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Ecoacoustics-or acoustic ecology-aids in monitoring elusive and protected species in several ecological contexts. For example, passive acoustic monitoring (PAM), which involves autonomous acoustic sensors, is widely used to detect various taxonomic groups in terrestrial and aquatic ecosystems, from birds and bats to fish and cetaceans. Here, we illustrate the potential of ecoacoustics to monitor soil biodiversity (specifically fauna)-a crucial endeavour given that 59% of species live in soil yet 75% of soils are affected by degradation. We describe the sources of sound in the soil (e.g. biological, geological and anthropogenic) and the ability of acoustic technology to detect and differentiate between these sounds, highlighting opportunities and current gaps in knowledge. We also propose a roadmap for the future development of optimized hardware, analytical pipelines and experimental approaches. Soil ecoacoustics is an emerging field with considerable potential to improve soil biodiversity monitoring and 'soil health' diagnostics. Indeed, early studies suggest soil ecoacoustics can be successfully applied in various ecosystems (e.g. grasslands, temperate, tropical and arid forests) and land uses (e.g. agriculture, viticulture, natural and restored ecosystems). Given the low cost, minimal intrusiveness, and effectiveness in supporting soil biodiversity assessments and biosecurity risks, we advocate for the advancement of soil ecoacoustics for future land management applications.

Despite mounting evidence of their importance in human health and ecosystem functioning, the definition and measurement of 'healthy microbiomes' remain unclear. More advanced knowledge exists on health associations for compounds used or produced by microbes. Environmental microbiome exposures (especially via soils) also help shape, and may supplement, the functional capacity of human microbiomes. Given the synchronous interaction between microbes, their feedstocks, and micro-environments, with functional genes facilitating chemical transformations, our objective was to examine microbiomes in terms of their capacity to process compounds relevant to human health. Here we integrate functional genomics and biochemistry frameworks to derive new quantitative measures of in silico potential for human gut and environmental soil metagenomes to process a panel of major compound classes (e.g., lipids, carbohydrates) and selected biomolecules (e.g., vitamins, short-chain fatty acids) linked to human health. Metagenome functional potential profile data were translated into a universal compound mapping 'landscape' based on bioenergetic van Krevelen mapping of function-level meta-compounds and corresponding functional relative abundances, reflecting imprinted genetic capacity of microbiomes to metabolize an array of different compounds. We show that measures of 'compound processing potential' associated with human health and disease (examining atherosclerotic cardiovascular disease, colorectal cancer, type 2 diabetes and anxious-depressive behavior case studies), and displayed seemingly predictable shifts along gradients of ecological disturbance in plant-soil ecosystems (three case studies). Ecosystem quality explained 60-92 % of variation in soil metagenome compound processing potential measures in a post-mining restoration case study dataset. With growing knowledge of the varying proficiency of environmental microbiota to process human health associated compounds, we might design environmental interventions or nature prescriptions to modulate our exposures, thereby advancing microbiota-oriented approaches to human health. Compound processing potential offers a simplified, integrative approach for applying metagenomics in ongoing efforts to understand and quantify the role of microbiota in environmental- and human-health., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Land use has a critical role to play in both climate change mitigation and biodiversity conservation, and increasingly there have been calls to integrate policies for concurrently meeting Paris Agreement commitments and the UN decade on ecosystem restoration 2021-2030. Currently however, investment activities have been dominated by climate change mitigation activities, including through the development of carbon markets (both voluntary and compliance markets). Whilst climate change mitigation is to be welcomed, the prioritization of carbon in avoided deforestation and reforestation can lead to suboptimal or negative outcomes for biodiversity. Restoration of degraded native vegetation may provide an opportunity for concurrent production of both carbon and biodiversity benefits, by harnessing existing carbon markets without the need to trade-off biodiversity outcomes. Here we demonstrate that carbon sequestered by restoring degraded temperate woodland can pay the price of the restored biodiversity. This is shown using conservative carbon prices in an established market (during both a voluntary and compliance market phase), and the restoration price revealed by a 10-year conservation incentive payment scheme. When recovery rates are high, market prices for carbon could pay the full price of restoration, with additional independent investment needed in cases where recovery trajectories are slower. Using carbon markets to fund restoration of degraded native vegetation thereby provides a solution for constrained resources and problematic trade-offs between carbon and biodiversity outcomes. Multi-attribute markets offer the potential to greatly increase the extent of restoration for biodiversity conservation, while providing an affordable source of carbon sequestration and enhancing economic benefits to landowners., (© 2024. The Author(s).)

The application of nitrogen (N) and phosphorus (P) fertilizers to soils is required to maintain crop yields, so the sufficient and timely delivery of nutrients to match crop demand is important in fertilizer management. We quantified temporal growth responses of tomato plants with different rates of N and P application using high-throughput shoot phenotyping. The tomato plants were grown in soil that had organic, inorganic or a combination of sources of P incorporated. Additional N was added to each pot at low and high rates, 13 days after planting. At the same rate of total P application, the inorganic P source resulted in greater shoot growth at the early time points. Later on, the plants supplied with organic or mixed P sources grew faster than those that received the inorganic P source, resulting in comparable shoot biomass in all treatments at the time of destructive harvest. The shoot phenotyping data demonstrated that readily available soil P was important for early tomato growth while available N was more important in later stages of vegetative growth. These results suggest that a fertilizer formulation of combined inorganic and organic P sources may be able to sustain rapid and great shoot growth in tomato plants, while also reducing additional N input., (© The Author(s) 2023. Published by Oxford University Press on behalf of the Annals of Botany Company.)

Grassland plants allocate photosynthetically fixed carbon (C) belowground to root biomass and rhizodeposition, but also to support arbuscular mycorrhizal fungi (AMF). These C allocation pathways could increase nutrient scavenging, but also mining of nutrients through enhanced organic matter decomposition. While important for grassland ecosystem functioning, methodological constraints have limited our ability to measure these processes under field conditions. We used 13 CO 2 and 15 N pulse labelling methods to examine belowground C allocation to root biomass production, rhizodeposition and AMF colonisation during peak plant growth in a grassland field experiment after three years of N fertilisation (0 and 40 kg N ha -1 year -1 ) and defoliation frequency treatments ("low" and "high", with 3-4 and 6-8 simulated grazing events per year, mimicking moderate and intense grazing, respectively). Moreover, we quantified the consequences for plant nitrogen (N) uptake and decomposition of soil organic C (SOC). Nitrogen fertilisation increased rhizodeposition and AMF colonisation (by 63 % and 54 %), but reduced root biomass (by 25 %). With high defoliation frequency, AMF colonisation increased (by 60 %), but both root biomass and rhizodeposition declined (by 35 % and 58 %). Plant N uptake was highest without N fertilisation and low defoliation frequency, and positively related to root biomass and the number of root tips. Therefore, when N supply is low and the capacity to produce C through photosynthesis is high, belowground C allocation to root production and associated root tips was important to scavenge for N in the soil. In contrast, the strong positive relationship between the rate of rhizodeposition and SOC decomposition, suggests that rhizodeposition may help plants to mine for nutrients locked in SOC. Taken together, the results of this study suggest that belowground C allocation pathways affected by N fertilisation and defoliation frequency affect plant N scavenging and mining with important consequences for long-term grassland C dynamics., Competing Interests: Declaration of competing interest Authors declare that there is no conflict of interest., (Crown Copyright © 2022. Published by Elsevier B.V. All rights reserved.)

