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Litter decomposition is a key process governing carbon and nutrient cycles in forest ecosystems that is expected to be impacted by increasing atmospheric carbon dioxide (CO2) concentrations. We conducted two complementary field studies to assess the effects of elevated CO2 on Eucalyptus tereticornis litter decomposition processes. First, we used bags of two different mesh sizes to assess the effect of macrofauna and elevated CO2 over 24 months on mass loss of litter grown under ambient CO2. We then assessed the effect of elevated CO2 during the decomposition of litter grown under each combination of (i) ambient CO2 or elevated CO2 and (ii) during a psyllid outbreak that triggered significant canopy loss or later in canopy developing when psyllid densities were low. Both macrofauna and elevated CO2 enhanced mass loss at late decay stages in the first study, with no interactive effect. Again, mass loss was greater at elevated CO2 at late decay stages in the second study, particularly for non‐psyllid‐impacted litter grown at elevated CO2. In both studies, CO2 concentration during decomposition influenced fungal assemblages and these effects were observed before any effects on decomposition were observed, with some fungi linked to saprotrophic guilds being found with higher frequency under elevated CO2. CO2 concentrations under which leaves developed and whether leaves were psyllid‐impacted was also important in shaping fungal assemblages. Synthesis. The positive effect on mass loss at late decay stages is contrary to previous findings where elevated CO2 generally reduced decomposition rates. Our results show that elevated CO2 effects on decay rates are context‐specific. Further research is required to establish the mechanisms through which this occurs to better model elevated CO2 effects on global carbon dynamics. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Climate change is manifesting through increased intensity and frequency of extreme events such as droughts and floods. Drought causes significant stress by limiting water availability, resulting in reduced plant growth and belowground carbon (C) inputs as well as plant nutrient uptake and microbial activity, thus impacting C and nutrient cycling. Severe floods can increase leaching of nutrients, which affect nutrient availability for plants and microorganisms potentially compounding drought-induced effects on C and nutrient cycles. However, few studies have assessed the interactions between drought and floods, constraining our ability to predict ecosystem-level effects of projected climate shifts toward fewer but larger rainfall events with longer dry spells between events. We conducted a study to assess how long-term drought moderates the effect of flooding on soil C, nitrogen (N) and phosphorus (P) pools across a rainfall gradient in south-eastern Australia. We collected soil monoliths from field rainfall manipulation facilities with a 5–7 years history of simulated reduced rainfall at three sites representing a rainfall gradient (∼200–800 mm) and exposed them to a 1-in-100-year flood event under laboratory conditions. We assessed nutrients and C in soil and microbial pools before and after the flood and in flood-induced leachates. The results showed that flooding caused significantly greater losses of N in leachates, with greater effect sizes in the drought treatments compared to ambient rainfall. This response was particularly pronounced for nitrate (152 % increase on average), especially at the site with the highest mean annual precipitation (>25-fold increase). This suggest that drought may significantly reduce the capacity of ecosystems to retain N following flood events, particularly in mesic ecosystems where C and nutrient pools are greater. • Flood resulted in great losses of nitrogen in leachates, particularly as nitrate. • More losses of nitrogen in leachates were observed in the drought treatments compared to ambient rainfall. • Greater nitrogen losses were recorded in the sites with higher precipitation. [ABSTRACT FROM AUTHOR]

Emerging knowledge of plant–soil biotic interactions and the role of soil organisms in shaping the world aboveground is advancing our understanding of ecosystem function. Nematodes are the most abundant animals on Earth. They are morphologically and functionally diverse, and play key roles in ecosystem function, making them ideal for developing a trait-based understanding of adaptation to the environment and for assessing their contributions to ecosystem function. Trait-based approaches allow us to capture the functional attributes of organisms beyond their taxonomic identity, provide insights on evolutionary fitness, and make global comparisons possible. We propose the nematode economics spectrum (NES), analogous to the plant economic spectrum, which describes the tradeoffs among growth, reproduction, and survival, potentially enabling us to predict the impacts of global change on nematode ecological strategies and the associated changes in ecosystem function. Trait-based approaches are being increasingly adopted to understand species' ecological strategies and how organisms influence ecosystem function. Trait-based research on soil organisms, however, remains poorly developed compared with that for plants. The abundant and diverse soil nematodes are prime candidates to advance trait-based approaches belowground, but a unified trait framework to describe nematode ecological strategies and assess their linkages with ecosystem function is lacking. We categorized nematode traits as morphological, physiological, life history, and community clusters, and proposed the nematode economics spectrum (NES) to better understand nematode ecological strategies and their association with ecosystem function. We argue that bridging the NES and the plant economics spectrum will facilitate a more holistic understanding of ecosystem carbon and nutrient cycling under global change. [ABSTRACT FROM AUTHOR]

Aims: Precipitation and soil nutrients play an important role in regulating grassland productivity. However, little is known regarding the sensitivity of grasslands to changes in water and nutrient availability and the mechanisms driving productivity responses. Methods: We examined the effects of extreme drought (65% rainfall reduction) and phosphorus fertilization on aboveground net primary production (ANPP) and plant functional traits (PFTs) of four dominant mesic grassland species in a semi-natural grassland in southeast Australia. We used piecewise structural equation modelling to determine which PFTs contribute to the treatment effects on ANPP. Results: Reduced rainfall decreased ANPP by 29% while P addition increased ANPP by 62% at the community-level. Significant drought-related reductions in ANPP were apparent for Setaria parviflora, while Cynodon dactylon was the only species exhibiting increased ANPP under P addition. There was no interaction between rainfall and P addition. Structural equation modelling indicated specific root length was a key trait underpinning community-level ANPP responses to P; this was, however, primarily driven by a single dominant (~61% of community biomass) species (Cynodon). Conclusions: Our results indicate the negative impacts of drought on ANPP – driven primarily by Setaria– were not ameliorated by P addition. The positive effect of P addition on community-level ANPP was attributed to the response of the most dominant species, Cynodon, and mediated by changes in specific root length. This study highlights the importance of understanding the link between belowground traits and ANPP for predicting dominant species' response to global change drivers. [ABSTRACT FROM AUTHOR]

Global change models indicate that rainfall patterns are likely to shift towards more extreme events concurrent with increasing atmospheric carbon dioxide concentration ([CO2]). Both changes in [CO2] and rainfall regime are known to impact above- and belowground communities, but the interactive effects of these global change drivers have not been well explored, particularly belowground. In this experimental study, we examined the effects of elevated [CO2] (ambient + 240 ppm; [eCO2]) and changes in rainfall patterns (seasonal drought) on soil microbial communities associated with forest ecosystems. Our results show that bacterial and archaeal communities are highly resistant to seasonal drought under ambient [CO2]. However, substantial taxa specific responses to seasonal drought were observed at [eCO2], suggesting that [eCO2] compromise the resistance of microbial communities to extreme events. Within the microbial community we were able to identify three types of taxa specific responses to drought: tolerance, resilience and sensitivity that contributed to this pattern. All taxa were tolerant to seasonal drought at [aCO2], whereas resilience and sensitivity to seasonal drought were much greater in [eCO2]. These results provide strong evidence that [eCO2] moderates soil microbial community responses to drought in forests, with potential implications for their long-term persistence and ecosystem functioning. [ABSTRACT FROM AUTHOR]

• Comprehensive study of 36 Australian EPN strains. • All EPN strains infected and killed larvae of Bactrocera tryoni. • Most EPN strains (84%) also caused pupal mortality. • EPN strain baited with B. tryoni was virulent against both developmental stages. • Seven EPN strains are promising candidates to control B. tryoni. Queensland fruit fly (Bactrocera tryoni) is Australia's most significant horticultural pest, yet limited options are available for its biological control. Here, we assessed the virulence and reproductive potential of 32 newly isolated Australian entomopathogenic nematode (EPN) strains of Heterorhabditis bacteriophora , Heterorhabditis indica, Heterorhabditis marelatus , Heterorhabditis zealandica and Steinernema feltiae against the late third larval instar and pupal stages of B. tryoni under laboratory conditions, and compared their performance with four commercially available strains of H. bacteriophora , H. zealandica , S. feltiae and S. carpocapsae. All EPN strains caused significant larval mortality, and, remarkably, 29 also pupal mortality. Among the EPN strains the mean LD 50 value, presented as the number of infective juveniles (IJs) per B. tryoni individual, ranged from 25 to 114 IJs per larva, and from 114 to 360 per pupa; therefore, 3.2 to 4.6× more IJs were required to kill pupae. The penetration rates of IJs in B. tryoni larvae varied from 2 to 6.8%, and the number of IJs recovered per larva varied between 2,100 to 5,683. Our findings highlight the potential of Australian EPN strains for controlling larval and pupal stages of B. tryoni. Overall, based on the three tested traits, one H. zealandica strain (Hz.NAR1), three H. indica strains (Hi.ECCH, Hi.HRN and Hi.HIE2), one H. bacteriophora strain (Hb.HIE), one H. marelatus strain (Hm.ENCBF2) and one S. feltiae strain (Sf.Y13) were found the most promising candidates as potential biological control agents against the soil inhabiting stages of B. tryoni. Further laboratory testing is required to assess their persistence under a broader range of environmental conditions before their biological control efficacy can be trialled under field conditions. [ABSTRACT FROM AUTHOR]

