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Soil emissions of nitrous oxide (N2O), a potent greenhouse gas associated with agricultural systems, can be reduced by the activity of arbuscular mycorrhizal (AM) fungi. It is unclear, however, whether climate change may impact this ecosystem service provided by AM fungi. To assess the extent that warming may affect AM fungal mediation of N2O emissions from pastures, we grew lucerne (Medicago sativa, also called alfalfa) and tall fescue (Festuca arundinacea) under ambient (aT) and elevated (eT) temperature (+4 °C) regimes in the presence or absence of the AM fungus Rhizophagus irregularis. N2O emissions were measured from pots at five timepoints over a four-month period, while total plant biomass, nitrogen, phosphorus and mycorrhizal parameters (root length colonised and extraradical hyphal biomass in soil) were measured following a final destructive harvest. For both species, AM fungi significantly reduced N2O fluxes to a similar extent under both temperatures. The N2O reduction due to AM fungal inoculation was not influenced by warming. Overall, AM fungi were shown to reduce N2O emissions under current and predicted future warming scenarios for these two common pasture species, highlighting the role of microbial symbionts in mediating terrestrial feedbacks to future climate change.

Breeding for favourable root traits in food and energy crops should be considered in the context of interactions with soil biota, notably those that can increase the nutrient use efficiency of crops. Arbuscular mycorrhizal (AM) fungi can provide services to plants but a better understanding of the interactions between root traits and AM fungi is required to maximise these benefits. One source of intraspecific variation in root architecture is the allocation of resources to different root types. We hypothesized that different root types would have different traits and be colonised differently by AM fungi, either in the amount of colonisation or identity of colonisers. We studied communities colonising the seminal, coleoptile nodal and leaf nodal roots of seven Brachypodium distachyon accessions grown in three crop or pasture soils. Leaf nodal roots had low specific root length compared to coleoptile nodal and seminal roots, yet all three root types harboured similar AM fungal communities and levels of colonisation. Most of the variation in the AM fungal communities was explained by soil; significant proportions were explained by plant accession and root type but these effects were weak. Differential allocation of resources between root types is not a trait that could be selected to maximise beneficial interactions with AM fungi and we found no link between a root phenotypic trait (specific root length) and AM fungal colonisation. Accessions did vary in extent of colonisation by arbuscules, meaning B. distachyon may be a useful model to study mechanisms underlying the symbiotic interface and mycorrhizal growth response of cereals.

Mycorrhizal fungi have been linked to fire processes in natural ecosystems via their effects on litter decomposability but, to our knowledge, relationships between mycorrhizal fungi and leaf traits directly associated with aspects of flammability have not been studied. Here, we assessed the relationships among leaf traits and host mycorrhizal type for 77 species of Australian trees and shrubs to determine whether mycorrhizal type can explain variation in three aspects of leaf flammability (ignitability, fire duration, and smoulder duration). Several associations were observed between mycorrhizal type and leaf traits directly linked to flammability measures, including specific leaf area, leaf mass, leaf moisture content, and leaf chemistry. The observed patterns suggest that interactions between mycorrhizal fungi and their host plants during the growth and senescence of leaves may have subsequent effects on fire processes. However, further work is necessary to evaluate the importance of these effects in real ecosystems, including whether plants or fungi are responsible for these patterns, and we propose four questions that will further progress in this area.

Plant nutritional quality is dependent on soil nutrients and co-evolved soil microbial symbionts. Most plants associate with arbuscular mycorrhizal (AM) fungi, which alter their nutritional quality and silicon (Si) uptake from the soil. High Si concentrations reduce plant nutritional quality and can act as an effective defence both aboveground and belowground. The growth and immune function of insect herbivores is dependent on the quality of their host plants, hence the AM symbiosis and Si concentrations can impact insect growth and immunity via changes in host plant quality. The effects of AM fungi or Si on root herbivores are poorly quantified, while impacts on insect immunity are unknown. We investigated the effects of host plant colonisation by AM fungi and high root Si concentrations on plant quality alongside the growth of a root feeding insect and the immune response to entomopathogenic nematode infection. Two sugarcane varieties (Saccharum species hybrids L.) were grown under fully factorial treatment combinations of ± Si and AM/non-AM. Root feeding insects (Dermolepida albohirtum Waterhouse) fed on the plants and their immune function was assessed in a bioassay, while insect growth and root consumption were assessed in a feeding trial. We found high Si concentrations decreased insect growth and root consumption, the latter by 71%. Insect growth was reduced on plants associated with AM fungi, which was dependent on Si treatment and plant variety. Insect immunity increased by 62% on AM colonised plants, which negatively correlated with insect growth. These results demonstrate that the impacts of the AM symbiosis on root feeding insects can depend on Si availability and plant variety. Our study suggests that AM fungi can prime insect immunity, independent of host plant quality or Si concentrations, and the negative effects of AM fungi on soil dwelling insects involves immune function stimulation which, due to a growth-immunity trade-off, results in growth reduction.

Studies have shown that arbuscular mycorrhizal (AM) fungi can reduce the performance of typically detrimental root feeding insects, yet the mechanisms remain unclear. This study aimed to investigate the effects of different sources of AM inocula on plant resistance to a root feeding insect in two different soils with different silicon (Si) concentrations. Sugarcane (Saccharum spp. hybrid) was grown in high or low Si soil; plants were treated with either an inoculum comprising the native AM fungi, a commercial AM fungal inoculum or with no AM fungi. Root herbivore (Dermolepida albohirtum) performance was measured in a feeding assay. In the low Si soil AM fungi increased root Si concentrations and reduced root herbivore performance. Both commercial and native AM treatments increased root Si and also reduced root herbivore growth rates by 107% and 81%, respectively. AM colonisation positively correlated with root Si concentrations. Distinct from this, in the high Si soil AM fungi had no impact on root Si or root herbivore growth. However, root consumption was reduced; a response independent of Si concentrations. Our study suggests AM fungi can enhance Si based plant defences against root herbivores, but also highlights that interactions between AM fungi and root herbivores involves multiple mechanisms requiring further research.