Microbial inoculants containing arbuscular mycorrhizal (AM) fungi are potential tools in increasing the sustainability of our food production systems. Given the demand for sustainable agriculture, the production of such inoculants has potential economic value and has resulted in a variety of commercial inoculants currently being advertised. However, their use is limited by inconsistent product efficacy and lack of consumer confidence. Here, we propose a framework that can be used to assess the quality and reliability of AM inoculants. First, we set out a range of basic quality criteria which are required to achieve reliable inoculants. This is followed by a standardized bioassay which can be used to test inoculum viability and efficacy under controlled conditions. Implementation of these measurements would contribute to the adoption of AM inoculants by producers with the potential to increase sustainability in food production systems., Competing Interests: The authors declare no competing interests., (© 2022 The Author(s).)

While interest in arbuscular mycorrhizal (AM) fungal effects on soil phosphorus (P) have recently increased, field experiments on this topic are lacking. While microcosm studies provided valuable insights, the lack of field studies represents a knowledge gap. Here, we present a field study in which we grew a mycorrhiza-defective tomato (Solanum lycopersicum L.) genotype (named rmc) and its mycorrhizal wild-type progenitor (named 76R) with and without additional fertiliser, using a drip-irrigation system to examine the impacts of the AM symbiosis on soil P availability and plant growth and nutrition. AM effects on fruit biomass and nutrients, soil nutrient availability, soil moisture and the soil bacterial community were examined. At the time of harvest, the AM tomato plants without fertiliser had the same early season fruit biomass and fruit nutrient concentrations as plants that received fertiliser. The presence of roots reduced the concentration of available soil P, ammonium and soil moisture in the top 10 cm soil layer. Arbuscular mycorrhizas did not significantly affect soil P availability, soil moisture, or 16S bacterial community composition. These findings suggest an indirect role for AM fungi in tomato production but not necessarily a direct role in determining soil physicochemical traits, during the one season that this experiment was conducted. While longer-term field studies may be required in the future, the present study provides new insights into impacts of AM fungi on P availability and uptake in a field soil system., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Achieving sustainable agricultural development requires the efficient use of nutrient resources for crop production. Recovering nutrients from animal manures may play a key role in achieving this. Animal manures typically have low nutrient concentrations, and in ratios that are often not ideal for balanced crop nutrition. Here, combinations of organic and inorganic phosphorus (P) were formulated as granular products (organomineral fertilisers) with granule size suitable for transport and spreading. The fertilisers were produced by granulating powdered chicken litter with MAP and urea powders making the following formulations: 0:4, 1:3, 2:2, 3:1, 4:0. The kinetics of NH 4 + -N and P release from the fertilisers, and the effects on tomato growth and nutrition, as well as arbuscular mycorrhizal formation in roots following fertiliser application, were determined. Cumulative NH 4 + -N release ceased within 12 h, and was lower in the formulations with higher proportions of chicken litter. The cumulative P released reached approximately 80% of total P in all formulations, and the time to obtain maximum P dissolution was 19 days in the formulation that contained only chicken litter. The organomineral fertilisers increased tomato shoot growth by 15-28% compared to the chicken litter only, MAP only and MAP/urea formulations. Reasonable levels of mycorrhizal colonisation of tomato roots was achieved with the organomineral fertilisers. The results demonstrated that optimum plant growth does not depend solely on immediately available P, and that timing of nutrient supply to match plant demand is important. The combination of chicken litter with MAP sustained nutrient supply and improved plant growth. Taken together, organomineral fertiliser formulations are potential alternatives to inorganic P fertilisers that can improve crop growth and nutrition, while provide a sustainable use for animal production wastes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Biological sources of carbon sequestration such as revegetation have been highlighted as important avenues to combat climate change and meet global targets by the global community including the Paris Climate Agreement. However, current and projected carbon prices present a considerable barrier to broad-scale adoption of tree planting as a key mitigation strategy. One avenue to provide additional economic and environmental incentives to encourage wider adoption of revegetation is the bundling or stacking of additional co-beneficial ecosystem services that can be realized from tree planting. Using the World's largest land-based carbon credit trading scheme, the Australian Emissions Reduction Scheme (ERF), we examine the potential for three pairs of ecosystem services, where the carbon sequestration value of land use change is paired with an additional co-benefit with strong prospects for local tangible benefits to land owners/providers. Two cases consider agricultural provisioning values that can be realized by the landowners in higher returns: increased pollination services and reduced lamb mortality. The third case examined payments for tree plantings along riparian buffers, with payments to farmers by a water utility who realizes the benefit from reduced treatment cost due to water quality improvements. Economic incentives from these co-benefit case studies were found to be mixed, with avoided treatment costs from water quality paired with carbon payments the most promising, while pollination and reduced lamb mortality paired with carbon payments were unable to bridge the economic gap except under the most optimistic assumptions. We conclude that the economics case for significant land use change are likely to be geographically dispersed and only viable in relatively niche landscape positions in high establishment, high opportunity cost areas even when carbon payments are augmented with the value of co-benefits classified as providing direct and local benefits., (© 2021 John Wiley & Sons Ltd.)

Earthworms are an important soil taxon as ecosystem engineers, providing a variety of crucial ecosystem functions and services. Little is known about their diversity and distribution at large spatial scales, despite the availability of considerable amounts of local-scale data. Earthworm diversity data, obtained from the primary literature or provided directly by authors, were collated with information on site locations, including coordinates, habitat cover, and soil properties. Datasets were required, at a minimum, to include abundance or biomass of earthworms at a site. Where possible, site-level species lists were included, as well as the abundance and biomass of individual species and ecological groups. This global dataset contains 10,840 sites, with 184 species, from 60 countries and all continents except Antarctica. The data were obtained from 182 published articles, published between 1973 and 2017, and 17 unpublished datasets. Amalgamating data into a single global database will assist researchers in investigating and answering a wide variety of pressing questions, for example, jointly assessing aboveground and belowground biodiversity distributions and drivers of biodiversity change.

Rhizodeposition plays an important role in below-ground carbon (C) cycling. However, quantification of rhizodeposition in intact plant-soil systems has remained elusive due to methodological issues. We used a 13 C-CO 2 pulse-labelling method to quantify the contribution of rhizodeposition to below-ground respiration. Intact plant-soil cores were taken from a grassland field, and in half, shoots and roots were removed (unplanted cores). Both unplanted and planted cores were assigned to drought and nitrogen (N) treatments. Afterwards, shoots in planted cores were pulse labelled with 13 C-CO 2 and then clipped to determine total below-ground respiration and its δ 13 C. Simultaneously, δ 13 C was measured for the respiration of live roots, soils with rhizodeposits, and unplanted treatments, and used as endmembers with which to determine root respiration and rhizodeposit C decomposition using two-source mixing models. Rhizodeposit decomposition accounted for 7-31% of total below-ground respiration. Drought reduced decomposition of both rhizodeposits and soil organic carbon (SOC), while N addition increased root respiration but not the contribution of rhizodeposit C decomposition to below-ground respiration. This study provides a new approach for the partitioning of below-ground respiration into different sources, and indicates that decomposition of rhizodeposit C is an important component of below-ground respiration that is sensitive to drought and N addition in grassland ecosystems., (© 2020 The Authors. New Phytologist © 2020 New Phytologist Foundation.)