Altered precipitation patterns resulting from climate change will have particularly significant consequences in water-limited ecosystems, such as arid to semi-arid ecosystems, where discontinuous inputs of water control biological processes. Given that these ecosystems cover more than a third of Earth's terrestrial surface, it is important to understand how they respond to such alterations. Altered water availability may impact both aboveground and belowground communities and the interactions between these, with potential impacts on ecosystem functioning; however, most studies to date have focused exclusively on vegetation responses to altered precipitation regimes. To synthesize our understanding of potential climate change impacts on dryland ecosystems, we present here a review of current literature that reports the effects of precipitation events and altered precipitation regimes on belowground biota and biogeochemical cycling. Increased precipitation generally increases microbial biomass and fungal:bacterial ratio. Few studies report responses to reduced precipitation but the effects likely counter those of increased precipitation. Altered precipitation regimes have also been found to alter microbial community composition but broader generalizations are difficult to make. Changes in event size and frequency influences invertebrate activity and density with cascading impacts on the soil food web, which will likely impact carbon and nutrient pools. The long-term implications for biogeochemical cycling are inconclusive but several studies suggest that increased aridity may cause decoupling of carbon and nutrient cycling. We propose a new conceptual framework that incorporates hierarchical biotic responses to individual precipitation events more explicitly, including moderation of microbial activity and biomass by invertebrate grazing, and use this framework to make some predictions on impacts of altered precipitation regimes in terms of event size and frequency as well as mean annual precipitation. While our understanding of dryland ecosystems is improving, there is still a great need for longer term in situ manipulations of precipitation regime to test our model. [ABSTRACT FROM AUTHOR]

Soils represent a significant reservoir of biological diversity that underpins a broad range of key processes and moderate ecosystem service provision. Our understanding of the role that soil organisms play in ecosystems is still developing, but the increased investigation into biodiversity-ecosystem functioning relationships in soils over the past couple of decades has provided insights that have greatly enhanced our ability to sustainably manage soil biodiversity. In this review, we synthesize emerging knowledge of soil biodiversity as a natural resource that supports the functioning of terrestrial ecosystems and their delivery of ecosystem services. We explore how environmental changes alter soil biodiversity and how this in turn can affect ecosystem processes as well as resistance and resilience to environmental changes. We then discuss ways to include soil biodiversity in management strategies for sustainable production and biodiversity conservation. We conclude by highlighting key research challenges to further improve our knowledge of soil biodiversity and its management. [ABSTRACT FROM AUTHOR]

Aim To conduct the first global-scale investigation of soil nematode assemblages using a standardized approach to quantify how environmental and climatic variables influence family assemblage structure in nematodes and determine whether nematode families have restricted distributions. Location Global. Methods We collected soil nematodes within four 10 m × 10 m plots distributed evenly along a 900-m transect at each of 12 sites representing multiple ecosystem types across a latitudinal gradient (68° N to 77° S) on six continents. We assigned > 28,000 individuals to family level and trophic group morphologically. Results We recorded a total of 43 nematode families, but sites varied considerably in family richness (1-30). Families differed in their ranges with 12 families occurring at 10 or more sites, while 14 families occurred at three or fewer sites. Total nematode and trophic group abundances were generally related to soil characteristics, including bulk density and soil moisture, but we found no good predictor of family richness, diversity or evenness at the plot level. Family richness, diversity and evenness were considerably lower in the high-latitude polar desert than elsewhere, but only family diversity showed a significant, albeit weak, latitudinal gradient. Nematode assemblage composition was quite strongly related to climate: 65% and 58% of the variation in assemblage composition across sites could be accounted for by mean annual rainfall and temperature, respectively. Main conclusions Nematode families display macroecological patterns similar to other organisms, such as a positive abundance-range size relationship and restricted distribution of some families. Local nematode abundances were related to soil characteristics, but we found no relationships between family richness and environmental or climatic variables. Family composition was related to mean annual rainfall and temperature, suggesting that climate is a good predictor of local assemblage structure. As a result, climate change may have a significant impact on nematode assemblages, with potential implications for ecosystem functioning. [ABSTRACT FROM AUTHOR]

A new understanding of soil organic matter (SOM) formation and stabilization has emerged over the past decade, highlighting the importance of microbial activity, mineral association of organic matter and aggregate occlusion of organic matter to SOM persistence. To date, the contribution of microarthropods to litter decomposition and SOM formation processes has not received due consideration and theoretical and empirical models should be modified to include how these organisms impact SOM protection. Here, we highlight the biological, chemical and physical mechanisms by which microarthropods influence SOM formation both directly and indirectly. Although more data is needed to quantify the impacts of different microarthropods on SOM dynamics, we highlight areas where inclusion of microarthropods in emerging models of SOM formation could reduce model uncertainties. [ABSTRACT FROM AUTHOR]

Highlights: [•] EPNs widely deployed against root feeders have potential against fruit flies. [•] EPNs caused mortality in Bactrocera tryoni larvae while pupae were not susceptible. [•] Steinernema feltiae caused high mortality under various conditions. [•] Steinernema carpocapsae and Heterorhabditis bacteriophora caused high mortality under more restricted conditions. [ABSTRACT FROM AUTHOR]

The polar regions are experiencing rapid climate change with implications for terrestrial ecosystems. Here, despite limited knowledge, we make some early predictions on soil invertebrate community responses to predicted twenty-first century climate change. Geographic and environmental differences suggest that climate change responses will differ between the Arctic and Antarctic. We predict significant, but different, belowground community changes in both regions. This change will be driven mainly by vegetation type changes in the Arctic, while communities in Antarctica will respond to climate amelioration directly and indirectly through changes in microbial community composition and activity, and the development of, and/or changes in, plant communities. Climate amelioration is likely to allow a greater influx of non-native species into both the Arctic and Antarctic promoting landscape scale biodiversity change. Non-native competitive species could, however, have negative effects on local biodiversity particularly in the Arctic where the communities are already species rich. Species ranges will shift in both areas as the climate changes potentially posing a problem for endemic species in the Arctic where options for northward migration are limited. Greater soil biotic activity may move the Arctic towards a trajectory of being a substantial carbon source, while Antarctica could become a carbon sink. [ABSTRACT FROM AUTHOR]

Abstract: Soils support highly diverse communities, but due to the great spatial complexity at very fine scales and small size of soil organisms, our knowledge of what structures belowground communities remains limited. We used a spatially nested sampling regime (distances between samples of 0.06–122m) to develop an understanding of the relationship between soil mite and microbial community composition and properties of vegetation and underlying soil within two habitats: birch woodland and heather moorland. We found that variation in community composition of all four biotic groups investigated (Oribatida, Mesostigmata, fungi and bacteria – thus representing multiple trophic levels) was related to variation in soil properties and vegetation, but also space. These three factors (i.e. vegetation, soil properties and space) accounted for 17–36% of the variation in community composition of the biotic groups. The remaining, rather large, proportion of unexplained variation in community composition (64–87%) is likely to represent either random variation or variation related to unmeasured variables that are not spatially auto-correlated. Soil properties generally explained more variance in belowground communities than could vegetation composition. This should not be interpreted as evidence that soil properties exert a greater influence on belowground communities than vegetation composition per se, as the vegetation composition within a habitat is likely to vary at a larger spatial scale than the soil properties we measured. Vegetation composition had stronger explanatory power in the birch woodland and was more strongly related to fungal community composition than that of any other biotic group, particularly in heather moorland. This relationship may reflect the strong association between plants and their fungal symbionts and pathogens. We conclude that both vegetation composition and variation in soil properties influence belowground communities. However, the relative importance of these two factors depends on both habitat and the type of organism being studied. [Copyright &y& Elsevier]