Land management practices considerably influence ecosystem processes and functioning, particularly in dryland ecosystems where nutrient and water limitations have direct (via effects on productivity) and indirect (via effects on soil biota) effects on ecosystem properties. Fungi in soils and associated with roots play critical roles in soil nutrient cycling and plant nutrient acquisition, but their responses to land management practices in dryland ecosystems remain equivocal. Here we evaluate the responses of fungal communities in roots and soils associated with a Eucalyptus saligna plantation after six years of forest management practices (irrigation and fertilisation) and in two different microenvironments within treated plots, in the presence and absence of understorey grasses. We observed that the richness and evenness of fungal communities were higher in soil than in root samples, but these two parameters did not vary among any of the management treatments. Effects of fertilisation and irrigation on fungal community composition were observed and appeared to be related to variation in soil pH, moisture, and nitrogen availability. Both fertilisation and irrigation decreased the ratios of ectomycorrhizal fungi to total fungi and increased the frequencies of saprotrophic and/or plant pathogenic fungi. We observed that some OTUs were shared between soil and root-associated fungal communities but that fertilisation was associated with lower frequencies of shared OTUs, suggesting a decoupling of these communities. In the absence of grasses, where only tree roots were present, we observed fewer tight relationships between fungal occurrence in root and soil samples. Our findings highlight the importance of forest management practices for fungal community assembly processes in dryland ecosystems, which may have consequences for the predictability of fungal community dynamics and nutrient cycling.

Dieback causes a progressive reduction in plant population health, resulting in the death of plant parts and often plant death. It is prevalent in many invasive woody weeds in Australia and has been suggested as a potential mechanism for biocontrol of these species. Parkinsonia aculeata one such invasive tree in northern Australia. It has naturalised across a wide range of climatic zones and some populations have been heavily reduced by dieback occurrence. The cause(s) of dieback in parkinsonia remain elusive, although fungal endophytes have been previously implicated. In this study, we characterised the culturable fungal endophyte community of healthy and dieback-affected parkinsonia using culture-based techniques, and identified cultured isolates via amplicon sequencing of the internal transcribed spacer (ITS) of the rDNA operon. Eight isolates, identified as pathogens, were selected for a 10-week pathogenicity trial, including water stress treatments, on parkinsonia seedlings. We isolated a taxonomically diverse fungal community from parkinsonia, representing 54 unique species from 25 families. Communities were similar across healthy and dieback-affected plants, but differed by plant tissue. Of the eight putative pathogenic isolates tested in the pathogenicity trial, inoculation with Lasiodiplodia pseudotheobromae, Botryosphaeria dothidea and Pestalotiopsis mangiferae resulted in the largest lesions, but systemic infection or dieback-like symptoms were not observed in any treatment despite plant stress being induced by drought or inundation. We concluded that inoculation of parkinsonia with the tested putative fungal pathogens is unlikely to result in dieback, which has implications for future work in biocontrol of parkinsonia.

Fungi play many essential roles in ecosystems. They facilitate plant access to nutrients and water, serve as decay agents that cycle carbon and nutrients through the soil, water and atmosphere, and are major regulators of macro-organismal populations. Although technological advances are improving the detection and identification of fungi, there still exist key gaps in our ecological knowledge of this kingdom, especially related to function. Trait-based approaches have been instrumental in strengthening our understanding of plant functional ecology and, as such, provide excellent models for deepening our understanding of fungal functional ecology in ways that complement insights gained from traditional and -omics-based techniques. In this review, we synthesize current knowledge of fungal functional ecology, taxonomy and systematics and introduce a novel database of fungal functional traits (FunFun ). FunFun is built to interface with other databases to explore and predict how fungal functional diversity varies by taxonomy, guild, and other evolutionary or ecological grouping variables. To highlight how a quantitative trait-based approach can provide new insights, we describe multiple targeted examples and end by suggesting next steps in the rapidly growing field of fungal functional ecology.

Environmental forces and biotic interactions, both positive and negative, structure ecological communities, but their relative roles remain obscure despite strong theory. For instance, ecologically similar species, based on the principle of limiting similarity, are expected to be most competitive and show negative interactions. Specious communities that assemble along broad environmental gradients afford the most power to test theory, but the communities often are difficult to quantify. Microbes, specifically fungal endophytes of wood, are especially suited for testing community assembly theory because they are relatively easy to sample across a comprehensive range of environmental space with clear axes of variation. Moreover, endophytes mediate key forest carbon cycle processes, and although saprophytic fungi from dead wood typically compete, endophytic fungi in living wood may enhance success through cooperative symbioses. To classify interactions within endophyte communities, we analyzed fungal DNA barcode variation across 22 woody plant species growing in woodlands near Richmond, New South Wales, Australia. We estimated the response of endophytes to the measured wood environment (i.e., 11 anatomical and chemical wood traits) and each other using latent-variable models and identified recurrent communities across wood environments using model-based classification. We used this information to evaluate whether (1) co-occurrence patterns are consistent with strong competitive exclusion, and (2) a priori classifications by trophic mode and phylum distinguish taxa that are more likely to have positive vs. negative associations under the principle of limiting similarity. Fungal endophytes were diverse (mean = 140 taxa/sample), with differences in community composition structured by wood traits. Variation in wood water content and carbon concentration were associated with especially large community shifts. Surprisingly, after accounting for wood traits, fungal species were still more than three times more likely to have positive than negative co-occurrence patterns. That is, patterns consistent with strong competitive exclusion were rare, and positive interactions among fungal endophytes were more common than expected. Confirming the frequency of positive vs. negative interactions among fungal taxa requires experimental tests, and our findings establish clear paths for further study. Evidence to date intriguingly suggests that, across a wide range of wood traits, cooperation may outweigh combat for these fungi.

Atmospheric carbon dioxide enrichment (eCO2) can enhance plant carbon uptake and growth1,2,3,4,5, thereby providing an important negative feedback to climate change by slowing the rate of increase of the atmospheric CO2concentration6. While evidence gathered from young aggrading forests has generally indicated a strong CO2fertilization effect on biomass growth3,4,5, it is unclear whether mature forests respond to eCO2in a similar way. In mature trees and forest stands7,8,9,10, photosynthetic uptake has been found to increase under eCO2without any apparent accompanying growth response, leaving an open question about the fate of additional carbon fixed under eCO24, 5, 7,8,9,10,11. Here, using data from the first ecosystem-scale Free-Air CO2Enrichment (FACE) experiment in a mature forest, we constructed a comprehensive ecosystem carbon budget to track the fate of carbon as the forest responds to four years of eCO2exposure. We show that, although the eCO2treatment of ambient +150 ppm (+38%) induced a 12% (+247 gCm-2yr-1) increase in carbon uptake through gross primary production, this additional carbon uptake did not lead to increased carbon sequestration at the ecosystem level. Instead, the majority of the extra carbon was emitted back into the atmosphere via several respiratory fluxes, with increased soil respiration alone contributing ∼50% of the total uptake surplus. Our results call into question the predominant thinking that the capacity of forests to act as carbon sinks will be generally enhanced under eCO2, and challenge the efficacy of climate mitigation strategies that rely on CO2fertilization as a driver of increased carbon sinks in standing forests and afforestation projects.

