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PurposeForests play a critical role in terrestrial ecosystem carbon cycling and the mitigation of global climate change. Intensive forest management and global climate change have had negative impacts on the quality of forest soils via soil acidification, reduction of soil organic carbon content, deterioration of soil biological properties, and reduction of soil biodiversity. The role of biochar in improving soil properties and the mitigation of greenhouse gas (GHG) emissions has been extensively documented in agricultural soils, while the effect of biochar application on forest soils remains poorly understood. Here, we review and summarize the available literature on the effects of biochar on soil properties and GHG emissions in forest soils.Materials and methodsThis review focuses on (1) the effect of biochar application on soil physical, chemical, and microbial properties in forest ecosystems; (2) the effect of biochar application on soil GHG emissions in forest ecosystems; and (3) knowledge gaps concerning the effect of biochar application on biogeochemical and ecological processes in forest soils.Results and discussionBiochar application to forests generally increases soil porosity, soil moisture retention, and aggregate stability while reducing soil bulk density. In addition, it typically enhances soil chemical properties including pH, organic carbon stock, cation exchange capacity, and the concentration of available phosphorous and potassium. Further, biochar application alters microbial community structure in forest soils, while the increase of soil microbial biomass is only a short-term effect of biochar application. Biochar effects on GHG emissions have been shown to be variable as reflected in significantly decreasing soil N2O emissions, increasing soil CH4 uptake, and complex (negative, positive, or negligible) changes of soil CO2 emissions. Moreover, all of the aforementioned effects are biochar-, soil-, and plant-specific.ConclusionsThe application of biochars to forest soils generally results in the improvement of soil physical, chemical, and microbial properties while also mitigating soil GHG emissions. Therefore, we propose that the application of biochar in forest soils has considerable advantages, and this is especially true for plantation soils with low fertility.

PURPOSE: The rationale of this paper is to review the state of the art regarding the biotic and abiotic reactions that can influence Fe availability in soils. In soil, the management-induced change from oxic to anoxic environment results in temporal and spatial variations of redox reactions, which, in turn, affect the Fe dynamics and Fe mineral constituents. Measuring the Fe forms in organic complexes and the interaction between bacteria and Fe is a major challenge in getting a better quantitative understanding of the dynamics of Fe in complex soil ecosystems. MATERIALS AND METHODS: We review the existing literature on chemical and biochemical processes in soils related with the availability of Fe that influences plant nutrition. We describe Fe acquisition by plant and bacteria, and the different Fe–organic complexes in order to understand their relationships and the role of Fe in the soil carbon cycle. RESULTS AND DISCUSSION: Although total Fe is generally high in soil, the magnitude of its available fraction is generally very low and is governed by very low solubility of Fe oxides. Plants and microorganisms can have different strategies in order to improve Fe uptake including the release of organic molecules and metabolites able to form complexes with Feᴵᴵᴵ. Microorganisms appear to be highly competitive for Fe compared with plant roots. Crystalline Fe and poorly crystalline (hydro)oxides are also able to influence the carbon storage in soil. CONCLUSION: The solubility of crystalline Fe minerals in soil is usually very low; however, the interaction with plant, microbes, and organic substance can improve the formation of soluble Feᴵᴵᴵ complexes and increase the availability of Fe for plant growth. Microbes release siderophores and plant exudates (e.g., phytosiderophores, organic acids, and flavonoids), which can bind and solubilize the Fe present in minerals. The improved understanding of this topic can enable the identification of effective solutions for remedying Fe deficiency or, alternatively, restricting the onset of its symptoms and yield’s limitations in crops. Therefore, development and testing of new analytical techniques and an integrated approach between soil biology and soil chemistry are important prerequisites.

