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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. [ABSTRACT FROM AUTHOR]

Background: Periods of drought are projected to increase in intensity and frequency across many parts of the world, affecting freshwater availability for agriculture and limiting cropping productivity. Exploring innovative opportunities to utilise novel drought resistant crops should be prioritized to sustainably meet growing demand for food and fibre. The potential benefits of industrial hemp (Cannabis sativa L.) as a drought resistant fibre crop have been touted, but the underlying evidence base of such claims is conflicting. Hemp has several drought resistance traits that allow it to thrive under water deficit, including deep roots and effective stomatal regulation, but studies report varying results for water requirements and water use efficiency. Scope: In this context, we provide a comprehensive discussion of the current state of knowledge regarding fibre hemp water use in a range of environments and between varieties, highlighting physiological attributes that contribute to its drought resistance with a view to guiding and stimulating further research. Conclusions: With relatively low water requirements compared to other fibre crops, hemp shows great potential as a drought resistant crop, offering exciting possibilities to produce sustainable fibre in a changing climate. [ABSTRACT FROM AUTHOR]

Aims: Mycorrhiza and rhizodeposition are important for nutrient and water uptake but their role under variable water conditions remains unclear. We investigated how mycorrhiza and rhizodeposition contributed to plant uptake of water, nitrogen (N) and phosphorus (P) in response to water availability and variability. Methods: Two tomato genotypes (a mycorrhiza-defective tomato mutant, rmc, and its mycorrhizal wild-type progenitor, Solanum lycopersicum cv. Rio Grande 76R were grown in a greenhouse under different watering conditions (wet, medium, and dry conditions, and dry-rewet conditions). Results: We found that non-mycorrhizal plants were as successful as mycorrhizal plants in terms of N and water uptake under both reduced and variable water availability. However, we observed lower water use efficiency and shoot N recovery in mycorrhizal plants that could be driven by mycorrhizal requirements for water and N. Mycorrhizal plants were more extensively colonised and were more successful in taking up P under dry conditions compared to non-mycorrhizal plants. On the other hand, greater specific root exudation in non-mycorrhizal plants across all watering conditions resulted in relatively greater uptake of N than of P. Conclusions: A flexible carbon allocation towards mycorrhiza and root exudation may help plants in maintaining a balanced uptake of N and P under variable water conditions. [ABSTRACT FROM AUTHOR]

Purpose: Belowground carbon (C) allocation for nitrogen (N) acquisition plays a crucial role in determining primary productivity and plant competitiveness in legume-grass mixtures, but beyond modeling and qualitative assessments, this remains poorly understood, especially with regard to drought stress and interspecific interactions. Methods: We grew a legume (Trifolium repens) and a grass (Lolium perenne) in monocultures and as a 50:50 mixture (with same plant density), at 70% and 50% soil water holding capacity representing non-drought and drought conditions, for 104 days in a growth chamber experiment. By using continuous 13CO2 labelling and 15N pulse soil-labelling, we analyzed how drought and interspecific interaction affected belowground C allocation (including root biomass, root respiration and rhizodeposition) and N acquisition through soil N uptake and biological N fixation. Results: Drought increased belowground C allocation per unit of N acquisition in the legume, but not in the grass. Drought significantly reduced biological N fixation in the legume, so that the legume allocated relatively more C to take up soil N. Interspecific competition increased belowground C allocation per unit of N acquisition, which could be attributed to a reduction in biological N fixation by the legume and an increased abundance of the grass. Conclusions: We highlight that drought and interspecific competition for N strongly alter C allocation towards biological N fixation and soil N uptake. Our measurements provide important process-based information to improve modeling drought effects on productivity and composition in legume-grass mixtures. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Background and aims: The importance of plant-soil feedback is becoming widely acknowledged; however, how different soil conditions influence these interactions is still relatively unknown. Using soil from a degraded old-field and a remnant grassland, we aimed to explore home-field advantages in plant-soil feedbacks and plant responses to the abiotic and biotic soil conditions. We quantified the soil bacterial and fungal community from these sites and their responses to soil conditions and plant species.Methods: Sterilized old-field and remnant-grassland soil was inoculated with home or away soil in a reciprocal transplant experiment using a native grass, Rytidosperma auriculatum, and an invasive grass, Avena barbata, as test species. The soil fungal and bacterial communities were characterised using high throughput sequencing.Results: Plants had a greater growth response to microbes when an inoculant was added to its home soil. However, this relationship is complex, with microbial communities changing in response to the plant species and soil type.Conclusion: The apparent home-field advantage of the soil microbes shown in this study may restrict the utility of inoculants as a management tool. However, since we inoculated sterile soil, future work should focus on understanding how the inoculated microbial community interacts and competes with resident communities. [ABSTRACT FROM AUTHOR]