Highly variable phenotypic responses in mycorrhizal plants challenge our functional understanding of plant-fungal mutualisms. Using non-invasive high-throughput phenotyping, we observed that arbuscular mycorrhizal (AM) fungi relieved phosphorus (P) limitation and enhanced growth of Brachypodium distachyon under P-limited conditions, while photosynthetic limitation under low nitrogen (N) was exacerbated by the fungus. However, these responses were strongly dependent on host genotype: only the faster growing genotype (Bd3-1) utilised P transferred from the fungus to achieve improved growth under P-limited conditions. Under low N, the slower growing genotype (Bd21) had a carbon and N surplus that was linked to a less negative growth response compared with the faster growing genotype. These responses were linked to the regulation of N : P stoichiometry, couples resource allocation to growth or luxury consumption in diverse plant lineages. Our results attest strongly to a mechanism in plants by which plant genotype-specific resource economics drive phenotypic outcomes during AM symbioses. Refereed/Peer-reviewed

Offspring size is a key trait for understanding the reproductive ecology of species, yet studies addressing the ecological meaning of offspring size have so far been limited to macro-organisms. We consider this a missed opportunity in microbial ecology and provide what we believe is the first formal study of offspring-size variation in microbes using reproductive models developed for macro-organisms. We mapped the entire distribution of fungal spore size in the arbuscular mycorrhizal (AM) fungi (subphylum Glomeromycotina) and tested allometric expectations of this trait to offspring (spore) output and body size. Our results reveal a potential paradox in the reproductive ecology of AM fungi: while large spore-size variation is maintained through evolutionary time (independent of body size), increases in spore size trade off with spore output. That is, parental mycelia of large-spored species produce fewer spores and thus may have a fitness disadvantage compared to small-spored species. The persistence of the large-spore strategy, despite this apparent fitness disadvantage, suggests the existence of advantages to large-spored species that could manifest later in fungal life history. Thus, we consider that solving this paradox opens the door to fruitful future research establishing the relationship between offspring size and other AM life history traits.

The spatial distribution of arbuscular mycorrhizal (AM) fungal communities has been studied at many scales, from global to local, but few studies have explored variation within the root system of individual plants. Spatial variation within root systems might be expected partly due to differences in the physiology, morphology and anatomy of different roots, as well as due to spatial variation in the composition of inoculum in soil. Here, we assessed AM fungal community variability at various local scales: within individual plant root systems and among plants separated by distances of a few centimetres to up to several metres. To do so, we sampled roots from four plant species (two grasses and two forbs) growing in a grassland experiencing experimentally altered rainfall patterns in replicated field plots. We found that AM fungal communities were highly dissimilar both within the same individual and among different plants. Communities sampled within the same root system were as dissimilar as those sampled from adjacent neighbours, but less dissimilar from those sampled at larger distances. The degree of within root system variability was as high for each watering treatment but varied among plant species in a way that was dependent on root phosphorus content. Overall, our results show that community dissimilarity levels are high even within the root systems of individual plants, possibly due to localised community assembly processes (e.g., priority effects and interactions among AM fungal species), but that the degree of homogenisation within a root system is partly dependent on host plant attributes.

Nutrient losses due to leaching from agricultural soils can be substantial but, in some cases, soil microbes such as arbuscular mycorrhizal (AM) fungi can buffer those losses. An important knowledge gap, however, is the extent to which climate change may affect AM fungal mediation of leaching via warming and drought. To investigate this, we grew lucerne (Medicago sativa) and tall fescue (Festuca arundinacea), in the presence and absence of AM fungal inoculation (Rhizophagus irregularis), under different temperature [ambient: 26 °C (aT); elevated: 30 °C (eT)] and water [well-watered: 100% soil water holding capacity (WHC); droughted: 40% WHC] treatments. After four months of plant growth, leached nutrients (PO4−, NH4+ and NO3−), plant biomass, nitrogen (N), phosphorus (P), and mycorrhizal parameters (colonization and extraradical hyphae biomass) were measured. The presence of AM fungi significantly reduced P leaching with lucerne by 46% for both temperature treatments, but P loss with tall fescue was only reduced under aT (by 48%). The negation of this benefit for tall fescue under eT was associated with a reduction in mycorrhizal root colonization, while temperature did not alter mycorrhizal root colonization of lucerne. Watering regime was not observed to influence P loss via leaching. We did not find a mycorrhizal effect on N leaching for either species; however, we found that N leaching increased under drought with lucerne and responded interactively to warming and drought with tall fescue. Overall, AM fungi significantly reduced P leaching for both species, but warming eliminated this effect for tall fescue, suggesting that warming may differentially affect P leaching depending upon plant species.

Wollemi pine (Wollemia nobilis Jones, Hill & Allen) is a critically endangered conifer and living fossil. Translocation has been proposed as a conservation strategy to establish ‘back-ups’ to the wild population; however, knowledge regarding the environmental and biotic requirements of individuals planted in new environments is limited. An experimental translocation was established in a new location in the wild with Wollemi pines planted along a light and elevation gradient. Specific abiotic soil properties and associated microbial communities were linked to Wollemi pine performance in these new locations to inform best practice for future translocations. Our results indicate that soil properties can be used to select appropriate translocation sites that ensure initial establishment and growth. One year after translocation Wollemi pine had recruited a species-specific fungal community that persisted. Species-specific bacterial communities in their soil and roots formed in the second year after planting. Translocated Wollemi pines that were unhealthy and were not growing did not have the species-specific fungal community. The long-term functional consequence of this species-specific microbial community warrants ongoing investigation. This is one of the first studies to explicitly consider the role of microbial communities during the translocation of a rare plant and such approaches will be valuable for informing best translocation practice for other rare plant species.