PurposeSoil water repellency (SWR) can interrupt water infiltration that may decline plant growth and potentially trigger soil erosion. Until now research has been mainly focused on understanding the mechanisms of SWR at different scales by observation and modelling studies.Materials and methodsThis review systematically discusses the possible mechanisms at different scales of the occurrence and persistence of SWR from nanoscale to ecosystem scale.Results and discussionSoil characteristics are strongly related to the severity of SWR, particularly in soil organic matter and soil moisture. The presence of a higher amount of hydrophobic organic compounds and lower soil moisture content lead to higher water repellency, suggesting that the interaction at the nanoscale between organic compounds and water molecules primarily determines the persistence of SWR. The repeated alternation of drying-wetting process largely modifies the relationship between water molecules and soil particles that impacts the possibility of SWR from hydrophilic in wet condition to hydrophobic in dry condition. Within ecosystem scale, vegetation and microbes are original sources of SWR-inducing compounds influencing the distribution and prevalence of SWR. Nevertheless, the challenge of global climate change, drought and warming can increase SWR. Extreme SWR induces more serious runoff and overland flow that is enhanced by intensive precipitation.ConclusionsWe conclude that understanding the interaction of water molecules and organic compounds at soil particle surface is essential to understand SWR at the nanoscale. Expanding the mechanisms of SWR from nanoscale to a larger scale is fundamental to improve the remediation of soil pollution and mitigate global change.

Purpose Many agricultural and brownfield soils are polluted and more have become marginalised due to the introduction of new, risk-based legislation. The European Environment Agency estimates that there are at least 250,000 polluted sites in the member states that require urgent remedial action. There is also significant volumes of wastewaters and dredged polluted sediments. Phytotechnologies potentially offer a cost-effective in situ alternative to conventional technologies for remediation of low to medium-contaminated matrices, e.g. soils, sediments, tailings, solid wastes and waters. For further development, social and commercial acceptance, there is a clear requirement for up-to-date information on successes and failures of these technologies based on evidence from the field. This review reports the outcomes from several integrated experimental attempts to address this at both field and market level in the 29 countries participating in COST Action 859. Results and discussion This review offers insight into the deployment of promising and emergent in situ phytotechnologies, for sustainable remediation and management of contaminated soils and water, that integrative research findings produced between 2004 and 2009 by members of COST Action 859. Many phytotechnologies are at the demonstration level, but relatively few have been applied in practice on large sites. They are not capable of solving all problems. Those options that may prove successful at market level are (a) phytoextraction of metals, As and Se from marginally contaminated agricultural soils, (b) phytoexclusion and phytostabilisation of metal- and As-contaminated soils, (c) rhizodegradation of organic pollutants and (d) rhizofiltration/rhizodegradation and phytodegradation of organics in constructed wetlands. Each incidence of pollution in an environmental compartment is different and successful sustainable management requires the careful integration of all relevant factors, within the limits set by policy, social acceptance and available finances. Many plant stress factors that are not evident in short-term laboratory experiments can limit the effective deployment of phytotechnologies at field level. The current lack of knowledge on physicochemical and biological mechanisms that underpin phytoremediation, the transfer of contaminants to bioavailable fractions within the matrices, the long-term sustainability and decision support mechanisms are highlighted to identify future R&D priorities that will enable potential end-users to identify particular technologies to meet both statutory and financial requirements. Conclusions Multidisciplinary research teams and a meaningful partnership between stakeholders are primary requirements that determine long-term ecological, ecotoxicological, social and financial sustainability of phytotechnologies and to demonstrate their efficiency for the solution of large-scale pollution problems. The gap between research and development for the use of phytoremediation options at field level is partly due to a lack of awareness by regulators and problem owners, a lack of expertise and knowledge by service providers and contractors, uncertainties in long-term effectiveness and difficulties in the transfer of particular metabolic pathways to productive and widely available plants. Networks such as COST Action 859 are highly relevant to the integration of research activity, maintenance of projects that demonstrate phytoremediation at a practical field scale and to inform potential end-users on the most suitable techniques. Biomass for energy and other financial returns, biodiversity and ecological consequences, genetic isolation and transfer of plant traits, management of plant-microorganism consortia in terrestrial systems and constructed wetlands, carbon sequestration and soil and water multi-functionality are identified as key areas that need to be incorporated into existing phytotechnologies.