A wines' terroir, represented as wine traits with regional distinctiveness, is a reflection of both the biophysical and human-driven conditions in which the grapes were grown and wine made. Soil is an important factor contributing to the uniqueness of a wine produced by vines grown in specific conditions. Here, we evaluated the impact of environmental variables on the soil bacteria of 22 Barossa Valley vineyard sites based on the 16S rRNA gene hypervariable region 4. In this study, we report that both dispersal isolation by geographic distance and environmental heterogeneity (soil plant-available P content, elevation, rainfall, temperature, spacing between row and spacing between vine) contribute to microbial community dissimilarity between vineyards. Vineyards located in cooler and wetter regions showed lower beta diversity and a higher ratio of dominant taxa. Differences in soil bacterial community composition were significantly associated with differences in fruit and wine composition. Our results suggest that environmental factors affecting wine terroir, may be mediated by changes in microbial structure, thus providing a basic understanding of how growing conditions affect interactions between plants and their soil bacteria., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Zhou, Cavagnaro, De Bei, Nelson, Stephen, Metcalfe, Gilliham, Breen, Collins and Rodríguez López.)

While the impact of arbuscular mycorrhizal fungi (AMF) on phosphorus (P) uptake is well understood, the mechanism(s) of how these fungi affect P leaching from soil is still unclear. Here we present results of a study in which we grew a mycorrhiza-defective tomato (Solanum lycopersicum L.) genotype (named rmc) and its mycorrhizal wild-type progenitor (named 76R) in microcosms containing non-sterile soil, to examine the influence of roots and AMF on P leaching. More P was leached from the planted microcosms as compared to the plant-free controls. Further, although there was more plant biomass and greater P uptake in the mycorrhizal plant treatments, these treatments were associated with the most leaching of total P, reactive P, and dissolved organic carbon (DOC). There was a strong correlation between the total P and DOC leached, suggesting that root and fungal exudates may have affected P leaching. These findings provide new insights into the impact of roots and AMF on nutrient leaching in soils., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Zinc is essential for the functioning of many enzymes and plant processes and the malting process. Arbuscular mycorrhizal fungi (AMF) can improve zinc (Zn) uptake in the important cereal crop barley (Hordeum vulgare) on Zn-deficient soils. Here we investigated the impacts of Zn fertilisation and AMF on the yield and grain quality of malting barley cultivars. Five barley genotypes were inoculated or not with the AMF Rhizophagus irregularis, and grown in pots either fertilised with Zn or not. Measurements of Zn nutrition and yield were made for all cultivars. Further analyses of grain biochemical composition, including starch, β-glucan and arabinoxylan contents, and analysis of ATR-MIR spectra were made in two contrasting cultivars. Mycorrhizal colonisation generally resulted in decreased biomass, but increased grain dimensions and mean grain weight. Barley grain yield and biochemical qualities were highly variable between cultivars, and the ATR-MIR spectra revealed grain compositional differences between cultivars and AMF treatments. Mycorrhizal fungi can affect barley grain Zn concentration and starch content, but grain biochemical traits including β-glucan and arabinoxylan contents were more conserved by the cultivar, and unaffected by AMF inoculation. The ATR-MIR spectra revealed that there are other grain characteristics affected by AMF that remain to be elucidated.

Post-fire litter layers are composed of leaves and woody debris that predominantly fall during or soon after the fire event. These layers are distinctly different to pre-fire litters due to their common origin and deposition time. However, heterogeneity can arise from the variable thermal conditions in the canopy during fire. Therefore, in this study, we used thermally altered pine needles (heated to 40 °C, 150 °C, 260 °C and 320 °C for 1 h) in a laboratory incubation study for 43 days. These samples were measured for respiration throughout and extracted for DNA at the experiment's end; soil ribosomal RNA was analysed using Illumina sequencing (16S and internal transcribed spacer amplicons). The addition of pine needles heated to 40 °C or 150 °C caused a substantial shift in community structure, decreased alpha diversity and significantly increased soil respiration relative to the control treatment. In contrast, pine needles heated to 260 °C or 320 °C had little effect on microbial community structure or soil respiration. These results indicate that highly thermally altered needles are not microbially decomposed during the first 43 days of exposure and therefore that biomass temperature may have significant effects on post-fire litter decomposition and carbon flux. This research outlines an important knowledge gap in forest fire responses that may affect post-fire carbon emission estimates.

Current climate change models project that water availability will become more erratic in the future. With soil nitrogen (N) supply coupled to water availability, it is important to understand the combined effects of variable water and N supply on food crop plants (above- and below-ground). Here we present a study that precisely controls soil moisture and compares stable soil moisture contents with a controlled wetting-drying cycle. Our aim was to identify how changes in soil moisture and N concentration affect shoot-root biomass, N acquisition in wheat, and soil N cycling. Using a novel gravimetric platform allowing fine-scale control of soil moisture dynamics, a 3 × 3 factorial experiment was conducted on wheat plants subjected to three rates of N application (0, 25 and 75 mg N/kg soil) and three soil moisture regimes (two uniform treatments: 23.5 and 13% gravimetric moisture content (herein referred to as Well-watered and Reduced water, respectively), and a Variable treatment which cycled between the two). Plant biomass, soil N and microbial biomass carbon were measured at three developmental stages: tillering (Harvest 1), flowering (Harvest 2), and early grain milk development (Harvest 3). Reduced water supply encouraged root growth when combined with medium and high N. Plant growth was more responsive to N than the water treatments imposed, with a 15-fold increase in biomass between the high and no added N treatment plants. Both uniform soil water treatments resulted in similar plant biomass, while the Variable water treatment resulted in less biomass overall, suggesting wheat prefers consistency whether at a Well-watered or Reduced water level. Plants did not respond well to variable soil moisture, highlighting the need to understand plant adaptation and biomass allocation with resource limitation. This is particularly relevant to developing irrigation practices, but also in the design of water availability experiments., (Crown Copyright © 2019. Published by Elsevier B.V. All rights reserved.)

The positive effects of arbuscular mycorrhizal fungi (AMF) have been demonstrated for plant biomass, and zinc (Zn) and phosphorus (P) uptake, under soil nutrient deficiency. Additionally, a number of Zn and P transporter genes are affected by mycorrhizal colonisation or implicated in the mycorrhizal pathway of uptake. However, a comprehensive study of plant physiology and gene expression simultaneously, remains to be undertaken. Medicago truncatula was grown at different soil P and Zn availabilities, with or without inoculation of Rhizophagus irregularis. Measures of biomass, shoot elemental concentrations, mycorrhizal colonisation, and expression of Zn transporter (ZIP) and phosphate transporter (PT) genes in the roots, were taken. Mycorrhizal plants had a greater tolerance of both P and Zn soil deficiency; there was also evidence of AMF protecting plants against excessive Zn accumulation at high soil Zn. The expression of all PT genes was interactive with both P availability and mycorrhizal colonisation. MtZIP5 expression was induced both by AMF and soil Zn deficiency, while MtZIP2 was down-regulated in mycorrhizal plants, and up-regulated with increasing soil Zn concentration. These findings provide the first comprehensive physiological and molecular picture of plant-mycorrhizal fungal symbiosis with regard to soil P and Zn availability. Mycorrhizal fungi conferred tolerance to soil Zn and P deficiency and this could be linked to the induction of the ZIP transporter gene MtZIP5, and the PT gene MtPT4.