Phenolic compounds play a role in plant defense against herbivores. For some herbivorous insects, particularly root herbivores, host plants with high phenolic concentrations promote insect performance and tissue consumption. This positive relationship between some insects and phenolics, however, could reflect a negative correlation with other plant defenses acting against insects. Silicon is an important element for plant growth and defense, particularly in grasses, as many grass species take up large amounts of silicon. Negative impact of a high silicon diet on insect herbivore performance has been reported aboveground, but is unreported for belowground herbivores. It has been hypothesized that some silicon accumulating plants exhibit a trade-off between carbon-based defense compounds, such as phenolics, and silicon-based defenses. Here, we investigated the impact of silicon concentrations and total phenolic concentrations in sugarcane roots on the performance of the root-feeding greyback canegrub (Dermolepida albohirtum). Canegrub performance was positively correlated with root phenolics, but negatively correlated with root silicon. We found a negative relationship in the roots between total phenolics and silicon concentrations. This suggests the positive impact of phenolic compounds on some insects may be the effect of lower concentrations of silicon compounds in plant tissue. This is the first demonstration of plant silicon negatively affecting a belowground herbivore.

Breeding disease-resistant varieties is one of the most effective and economical means to combat soilborne diseases in pulse crops. Commonalities between pathogenic and mutualistic microbe colonization strategies, however, raises the concern that reduced susceptibility to pathogens may simultaneously reduce colonization by beneficial microbes. We investigate here the degree of overlap in the transcriptional response of the Phytophthora medicaginis susceptible chickpea variety 'Sonali' to the early colonization stages of either Phytophthora, rhizobial bacteria or arbuscular mycorrhizal fungi. From a total of 6476 genes differentially expressed in Sonali roots during colonization by any of the microbes tested, 10.2% were regulated in a similar manner regardless of whether it was the pathogenic oomycete or a mutualistic microbe colonizing the roots. Of these genes, 49.7% were oppositely regulated under the same conditions in the moderately Phytophthora resistant chickpea variety 'PBA HatTrick'. Chickpea varieties with improved resistance to Phytophthora also displayed lower colonization by rhizobial bacteria and mycorrhizal fungi leading to an increased reliance on N and P from soil. Together, our results suggest that marker-based breeding in crops such as chickpea should be further investigated such that plant disease resistance can be tailored to a specific pathogen without affecting mutualistic plant:microbe interactions.

The critically endangered Wollemi pine (Wollemia nobilis W. Jones, K. Hill & J. Allen) has very low levels of recruitment in the wild. Wollemi pine grows on shallow soils of poor nutrient status and high acidity and is likely to be highly dependent on microorganisms such as mycorrhizal fungi and other microorganisms that contribute to nutrient cycling in soils. The microbial communities present in soil around wild Wollemi pine and the specificity of subsequent assembly in seedling roots has never been assessed. We analysed soil fungal and bacterial communities associated with wild Wollemi pine and neighbouring co-dominant, coachwood. Root-associated assemblages in seedlings were evaluated in the presence of inoculum collected from under Wollemi pine or coachwood (Ceratopetalum apetalum) in the field. Variation partitioning revealed that fungal and bacterial community assembly in soil were associated with different processes, with fungi more strongly influenced by spatial factors and bacteria influence equally by spatial and edaphic factors. Variation in soil microbial communities in the wild affected fungal, but not bacterial assembly in roots of Wollemi pine seedlings. Wollemi pine recruited a distinct bacterial community in its roots regardless of soil origin.

In their analysis of arbuscular mycorrhizal fungal communities sampled from roots collected around the globe, Davison et al. (2015, Science 349: 970) demonstrated that these fungi exhibit low endemism and suggested that their biogeography is largely determined by local environmental conditions. Here, we show that, within similar environments, these communities are largely unpredictable based on environmental conditions and exhibit patterns that are either consistent with neutral models of community assembly or are more stochastic than what models based on environmental filtering, niche-based assembly, or neutrality would predict. We also show that the degree of unpredictability is related to geography and the characteristics of the host plant, suggesting opportunities for future research to understand assembly processes in mycorrhizal fungal communities.

C4 photosynthesis evolved multiple times in diverse lineages. Most physiological studies comparing C4 plants were not conducted at the low atmospheric CO2 prevailing during their evolution. Here, 24 C4 grasses belonging to three biochemical subtypes [nicotinamide adenine dinucleotide malic enzyme (NAD-ME), phosphoenolpyruvate carboxykinase (PCK) and nicotinamide adenine dinucleotide phosphate malic enzyme (NADP-ME)] and six major evolutionary lineages were grown under ambient (400 μL L(-1) ) and inter-glacial (280 μL L(-1) ) CO2 . We hypothesized that nitrogen-related and water-related physiological traits are associated with subtypes and lineages, respectively. Photosynthetic rate and stomatal conductance were constrained by the shared lineage, while variation in leaf mass per area (LMA), leaf N per area, plant dry mass and plant water use efficiency were influenced by the subtype. Subtype and lineage were equally important for explaining variations in photosynthetic nitrogen use efficiency (PNUE) and photosynthetic water use efficiency (PWUE). CO2 treatment impacted most parameters. Overall, higher LMA and leaf N distinguished the Chloridoideae/NAD-ME group, while NADP-ME and PCK grasses were distinguished by higher PNUE regardless of lineage. Plants were characterized by high photosynthesis and PWUE when grown at ambient CO2 and by high conductance at inter-glacial CO2 . In conclusion, the evolutionary and biochemical diversity among C4 grasses was aligned with discernible leaf physiology, but it remains unknown whether these traits represent ecophysiological adaptation.

Elevated atmospheric carbon dioxide concentrations (eCO2) 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 eCO2 (ambient +150 ppm) at the Eucalyptus Free-Air CO2 Enrichment (EucFACE) facility using high-throughput sequencing of the mitochondrial cytochrome oxidase 1 (COI) gene. Our aims were to i) quantify the effect of eCO2 on mite abundance and diversity, and ii) evaluate metabarcoding as a reliable approach for the rapid assessment of oribatid mite assemblages. Three years of eCO2 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 NH4+, 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.