Background: ''The enigma of soil animal species diversity'' was the title of a popular article by J. M. Anderson published in 1975. In that paper, Anderson provided insights on the great richness of species found in soils, but emphasized that the mechanisms contributing to the high species richness belowground were largely unknown. Yet, exploration of the mechanisms driving species richness has focused, almost exclusively, on above-ground plant and animal communities, and nearly 35 years later we have several new hypotheses but are not much closer to revealing why soils are so rich in species. One persistent but untested hypothesis is that species richness is promoted by small-scale environmental heterogeneity. Methodology/Principal Findings: To test this hypothesis we manipulated small-scale heterogeneity in soil properties in a one-year field experiment and investigated the impacts on the richness of soil fauna and evenness of the microbial communities. We found that heterogeneity substantially increased the species richness of oribatid mites, collembolans and nematodes, whereas heterogeneity had no direct influence on the evenness of either the fungal, bacterial or archaeal communities or on species richness of the large and mobile mesostigmatid mites. These results suggest that the heterogeneity-species richness relationship is scale dependent. Conclusions: Our results provide direct evidence for the hypothesis that small-scale heterogeneity in soils increase species richness of intermediate-sized soil fauna. The concordance of mechanisms between above and belowground communities suggests that the relationship between environmental heterogeneity and species richness may be a general property of ecological communities. [ABSTRACT FROM AUTHOR]

Aim We used a landscape-scale study of birch invasion onto heather moorland to determine the consistency of changes in vegetation type and soil properties and in the community composition of five soil organism groups. Our aim was to determine whether the degree to which soil organisms respond to natural changes and/or induced changes (e.g. changes in land-use type and climate) in habitat is consistent across trophic and taxonomic groups in the context of conservation policies for birch woodland and heather moorland. Location Mainland Scotland. Methods We sampled mesostigmatid mites, oribatid mites, fungi, bacteria and archaea in adjacent patches of birch woodland (dominated by Betula pubescens) and heather moorland (dominated by Calluna vulgaris) at 12 sites for which annual rainfall ranged between 713 and 2251 mm. Differences in community composition were visualized using non-metric multidimensional scaling based on Bray–Curtis dissimilarities. The factors contributing to differences between habitats within sites were explored using general linear models and those among sites using redundancy analysis. Results The communities of all groups differed between habitats within sites, but only the oribatid mites and fungi differed consistently between habitats across sites. Within sites, dissimilarity in fungal communities was positively related to the difference in C. vulgaris cover between habitats, whereas dissimilarities in bacteria and archaea were positively related to differences in soil pH and C:N ratio between habitats, respectively. Main conclusions The influence of vegetation type and soil properties differed between groups of soil organisms, albeit in a predictable manner, across the 12 sites. Organisms directly associated with plants (fungi), and organisms with microhabitat and resource preferences (Oribatida) were strongly responsive to changes in habitat type. The response of organisms not directly associated with plants (bacteria, archaea) depended on differences in soil properties, while organisms with less clear microhabitat and resource preferences (Mesostigmata) were not strongly responsive to either vegetation type or soil properties. These results show that it is possible to predict the impact of habitat change on specific soil organisms depending on their ecology. Moreover, the community composition of all groups was related to variation in precipitation within the study area, which shows that external factors, such as those caused by climate change, can have a direct effect on belowground communities. [ABSTRACT FROM AUTHOR]

Abstract: Microarthropods are mainly found in the organic layer of soils but show high spatial variability in abundance that remains poorly understood. A factor that could be influencing the abundance of microarthropods is the soil pore volume. Consequently, we tested the hypothesis that mite abundance is related to soil pore volume in two contrasting habitats. Heather moorland and birch woodland, with contrasting humus forms, showed high within-habitat variation in soil pore volume and mite abundance. The abundance of oribatid mites in both habitats and the abundance of mesostigmatid mites in heather moorland were strongly and positively related to the volume of pores in the range 60–300μm. This supports the hypothesis that mite abundance is influenced by soil pore volume and we stress that soil structure should be considered as an explanatory variable when studying microarthropod communities. [Copyright &y& Elsevier]

Abstract: Luronium natans (L.) Rafin. is a very rare macrophyte even though it has the ability to grow in a wide variety of habitat types. Previous studies leave two possibilities for this pattern: the species has a poor ability to disperse and establish or it is unable to grow and develop a sustainable population after colonization. Experiments on establishment of shoots, seed bank dynamics, seed germination and genetic analysis (AFLP) were conducted to establish whether L. natans disperse to new habitats within hydrologically linked water systems by means of vegetative shoots or by seeds. Shoots had high ability to establish by roots (52% in autumn shoots), but only when subjected to water depths <4cm. Seeds of L. natans has a high germinate rate (mean of 51–60%), and the density of seeds in the seed bank ranged from 635 to 3354m−2 during a year. Analysis of the genetic diversity showed that samples could be differentiated to individuals with higher diversity between populations than within population. Low ability of shoots to establish if not subjected to low water depth, high germination rate of seeds, substantial seed bank and a high genetic diversity all indicate that most colonization events depend on sexual reproduction. Genetic diversity in L. natans seems to depend on habitat type and management. Habitats subjected to high water velocities or management with weed cutting generally have a lower genetic diversity (5–6%) than habitats subjected to dredging (11%), indicating that the latter habitats favor sexual reproduction. [Copyright &y& Elsevier]

Question: Climate change has been shown to cause shifts in plant–soil feedbacks (PSFs) that may affect plant community dynamics, but the effect of prolonged drought is uncertain. We asked whether prolonged drought legacies cause shifts in PSFs due to changes in plant–soil biotic interactions. Location: Richmond, New South Wales, Australia. Methods: We collected soils from a five‐year field‐based rainfall manipulation experiment simulating ambient rainfall and drought (50% reduction) in a mesic temperate grassland. PSFs of twelve plant species representing four functional groups (C3 and C4 grasses, forbs, and legumes) were assessed when grown alone and in mixed cultures (one species from each of the four functional groups) under laboratory conditions following a standard PSF protocol in soils with ambient rainfall and drought legacies. All soils were sterilised and then re‐inoculated to create the respective treatments including a non‐inoculated control for biota‐mediated PSFs. Results: PSFs varied considerably among species and functional types in both legacy treatments. Overall, C3 grasses displayed less negative and C4 grasses less positive PSFs in soils with a legacy of prolonged drought compared with soils with ambient rainfall legacies, while PSFs for forbs and legumes were not significantly different from zero in either rainfall treatment. However, PSFs differed between species within functional groups. For example, Plantago showed positive PSFs in soils with ambient rainfall legacies but negative PSFs in soils with drought legacies while the opposite was observed for Medicago. PSFs of the mixed communities showed a trend to shift from positive to neutral in soils with drought legacies, with significant differences in PSFs observed when comparing home vs sterile soils, suggesting that drought may destabilise plant communities. Conclusions: Our results provide evidence that prolonged drought legacies can modify plant community dynamics due to species‐specific changes in PSFs that persist after droughts are alleviated. [ABSTRACT FROM AUTHOR]

Grasslands across arid and semi‐arid regions are predicted to experience reductions in precipitation frequency. Besides, grassland degradation has become a serious problem in many of these areas. Despite increasing evidence suggesting compound effects of these synchronous alterations on biotic and abiotic ecosystem constituents, we still do not know how they will impact the coupling among ecosystem constituents and its consequences on ecosystem functioning.Here, we assessed the effects of decreased precipitation frequency and grassland degradation on ecosystem coupling, quantified based on the mean strength of pairwise correlations among multispecies communities and their physicochemical environment, individual functions and ecosystem multifunctionality, and reported their relationships within a mechanistic plant–nematode–micro‐organism–soil interactions framework.Decreased precipitation frequency led to poorly coupled ecosystems, and reduced aboveground plant biomass, soil water content, soil nutrient levels, soil biota abundance and multifunctionality. By contrast, belowground plant biomass and soil potential enzyme activities increased under decreased precipitation frequency treatment. Severe degradation resulted in decoupled ecosystems and suppressed most of individual functions and multifunctionality. Using structural equation modelling, we showed that coupling had a strong direct positive effect on multifunctionality (standardized total effect: 0.74), while multifunctionality was weakened by greater soil water variation (−0.54) and higher soil pH (−0.53).The great sensitivity of ecosystem coupling to altered precipitation regimes and degradation highlights the importance of considering interactions among biotic and abiotic components when predicting early ecological impacts under changing environments. Moreover, the positive relationship between ecosystem coupling and functioning suggests that restoration of degraded grasslands may be achieved by intensifying ecological interactions. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Analyses of diverse aboveground and belowground indicators should underpin assessments of ecosystem recovery, yet monitoring many indicators is costly and their integration is challenging. Our objective was to combine indicators through a Bayesian hierarchical model to provide a comprehensive assessment of ecosystem status and identify a cost‐effective subset of indicators to provide an accurate estimate of ecosystem recovery. We assessed 59 aboveground–belowground indicators, classified into nine components of composition, structure, and function, to estimate the ecosystem status of restored rock spoils and reference forests in south‐eastern Australia. Overall ecosystem status, which integrates across ecosystem components and supporting indicators, was lower within restored forests but positively correlated with forest age. Reference forests had greater aboveground and belowground biotic structure, organic matter supply, and soil carbon stability, and trends were consistent among all of their supporting indicators. A subset of organic matter quality and nutrient cycling indicators were greater within restored forests, suggesting high ecosystem process rates, but that soil carbon may be more vulnerable to loss. Aboveground biotic structure was correlated with organic matter supply and quality, stability of soil carbon, the cycling of nutrients, and belowground biotic structure, providing evidence of aboveground–belowground coupling. A combination of four indicators representing belowground biotic structure, soil carbon stability, organic matter supply, and aboveground composition, provided a good estimate of ecosystem status at a third of the cost. Although ecosystem status can be monitored with a small set of indicators, a diversity of aboveground–belowground indicators provide a robust and comprehensive assessment of recovery. [ABSTRACT FROM AUTHOR]