Purpose Denitrification has been extensively studied in soils from temperate zones in industrialized countries. However, few studies quantifying denitrification rates in soils from tropical and subtropical zones have been reported. Denitrification mechanisms in tropical/subtropical soils may be different from other soils due to their unique soil characteristics. The identification of denitrification in the area is crucial to understand the role of denitrification in the global nitrogen (N) cycle in terrestrial ecosystems and in the interaction between global environmental changes and ecosystem responses. Materials and methods We review the existing literature on microbially mediated denitrification in tropical/subtropical soils, attempting to provide a better understanding about and new research directions for denitrification in these regions. Results and discussion Tropical and subtropical soils might be characterized by generally lower denitrification capacity than temperate soils, with greater variability due to land use and management practices varying temporally and spatially. Factors that influence soil water content and the nature and rate of carbon (C) and N turnover are the landscape-scale and field-scale controls of denitrification. High redox potential in the field, which is mainly attributed to soil oxide enrichment, may be at least one critical edaphic variable responsible for slow denitrification rates in the humid tropical and subtropical soils. However, soil pH is not responsible for these slow denitrification rates. Organic C mineralization is more important than total N content and C/N in determining denitrification capacity in humid subtropical soils. There is increasing evidence that the ecological consequence of denitrification in tropical and subtropical soils may be different from that of temperate zones. Contribution of denitrification in tropical and subtropical regions to the global climate warming should be considered comprehensively since it could affect other greenhouse gases, such as methane (CH 4 ) and carbon dioxide (CO 2 ), and N deposition. Conclusions Tropical/subtropical soils have developed several N conservation strategies to prevent N losses via denitrification from the ecosystems. However, the mechanisms involved in the biogeochemical regulation of tropical and subtropical ecosystem responses to environmental changes are largely unknown. These works are important for accurately modeling denitrification and all other simultaneously operating N transformations.

Purpose Rising levels of nitrogen (N) deposition are influencing urban forest carbon (C) and N dynamics due to greater human disturbance compared to those in rural areas. N deposition in combination with increased atmospheric carbon dioxide (CO 2 ) and water limitation may alter C and N storage in urban forests. This review aimed to provide a better understanding of N and C storage under N deposition scenarios in urban forests. Results and discussion Globally, fuel combustion and biomass burning contribute in approximately 70 and 16 % of the NO x emission respectively. It is also estimated that NH y and NO x are two to four times higher in urban forests compared to rural areas. However, higher N deposition may not always result in increased N and C storage in urban forests. In fact, urban forests may even show early symptoms of N and C losses under climate change. For example, urban forests in fire-prone areas require higher frequency of burning to reduce the threat of wildfires, leading to an acceleration of C and N loss. Additionally, chronic N deposition may result in an early N loss in urban forests due to faster N saturation and soil acidification in urban forests compared to rural forests. Studies of N deposition on urban forests using N isotope composition (δ 15 N) also showed that N loss from urban forests can occur through the direct leaching of the deposited NO 3 − -N. We also noted that using different 15 N signal of soil and plant in combination of tree ring δ 15 N may provide a better understanding of N movement in urban forests. Conclusions Although urban forests may become a source of C and N faster than rural forests, N-limited urban forests may benefit from N deposition to retain both N and C stocks longer than non-N-limited urban forests. Appropriate management practices may also help to delay such symptoms; however, the main source of emission still needs to be managed to reduce both N deposition and rising atmospheric CO 2 in urban forests. Otherwise, the N and C stocks in urban forests may further decline when prolonged drought conditions under global climate change increase the frequency of fires and reduce plant photosynthesis.

Introduction The objective of this review was to provide a better understanding of how global climate change and fire influence the occurrence of understorey legumes and thereby biological nitrogen (N) fixation rates in forest ecosystems. Legumes are interesting models since they represent an interface between the soil, plant, and microbial compartments, and are directly linked to nutrient cycles through their ability to fix N. As such, they are likely to be affected by environmental changes. Result and discussion Biological N fixation has been shown to increase under enriched CO 2 conditions, but is constrained by the availability of phosphorus and water. Climate change can also influence the species composition of legumes and their symbionts through warming, altered rainfall patterns, or changes in soil physicochemistry, which could modify the effectiveness of the symbiosis. Additionally, global climate change may increase the occurrence and intensity of forest wildfires thereby further influencing the distribution of legumes. The establishment of leguminous species is generally favored by fire, as is N 2 fixation. This fixed N could therefore replenish the N lost through volatilization during the fire. However, fire may also generate shifts in the associated microbial community which could affect the outcome of the symbiosis. Conclusion Understorey legumes are important functional species, and even when they cannot reasonably be expected to reestablish the nutrient balance in forest soils, they may be used as indicators to monitor nutrient fluxes and the response of forest ecosystems to changing environmental conditions. This would be helpful to accurately model ecosystem N budgets, and since N is often a limiting factor to plant growth and a major constraint on C storage in ecosystems, would allow us to assess more precisely the potential of these forests for C sequestration.