There is a growing recognition of the role of arbuscular mycorrhizal fungi (AMF) in food security, specifically the potential for AMF to enhance the yield and mineral nutrition-including phosphorus, zinc (Zn), and iron (Fe)-of food crops. However, the bioavailability of Zn and Fe for humans in the grain of cereal crops can be overestimated by failing to consider the abundance of phytic acid (PA). This is because PA can chelate the micronutrients, making them difficult to absorb. In order to understand the effect of an AM fungus and soil Zn concentration on the productivity and nutritional quality of food parts, this study examined the growth and nutritional responses of durum wheat, with and without inoculation with Rhizophagus irregularis, at five soil Zn concentrations. Growth and nutrient responses of the plants to soil Zn amendment was stronger than responses to AMF. However, the protective effect of AMF under soil Zn toxicity conditions was observed as reduced Zn concentration in the mycorrhizal durum wheat grain at Zn50. Here, AMF inoculation increased the concentration of PA in durum wheat grain but had no effect on the concentration of Zn and Fe; this consequently reduced the predicted bioavailability of grain Zn and Fe, which could lead to a decrease in nutritional quality of the grain. This research suggests that in soil with low (available) phosphorus and Zn concentrations, AMF may reduce the food quality of durum wheat because of an increase in PA concentration, and thus, a decrease in the bioavailability of Zn and Fe.

The formation of arbuscular mycorrhizas (AM) can result in positive, neutral or negative responses in the growth and mineral nutrition of host plants, particularly that of P, Zn and other micronutrients. This study examined the growth and nutritional responses of 15 agriculturally important plant species, including cereals, legumes and vegetables, with and without inoculation with the AM fungus (AMF) Rhizophagus irregularis. Furthermore, we explored whether the responses differed between different functional groups of plants such as monocots and dicots, C3 and C4 plants, and N-fixing and non-N-fixing plants. We found that that mycorrhizal colonisation of roots, plant growth and plant nutrient responses differed between plant species. Among the species analysed, leek (Allium ampeloprasum L. var. porrum) was the most mycorrhiza-responsive, displaying the highest mycorrhizal colonisation and biomass response, and the greatest increases in most mineral nutrients. In other plant species, the concentration of P, Cu, Zn and S were generally enhanced by inoculation with AMF. Furthermore, ionomes differed more greatly between plant species than in response to inoculation with AMF. This research further improves our understanding of the responses of different and diverse plant species to the formation of AM in terms of growth and ionomics under standardised growth conditions. The results of this study may be used in further studies and to inform agricultural practices.

Background: Increasing zinc (Zn) concentrations in crops is important for alleviation of human Zn deficiency. Arbuscular mycorrhizal fungi (AMF) contribute to plant Zn uptake, but their contribution to Zn in the edible portion of crops has not yet been investigated. This study aimed to quantify the mycorrhizal pathway of Zn uptake into grain of wheat and barley under varying soil Zn availabilities. Bread wheat (Triticum aestivum) and barley (Hordeum vulgare) were grown in pots with a hyphal compartment containing 65 Zn. Plants were inoculated with Rhizophagus irregularis and grown at three soil Zn concentrations. Radioactive Zn in grain and straw was measured and the contribution of AMF to Zn uptake was calculated., Results: The mycorrhizal pathway of Zn uptake contributed up to 24.3% of total above-ground Zn in wheat, and up to 12.7% of that Zn in barley. The greatest contribution by the mycorrhizal pathway was observed in barley at the lowest Zn addition, and in wheat at the highest one. In addition, grain yield of bread wheat was increased by AMF., Conclusions: These results suggest that AMF have a substantial role in uptake of Zn into cereals, and the proportional contribution by the MPU is dependent on plant species, as well as available soil Zn.

Increasing crop yield and fertiliser nitrogen (N)-use efficiency is important for productive agricultural systems with a reduced environmental footprint. The aim of this study was to assess the effect of slow release brown coal-urea (BCU) fertiliser on the gaseous N losses, biomass yield and N uptake by silver beet (Beta vulgaris L.) compared to commercial urea. Two soils were amended with urea, BCU 1 (22% N) or BCU 2 (17% N) as N-fertiliser at the rate of 50 or 100 kg N ha -1 . Five gas sampling periods were undertaken to measure the loss of N as N 2 O and NH 3 . After 10 weeks, biomass, N concentration, and N uptake of silver beet, and mineral and mineralisable N of post-harvest soil were measured. BCU substantially increased fertiliser N availability and uptake by silver beet, reduced N 2 O emission by 29% and NH 3 emission by 36% compared to urea alone, irrespective of soil type. Compared to urea, BCU blends increased biomass yield by 27% and 23% in a Tenosol and Dermosol soil, respectively. In addition, application of BCU fertiliser substantially enhanced the potentially mineralisable N and organic carbon content of soil. These results provide evidence that granulation of urea with brown coal (BC) can increase silver beet N-use efficiency and yield in different soil types, and more work is now required to validate this technology for other crops., (Copyright © 2018. Published by Elsevier B.V.)

Association with arbuscular mycorrhizal fungi (AMF) can impact on plant water relations; mycorrhizal plants can exhibit increased stomatal conductance (g s ) and root hydraulic conductance (normalized to root dry weight, L o ), and altered expression of aquaporins (AQP). Many factors regulate such responses; however, plant intraspecific diversity effects have yet to be explored. Twenty geographically diverse accessions of Medicago truncatula were inoculated with the AMF Funneliformis mosseae or mock-inoculated, and grown under well-watered conditions. Biomass, g s , shoot nutrient concentrations and mycorrhizal colonization were measured in all accessions, and L o and gene expression in five accessions. The diverse accessions varied in physiology and gene expression; some accessions were also larger or had higher g s when colonized by F. mosseae. In the five accessions, L o was higher in two accessions when colonized by AMF and also maintained within a much smaller range than the mock-inoculated plants. Expression of MtPIP1 correlated with both g s and L o , and when plants were more than 3% colonized, mycorrhizal colonization correlated with L o . Accession and AMF treatments had profound effects on M. truncatula, including several measures of plant water relations. Correlations between response variables, especially between molecular and physiological variables, across genotypes, highlight the findings of this study., (© 2018 John Wiley & Sons Ltd.)

Reducing the release rate of urea can increase its use efficiency and minimize negative effects on the environment. A novel fertilizer material that was formed by blending brown coal (BC) with urea, delayed fertilizer N release in controlled climatic conditions in a glasshouse, through strong retention facilitated by the extensive surface area, porous structure and chemical functional groups in the BC. However, the role of BC as a carrier of synthetic urea and the effect of their interaction with various soil types on the dynamics and mineralization of N remains largely unclear. Therefore, a soil column incubation study was conducted to assess the release, transformation and transportation of N from several different brown coal-urea (BCU) granules, compared to commercial urea. Blending and subsequent granulation of urea with BC substantially increased fertilizer N retention in soil by decreasing gaseous emissions and leaching of N compared to urea alone, irrespective of soil type. The BCU granule containing the highest proportion of BC had lower leaching and gaseous emissions and maintained considerably higher mineral and mineralizable N in topsoil. Possible modes of action of the BCU granules have been proposed, emphasizing the role of BC in enhancing N retention over a longer period of time. The results support the notion that BCU granules can be used as a slow release and enhanced efficiency fertilizer for increasing availability and use efficiency of N by crops.