Drylands comprise one-third of Earth's terrestrial surface area and support over two billion people. Most drylands are projected to experience altered rainfall regimes, including changes in total amounts and fewer but larger rainfall events interspersed by longer periods without rain. This transition will have ecosystem-wide impacts but the long-term effects on microbial communities remain poorly quantified. We assessed belowground effects of altered rainfall regimes (+ 65% and -65% relative to ambient) at six sites in arid and semi-arid Australia over a period of three years (2016–2019) coinciding with a significant natural drought event (2017–2019). Microbial communities differed significantly among semi-arid and arid sites and across years associated with variation in abiotic factors, such as pH and carbon content, along with rainfall. Rainfall treatments induced shifts in microbial community composition only at a subset of the sites (Milparinka and Quilpie). However, differential abundance analyses revealed that several taxa, including Acidobacteria, TM7, Gemmatimonadates and Chytridiomycota, were more abundant in the wettest year (2016) and that their relative abundance decreased in drier years. By contrast, the relative abundance of oligotrophic taxa such as Actinobacteria, Alpha-proteobacteria, Planctomycetes, and Ascomycota and Basidiomycota, increased during the prolonged drought. Interestingly, fungi were shown to be more sensitive to the prolonged drought and to rainfall treatment than bacteria with Basidiomycota mostly dominant in the reduced rainfall treatment. Moreover, correlation network analyses showed more positive associations among stress-tolerant dominant taxa following the drought (i.e., 2019 compared with 2016). Our result indicates that such stress-tolerant taxa play an important role in how whole communities respond to changes in aridity. Such knowledge provides a better understanding of microbial responses to predicted increases in rainfall variability and the impact on the functioning of semi-arid and arid ecosystems. [ABSTRACT FROM AUTHOR]

Aim Global biomes are often classified by mean annual temperature and precipitation, but there is significant overlap between biomes, making it difficult to interpret the role of climate in the distribution of biomes globally. Climate predictability (including long-term reliability of both seasonality and inter-annual variability) varies considerably between biomes and regulates biodiversity distribution, adaptation and evolution, but its global pattern has rarely been investigated. The aim of this study was to characterize climatic space quantitatively for major biomes of the world using temperature and precipitation predictability, and to interpret its biological implications under future climate change. Location Global. Time Period 1901-2012. Methods We calculated global gridded temperature and precipitation predictability based on an information theory approach, and compared climatic spaces defined by these measures within and across biomes. Results We show that temperature predictability has a clear latitudinal gradient, whereas precipitation predictability is geographically variable. We further show that temperature and precipitation predictability form distinct climatic spaces for major biomes across the globe, and importantly, temperature and precipitation predictability can robustly distinguish biomes that are overlapping in mean annual climate statistics. Main conclusions Climatic space created by temperature and precipitation predictability supplements the traditional biome-specific climatic spaces created by annual mean temperature and total precipitation. Quantifying measures of climate predictability helps us to understand adaptation strategies adopted by local organisms within and across biomes. Our results show that quantifying climate predictability is a simple and effective way to delineate more robustly biome climate space and its influences on macroecology and evolutionary biology, which in turn could underpin conservation efforts under future climate change, especially when prevailing climates are comparable in terms of magnitude. [ABSTRACT FROM AUTHOR]

Leaf hydraulic traits characterize plant drought tolerance and responses to climate change. Yet, plant hydraulics are biased towards northern hemisphere woody species. We collected rhizomes of several perennial grass species along a precipitation gradient in eastern Australia and grew them in an experimental pot study to investigate potential trade‐offs between drought tolerance and plant morphology.We measured the following leaf hydraulic traits: the leaf water potential (Ψleaf) at 50% and 88% loss of leaf hydraulic conductance (P50Kleaf and P88Kleaf), the Ψleaf at 50% loss of stomatal conductance (P50gs), leaf turgor loss point (TLP), leaf dry matter content (LDMC), leaf modulus of elasticity (ε), and the slope of the relationship between predawn and midday Ψleaf. We also measured basal area, tiller density, seed head density, root collar diameter, plant height, and aboveground biomass of each individual.As expected, grass species varied widely in leaf‐level drought tolerance, with loss of 88% hydraulic conductance occurring at a Ψleaf ranging from −1.52 to −4.01 MPa. However, all but one species lost leaf turgor, and most reached P50gs before this critical threshold. Taller more productive grass species tended to have drought vulnerable leaves characterized by low LDMC and less negative P88Kleaf. Species with greater tiller production experienced stomatal closure and lost turgor at more negative Ψleaf. Although our sample size was limited, we found no relationships between these species' traits and their climate of origin.Overall, we identified important hydraulic and morphological trade‐offs in Australian grasses that were surprisingly similar to those observed for woody plants: (1) xylem of taller species was less drought tolerant and (2) turgor loss occurs and stomatal closure begins before significant loss of Kleaf. These data build upon a small yet growing field of grass hydraulics and may be informative of species responses to further drought intensification in Australia. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Climate change has been shown to alter plant-soil feedbacks (PSFs, the impacts of plants on future communities via their impacts on soil biotic and abiotic properties), with implications for plant community dynamics. However, few studies have assessed effects on PSFs under field conditions or the mechanisms involved. We assessed drought effects on PSFs of four common grassland species (Lolium multiflorum, Medicago sativa , Plantago lanceolata, and Trifolium repens) in situ in a mesic grassland under ambient rainfall and prolonged drought conditions using a long-term rainfall manipulation system. The four species were first grown in monocultures in sub-plots of each of six ambient and drought plots to condition the soils. Then, each species was grown in a sub-plot conditioned by the same species ('home') and a sub-plot conditioned by each of the other three species ('away'). We found that three species (L. multiflorum, M. sativa and T. repens) produced higher biomass in their 'home' soil than away soil under ambient rainfall while they consistently grew better in away soil under drought conditions, indicating drought-induced negative shifts in PSFs. There were strong interaction effects of rainfall treatment and conditioning species on several phospholipid-derived fatty acids markers, including a marker associated with arbuscular mycorrhizal fungi (AMF). We found a significant positive correlation between PSFs and the AMF marker across all treatment combinations, indicating that PSFs were driven by changes in positive plant-soil biotic interactions. Furthermore, drought increased plant parasitic nematode abundances. We found a strong significant negative correlation between PSFs and plant parasitic nematodes across all treatment combinations, indicating that the drought-induced shifts to more negative PSFs were driven by increased negative plant-soil biotic interactions. Drought may therefore negatively impact common grassland species due to stronger negative PSFs but at the same time promote species co-existence by reducing the abundance of competitive species. • Drought induces negative PSFs in four common grassland plant species. • Negative PSFs were associated with greater root feeding nematode densities under drought. • PSF effect sizes were also correlated with indicators of beneficial plant-soil biotic interactions across all treatments. • Prolonged drought may promote species co-existence due to reduced plant competition. [ABSTRACT FROM AUTHOR]

Fungivory of mycorrhizal hyphae has a significant impact on fungal fitness and, by extension, on nutrient transfer between fungi and host plants in natural ecosystems. Mycorrhizal fungi have therefore evolved an arsenal of chemical compounds that are hypothesized to protect the hyphal tissues from being eaten, such as the protease inhibitors mycocypins. The genome of the ectomycorrhizal fungus Laccaria bicolor has an unusually high number of mycocypin‐encoding genes. We have characterized the evolution of this class of proteins, identified those induced by symbiosis with a host plant and characterized the biochemical properties of two upregulated L. bicolor mycocypins. More than half of L. bicolor mycocypin‐encoding genes are differentially expressed during symbiosis or fruiting body formation. We show that two L. bicolor mycocypins that are strongly induced during symbiosis are cysteine protease inhibitors and exhibit similar but distinct localization in fungal tissues at different developmental stages and during interaction with a host plant. Moreover, we show that these L. bicolor mycocypins have toxic and feeding deterrent effect on nematodes and collembolans, respectively. Therefore, L. bicolor mycocypins may be part of a mechanism by which this species deters grazing by different members of the soil food web. [ABSTRACT FROM AUTHOR]