Chemical ecology provides unique perspectives for managing plant/human interactions to achieve food security. Allelochemicals function as chemical defences of crop plants, enhancing yields. While ingested allelochemicals can confer health benefits to humans, at higher concentrations they are often toxic. The delicate balance between their positive and negative effects in crop plants is influenced by many factors. Some of these—how environment affects optimal levels of defence, how metabolic interactions with nutrients affect toxicity of ingested allelochemicals—are the province of chemical ecology. These biological factors, however, interact with social factors, and neither can be studied independently. Chemical ecologists must work together with social scientists to understand the overall system. Here, we illustrate such an integrative approach, analysing the interactions between people and the major tropical crop manioc, which contains cyanogenic glucosides. Polymorphism for cyanogen levels in manioc facilitates analysis of how costs and benefits of crop defences vary among social systems. We first show how people/manioc interactions diversified in this crop’s Amazonian homeland, then turn to the remarkable cultural adaptations of African farmers since manioc’s introduction 400 years ago. Finally, we evaluate new coevolutionary challenges in parts of Africa where people are still unfamiliar with a potentially dangerous crop. Current environmental and social catastrophes have restricted farmers’ options, resulting in acute problems in health of humans and ecosystems. We show that high cyanogen levels confer important agronomic advantages, but also impose costs and constraints that can only be understood when biology is coupled with analysis of social, cultural and economic factors. Detoxifying manioc technologically requires know-how, time, water and other resources. Detoxifying residual dietary cyanogens metabolically depends on being able to grow, or to buy, the nutrients required for detoxification, primarily sulphur-rich proteins. Solutions that appear adaptive today may not be in the future, as changing climate, rising atmospheric CO2 levels and decreased access to fertilizers affect productivity of crops and the nutrient and allelochemical composition of the foods they are used to produce. [ABSTRACT FROM AUTHOR]

Inhibitory experiments were conducted to investigate the responses of the population sizes of ammonia-oxidizing archaea (AOA) and bacteria (AOB) and the potential nitrification rates (PNRs) to Cu contamination in four Chinese soils. PNR was determined using a substrate-induced nitrification (SIN) assay, and the population size of the nitrifiers represented by amoA gene abundances was quantified using a real-time polymerase chain reaction (qPCR) assay. Both population size and PNR of the ammonia oxidizers reduced considerably at high Cu concentrations in all the soils. Bacterial amoA gene abundance was reduced by from 107-fold (Hailun soil) to more than 232-fold (Hangzhou soil) at the highest Cu concentrations (2,400 mg kg−1 Cu for Hailun, Langfang and Guangzhou soils and 1,600 mg kg−1 Cu for Hangzhou soil), while reduction in archaeal amoA gene abundance was from 10-fold (Langfang soil) to 89-fold (Hangzhou soil). AOA seemed more tolerant to Cu contamination than AOB. Nitrification rates were inhibited by more than 50% at a Cu concentration of 600 mg kg−1, and by more than 90% at the highest Cu concentrations in all soils. These results indicated that both AOA and AOB can be inhibited by toxic metals, highlighting the need to consider the role of AOA in nitrification in soils. [ABSTRACT FROM AUTHOR]

Many of the world’s soils are zinc (Zn) deficient. Consequently, many crops experience reduced growth, yield and tissue Zn concentrations. Reduced concentrations of Zn in the edible portions of crops have important implications for human Zn nutrition; this is a cause of global concern. Most terrestrial plant species form arbuscular mycorrhizas (AM) with a relatively limited number of specialized soil fungi. Arbuscular mycorrhizal fungi (AMF) can take up nutrients, including Zn, and transfer them to the plant, thereby enhancing plant nutrition. Under high soil Zn concentrations the formation of AM can also ‘protect’ against the accumulation of Zn in plant tissues to high concentrations. Here, a short review focusing on the role of AM in enhancing plant Zn nutrition, principally under low soil Zn concentrations, is presented. Effects of Zn on the colonisation of roots by AMF, direct uptake of Zn by AMF, the role of AM in the Zn nutrition of field grown plants, and emerging aspects of Zn molecular physiology of AM, are explored. Emergent knowledge gaps are identified and discussed in the context of potential future research. [ABSTRACT FROM AUTHOR]