The positive effects of arbuscular mycorrhizal fungi (AMF) on the zinc (Zn) nutrition of a number of cereal species has been demonstrated, but for Hordeum vulgare (barley), this has been scarcely investigated. Zn is taken up by ZIP transporters in the roots, and several barley ZIP transporter genes are up-regulated under Zn deficient conditions. We grew a modern cultivar of barley (cv. Compass) at five different soil Zn concentrations ranging from no addition through to a toxic concentration. The plants were either inoculated with the AMF Rhizophagus irregularis, or mock-inoculated. At harvest, measurements of biomass, tissue Zn concentration, and expression of ZIP transporter genes were taken. Inoculation of barley with AMF resulted in improved grain and straw Zn concentrations, especially at low soil Zn concentrations, but did not increase the biomass of the plants. Of the five HvZIP genes tested that are up-regulated under low Zn conditions, one gene (HvZIP13) was significantly up-regulated by mycorrhizal colonisation at the lowest Zn treatment. Two other ZIP genes were down-regulated in mycorrhizal plants under low soil Zn. Inoculation with AMF has an effect on ZIP transporter genes in the roots of barley plants. Furthermore, AMF may be more useful for improving quality of barley grain in terms of Zn concentrations, rather than improving yield., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Reforestation of agricultural land with mixed-species environmental plantings of native trees and shrubs contributes to abatement of greenhouse gas emissions through sequestration of carbon, and to landscape remediation and biodiversity enhancement. Although accumulation of carbon in biomass is relatively well understood, less is known about associated changes in soil organic carbon (SOC) following different types of reforestation. Direct measurement of SOC may not be cost effective where rates of SOC sequestration are relatively small and/or highly spatially-variable, thereby requiring intensive sampling. Hence, our objective was to develop a verified modelling approach for determining changes in SOC to facilitate the inclusion of SOC in the carbon accounts of reforestation projects. We measured carbon stocks of biomass, litter and SOC (0-30cm) in 125 environmental plantings (often paired to adjacent agricultural sites), representing sites of varying productivity across the Australian continent. After constraining a carbon accounting model to observed measures of growth, allocation of biomass, and rates of litterfall and litter decomposition, the model was calibrated to maximise the efficiency of prediction of SOC and its fractions. Uncertainties in both measured and modelled results meant that efficiencies of prediction of SOC across the 125 contrasting plantings were only moderate, at 39-68%. Data-informed modelling nonetheless improved confidence in outputs from scenario analyses, confirming that: (i) reforestation on agricultural land highly depleted in SOC (i.e. previously under cropping) had the highest capacity to sequester SOC, particularly where rainfall was relatively high (>600mmyear -1 ), and; (ii) decreased planting width and increased stand density and the proportion of eucalypts enhanced rates of SOC sequestration. These results improve confidence in predictions of SOC following environmental reforestation under varying conditions. The calibrated model will be a useful tool for informing land managers and policy makers seeking to understand the dynamics of SOC following such reforestation., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Climate change will alter both the amount and pattern of precipitation and soil water availability, which will directly affect plant growth and nutrient acquisition, and potentially, ecosystem functions like nutrient cycling and losses as well. Given their role in facilitating plant nutrient acquisition and water stress resistance, arbuscular mycorrhizal (AM) fungi may modulate the effects of changing water availability on plants and ecosystem functions. The well-characterized mycorrhizal tomato (Solanum lycopersicum L.) genotype 76R (referred to as MYC+) and the mutant mycorrhiza-defective tomato genotype rmc were grown in microcosms in a glasshouse experiment manipulating both the pattern and amount of water supply in unsterilized field soil. Following 4 weeks of differing water regimes, we tested how AM fungi affected plant productivity and nutrient acquisition, short-term interception of a 15NH4+ pulse, and inorganic nitrogen (N) leaching from microcosms. AM fungi enhanced plant nutrient acquisition with both lower and more variable water availability, for instance increasing plant P uptake more with a pulsed water supply compared to a regular supply and increasing shoot N concentration more when lower water amounts were applied. Although uptake of the short-term 15NH4+ pulse was higher in rmc plants, possibly due to higher N demand, AM fungi subtly modulated NO3- leaching, decreasing losses by 54% at low and high water levels in the regular water regime, with small absolute amounts of NO3- leached (<1 kg N/ha). Since this study shows that AM fungi will likely be an important moderator of plant and ecosystem responses to adverse effects of more variable precipitation, management strategies that bolster AM fungal communities may in turn create systems that are more resilient to these changes., (© 2017 John Wiley & Sons Ltd.)

Synthetic nitrogen (N) fertilisers, such as urea, are susceptible to rapid dissipation from soil. More gradual release of mineral N from fertiliser may reduce the off-site movement of mineral N, thereby enhancing N supply to crops and minimising negative off-site impacts. We hypothesised that granulation of urea with humified brown coal (BC) delays mineral N release and maintains higher concentrations of N in soil than conventional urea granules. Four different brown coal-urea granules, with C:N ratios of 1-10, were prepared by pan granulation. Advanced spectroscopic and X-ray powder diffraction (XRD) techniques confirmed loading of urea-N into the BC structure. Nitrogen-release from BCU granules was slower than from urea, resulting in higher N retention over a longer period for increasing growth and N uptake by crop plants. This trend increased with higher loading of BC, emphasising the significant role of BC in N retention. These findings support the hypothesis that BC is suitable for developing slow release N fertilisers., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Vitis vinifera (grapevine) is one of the most important fruit crops, both for fresh consumption and wine and spirit production. The term terroir is frequently used in viticulture and the wine industry to relate wine sensory attributes to its geographic origin. Although, it can be cultivated in a wide range of environments, differences in growing conditions have a significant impact on fruit traits that ultimately affect wine quality. Understanding how fruit quality and yield are controlled at a molecular level in grapevine in response to environmental cues has been a major driver of research. Advances in the area of genomics, epigenomics, transcriptomics, proteomics and metabolomics, have significantly increased our knowledge on the abiotic regulation of yield and quality in many crop species, including V. vinifera . The integrated analysis of multiple 'omics' can give us the opportunity to better understand how plants modulate their response to different environments. However, 'omics' technologies provide a large amount of biological data and its interpretation is not always straightforward, especially when different 'omic' results are combined. Here we examine the current strategies used to integrate multi-omics, and how these have been used in V. vinifera . In addition, we also discuss the importance of including epigenomics data when integrating omics data as epigenetic mechanisms could play a major role as an intermediary between the environment and the genome.