Human‐induced disturbance has substantially influenced the structure and function of terrestrial ecosystems globally. However, the extent to which multiple ecosystem functions (multifunctionality) recover following anthropogenic disturbance (ecosystem recovery) remains poorly understood.We report on the first study examining the temporal dynamics in recovery of multifunctionality from 3 to 12 years after the commencement of rehabilitation following mining‐induced disturbance, and relate this information to changes in biota. We examined changes in 57 biotic (plants, microbial) and functional (soil) attributes associated with biodiversity and ecosystem services at four open‐cut coal mines in eastern Australia.Increasing time since commencement of rehabilitation was associated with increases in overall multifunctionality, soil microbial abundance, plant productivity, plant structure and soil stability, but not nutrient cycling, soil carbon sequestration nor soil nutrients. However, the temporal responses of individual ecosystem properties varied widely, from strongly positive (e.g. litter cover, fine and coarse frass, seed biomass, microbial and fungal biomass) to strongly negative (groundstorey foliage cover). We also show that sites with more developed biota tended to have greater ecosystem multifunctionality. Moreover, recovery of plant litter was closely associated with recovery of most microbial components, soil integrity and soil respiration. Overall, however, rehabilitated sites still differed from reference ecosystems a decade after commencement of rehabilitation.Synthesis and applications. The dominant role of plant and soil biota and litter cover in relation to functions associated with soil respiration, microbial function, soil integrity and C and N pools suggests that recovering biodiversity is a critically important priority in rehabilitation programs. Nonetheless, the slow recovery of most functions after a decade indicates that rehabilitation after open‐cut mining is likely to protracted. [ABSTRACT FROM AUTHOR]

Soil invertebrates are members of terrestrial ecosystems, contributing to the processing of organic matter, resulting in carbon and nutrient cycling that is essential for continuous productivity. By linking species delineations, morphological traits and measured or inferred functional roles, we demonstrate a method for functional identification of soil faunal assemblages based on molecular information. Here we align the genetic inter‐relatedness and functional trait expression in nematodes and springtails. Nematodes were assigned feeding guild, plant parasitic feeding type and coloniser‐persister (c‐p) value, with springtail sequences assigned to soil vertical stratification level, soil moisture preference and a selection of morphological traits. We found that both nematode and springtail feeding preferences show significant phylogenetic clustering. In contrast, greater dispersal was found amongst nematode coloniser‐persister (c‐p) values and springtail soil vertical stratification level and moisture preferences. Minimum patristic (p) distances between species supported the clustering amongst nematode feeding guilds, with plant feeders being separated from all other guilds by at least p = 0.99. Distances between endoparasitic, ectoparasitic and sedentary plant parasitic nematodes were also distinct with minimal distances of p = 0.35–0.72 between parasitic types. Springtail stratification level and soil moisture preferences showed greater dispersion across phylogenies, with negligible between‐group minimum patristic distances. However, nematode c‐p values and springtail moisture preference alignments indicate some genetic conservation at the genus level. These results indicate how ecosystems can direct trait conservation beyond that of environmental stimuli. Being able to assign functional traits to novel sequences will allow individual species' likely contribution to ecosystem functioning to be inferred without the need for exact taxonomic identification. More broadly, such information can advance our understanding of the evolution of soil faunal traits and the contribution of diverse soil assemblages to functional soil systems, particularly those with a high proportion of undescribed species. [ABSTRACT FROM AUTHOR]

Cattle grazing profoundly affects abiotic and biotic characteristics of ecosystems. While most research has been performed on grasslands, the effect of large managed ungulates on forest ecosystems has largely been neglected. Compared to a baseline seminatural state, we investigated how long‐term cattle grazing of birch forest patches affected the abiotic state and the ecological community (microbes and invertebrates) of the soil subsystem. Grazing strongly modified the soil abiotic environment by increasing phosphorus content, pH, and bulk density, while reducing the C:N ratio. The reduced C:N ratio was strongly associated with a lower microbial biomass, mainly caused by a reduction of fungal biomass. This was linked to a decrease in fungivorous nematode abundance and the nematode channel index, indicating a relative uplift in the importance of the bacterial energy‐channel in the nematode assemblages. Cattle grazing highly modified invertebrate community composition producing distinct assemblages from the seminatural situation. Richness and abundance of microarthropods was consistently reduced by grazing (excepting collembolan richness) and grazing‐associated changes in soil pH, Olsen P, and reduced soil pore volume (bulk density) limiting niche space and refuge from physical disturbance. Anecic earthworm species predominated in grazed patches, but were absent from ungrazed forest, and may benefit from manure inputs, while their deep vertical burrowing behavior protects them from physical disturbance. Perturbation of birch forest habitat by long‐term ungulate grazing profoundly modified soil biodiversity, either directly through increased physical disturbance and manure input or indirectly by modifying soil abiotic conditions. Comparative analyses revealed the ecosystem engineering potential of large ungulate grazers in forest systems through major shifts in the composition and structure of microbial and invertebrate assemblages, including the potential for reduced energy flow through the fungal decomposition pathway. The precise consequences for species trophic interactions and biodiversity–ecosystem function relationships remain to be established, however. [ABSTRACT FROM AUTHOR]

Nitrogen (N) inputs to terrestrial ecosystems are increasing faster than phosphorus (P) inputs, causing N:P imbalances and substantial changes in the diversity and structure of plant, soil microbial, and fauna communities. The responses of the soil micro-food web to N:P imbalances remain unclear but are crucial to understanding the impacts on ecosystem functioning. We investigated the effect of N and P additions on plant communities, edaphic properties, and nematode species diversity and composition, and assessed shifts in soil micro-food web complexity using nematode-based indices and structural equation modeling (SEM) in a nine-year nutrient addition experiment in an alpine meadow on the Tibetan Plateau. We found that N addition decreased the structure index (SI) and enrichment index (EI), indicating that N enrichment led to a simplification of the soil micro-food web. The addition of P alleviated the negative effect of N on soil micro-food web complexity but did not restore nematode community composition. The SEM supported the hypothesis that N addition simplified soil micro-food webs through increases in the N:P ratio and associated reductions in plant species richness, while P addition ameliorated the effect of N by decreasing the soil N:P ratio and increasing plant species richness. Our results highlight the positive effects of plant diversity in maintaining the complexity of the soil micro-food web. Our findings provide information that can be used to guide sustainable management and restoration of grasslands to alleviate the projected effects of future N:P imbalances on the soil micro-food web. However, efforts should be made to avoid nutrient deposition given the observed effects on both plant and nematode communities that could not be restored by alleviating the N:P imbalance through P addition. • Phosphorus alleviates soil micro-food web simplification caused by excess nitrogen. • Nematode community composition remains unrestored despite phosphorus addition. • Plant diversity is crucial for maintaining complex soil micro-food webs. • Modifying nitrogen/phosphorus ratio alone can't fully restore communities. [ABSTRACT FROM AUTHOR]

Drylands support a substantial proportion of the worlds biodiversity and are important to food production but are sensitive to changes in rainfall regimes. Altered rainfall has been shown to impact plant growth and soil microbial activity in drylands but the longer-term effect on belowground communities and biogeochemical cycles remains uncertain. We explored how four years of reduced and increased rainfall influenced soil total and available carbon (C), nitrogen (N) and phosphorus (P) content, microbial biomass and potential extracellular enzyme activity under field conditions at six dryland sites in eastern Australia. The study coincided with a severe 3-year drought that resulted in low standing plant biomass and soil C content at all sites. Microbial biomass attributes varied considerably across sites, with rainfall treatment effects limited to decreased fungal biomass and lower fungal:bacterial ratios in semi-arid Nyngan and reduced fungal:bacterial ratios and microbial biomass C in semi-arid Quilpie in reduced treatments compared with increased rainfall plots. Similarly, available soil C, N and P varied considerably among sites, with more available N and P at four and all sites, respectively, in reduced rainfall treatments particularly when compared with increased rainfall treatments. Rainfall treatments consistently influenced enzyme activity across all sites, with higher rates in increased rainfall plots indicative of greater microbial activity and enhanced nutrient cycling. Enzymatic activity associated with N cycling showed a negative relationship with available N while enzymes associated with P cycling related positively to available C and negatively to available P. This indicates that microbes invested more in production of enzymes associated with less available nutrients. Enzyme activity was not related to microbial biomass suggesting a disconnect between biomass and enzyme production and that rainfall treatments altered the ecosystem's specific enzyme activity (activity per unit of microbial biomass). Our results suggest that altered rainfall consistently impacted dryland ecosystem function, but that microbial biomass is a poor proxy for rainfall-induced changes in soil processes. • Prolonged drought has detrimental impact on plant productivity and soil carbon in drylands. • Microbial biomass appears resistant to altered rainfall regimes, but have strong effects on enzymatic activity. • Enzymatic activity was depended on available nutrient pools while microbial biomass was relying on total nutrient pools. • Reductions in water availability created asynchrony between microbial biomass and enzymatic activity. [ABSTRACT FROM AUTHOR]