Soil carbon and nutrient availability play crucial roles in ecosystem sustainability, and they are controlled by the interaction of climatic, biotic, and soil physico-chemical variables. Although soil physico-chemical properties have been recognized as vital variables for predicting soil organic carbon (SOC) and nutrients, their relative influence across broad geographical scales has yet to be evaluated when simultaneously considering many other drivers. Using boosted regression tree and structural equation modelling analyses of observations from topsoil (0–10 cm) and subsoil (20–30 cm) at 628 sites across Australia, we investigated the effects and relative influence of climate (mean annual temperature and aridity index), plant productivity, soil biodiversity (bacterial and fungal richness), and soil physical (clay and silt) and chemical (pH and iron) properties on SOC content and nutrient availability (i.e. nitrogen, phosphorus, and potassium). Among these variables, we found that soil physico-chemical properties primarily predicted the continent-scale SOC storage and nutrient availability. In contrast, climate, plant productivity, and soil biodiversity played relatively small roles. The importance of physico-chemical properties was evident across soil depths and ecosystem types (i.e. tropical, temperate, arid, and cropland). Our findings point to the need to better understand the role of soil physico-chemical properties in soil carbon and nutrient cycling and including these variables in predictions of SOC and nutrient dynamics at the ecosystem to continental scale.

Spore size, colour and melanin content are hypothesised to be functional in relation to environmental stress. Here, we studied AM fungal spores in arid environments of Australia and in an experimental platform simulating altered rainfall. We used microscopy and image analysis to measure spore colour and size, and a quantitative colorimetric assay to estimate melanin content in spores. In arid sites, melanin content tended to increase with increasing aridity. We observed a large range of spore colours at all sites but found a higher proportion of both dark and light spores, and fewer intermediate colours, in drier sites. Spore abundance and size varied among sites, but neither were related to aridity. In the experimental platform established in a grassland, we found no evidence that altered rainfall influenced spore traits. This study identifies traits associated with environmental stress to inform future work into AM fungal life history and assembly processes.

Increased soil carbon (C) gains projected to occur with elevated CO2 (eCO2) might be negated by higher C losses via soil organic matter (SOM) decomposition. The impact of eCO2 on soil C is usually measured as a change in total soil C which inevitably confounds C gains and losses occurring simultaneously. Furthermore, the impacts of eCO2 on C gains and losses may differ for contrasting soil organic substrates due to their distinctive physicochemical and microbiological characteristics. Projecting the impacts of eCO2 on soil C greatly depends on quantifying its individual effects on C gains and losses, which is rarely done in field settings. We used a novel combination of litter bag and isotopic approaches to study temporal C dynamics in two organic substrates: root litter and mineral soil C (SOM-C) to assess C dynamics in a mature Eucalyptus woodland under CO2 enrichment (EucFACE). We aimed to isotopically separate different C pools for both substrates: a new C pool (Cnew, plant-derived C from the study site) and a pre-existent, old C pool (Cold, present in the original substrates). We also performed comprehensive microbial community analyses to investigate relationships between microbial community structure and individual C pools. We found higher root litter mass losses and slightly greater SOM-C Cold losses with eCO2 during summer months. Gains of Cnew were not affected by eCO2, except for SOM-C during summer, which is linked with the observed Cold losses from SOM-C. Moreover, fungal abundance in root litter increased with eCO2 but decreased in SOM-C. Temporal changes rather than eCO2-induced changes in microbial communities were related to C dynamics. Taken together our results suggest that eCO2 did not lead to significant Cnew gains but instead lead to moderate enhancement of Cnew and Cold losses, suggesting limited capacity for increased C sequestration of this mature woodland.

Cryptococcosis is a fungal infection caused by members of the Cryptococcus gattii and C. neoformans species complexes. The C. gattii species complex has a strong environmental association with eucalypt hollows (particularly Eucalyptus camaldulensis), which may present a source of infection. It remains unclear whether a specific mycobiome is required to support its environmental survival and growth. Conventional detection of environmental Cryptococcus spp. involves culture on differential media, such as Guizotia abyssinica seed agar. Next‐generation sequencing (NGS)‐based culture‐independent identification aids in contextualising these species in the environmental mycobiome. Samples from 23 Australian tree hollows were subjected to both culture‐ and amplicon‐based metagenomic analysis to characterize the mycobiome and assess relationships between Cryptococcus spp. and other fungal taxa. The most abundant genera detected were Coniochaeta, Aspergillus, and Penicillium, all being commonly isolated from decaying wood. There was no correlation between the presence of Cryptococcus spp. in a tree hollow and the presence of any other fungal genus. Some differences in the abundance of numerous taxa were noted in a differential heat tree comparing samples with or without Cryptococcus‐NGS reads. The study expanded the known environmental niche of the C. gattii and C. neoformans species complexes in Australia with detections from a further five tree species. Discrepancies between the detection of Cryptococcus spp. using culture or NGS suggest that neither is superior per se and that, rather, these methodologies are complementary. The inherent biases of amplicon‐based metagenomics require cautious interpretation of data through consideration of its biological relevance.

Fungal communities often form on ephemeral substrates and dispersal is critical for the persistence of fungi among the islands that form these metacommunities. Within each substrate, competition for space and resources is vital for the local persistence of fungi. The capacity to detect and respond by dispersal away from unfavorable conditions may confer higher fitness in fungi. Informed dispersal theory posits that organisms are predicted to detect information about their surroundings which may trigger a dispersal response. As such, we expect that fungi will increase allocation to dispersal in the presence of a strong competitor.In a laboratory setting, we tested how competition with other filamentous fungi affected the development of conidial pycnidiomata (asexual fruiting bodies) in Phacidium lacerum over 10 days. Phacidium lacerum was not observed to produce more asexual fruiting bodies or produce them earlier when experiencing interspecific competition with other filamentous fungi. However, we found that a trade‐off existed between growth rate and allocation to dispersal. We also observed a defensive response to specific interspecific competitors in the form of hyphal melanization of the colony which may have an impact on the growth rate and dispersal trade‐off.Our results suggest that P. lacerum have the capacity to detect and respond to competitors by changing their allocation to dispersal and growth. However, allocation to defence may come at a cost to growth and dispersal. Thus, it is likely that optimal life history allocation in fungi constrained to ephemeral resources will depend on the competitive strength of neighbors surrounding them.

Future climate scenarios predict changes in rainfall regimes. These changes are expected to affect plants via effects on the expression of root traits associated with water and nutrient uptake. Associated microorganisms may also respond to these new precipitation regimes, either directly in response to changes in the soil environment or indirectly in response to altered root trait expression. We characterized arbuscular mycorrhizal (AM) fungal communities in an Australian grassland exposed to experimentally altered rainfall regimes. We used Illumina sequencing to assess the responses of AM fungal communities associated with four plant species sampled in different watering treatments and evaluated the extent to which shifts were associated with changes in root traits. We observed that altered rainfall regimes affected the composition but not the richness of the AM fungal communities, and we found distinctive communities in the increased rainfall treatment. We found no evidence of altered rainfall regime effects via changes in host physiology because none of the studied traits were affected by changes in rainfall. However, specific root length was observed to correlate with AM fungal richness, while concentrations of phosphorus and calcium in root tissue and the proportion of root length allocated to fine roots were correlated to community composition. Our study provides evidence that climate change and its effects on rainfall may influence AM fungal community assembly, as do plant traits related to plant nutrition and water uptake. We did not find evidence that host responses to altered rainfall drive AM fungal community assembly in this grassland ecosystem.