Reforestation of agricultural lands with mixed-species environmental plantings can effectively sequester C. While accurate and efficient methods for predicting soil organic C content and composition have recently been developed for soils under agricultural land uses, such methods under forested land uses are currently lacking. This study aimed to develop a method using infrared spectroscopy for accurately predicting total organic C (TOC) and its fractions (particulate, POC; humus, HOC; and resistant, ROC organic C) in soils under environmental plantings. Soils were collected from 117 paired agricultural-reforestation sites across Australia. TOC fractions were determined in a subset of 38 reforested soils using physical fractionation by automated wet-sieving and 13 C nuclear magnetic resonance (NMR) spectroscopy. Mid- and near-infrared spectra (MNIRS, 6000-450 cm -1 ) were acquired from finely-ground soils from environmental plantings and agricultural land. Satisfactory prediction models based on MNIRS and partial least squares regression (PLSR) were developed for TOC and its fractions. Leave-one-out cross-validations of MNIRS-PLSR models indicated accurate predictions (R 2  > 0.90, negligible bias, ratio of performance to deviation > 3) and fraction-specific functional group contributions to beta coefficients in the models. TOC and its fractions were predicted using the cross-validated models and soil spectra for 3109 reforested and agricultural soils. The reliability of predictions determined using k-nearest neighbour score distance indicated that >80% of predictions were within the satisfactory inlier limit. The study demonstrated the utility of infrared spectroscopy (MNIRS-PLSR) to rapidly and economically determine TOC and its fractions and thereby accurately describe the effects of land use change such as reforestation on agricultural soils., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Plant strategies to cope with future droughts may be enhanced by associations between roots and soil microorganisms, including arbuscular mycorrhizal (AM) fungi. But how AM fungi affect crop growth and yield, together with plant physiology and soil carbon (C) dynamics, under water stress in actual field conditions is not well understood. The well-characterized mycorrhizal tomato (Solanum lycopersicum L.) genotype 76R (referred to as MYC+) and the mutant nonmycorrhizal tomato genotype rmc were grown in an organic farm with a deficit irrigation regime and control regime that replaced evapotranspiration. AM increased marketable tomato yields by ~25% in both irrigation regimes but did not affect shoot biomass. In both irrigation regimes, MYC+ plants had higher plant nitrogen (N) and phosphorus (P) concentrations (e.g. 5 and 24% higher N and P concentrations in leaves at fruit set, respectively), 8% higher stomatal conductance (gs), 7% higher photosynthetic rates (Pn), and greater fruit set. Stem water potential and leaf relative water content were similar in both genotypes within each irrigation regime. Three-fold higher rates of root sap exudation in detopped MYC+ plants suggest greater capacity for water uptake through osmotic driven flow, especially in the deficit irrigation regime in which root sap exudation in rmc was nearly absent. Soil with MYC+ plants also had slightly higher soil extractable organic C and microbial biomass C at anthesis but no changes in soil CO2 emissions, although the latter were 23% lower under deficit irrigation. This study provides novel, field-based evidence for how indigenous AM fungi increase crop yield and crop water use efficiency during a season-long deficit irrigation and thus play an important role in coping with increasingly limited water availability in the future., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Cassava is an important dietary component for over 1 billion people, and its ability to yield under drought has led to it being promoted as an important crop for food security under climate change. Despite its known photosynthetic plasticity in response to temperature, little is known about how temperature affects plant toxicity or about interactions between temperature and drought, which is important because cassava tissues contain high levels of toxic cyanogenic glucosides, a major health and food safety concern. In a controlled glasshouse experiment, plants were grown at 2 daytime temperatures (23 °C and 34 °C), and either well-watered or subject to a 1 month drought prior to harvest at 6 months. The objective was to determine the separate and interactive effects of temperature and drought on growth and toxicity. Both temperature and drought affected cassava physiology and chemistry. While temperature alone drove differences in plant height and above-ground biomass, drought and temperature × drought interactions most affected tuber yield, as well as foliar and tuber chemistry, including C : N, nitrogen and cyanide potential (CNp; total cyanide released from cyanogenic glucosides). Conditions that most stimulated growth and yield (well-watered × high temperature) effected a reduction in tuber toxicity, whereas drought inhibited growth and yield, and was associated with increased foliar and tuber toxicity. The magnitude of drought effects on tuber yield and toxicity were greater at high temperature; thus, increases in tuber CNp were not merely a consequence of reduced tuber biomass. Findings confirm that cassava is adaptable to forecast temperature increases, particularly in areas of adequate or increasing rainfall; however, in regions forecast for increased incidence of drought, the effects of drought on both food quality (tuber toxicity) and yield are a greater threat to future food security and indicate an increasing necessity for processing of cassava to reduce toxicity., (© 2016 John Wiley & Sons Ltd.)

A significant challenge facing the study of arbuscular mycorrhiza is the establishment of suitable non-mycorrhizal treatments that can be compared with mycorrhizal treatments. A number of options are available, including soil disinfection or sterilisation, comparison of constitutively mycorrhizal and non-mycorrhizal plant species, comparison of plants grown in soils with different inoculum potential and the comparison of mycorrhiza-defective mutant genotypes with their mycorrhizal wild-type progenitors. Each option has its inherent advantages and limitations. Here, the potential to use mycorrhiza-defective mutant and wild-type genotype plant pairs as tools to study the functioning of mycorrhiza is reviewed. The emphasis of this review is placed on non-legume plant species, as mycorrhiza-defective plant genotypes in legumes have recently been extensively reviewed. It is concluded that non-legume mycorrhiza-defective mutant and wild-type pairs are useful tools in the study of mycorrhiza. However, the mutant genotypes should be well characterised and, ideally, meet a number of key criteria. The generation of more mycorrhiza-defective mutant genotypes in agronomically important plant species would be of benefit, as would be more research using these genotype pairs, especially under field conditions.

We investigated effects of Ag2S engineered nanomaterials (ENMs), polyvinylpyrrolidone (PVP) coated Ag ENMs (PVP-Ag), and Ag(+) on arbuscular mycorrhizal fungi (AMF), their colonization of tomato (Solanum lycopersicum), and overall microbial community structure in biosolids-amended soil. Concentration-dependent uptake was measured in all treatments. Plants exposed to 100 mg kg(-1) PVP-Ag ENMs and 100 mg kg(-1) Ag(+) exhibited reduced biomass and greatly reduced mycorrhizal colonization. Bacteria, actinomycetes and fungi were inhibited by all treatment classes, with the largest reductions measured in 100 mg kg(-1) PVP-Ag ENMs and 100 mg kg(-1) Ag(+). Overall, Ag2S ENMs were less toxic to plants, less disruptive to plant-mycorrhizal symbiosis, and less inhibitory to the soil microbial community than PVP-Ag ENMs or Ag(+). However, significant effects were observed at 1 mg kg(-1) Ag2S ENMs, suggesting that the potential exists for microbial communities and the ecosystem services they provide to be disrupted by environmentally relevant concentrations of Ag2S ENMs., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Two pathways exist for plant Pi uptake from soil: via root epidermal cells (direct pathway) or via associations with arbuscular mycorrhizal (AM) fungi, and the two pathways interact in a complex manner. This study investigated distal and local effects of AM colonization on direct root Pi uptake and root growth, at different soil P levels. Medicago truncatula was grown at three soil P levels in split-pots with or without AM fungal inoculation and where one root half grew into soil labelled with (33)P. Plant genotypes included the A17 wild type and the mtpt4 mutant. The mtpt4 mutant, colonized by AM fungi, but with no functional mycorrhizal pathway for Pi uptake, was included to better understand effects of AM colonization per se. Colonization by AM fungi decreased expression of direct Pi transporter genes locally, but not distally in the wild type. In mtpt4 mutant plants, direct Pi transporter genes and the Pi starvation-induced gene Mt4 were more highly expressed than in wild-type roots. In wild-type plants, less Pi was taken up via the direct pathway by non-colonized roots when the other root half was colonized by AM fungi, compared with non-mycorrhizal plants. Colonization by AM fungi strongly influenced root growth locally and distally, and direct root Pi uptake activity locally, but had only a weak influence on distal direct pathway activity. The responses to AM colonization in the mtpt4 mutant suggested that in the wild type, the increased P concentration of colonized roots was a major factor driving the effects of AM colonization on direct root Pi uptake., (© The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.)