• Grazing and N addition have interactive effects on soil nematode communities. • The presence of cattle decreased nematode abundance and diversity in ambient N plots. • Cattle grazing increased nematode abundance and diversity in N addition plots. • Nematodes were affected by increasing relative biomass of grasses and soil NO 3 −-N. • Cattle grazing is useful to off-set the effects of N deposition on soil nematodes. Livestock grazing and atmospheric nitrogen (N) deposition have been reported as important factors affecting soil communities. However, how different large herbivore grazing and N addition may interact to affect soil biota in grassland ecosystems is unclear. Nematodes are the most abundant metazoan in soil ecosystems, play critical roles in regulating carbon and nutrient dynamics, and are valuable bioindicators. We examined the independent and interactive effects of grazing regimes (no grazing; sheep grazing; cattle grazing; mixed grazing of sheep and cattle) and N addition (ambient N; N addition) on soil nematodes in a meadow steppe. We found that grazing and N addition interacted to influence total nematode abundance, trophic group abundance, generic richness, diversity and several nematode-based indices (maturity index, channel ratio, enrichment index). In cattle grazing treatment, N addition significantly increased total nematode abundance, and the abundance of bacterial feeders, plant feeders, and omnivore-predators, and generic richness. By contrast, in the sheep and mixed grazing treatments, N addition had a negative effect on the same variables. Moreover, N addition reduced nematode maturity, enrichment and structure indices, and enhanced nematode channel ratio, in most grazing treatments, except mixed grazing where N addition had no effect on these variables. Structural equation modeling (SEM) revealed that N addition indirectly reduced nematode abundance and richness through increased soil NO 3 −-N content, whereas the effects of grazing were associated with increased relative biomass of grasses. Our results suggested that the response of soil nematodes to N addition strongly depended on herbivore assemblages. Nitrogen addition enhanced soil nematode diversity and maintained a relatively complex and mature soil food web in the presence of cattle rather than sheep grazing. Furthermore, our study highlighted that under N deposition, cattle grazing could benefit the soil nematode community. [ABSTRACT FROM AUTHOR]

Background and aims: Dominant plants shape belowground communities, which in turn influences ecosystem functioning. Similarly, herbivores affect belowground communities through physical disturbance and redistribution of organic inputs, but also through their interactions with plants themselves. However, we know little about how grazing moderates the effects of dominant plants on belowground organisms.We established a three-year shrub removal experiment in a grazed and an ungrazed alpine meadow on the Qinghai-Tibet plateau to assess how grazing moderates the effects of a dominant plant, Dasiphora fruticosa, on nematode communities. We used piecewise structural equation modelling to assess how grazing moderates the direct effects of dominant plants and, indirect effects via changes in edaphic variables and microbial pathways.We found that 1) grazing significantly decreased nematode diversity mainly due to a reduction in omnivores; 2) there was a significant grazing by shrub interaction effect on nematode diversity, whereby shrub had a positive direct effect on nematode diversity only in the grazed meadow; 3) in the ungrazed alpine meadow, microbial diversity was a strong predictor of nematode, while in the grazed meadow, grazing suppressed the microbial pathways of shrub presence.The study shows that grazing decreases the diversity of soil communities and suppresses the interactions among soil biota, while shrub presence plays a vital role in alleviating the negative effects of grazing on understory communities. Therefore, the findings further highlight herbivory in inducing facilitation of dominant shrubs on understory community stabilization and ecosystem functioning in alpine meadows of the Qinghai-Tibetan plateau.Methods: Dominant plants shape belowground communities, which in turn influences ecosystem functioning. Similarly, herbivores affect belowground communities through physical disturbance and redistribution of organic inputs, but also through their interactions with plants themselves. However, we know little about how grazing moderates the effects of dominant plants on belowground organisms.We established a three-year shrub removal experiment in a grazed and an ungrazed alpine meadow on the Qinghai-Tibet plateau to assess how grazing moderates the effects of a dominant plant, Dasiphora fruticosa, on nematode communities. We used piecewise structural equation modelling to assess how grazing moderates the direct effects of dominant plants and, indirect effects via changes in edaphic variables and microbial pathways.We found that 1) grazing significantly decreased nematode diversity mainly due to a reduction in omnivores; 2) there was a significant grazing by shrub interaction effect on nematode diversity, whereby shrub had a positive direct effect on nematode diversity only in the grazed meadow; 3) in the ungrazed alpine meadow, microbial diversity was a strong predictor of nematode, while in the grazed meadow, grazing suppressed the microbial pathways of shrub presence.The study shows that grazing decreases the diversity of soil communities and suppresses the interactions among soil biota, while shrub presence plays a vital role in alleviating the negative effects of grazing on understory communities. Therefore, the findings further highlight herbivory in inducing facilitation of dominant shrubs on understory community stabilization and ecosystem functioning in alpine meadows of the Qinghai-Tibetan plateau.Results: Dominant plants shape belowground communities, which in turn influences ecosystem functioning. Similarly, herbivores affect belowground communities through physical disturbance and redistribution of organic inputs, but also through their interactions with plants themselves. However, we know little about how grazing moderates the effects of dominant plants on belowground organisms.We established a three-year shrub removal experiment in a grazed and an ungrazed alpine meadow on the Qinghai-Tibet plateau to assess how grazing moderates the effects of a dominant plant, Dasiphora fruticosa, on nematode communities. We used piecewise structural equation modelling to assess how grazing moderates the direct effects of dominant plants and, indirect effects via changes in edaphic variables and microbial pathways.We found that 1) grazing significantly decreased nematode diversity mainly due to a reduction in omnivores; 2) there was a significant grazing by shrub interaction effect on nematode diversity, whereby shrub had a positive direct effect on nematode diversity only in the grazed meadow; 3) in the ungrazed alpine meadow, microbial diversity was a strong predictor of nematode, while in the grazed meadow, grazing suppressed the microbial pathways of shrub presence.The study shows that grazing decreases the diversity of soil communities and suppresses the interactions among soil biota, while shrub presence plays a vital role in alleviating the negative effects of grazing on understory communities. Therefore, the findings further highlight herbivory in inducing facilitation of dominant shrubs on understory community stabilization and ecosystem functioning in alpine meadows of the Qinghai-Tibetan plateau.Conclusion: Dominant plants shape belowground communities, which in turn influences ecosystem functioning. Similarly, herbivores affect belowground communities through physical disturbance and redistribution of organic inputs, but also through their interactions with plants themselves. However, we know little about how grazing moderates the effects of dominant plants on belowground organisms.We established a three-year shrub removal experiment in a grazed and an ungrazed alpine meadow on the Qinghai-Tibet plateau to assess how grazing moderates the effects of a dominant plant, Dasiphora fruticosa, on nematode communities. We used piecewise structural equation modelling to assess how grazing moderates the direct effects of dominant plants and, indirect effects via changes in edaphic variables and microbial pathways.We found that 1) grazing significantly decreased nematode diversity mainly due to a reduction in omnivores; 2) there was a significant grazing by shrub interaction effect on nematode diversity, whereby shrub had a positive direct effect on nematode diversity only in the grazed meadow; 3) in the ungrazed alpine meadow, microbial diversity was a strong predictor of nematode, while in the grazed meadow, grazing suppressed the microbial pathways of shrub presence.The study shows that grazing decreases the diversity of soil communities and suppresses the interactions among soil biota, while shrub presence plays a vital role in alleviating the negative effects of grazing on understory communities. Therefore, the findings further highlight herbivory in inducing facilitation of dominant shrubs on understory community stabilization and ecosystem functioning in alpine meadows of the Qinghai-Tibetan plateau. [ABSTRACT FROM AUTHOR]

Abiotic factors are major determinants of soil animal distributions and their dominant role is pronounced in extreme ecosystems, with biotic interactions seemingly playing a minor role. We modelled co-occurrence and distribution of the three nematode species that dominate the soil food web of the McMurdo Dry Valleys (Antarctica). Abiotic factors, other biotic groups, and autocorrelation all contributed to structuring nematode species distributions. However, after removing their effects, we found that the presence of the most abundant nematode species greatly, and negatively, affected the probability of detecting one of the other two species. We observed similar patterns in relative abundances for two out of three pairs of species. Harsh abiotic conditions alone are insufficient to explain contemporary nematode distributions whereas the role of negative biotic interactions has been largely underestimated in soil. The future challenge is to understand how the effects of global change on biotic interactions will alter species coexistence. Tancredi Caruso et al. analyze biodiversity survey data from the McMurdo Dry Valleys, an extreme desert ecosystem in Antarctica in which abiotic factors are thought to determine species distributions. Focusing on three nematode species, they find that abiotic factors alone cannot explain the data and interaction between species have been historically underestimated. [ABSTRACT FROM AUTHOR]