Summary Climate change models predict more extreme rainfall patterns, ranging from droughts to deluges, which will inevitably affect primary productivity in many terrestrial ecosystems. Insects within the ecosystem, living above- and below-ground, may modify plant responses to water stress. For example, some functional groups improve soil conditions via resource provision, potentially alleviating water stress. Enhanced resource provision may, however, render plants more susceptible to herbivores and negate beneficial effects. Using a model system, we tested how plants (Brassica oleracea) responded to drought, ambient and increased precipitation scenarios when interacting with both a soil conditioning ecosystem engineer (dung beetles; Bubas bison) and an above-ground herbivore, the major crop pest diamondback moth (Plutella xylostella). Dung beetles enhanced soil water retention by 10% and promoted growth in plants subjected to drought by 280%, relieving the impacts of water stress on plants. Under drought conditions, plants grown with dung beetles had c. 30% more leaves and were over twice as tall as those without dung beetles. Dung beetles produced a 2·7-fold increase in nitrogen content and more than a threefold increase in carbon content of the shoots, though shoot concentrations of nitrogen and carbon were unchanged. Carbon concentrations in roots, however, were increased by dung beetles under both ambient and increased precipitation regimes. Increased precipitation reduced root and shoot nitrogen concentrations by 16% and 30%, relative to plants under ambient regimes, respectively, most likely due to dilution effects of increased plant growth under increased precipitation. Soil carbon and nitrogen concentrations were largely unaffected. While dung beetles enhanced plant growth and nitrogen content in plants experiencing drought, the anticipated increase in plant suitability to herbivores did not arise, possibly because shoot nitrogen concentrations and C:N ratio were unaffected. To our knowledge, this is the first report of an insect ecosystem engineer alleviating the effects of predicted drought events on plants via physical manipulation of the soil matrix. Moreover, their effects did not change plant suitability to an above-ground herbivore, pointing to potential beneficial role for insect ecosystem engineers in climate change adaptation and crop protection.

Non-native plants introduced to new habitats can have significant ecological impact. In many cases, even though they interact with the same community of potential herbivores as their new native competitors, they regularly receive less damage. Plants produce secondary metabolites in their leaves that serve a range of defensive functions, including resistance to herbivores and pathogens. Abiotic factors such as nutrient availability can influence the expression of defensive traits, with some species exhibiting increased chemical defense in low-nutrient conditions. Plants in the genus Lonicera are known to produce a diverse array of these secondary metabolites, yet non-native Lonicera species sustain lower amounts of herbivore damage than co-occurring native Lonicera species in North America. In this study, we searched for evidence of biochemical novelty in non-native species, and quantified its association with resistance to herbivores. In order to achieve this, we evaluated the phenolic and iridoid glycoside profiles in leaves of native and non-native Lonicera species grown under high and low fertilization treatments in a common garden. We then related these profiles to naturally occurring herbivore damage on whole plants in the garden. Herbivore damage was greater on native Lonicera, and chemical profiles and concentrations of selected putative defense compounds varied by species. Geographic origin was an inconsistent predictor of chemical variation in detected phenolics and iridoid glycosides (IGs). Overall, fertilization did not affect herbivore damage or measures of phenolics or IGs, but there were some fertilization effects within species. While we cannot conclude that non-natives were more chemically novel than native Lonicera species, chemical defense profiles and concentrations of specific compounds varied by species. Reduced attraction or deterrence of oviposition, specific direct resistance traits, or a combination of both may contribute to reduced herbivory and competitive advantages for non-native Lonicera in North America.

Microbial communities are enigmatically diverse. We propose a novel view of processes likely affecting microbial assemblages, which could be viewed as the Great American Interchange en miniature: the wholesale exchange among microbial communities resulting from moving pieces of the environment containing entire assemblages. Incidental evidence for such 'community coalescence' is accumulating, but such processes are rarely studied, likely because of the absence of suitable terminology or a conceptual framework. We provide the nucleus for such a conceptual foundation for the study of community coalescence, examining factors shaping these events, links to bodies of ecological theory, and we suggest modeling approaches for understanding coalescent communities. We argue for the systematic study of community coalescence because of important functional and applied consequences.

Background and aims Dieback is pervasive in many populations of invasive woody weeds globally. Previous studies on dieback have focused on specific potential causative biotic agents, but most cases remain unexplained. The potential role of endophytic microbial communities in dieback, including the relative importance of endophytes with pathogenic or protective capabilities, remains poorly studied. We tested whether changes in archaeal, bacterial and fungal endophyte community structure is associated with dieback occurrence in the invasive, leguminous tree, Parkinsonia aculeata L. (parkinsonia). Methods We sampled roots, stems and stem tips from healthyanddieback-affectedparkinsoniaandconducted terminal restriction fragment length polymorphism (TRFLP) analysis on DNA extracted from these samples using domain-specific primers for archaea, bacteria and higher fungi. Results Microbial community composition strongly differed with parkinsonia disease status (archaea, bacteria and fungi) and plant part (archaea and fungi). Plant part and disease status effects were strongest in archaea. We also found evidence implicating both pathogenic and potentially protective endophytes in the onset of dieback. Conclusions This is the first study that has shown significant associations between changes in endophyte community composition and dieback presence. Our results highlight the complexity of those changes and provide support for the hypothesis that diverse pathogenic and protective endophytes may be implicated in dieback.

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

Fungal ecology lags behind in the use of traits (i.e. phenotypic characteristics) to understand ecological phenomena. We argue that this is a missed opportunity and that the selection and systematic collection of trait data throughout the fungal kingdom will reap major benefits in ecological and evolutionary understanding of fungi. To develop our argument, we first employ plant trait examples to show the power of trait-based approaches in understanding ecological phenomena such as identifying species allocation resources patterns, inferring community assembly and understanding diversityeecosystem functioning relationships. Second, we discuss ecologically relevant traits in fungi that could be used to answer such ecological phenomena and can be measured on a large proportion of the fungal kingdom. Third, we identify major challenges and opportunities for widespread, coordinated collection and sharing of fungal trait data. The view that we propose has the potential to allow mycologists to contribute considerably more influential studies in the area of fungal ecology and evolution, as has been demonstrated by comparable earlier efforts by plant ecologists. This represents a change of paradigm, from community profiling efforts through massive sequencing tools, to a more mechanistic understanding of fungal ecology.