Substantial amounts of nutrients are lost from soils via leaching and as gaseous emissions. These losses can be environmentally damaging and expensive in terms of lost agricultural production. Plants have evolved many traits to optimize nutrient acquisition, including the formation of arbuscular mycorrhizas (AM), associations of plant roots with fungi that acquire soil nutrients. There is emerging evidence that AM have the ability to reduce nutrient loss from soils by enlarging the nutrient interception zone and preventing nutrient loss after rain-induced leaching events. Until recently, this important ecosystem service of AM had been largely overlooked. Here we review the role of AM in reducing nutrient loss and conclude that this role cannot be ignored if we are to increase global food production in an environmentally sustainable manner., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Reforestation has large potential for mitigating climate change through carbon sequestration. Native mixed-species plantings have a higher potential to reverse biodiversity loss than do plantations of production species, but there are few data on their capacity to store carbon. A chronosequence (5-45 years) of 36 native mixed-species plantings, paired with adjacent pastures, was measured to investigate changes to stocks among C pools following reforestation of agricultural land in the medium rainfall zone (400-800 mm yr(-1)) of temperate Australia. These mixed-species plantings accumulated 3.09 ± 0.85 t C ha(-1) yr(-1) in aboveground biomass and 0.18 ± 0.05 t C ha(-1) yr(-1) in plant litter, reaching amounts comparable to those measured in remnant woodlands by 20 years and 36 years after reforestation respectively. Soil C was slower to increase, with increases seen only after 45 years, at which time stocks had not reached the amounts found in remnant woodlands. The amount of trees (tree density and basal area) was positively associated with the accumulation of carbon in aboveground biomass and litter. In contrast, changes to soil C were most strongly related to the productivity of the location (a forest productivity index and soil N content in the adjacent pasture). At 30 years, native mixed-species plantings had increased the stability of soil C stocks, with higher amounts of recalcitrant C and higher C:N ratios than their adjacent pastures. Reforestation with native mixed-species plantings did not significantly change the availability of macronutrients (N, K, Ca, Mg, P, and S) or micronutrients (Fe, B, Mn, Zn, and Cu), content of plant toxins (Al, Si), acidity, or salinity (Na, electrical conductivity) in the soil. In this medium rainfall area, native mixed-species plantings provided comparable rates of C sequestration to local production species, with the probable additional benefit of providing better quality habitat for native biota. These results demonstrate that reforestation using native mixed-species plantings is an effective alternative for carbon sequestration to standard monocultures of production species in medium rainfall areas of temperate continental climates, where they can effectively store C, convert C into stable pools and provide greater benefits for biodiversity., (© 2014 John Wiley & Sons Ltd.)

Arbuscular mycorrhizas (AM) can increase plant acquisition of P and N. No published studies have investigated the impact of P and AM on the allocation of N to the plant defence, cyanogenic glucosides. We investigated the effects of soil P and AM on cyanogenic glucoside (dhurrin) concentration in roots and shoots of two forage sorghum lines differing in cyanogenic potential (HCNp). Two harvest times allowed plants grown at high and low P to be compared at the same age and the same size, to take account of known ontogenetic changes in shoot HCNp. P responses were dependent on ontogeny and tissue type. At the same age, P-limited plants were smaller and had higher shoot HCNp but lower root HCNp. Ontogenetically controlled comparisons showed a P effect of lesser magnitude, and that there was also an increase in the allocation of N to dhurrin in shoots of P-limited plants. Colonization by AM had little effect on shoot HCNp, but increased root HCNp and the allocation of N to dhurrin in roots. Divergent responses of roots and shoots to P, AM and with ontogeny demonstrate the importance of broadening the predominantly foliar focus of plant defence studies/theory, and of ontogenetically controlled comparisons., (© 2013 John Wiley & Sons Ltd.)

The long-term efficacy of stormwater treatment systems requires continuous pollutant removal without substantial re-release. Hence, the division of incoming pollutants between temporary and permanent removal pathways is fundamental. This is pertinent to nitrogen, a critical water body pollutant, which on a broad level may be assimilated by plants or microbes and temporarily stored, or transformed by bacteria to gaseous forms and permanently lost via denitrification. Biofiltration systems have demonstrated effective removal of nitrogen from urban stormwater runoff, but to date studies have been limited to a 'black-box' approach. The lack of understanding on internal nitrogen processes constrains future design and threatens the reliability of long-term system performance. While nitrogen processes have been thoroughly studied in other environments, including wastewater treatment wetlands, biofiltration systems differ fundamentally in design and the composition and hydrology of stormwater inflows, with intermittent inundation and prolonged dry periods. Two mesocosm experiments were conducted to investigate biofilter nitrogen processes using the stable isotope tracer 15NO3(-) (nitrate) over the course of one inflow event. The immediate partitioning of 15NO3(-) between biotic assimilation and denitrification were investigated for a range of different inflow concentrations and plant species. Assimilation was the primary fate for NO3(-) under typical stormwater concentrations (∼1-2 mg N/L), contributing an average 89-99% of 15NO3(-) processing in biofilter columns containing the most effective plant species, while only 0-3% was denitrified and 0-8% remained in the pore water. Denitrification played a greater role for columns containing less effective species, processing up to 8% of 15NO3(-), and increased further with nitrate loading. This study uniquely applied isotope tracing to biofiltration systems and revealed the dominance of assimilation in stormwater biofilters. The findings raise important questions about nitrogen release upon plant senescence, seasonally and in the long term, which have implications on the management and design of biofiltration systems.

Cassava (Manihot esculenta Crantz) is the staple food source for over 850million people worldwide. Cassava contains cyanogenic glucosides and can be toxic to humans, causing paralysing diseases such as konzo, and even death if not properly processed. Konzo epidemics are often associated with times of drought. This may be due to a greater reliance on cassava as it is drought tolerant, but it may also be due to an increase in cyanogenic glucosides. Episodic droughts are forecast to become more common in many cassava-growing regions. We therefore sought to quantify the effect of water-stress on both yield and cyanogenic glucoside concentration (CNc) in the developing tubers of cassava. Five-month-old plants were grown in a glasshouse and either well watered or droughted for 28 days. A subset of droughted plants was re-watered half way through the experiment. Droughted plants had 45% fewer leaves and lower tuber yield, by 83%, compared with well-watered plants. CNc was 2.9-fold higher in the young leaves of droughted plants, whereas CNc in tubers from droughted plants was 4-fold greater than in tubers from well-watered plants. Re-watered plants had a similar biomass to control plants, and lower CNc than droughted plants. These findings highlight the important link between food quality and episodic drought.