It is well established that aboveground-belowground interactions moderate ecosystem functioning. The direct and indirect effects of plants on belowground communities have been explored by many studies; however, few studies have considered how grazing moderate the direction and intensity of these effects. In this study, we explored how grazing by yak moderates the effect of the shrub Dasiphora fruticosa on nematode communities through a short-term shrub removal experiment in a grazed and ungrazed alpine meadow on the Tibetan plateau. We used structural equation modelling (SEM) to assess both the direct effects of D. fruticosa and indirect effects mediated by changes in understorey vegetation composition and edaphic properties, on nematode communities. The presence of D. fruticosa had no significant impact on the abundance of nematodes in the ungrazed meadow. By contrast, D. fruticosa had a strong negative direct effect on nematode abundance, but also a positive indirect effect due to greater grass biomass, in the grazed meadow. The effect of D. fruticosa on nematode community composition was limited, with only a marginally significant direct effect on nematode community composition in the grazed meadow. Instead, nematode community composition was strongly related to soil water content and organic matter content in both grazing treatments, and soil pH in the grazed meadow. Our results indicate that grazing moderate aboveground-belowground linkages through direct and indirect shrub effects on nematode abundance, but have limited effects on nematode community composition. [ABSTRACT FROM AUTHOR]

Terrestrial microinvertebrates in Antarctica are potentially exposed to contaminants due to the concentration of human activity on ice-free areas of the continent. As such, knowledge of the response of Antarctic microinvertebrates to contaminants is important to determine the extent of anthropogenic impacts. Antarctic Philodina sp. were extracted from soils and mosses at Casey station, East Antarctica and exposed to aqueous Cu for 96 h. The Philodina sp. was sensitive to excess Cu, with concentrations of 36 μg L−1 Cu (48 h) and 24 μg L−1 Cu (96 h) inhibiting activity by 50%. This is the first study to be published describing the ecotoxicologically derived sensitivity of a rotifer from a terrestrial population to metals, and an Antarctic rotifer to contaminants. It is also the first study to utilise bdelloid rotifer cryptobiosis (chemobiosis) as a sublethal ecotoxicological endpoint. This preliminary investigation highlights the need for further research into the responses of terrestrial Antarctic microinvertebrates to contaminants. [Display omitted] • First investigation of the sensitivity of a terrestrial population of Antarctic rotifers to Cu. • The 96 h EC 50 for copper for Philodina sp. was 24 μg Cu L−1. • Chemobiosis provided a novel and useful behavioural endpoint. • This research will assist in developing Antarctic specific soil quality guidelines. [ABSTRACT FROM AUTHOR]

Soil fauna have been found to accelerate litter decomposition rates across many ecosystems, but little is known about their impact on soil organic matter formation during decomposition and their influence on ecosystem carbon and nitrogen cycling during this process. In a three-year litterbag-free decomposition study, we suppressed microarthropod abundance by 38% and tracked the fate of 13C- and 15N-labeled litter into different soil organic matter fractions and the microbial community. Microarthropod suppression slowed litter mass loss and decreased litter carbon input into the soil and soil microbes during the first 18 months of decomposition. The microarthropod suppression did not alter the total amount of carbon and nitrogen incorporated in the soil after complete surface litter mass loss. However, lower early-stage microbial carbon uptake due to lower early-stage litter inputs to the soil, as well as a significant decrease in the C:N ratio of litter-derived organic matter inputs to the mineral soil fractions, made less nitrogen available for plant uptake in the microarthropod suppression treatment. Thus, the acceleration of early-stage, more labile litter inputs to the soil altered the timing and availability of carbon and nitrogen inputs to the soil. A simulation of these effects on the tallgrass prairie ecosystem using the DayCent model predicts lower net primary productivity and lower total soil C and N mineralization when soil microarthropods are less abundant. Our results highlight the importance of soil microarthropods for ecosystem functioning through their role in transforming decomposing litter organic matter into soil organic matter and the feedback of this process to ecosystem productivity and soil C sequestration. [ABSTRACT FROM AUTHOR]

Grazing by herbivores plays a key role in grassland ecosystems, but its effects on soil fauna biodiversity are not clear in alpine meadow ecosystems, especially on the Tibetan plateau. We investigated the effects of long-term grazing disturbance of varying intensities (low disturbed site, medially disturbed site, and seriously disturbed site) on ecosystem biodiversity and functional process using soil nematode communities. Soil physicochemical characteristics and plant communities were also measured to explore the relationships between soil nematode communities structure and key environment variable. Soil samples were collected in May, June, August, and October, 2013. The abundance of total nematode communities, plant feeders and bacterivores increased with the grazing intensity increase, and predators decreased with grazing intensity increase. Low disturbed site has the lowest abundance of fungivores. Grazing disturbance has no significant influence on abundance of omnivores ( P > 0.05). Species richness was highest on seriously disturbed site and lowest on low disturbed site. MI and SI decreased as grazing intensity increase. The highest NCR was found in low disturbed site and the lowest in medially disturbed site. The highest EI was found in medially disturbed site and the lowest in low disturbed site. Principal component analysis (PCA) showed that nematode communities could be separated by three different grazing disturbance intensity sites. Redundancy analysis (RDA) showed that Helicotylenchus , Acrobeloides and Labronema were positively correlated with higher plant communities diversity. Filenchus was positively correlated with forbs biomass. Some omnivores such as Eudorylaimus and Aporcelaimus was positively correlated with soil moisture and rich nutrient resources, meanwhile, Enchodelus and Coomansus was positively correlated with biomass of sedges and grasses. Anaplectus and Prismatolaimus significantly correlated with soil moisture, nutrient resources and biomass of sedges and grasses. This study revealed that grazing herbivores can change composition, structure and diversity of soil nematode communities, and then reflect radical shift in below-ground soil faunal biodiversity and processes in alpine meadow on the Tibetan plateau. [ABSTRACT FROM AUTHOR]

Highlights: [•] Naphthalene addition to soil significantly reduces micro-arthropod abundance. [•] Naphthalene addition to soil does not alter nematodes or microbial communities. [•] Naphthalene-C does not significantly contribute to the soil CO2 efflux. [•] Bacteria can assimilate naphthalene-C with the highest incorporation in Gram−. [ABSTRACT FROM AUTHOR]

Linkages between aboveground and belowground communities are a key but globally under-researched component of responses to environmental change. Given the logistical complications to studying these relationships, much of our knowledge derives from laboratory experiments and localized field studies which have so far yielded inconsistent results. Because environmental factors may alter relationships between above- and belowground communities, there is a need for broad-scale field studies testing these interactions. The Antarctic Peninsula provides an ideal test setting, given the relatively simple communities both above- and belowground. The Peninsula is also experiencing rapid environmental changes, including alterations in species diversity and distribution both above- and belowground. Thus, an improved understanding of the broad-scale consequences of altered environments and vegetation communities for the soil microbiome is of high priority. To determine the nature and strength of the relationship between in situ plant and soil communities across a broad spatial scale and range of environmental conditions, we sampled soil communities at 9 locations (spanning 60–72°S along the Scotia Arc and Antarctic Peninsula) beneath the major aboveground habitats (moss, grass, lichen, algae and bare soil). We measured a comprehensive suite of soil physicochemical properties, microbial (bacterial and fungal) diversity and composition, and invertebrate abundance and community composition to determine the relationships between plant and soil communities. Our results suggest that, with increased environmental severity, plant cover types become more important for influencing the physicochemical soil environment, and therefore the soil microbial communities. Although we found site-specific relationships, broad-scale patterns reveal significant differences among bare soils and vegetated soils, particularly soils beneath grass and moss. This suggests that expansion of vegetation communities under current climate warming projections will be accompanied by shifts in the soil microbiome, with important implications for the ecosystem functioning with which they are associated. • We investigated plant-soil linkages across local & broad environmental gradients. • Plant cover type influenced soil bacterial, fungal, and invertebrate communities. • Aboveground-belowground linkages were strongest at moderate environmental severity. • Biological domains differed in their response to aboveground plant communities. • Antarctic "greening" with climate change will thus result in shifts in soil community. [ABSTRACT FROM AUTHOR]