Aims Soil biota regulate essential ecosystem processes but our understanding of how soil fertility constrains biotic interactions remains limited. We investigated belowground responses to short-term phosphorus (P) fertilization in a P-limited woodland.

In this perspectives paper we highlight a heretofore underused statistical method in soil ecological research, structural equation modeling (SEM). SEM is commonly used in the general ecological literature to develop causal understanding from observational data, but has been more slowly adopted by soil ecologists. We provide some basic information on the many advantages and possibilities associated with using SEM and provide some examples of how SEM can be used by soil ecologists to shift focus from describing patterns to developing causal understanding and inspiring new types of experimental tests. SEM is a promising tool to aid the growth of soil ecology as a discipline, particularly by supporting research that is increasingly hypothesis-driven and interdisciplinary, thus shining light into the black box of interactions belowground.

Global change alters the composition and functioning of ecosystems by creating novel environmental conditions and thereby selecting for specific traits of organisms. Thus, trait-based approaches are promising tools to more mechanistically understand compositional and functional shifts in ecological communities as well as the dependency of response and effect traits upon global change. Such approaches have been particularly successful for the study of plant communities in terrestrial ecosystems. However, given the intimate linkages between aboveground and belowground compartments as well as the significance of plants as integrating organisms across those compartments, the role of plant traits in affecting soils communities has been understudied. This special issue contains empirical studies and reviews of plant trait effects on soil organisms and functions. Based on those contributions, we discuss here plasticity in trait expression, the context-dependency of plant trait effects, time lags in soil biotic responses to trait expression, and limitations of measured plant traits. We conclude that plant trait-based approaches are an important tool to advance soil ecological research, but also identify critical limitations and next steps.

The ecological drivers of soil biodiversity in the Southern Hemisphere remain underexplored. Here, in a continental survey comprising 647 sites, across 58 degrees of latitude between tropical Australia and Antarctica, we evaluated the major ecological patterns in soil biodiversity and relative abundance of ecological clusters within a co-occurrence network of soil bacteria, archaea and eukaryotes. Six major ecological clusters (modules) of co-occurring soil taxa were identified. These clusters exhibited strong shifts in their relative abundances with increasing distance from the equator. Temperature was the major environmental driver of the relative abundance of ecological clusters when Australia and Antarctica are analyzed together. Temperature, aridity, soil properties and vegetation types were the major drivers of the relative abundance of different ecological clusters within Australia. Our data supports significant reductions in the diversity of bacteria, archaea and eukaryotes in Antarctica vs. Australia linked to strong reductions in temperature. However, we only detected small latitudinal variations in soil biodiversity within Australia. Different environmental drivers regulate the diversity of soil archaea (temperature and soil carbon), bacteria (aridity, vegetation attributes and pH) and eukaryotes (vegetation type and soil carbon) across Australia. Together, our findings provide new insights into the mechanisms driving soil biodiversity in the Southern Hemisphere.

Experimental evidence from a mature, phosphorous-limited, eucalypt forest finds that aboveground productivity was not significantly stimulated by elevated CO2. Findings suggest that this effect may be limited across much of the tropics. Rising atmospheric CO2 stimulates photosynthesis and productivity of forests, offsetting CO2 emissions1,2. Elevated CO2 experiments in temperate planted forests yielded ∼23% increases in productivity3 over the initial years. Whether similar CO2 stimulation occurs in mature evergreen broadleaved forests on low-phosphorus (P) soils is unknown, largely due to lack of experimental evidence4. This knowledge gap creates major uncertainties in future climate projections5,6 as a large part of the tropics is P-limited. Here, we increased atmospheric CO2 concentration in a mature broadleaved evergreen eucalypt forest for three years, in the first large-scale experiment on a P-limited site. We show that tree growth and other aboveground productivity components did not significantly increase in response to elevated CO2 in three years, despite a sustained 19% increase in leaf photosynthesis. Moreover, tree growth in ambient CO2 was strongly P-limited and increased by ∼35% with added phosphorus. The findings suggest that P availability may potentially constrain CO2-enhanced productivity in P-limited forests; hence, future atmospheric CO2 trajectories may be higher than predicted by some models. As a result, coupled climate–carbon models should incorporate both nitrogen and phosphorus limitations to vegetation productivity7 in estimating future carbon sinks.

The ecological interactions that occur in and with soil are of consequence in many ecosystems on the planet. These interactions provide numerous essential ecosystem services, and the sustainable management of soils has attracted increasing scientific and public attention. Although soil ecology emerged as an independent field of research many decades ago, and we have gained important insights into the functioning of soils, there still are fundamental aspects that need to be better understood to ensure that the ecosystem services that soils provide are not lost and that soils can be used in a sustainable way. In this perspectives paper, we highlight some of the major knowledge gaps that should be prioritized in soil ecological research. These research priorities were compiled based on an online survey of 32 editors of Pedobiologia – Journal of Soil Ecology. These editors work at universities and research centers in Europe, North America, Asia, and Australia. The questions were categorized into four themes: (1) soil biodiversity and biogeography, (2) interactions and the functioning of ecosystems, (3) global change and soil management, and (4) new directions. The respondents identified priorities that may be achievable in the near future, as well as several that are currently achievable but remain open. While some of the identified barriers to progress were technological in nature, many respondents cited a need for substantial leadership and goodwill among members of the soil ecology research community, including the need for multi-institutional partnerships, and had substantial concerns regarding the loss of taxonomic expertise. nonPeerReviewed

An increasing number of ecological studies compare the diversity of microbial taxa along environmental gradients or between imposed treatments. Estimates are often based on analysis-of-variance of taxon-richness inferred from pyrosequencing data. We conducted a reanalysis of three 454-pyrosequencing studies on arbuscular-mycorrhizal-fungal diversity to evaluate the suitability of using the Leinster and Cobbold diversity-indices (LCdis) to assess diversity. We expected that the potential of LCdis to consider phylogenic relationships could resolve problems arising from ambiguous species-delineation in microbial-systems. Our reanalysis showed that comparisons between studies differing considerably in sequencing depth may be risky. Moreover, we show that LCdis not only reproduce the results of analyses of variance but can also resolve issues connected to variation in sequence read number, while additionally representing a less conservative metric of diversity than analysis-of-variance of taxa-richness. Based on these results we advocate the use of inclusive diversity indices in ecological studies targeting microbial communities.