The capacity of mycorrhizal and non-mycorrhizal root systems to reduce nitrate (NO₃⁻) and ammonium (NH₄⁺) loss from soils via leaching was investigated in a microcosm-based study. A mycorrhiza defective tomato mutant and its mycorrhizal wildtype progenitor were used in this experiment in order to avoid the indirect effects of establishing non-mycorrhizal control treatments on soil nitrogen cycling and the wider soil biota. Mycorrhizal root systems dramatically reduced nitrate loss (almost 40 times less) via leaching, compared to their non-mycorrhizal counterparts, following a pulse application of ammonium nitrate to experimental microcosms. The capacity of AM to reduce nutrient loss via leaching has received relatively little attention, but as demonstrated here, can be significant. Taken together, these data highlight the need to consider the potential benefits of AM beyond improvements in plant nutrition alone.

The ability to reuse winery wastewater would be of significant benefit to the wine industry, as it could potentially be a cost-effective method of wastewater management, whilst at the same time providing a valuable water resource. This study investigated the effects of different dilutions of a semi-synthetic winery wastewater on the growth and germination of four common crop species in a glasshouse study; barley (Hordeum vulgare), millet (Pennisetum glaucum), lucerne (Medicago sativa) and phalaris (Phalaris aquatica). The wastewater caused a significant delay in the germination of lucerne, millet and phalaris, although overall germination percentage of all species was not affected. Vegetative growth was significantly reduced in all species, with millet being the most severely affected. The germination index of barley correlated very highly (r(2)=0.99) with barley biomass, indicating that barley seed germination bioassays are highly relevant to plant growth, and therefore may be of use as a bioassay for winery wastewater toxicity., (Copyright 2010 Elsevier B.V. All rights reserved.)

Global food security in a changing climate depends on both the nutritive value of staple crops as well as their yields. Here, we examined the direct effect of atmospheric CO(2) on cassava (Manihot esculenta Cranz., manioc), a staple for 750 million people worldwide. Cassava is poor in nutrients and contains high levels of cyanogenic glycosides that break down to release toxic hydrogen cyanide when damaged. We grew cassava at three concentrations of CO(2) (C(a): 360, 550 and 710 ppm) supplied together with nutrient solution containing either 1 mM or 12 mM nitrogen. We found that total plant biomass and tuber yield (number and mass) decreased linearly with increasing C(a). In the worst-case scenario, tuber mass was reduced by an order of magnitude in plants grown at 710 ppm compared with 360 ppm CO(2). Photosynthetic parameters were consistent with the whole plant biomass data. It is proposed that since cassava stomata are highly sensitive to other environmental variables, the decrease in assimilation observed here might, in part, be a direct effect of CO(2) on stomata. Total N (used here as a proxy for protein content) and cyanogenic glycoside concentrations of the tubers were not significantly different in the plants grown at elevated CO(2). By contrast, the concentration of cyanogenic glycosides in the edible leaves nearly doubled in the highest C(a). If leaves continue to be used as a protein supplement, they will need to be more thoroughly processed in the future. With increasing population density, declining soil fertility, expansion into marginal farmland, together with the predicted increase in extreme climatic events, reliance on robust crops such as cassava will increase. The responses to CO(2) shown here point to the possibility that there could be severe food shortages in the coming decades unless CO(2) emissions are dramatically reduced, or alternative cultivars or crops are developed.

The effects of colonisation of roots by arbuscular mycorrhizal fungi (AMF) on soil respiration, plant growth, nutrition, and soil microbial communities were assessed using a mycorrhiza-defective tomato (Solanum lycopersicum L.) mutant and its mycorrhizal wild-type progenitor. Plants were grown in rhizocosms in an automated respiration monitoring system over the course of the experiment (79 days). Soil respiration was similar in the two tomato genotypes, and between P treatments with plants. Mycorrhizal colonisation increased P and Zn content and decreased root biomass, but did not affect aboveground plant biomass. Soil microbial biomass C and soil microbial communities based on phospholipid fatty acid (PLFA) analysis were similar across all treatments, suggesting that the two genotypes differed little in their effect on soil activity. Although approximately similar amounts of C may have been expended belowground in both genotypes, they may have differed in the relative C allocation to root construction v. respiration. Further, net soil respiration did not differ between the two tomato genotypes, but root dry weight was lower in mycorrhizal roots, and respiration of mycorrhizal roots per unit dry weight was higher than nonmycorrhizal roots. This indicates that the AM contribution to soil respiration may indeed be significant, and nutrient uptake per unit C expenditure belowground in this experiment appeared to be higher in mycorrhizal plants.

This review considers some of the mechanistic processes that involve roots in the soil nitrogen (N) cycle, and their implications for the ecological functions that retain N within ecosystems: 1) root signaling pathways for N transport systems, and feedback inhibition, especially for NO(3)(-) uptake; 2) dependence on the mycorrhizal and Rhizobium/legume symbioses and their tradeoffs for N acquisition; 3) soil factors that influence the supply of NH(4)(+) and NO(3)(-) to roots and soil microbes; and 4) rhizosphere processes that increase N cycling and retention, such as priming effects and interactions with the soil food web. By integrating information on these plant-microbe-soil N processes across scales and disciplinary boundaries, we propose ideas for better manipulating ecological functions and processes by which the environment provides for human needs, i.e., ecosystem services. Emphasis is placed on agricultural systems, effects of N deposition in natural ecosystems, and ecosystem responses to elevated CO(2) concentrations. This shows the need for multiscale approaches to increase human dependence on a biologically based N supply.

Arbuscular mycorrhizas are predicted to be important in defining plant responses to elevated atmospheric CO 2 concentrations. A mycorrhiza-defective tomato (Solanum lycopersicum L.) mutant with reduced mycorrhizal colonisation (rmc) and its mycorrhizal wild-type progenitor (76R MYC+) were grown under ambient and elevated atmospheric CO 2 concentrations (eCO 2 ) in a controlled environment chamber-based pot study. Plant growth, nutrient contents and mycorrhizal colonisation were measured four times over a 72-day period. The 76R MYC+ plants generally had higher concentrations of P, N and Zn than their rmc counterparts. Consistent with earlier studies, mycorrhizal colonisation was not affected by eCO 2 . Growth of the two genotypes was very similar under ambient CO 2 conditions. Under eCO 2 the mycorrhizal plants initially had higher biomass, but after 72 days, biomass was lower than for rmc plants, suggesting that in this pot study the costs of maintaining carbon inputs to the fungal symbiont outweighed the benefits with time.

Colonization of two plant species by Glomus intraradices was studied to investigate the two morphological types (Arum and Paris), their symbiotic interfaces and metabolic activities. Root pieces and sections were stained to observe the colonization and metabolic activity of all mycorrhizal structures. There were no growth responses observed in the plants caused by mycorrhizal symbiosis. The two morphological types had a similar percentage of root colonized, but the Arum-type had higher metabolic activity. Most of the mycorrhizal structures (88%) showed succinate dehydrogenase activity; about half showed acid phosphatase activity; and a small percentage showed alkaline phosphatase activity. Phosphatase activity was highest in arbuscules and low in intercellular hyphae in the Arum-type colonization. In the Paris-type, hyphal coils and arbusculate coils showed a similar intermediate percentage of phosphatase activity. We conclude that acid phosphatase is more important than alkaline phosphatase in both colonization types. We discuss the possibility that, whereas arbuscules in Arum-type are the main site for phosphorus release to the host plant, both the hyphal and arbusculate coils may be involved in the Paris-type.