatments, suggesting that differences in pollinator preference were driven by other floral traits. Mycorrhizae influenced leaf K and Na, but these differences in leaf nutrients did not correspond to variation in herbivore attack. Overall, we found that AMF indirectly influence both antagonistic and mutualistic insects, but impacts depend on the identity of both the fungal partner and the interacting insect, underscoring the context-dependency of plant-AMF interactions. [ABSTRACT FROM AUTHOR]

Aims Although ecological interactions are often conceptualized and studied in a pairwise framework, ecologists recognize that the outcomes of these interactions are influenced by other members of the community. Interactions (i) between plants and insect herbivores and (ii) between plants and mycorrhizal fungi are ubiquitous in terrestrial ecosystems and may be linked via common host plants. Previous studies suggest that colonization by arbuscular mycorrhizal fungi (AMF) can modify plants’ induced responses to herbivore attack, but these indirect effects of fungal symbionts are poorly understood. I investigated the role of AMF in induced plant response to a generalist herbivore. Methods I manipulated AMF status and herbivory in Cucumis sativus L. (cucumber, Cucurbitaceae) in a greenhouse to investigate induced responses in the presence and absence of the mycorrhizal fungus Glomus intraradices (Glomeraceae). Spodoptera exigua Hübner (Noctuidae) were used to manipulate prior damage and later as assay caterpillars. I also measured G. intraradices and herbivory effects on plant N and effects on plant growth. Important Findings AMF status affected the induced response of C. sativus, underscoring the importance of incorporating the roles of plant symbionts into plant defense theory. Assay caterpillars ate significantly more leaf tissue only on mycorrhizal plants that had experienced prior damage. Despite more consumption, biomass change in these caterpillars did not differ from those feeding on plants with other treatment combinations. Leaf N content was reduced by G. intraradices but unaffected by herbivory treatments, suggesting that the observed differences in assay caterpillar feeding were due to changes in defensive chemistry that depended on AMF. [ABSTRACT FROM AUTHOR]

Copyright of Basic & Applied Ecology is the property of Urban & Fischer Verlag and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Livestock grazing can affect both above- and below-ground communities, however, the effects of grazing intensity on vertical distribution of root traits and their associations with belowground food webs are still unclear. Based on a 5-year grazing intensity experiment (i.e., no grazing, moderate grazing and heavy grazing) in a Tibetan plateau meadow, we investigated how grazing-induced changes in root traits affected soil biota (microbes and nematodes) from the surface (0–10 cm) and subsurface soils (10–20 cm). Our results showed that moderate grazing increased nematode abundance and structure complexity of the soil micro-food webs compared to no and heavy grazing, and predominantly increased herbivores and fungivores regardless of soil layers. Shifts in herbivores and fungivores were mainly driven by root quantity and quality, emphasizing the stronger bottom-up effects on the lower trophic levels of nematodes. Grazing decreased the number of omnivores-predators in the surface soil compared to no grazing, which therefore weakened predation pressure on soil nematodes lower in the trophic structure, including root herbivores, while that effect was far less pronounced in the subsurface soil. Our study demonstrated that changes in root quantity and quality were highly associated with the complexity of the soil micro-food webs under grazing scenarios. These findings warranted the ideas that combined aboveground herbivore-root-soil micro-food webs as an ecological holo is essential for sustainable management of grassland. [Display omitted] • Structure complexity of soil micro-food webs showed hump-shaped responses to grazing intensity. • The carbon\nitrogen ratio of plant root was decreased by grazing compared to no grazing scenarios. • Moderate grazing strengthened the herbivory and fungal pathways of nematode community. • The abundance of herbivores and fungivores were positively correlated with plant root quantity and quality. [ABSTRACT FROM AUTHOR]

In addition to the effect of litter quality (LQ) on decomposition, increasing evidence is demonstrating that carbon mineralisation can be influenced by the past resource history, mainly through following two processes: (i) decomposer communities from recalcitrant litter environments may have a wider functional ability to decompose a wide range of litter species than those originating from richer environments, i.e. the functional breadth (FB) hypothesis; and/or (ii) decomposer communities may be specialized towards the litter they most frequently encounter, i.e. the home‐field advantage (HFA) hypothesis. Nevertheless, the functional dissimilarities among contrasting microbial communities, which are generated by the FB and the HFA, have rarely been simultaneously quantified in the same experiment, and their relative contributions over time have never been assessed. To test these hypotheses, we conducted a reciprocal transplant decomposition experiment under controlled conditions using litter and soil originating from four ecosystems along a land‐use gradient (forest, plantation, grassland and cropland) and one additional treatment using 13C labelled flax litter allowing us to assess the priming effect (PE) in each ecosystem. We found substantial effects of LQ on carbon mineralisation (more than two‐thirds of the explained variance), whereas the contribution of the soil type was fairly low (less than one‐tenth), suggesting that the contrasting soil microbial communities play only a minor role in regulating decomposition rates. Although the results on PE showed that we overestimated litter‐derived CO2 fluxes, litter‐microbe interactions contributed significantly to the unexplained variance observed in carbon mineralisation models. The magnitudes of FB and HFA were relatively similar, but the directions of these mechanisms were sometimes opposite depending on the litter and soil types. FB and HFA estimates calculated on parietal sugar mass loss were positively correlated with those calculated on enzymatic activity, confirming the idea that the interaction between litter quality and microbial community structure may modify the trajectory of carbon mineralisation via enzymatic synthesis. We conclude that although litter quality was the predominant factor controlling litter mineralisation, the local microbial communities and interactions with their substrates can explain a small (< 5%) but noticeable portion of carbon fluxes.This article is protected by copyright. All rights reserved. [ABSTRACT FROM AUTHOR]