Background and aims: Rhizodeposition is organic matter released by living plant roots that can be transformed by microbes into particulate organic matter (POM), but that can also become more stable through the adsorption of organic matter onto soil minerals (mineral-associated organic matter, MAOM), thereby playing an important role in mitigating climate change. We examined how root-derived carbon (C) as a proxy for rhizodeposition contributed to POM and MAOM formation in a grassland affected by nitrogen (N) fertilisation and defoliation frequency, and to what degree rhizodeposition was incorporated into microbial biomass.We applied N fertiliser (0 vs. 40 kg N ha−1 yr−1) and defoliation frequencies (3–4 vs. 6–8 clipping events year−1, simulating low and high grazing intensity) for three years, then used a 13CO2 pulse labelling technique to examine the incorporation of rhizodeposition into microbial biomass, POM and MAOM fractions.With N fertilisation, rhizodeposition contributed less to the formation of MAOM compared to the formation of POM, while defoliation frequency decreased the contribution of rhizodeposition into both POM and MAOM, particularly with N fertilisation. Although the MAOM fraction was relatively rich in N (C: N ratio of 10.5 vs. 13.5 for POM), our results suggest that adding inorganic N promoted the formation of POM more than of MAOM from rhizodeposition.A large proportion of rhizodeposition was taken up by microbes that eventually could contribute to POM and MAOM formation. Our results provide insightful information regarding the stabilisation of rhizodeposition into different soil organic matter pools.Methods: Rhizodeposition is organic matter released by living plant roots that can be transformed by microbes into particulate organic matter (POM), but that can also become more stable through the adsorption of organic matter onto soil minerals (mineral-associated organic matter, MAOM), thereby playing an important role in mitigating climate change. We examined how root-derived carbon (C) as a proxy for rhizodeposition contributed to POM and MAOM formation in a grassland affected by nitrogen (N) fertilisation and defoliation frequency, and to what degree rhizodeposition was incorporated into microbial biomass.We applied N fertiliser (0 vs. 40 kg N ha−1 yr−1) and defoliation frequencies (3–4 vs. 6–8 clipping events year−1, simulating low and high grazing intensity) for three years, then used a 13CO2 pulse labelling technique to examine the incorporation of rhizodeposition into microbial biomass, POM and MAOM fractions.With N fertilisation, rhizodeposition contributed less to the formation of MAOM compared to the formation of POM, while defoliation frequency decreased the contribution of rhizodeposition into both POM and MAOM, particularly with N fertilisation. Although the MAOM fraction was relatively rich in N (C: N ratio of 10.5 vs. 13.5 for POM), our results suggest that adding inorganic N promoted the formation of POM more than of MAOM from rhizodeposition.A large proportion of rhizodeposition was taken up by microbes that eventually could contribute to POM and MAOM formation. Our results provide insightful information regarding the stabilisation of rhizodeposition into different soil organic matter pools.Results: Rhizodeposition is organic matter released by living plant roots that can be transformed by microbes into particulate organic matter (POM), but that can also become more stable through the adsorption of organic matter onto soil minerals (mineral-associated organic matter, MAOM), thereby playing an important role in mitigating climate change. We examined how root-derived carbon (C) as a proxy for rhizodeposition contributed to POM and MAOM formation in a grassland affected by nitrogen (N) fertilisation and defoliation frequency, and to what degree rhizodeposition was incorporated into microbial biomass.We applied N fertiliser (0 vs. 40 kg N ha−1 yr−1) and defoliation frequencies (3–4 vs. 6–8 clipping events year−1, simulating low and high grazing intensity) for three years, then used a 13CO2 pulse labelling technique to examine the incorporation of rhizodeposition into microbial biomass, POM and MAOM fractions.With N fertilisation, rhizodeposition contributed less to the formation of MAOM compared to the formation of POM, while defoliation frequency decreased the contribution of rhizodeposition into both POM and MAOM, particularly with N fertilisation. Although the MAOM fraction was relatively rich in N (C: N ratio of 10.5 vs. 13.5 for POM), our results suggest that adding inorganic N promoted the formation of POM more than of MAOM from rhizodeposition.A large proportion of rhizodeposition was taken up by microbes that eventually could contribute to POM and MAOM formation. Our results provide insightful information regarding the stabilisation of rhizodeposition into different soil organic matter pools.Conclusion: Rhizodeposition is organic matter released by living plant roots that can be transformed by microbes into particulate organic matter (POM), but that can also become more stable through the adsorption of organic matter onto soil minerals (mineral-associated organic matter, MAOM), thereby playing an important role in mitigating climate change. We examined how root-derived carbon (C) as a proxy for rhizodeposition contributed to POM and MAOM formation in a grassland affected by nitrogen (N) fertilisation and defoliation frequency, and to what degree rhizodeposition was incorporated into microbial biomass.We applied N fertiliser (0 vs. 40 kg N ha−1 yr−1) and defoliation frequencies (3–4 vs. 6–8 clipping events year−1, simulating low and high grazing intensity) for three years, then used a 13CO2 pulse labelling technique to examine the incorporation of rhizodeposition into microbial biomass, POM and MAOM fractions.With N fertilisation, rhizodeposition contributed less to the formation of MAOM compared to the formation of POM, while defoliation frequency decreased the contribution of rhizodeposition into both POM and MAOM, particularly with N fertilisation. Although the MAOM fraction was relatively rich in N (C: N ratio of 10.5 vs. 13.5 for POM), our results suggest that adding inorganic N promoted the formation of POM more than of MAOM from rhizodeposition.A large proportion of rhizodeposition was taken up by microbes that eventually could contribute to POM and MAOM formation. Our results provide insightful information regarding the stabilisation of rhizodeposition into different soil organic matter pools. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]