Classification schemes have been popular to tame the diversity of root-infecting fungi. However, the usefulness of these schemes is limited to descriptive purposes. We propose that a shift to a multidimensional trait-based approach to disentangle the saprotrophic–symbiotic continuum will provide a better framework to understand fungal evolutionary ecology. Trait information reflecting the separation of root-infecting fungi from free-living soil relatives will help to understand the evolutionary process of symbiosis, the role that species interactions play in maintaining their large diversity in soil and in planta , and their contributions at the ecosystem level. Methodological advances in several areas such as microscopy, plant immunology, and metatranscriptomics represent emerging opportunities to populate trait databases.

Peer-review is an integral part of the scientific process, but getting a sufficient number of busy scientists to provide constructive reviews on a manuscript can be a challenge. The majority of individuals that we polled have had experience in the last two years with having manuscripts rejected and then submitting them elsewhere and/or with receiving invitations to review the same manuscript for different journals. Many experienced these events multiple times in that period. Authors who have had manuscripts rejected from journals after review have the opportunity to improve their manuscripts in light of reviewer comments. However unless the next journal to receive the manuscript has the technical means to transfer reviews from the previous journal, most journals treat these submissions as if they had not undergone peer review. Providing authors the option to submit responses to previous reviewer comments with details about how the manuscript has been revised since rejection from the previous journal is a practical means to increase the efficiency of peer review, requiring fewer reviews and leading to more rapid publication. Pedobiologia – Journal of Soil Ecology invites authors to include previous reviewer reports and detailed responses with new submissions.

Increasing temperatures are leading to upward migration of plant species in mountains, with elevational shifts of the mountain tree-line being the most commonly documented response (“front-edge” of altitudinal advance). Rapid distributional and compositional shifts in soil microbial communities, especially ectomycorrhizal (ECM) fungi, under climate change are also expected as an indirect effect of the impacts on vegetation. However, and despite the potential consequences on ecosystem functioning, they have seldom been addressed. Here we test the hypothesis that distributional shifts in soil ECM fungal communities will follow climate-driven tree upward migration in a fir forest-high elevation shrubland ecotone. Using Illumina Miseq sequencing, we compare the ECM fungal community associated to roots of adult Abies pinsapo trees at the tree-line with that of individuals involved in the altitudinal advance above it. Our data showed a decreasing trend in ECM fungal species abundance, richness, and proportion of species with epigeous fruiting bodies toward higher altitudes above the tree-line. Agaricales, Boletales and Pezizales were the fungal orders most frequently shared between host-individuals from the tree-line and the upward-migration area. In the latter, the ECM fungal community was mainly affected by the distance from the tree-line. Our results, together with the fact that the tree upward-migration process began several decades ago, suggest that (i) there is a high host-symbiont specificity for the ECM fungal community associated with the relic species Abies pinsapo, (ii) the altitudinal shift in the ECM fungal community lags well behind climate-driven tree upward migration in this forest-high elevation shrubland ecotone, and (iii) ECM dispersal limitation (distance from the forest-edge source) is an important factor controlling the speed of ECM upward migration.

Anti-malaria interventions that rely on insecticides can be compromised by insecticide-resistance alleles among malaria vectors. We examined frequency changes of resistance alleles at two loci, knockdown resistance (kdr) and acetylcholinesterase-1 (ace-1), which confer resistance to pyrethroids and DDT, and carbamates, respectively. A total of 7,059 Anopheles gambiae sensu stricto mosquitoes were analyzed from multiple sites across continental Equatorial Guinea. A subset of sites included samples collected pre-intervention (2007) and post-intervention (2009-2011). Both L1014S and L1014F resistance alleles were observed in almost all pre-intervention collections. In particular, L1014F was already at substantial frequencies in M form populations (17.6-74.6%), and at high frequencies (> 50%) in all but two S form populations. Comparison before and throughout anti-vector interventions showed drastic increases in L1014F, presumably caused by intensified selection pressure imposed by pyrethroids used in vector control efforts. In light of these findings, inclusion of other insecticide classes in any anti-vector intervention can be considered prudent.

Plant-soil feedback, the reciprocal relationship between a plant and its associated microbial communities, has been proposed to be an important driver of plant populations and community dynamics. While rarely considered, understanding how plant-soil feedback contributes to plant rarity may have implications for conservation and management of rare species. Wollemi pine (Wollemia nobilis) is a critically endangered species, of which fewer than 100 trees are known to exist in the wild. Seedling survival within the first year after germination and subsequent recruitment of Wollemi pine is limited in the wild. We used a plant-soil feedback approach to investigate the functional effect of species-specific differences previously observed in the microbial communities underneath adult Wollemi pine and a neighboring species, coachwood (Ceratopetalum apetalum), and also whether additional variation in microbial communities in the wild could impact seedling growth. There was no evidence for seedling growth being affected by tree species associated with soil inocula, suggesting that plant-soil feedbacks are not limiting recruitment in the natural population. However, there was evidence of fungal, but not bacterial, community variation impacting seedling growth independently of plant-soil feedbacks. Chemical (pH) and physical (porosity) soil characteristics were identified as potential drivers of the functional outcomes of these fungal communities. The empirical approach described here may provide opportunities to identify the importance of soil microbes to conservation efforts targeting other rare plant species and is also relevant to understanding the importance of soil microbes and plant-soil feedbacks for plant community dynamics more broadly.

Community coalescence is a recently introduced term describing the interaction of entire communities and their environments. We here explicitly place the concept of community coalescence in a soil microbial context, exploring intrinsic and extrinsic drivers of such coalescence events. Examples of intrinsic events include the action of earthworms and the dynamics of soil aggregates, while extrinsic events are exemplified by tillage, flooding, litter-fall, outplanting, and the addition of materials containing microbial communities. Aspects of global change may alter the frequency or severity of coalescence events. We highlight functional consequences of community coalescence in soil, and suggest ways to experimentally tackle this phenomenon. Soil ecology as a whole stands to benefit from conceptualizing soil biodiversity in terms of dynamic coalescent microbial assemblages.