For centuries ecologists have studied how the diversity and functional traits of plant and animal communities vary across biomes. In contrast, we have only just begun exploring similar questions for soil microbial communities despite soil microbes being the dominant engines of biogeochemical cycles and a major pool of living biomass in terrestrial ecosystems. We used metagenomic sequencing to compare the composition and functional attributes of 16 soil microbial communities collected from cold deserts, hot deserts, forests, grasslands, and tundra. Those communities found in plant-free cold desert soils typically had the lowest levels of functional diversity (diversity of protein-coding gene categories) and the lowest levels of phylogenetic and taxonomic diversity. Across all soils, functional beta diversity was strongly correlated with taxonomic and phylogenetic beta diversity; the desert microbial communities were clearly distinct from the nondesert communities regardless of the metric used. The desert communities had higher relative abundances of genes associated with osmoregulation and dormancy, but lower relative abundances of genes associated with nutrient cycling and the catabolism of plant-derived organic compounds. Antibiotic resistance genes were consistently threefold less abundant in the desert soils than in the nondesert soils, suggesting that abiotic conditions, not competitive interactions, are more important in shaping the desert microbial communities. As the most comprehensive survey of soil taxonomic, phylogenetic, and functional diversity to date, this study demonstrates that metagenomic approaches can be used to build a predictive understanding of how microbial diversity and function vary across terrestrial biomes. [ABSTRACT FROM AUTHOR]

In the McMurdo Dry Valleys of Antarctica, stream biota is limited by the brief availability of liquid water. The benthic microbial mats harbor diatoms that have adapted to hydrologic stresses, including numerous endemic species. We found a strong relationship between diatom community composition and flow intermittency in a data set including seven streams that spanned a gradient in flow intermittency. In particular, two genera represented by numerous endemic species in Dry Valley habitats, Hantzschia and Luticola, had high abundances in moderately and highly intermittent streams, respectively. The Shannon Index of diversity was greatest in streams with intermediate flow intermittency, with lower diversity in more stable streams resulting from lower evenness, and lower diversity in highly intermittent streams resulting from lower richness. These results indicate that multiple metrics of biodiversity may be useful in assessing the response of diatom communities to changing hydrologic regime. We propose that flow intermittency acts as a species filter that increases habitat heterogeneity in Dry Valley streams and may allow endemic species to persist. Future Antarctic warming may alter diatom community composition and habitats that act as refugia for desiccation-tolerant taxa. [ABSTRACT FROM AUTHOR]

Litter decomposition is a key step in biogeochemical cycling and energy flow underlying ecosystem function. It is well established that dominant plants influence litter decomposition through their litter quality, and by modifying edaphic properties and soil microbial activity at the local scale. Despite this, the pathways through which dominant plants influence litter decomposition remains insufficiently understood. In an alpine meadow on the Tibetan Plateau, we manipulated vegetation structure by factorial removal of shrubs (Dasiphora fruticosa) and graminoids (mainly Elymus nutans) to elucidate their effects on litter decomposition of D. fruticosa and E. nutans via changes in edaphic properties and microbial assemblages. The decomposition of D. fruticosa litter was lower when graminoids were removed, while the removal of either of the dominant species had a negative effect on E. nutant litter decomposition. These effects were attributed to changes in the relative abundance of microbial groups associated with litter decomposition induced by the dominant plants. Specifically, shifts in a subset of the bacterial community was a good predictor of litter decomposition rates, particular of E. nutans , while shifts in the composition and richness of a subset of fungal explained well D. fruticosa litter decomposition rates. This is likely due to the affinity of bacteria to utilize high quality litter (i.e. greater N content), whereas fungi are considered dominant in decomposing more recalcitrant litter. We conclude that dominant plants moderate litter decomposition through their influences on microbial taxa associated with decomposition processes. Our results provide a better understanding of the relative importance of abiotic and biotic factors in controlling litter decomposition. • Dominant plants affect litter decomposition via microbial communities. • Bacterial and fungal communities have different effects on the litter decomposition. • Soil properties modify microbial communities' effect on the litter decomposition. [ABSTRACT FROM AUTHOR]

• Oribatid mite assemblages did not respond to 3 years of elevated CO2 in a Eucalyptus woodland. • Mite communities were more aligned with soil C, N and soil pH. • Oribatid mite morphotype and OTU richness were both positively correlated to soil N Content. • Demonstrates the utility of metabarcoding for monitoring shifts in soil faunal assemblages. Elevated atmospheric carbon dioxide concentrations (eCO 2) are known to significantly impact aboveground vegetation, with cascading effects on belowground systems. However, the effects of altered biogeochemical and hydrological cycles on belowground faunal assemblages remain unclear. Oribatid mites are abundant and hyperdiverse litter decomposers, with the potential to act as bioindicators of ecosystem disturbance. Here, we assessed oribatid mite assemblages under ambient and eCO 2 (ambient +150 ppm) at the Eucalyptus Free-Air CO 2 Enrichment (EucFACE) facility using high-throughput sequencing of the mitochondrial cytochrome oxidase 1 (COI) gene. Our aims were to i) quantify the effect of eCO 2 on mite abundance and diversity, and ii) evaluate metabarcoding as a reliable approach for the rapid assessment of oribatid mite assemblages. Three years of eCO 2 exposure resulted in lower soil pH but had no significant impact on mite abundances or oribatid mite assemblage structure. Instead, mite densities were found to correlate negatively with soil NH 4 +, while oribatid species richness using both morphological and metabarcoding datasets were positively correlated with total soil nitrogen content. Additionally, metabarcoding showed that oribatid mite assemblage structure was correlated with total soil carbon and nitrogen content, and soil pH. However, dissimilarity matrices based on the two approaches were not correlated, indicating that metabarcoding can be used as a proxy for shifts in assemblage structure but cannot be directly compared with morphological datasets. This study demonstrates how metabarcoding can rapidly assess belowground assemblages, providing a useful monitoring tool under current and future climate scenarios. [ABSTRACT FROM AUTHOR]

Belowground assemblages are tightly linked to the aboveground vegetation, and often differ between plant species and vegetation types due to direct and indirect influences. However, the relative contribution of these direct and indirect influences of plants on belowground organisms differs among taxa and remains poorly understood. We established a plant removal experiment to better understand the effects of dominant plant species on nematode assemblages in an alpine meadow on the Tibetan plateau. We quantified plant community diversity, soil microbial assemblage richness and edaphic properties to explore how a dominant shrub and graminoids affect nematode assemblage structure and community-weighted mean (CWM) biomass using structural equation modelling (SEM). We found contrasting responses of nematode richness and CWM biomass of nematodes to the removal of shrubs and graminoids, including an intriguing interaction between them. The latter indicates that interactions between shrubs and graminoids modify nematode communities rather than their independent effects. Our results further suggest that dominant plants predominantly indirectly influence nematode richness through changes in biotic variables, specifically understory diversity, and bacterial and fungal richness. However, the dominant plants had no direct and limited indirect effects on CWM nematode biomass, which instead increased with soil nitrogen content, and decreased with soil pH, carbon and ammonium content. Our results provide insight into the relative role of direct and indirect influences on belowground assemblages and highlight the importance of dominant plants in maintaining belowground diversity. By contrast, edaphic properties appear more important to belowground biomass, likely reflecting longer term influences of the plant community on resource availability and quality. Vegetation changes in grassland, such as reduced dominance of shrubs and graminoids, might therefore reduce soil biodiversity relatively rapidly but contribute to longer term impacts through changes in biogeochemical cycles. • The removal of shrubs and graminoids influences soil nematode communities. • Nematode richness is affected by shrubs and graminoids via forb diversity. • Nematode richness is affected by shrubs and graminoids via microbial richness. • Nematode biomass is related to soil properties, which are not related to the removal. [ABSTRACT FROM AUTHOR]

Abiotic and biotic factors control ecosystem biodiversity, but their relative contributions remain unclear. The ultraoligotrophic ecosystem of the Antarctic Dry Valleys, a simple yet highly heterogeneous ecosystem, is a natural laboratory well-suited for resolving the abiotic and biotic controls of community structure. We undertook a multidisciplinary investigation to capture ecologically relevant biotic and abiotic attributes of more than 500 sites in the Dry Valleys, encompassing observed landscape heterogeneities across more than 200 km2. Using richness of autotrophic and heterotrophic taxa as a proxy for functional complexity, we linked measured variables in a parsimonious yet comprehensive structural equation model that explained significant variations in biological complexity and identified landscape-scale and fine-scale abiotic factors as the primary drivers of diversity. However, the inclusion of linkages among functional groups was essential for constructing the best-fitting model. Our findings support the notion that biotic interactions make crucial contributions even in an extremely simple ecosystem. Charles Lee, Daniel Laughlin et al. use structural equation modeling to analyze ecological data from more than 500 sites in the Antarctic Dry Valleys. They find that although abiotic factors are the primary drivers of biodiversity variation, biotic interactions are needed to explain the data fully and may play previously underestimated roles. [ABSTRACT FROM AUTHOR]