PURPOSE: Climate change is likely to increase both intensity and frequency of drought stress. The responses of soil respiration (R ₛ) and its components (root respiration, R ᵣ; mycorrhizal respiration, R ₘ; and heterotrophic respiration, R ₕ) to drought stress can be different. This work aims to review the recent and current literature about the variations in R ₛ during the period of drought stress, to explore potential coupling processes and mechanisms between R ₛ and driving factors in the context of global climate change. RESULTS AND DISCUSSION: The sensitivity of soil respiration and its components to drought stress depended on the ecosystems and seasonality. Drought stress depressed R ₛ in mesic and xeric ecosystems, while it stimulated R ₛ in hydric ecosystems. The reductions in supply and availability of substrate decreased both auto- and heterotrophic respirations, leading to the temporal decoupling of root and mycorrhizal respiration from canopy photosynthesis as well as C allocation. Drought stress also reduced the diffusion of soluble C substrate, and activities of extracellular enzymes, consequently, limited microbial activity and reduced soil organic matter decomposition. Drought stress altered Q ₁₀ values and broke the coupling between temperature and soil respiration. Under drought stress conditions, R ₘ is generally less sensitive to temperature than R ᵣ and R ₕ. Elevated CO₂ concentration alleviated the negative effect of drought stress on soil respiration, principally due to the promotion of plant C assimilation subsequently, which increased substrate supply for respiration in both roots and soil microorganisms. Additionally, rewetting stimulated soil respiration dramatically in most cases, except for soil that experienced extreme drought stress periods. The legacy of drought stress can also regulate the response of soil respiration rate to rewetting events in terrestrial ecosystems through changing abiotic drivers and microbial community structure. CONCLUSIONS AND PERSPECTIVES: There is increasing evidence that drought stress can result in the decoupling of the above- and belowground processes, which are associated with soil respiration. However, studies on the variation in rates of soil respiration and its components under different intensities and frequencies of drought stress over the ecosystems should be reinforced. Meanwhile, molecular phylogenetics and functional genomics should be applied to link microbial ecology to the process of R ₛ. In addition, we should quantify the relationship between soil respiration and global change parameters (such as warming and elevated [CO₂]) under drought stress. Models simulating the rates of soil respiration and its components under global climate change and drought stress should also be developed.

Recent accelerated climate change has exacerbated existing environmental problems in the Mediterranean Basin that are caused by the combination of changes in land use, increasing pollution and declining biodiversity. For five broad and interconnected impact domains (water, ecosystems, food, health and security), current change and future scenarios consistently point to significant and increasing risks during the coming decades. Policies for the sustainable development of Mediterranean countries need to mitigate these risks and consider adaptation options, but currently lack adequate information — particularly for the most vulnerable southern Mediterranean societies, where fewer systematic observations schemes and impact models are based. A dedicated effort to synthesize existing scientific knowledge across disciplines is underway and aims to provide a better understanding of the combined risks posed.

The present review paper investigates how traditional indigenous practices supports sustainable agriculture. The paper is focused on analyzing different sustainable indigenous agricultural methods that have been developed and practiced by different indigenous communities for generations. The paper seeks to highlight the relevance in achieving SDGs. Furthermore, the review investigates on implementation of indigenous technologies to predict weather changes, incentives allocated for sustainable agricultural practices and agricultural initiatives proposed by G20 summit 2023 to adopt ‘smart, sustainable and serve’ (3S) strategies. Comprehensive literature search has been done among relevant academic databases with peer reviewed articles, reports and other publications related to traditional indigenous practices and their contribution to agricultural sustainability and SDGs. Indigenous agricultural methods such as intercropping, agroforestry, and organic farming show a profound awareness of ecological processes and place a strong emphasis on the preservation of biodiversity, soil fertility, water management, and sustainable land use. The paper records the vast knowledge and skills that indigenous societies have gathered over many generations and discuss the traditional indigenous practices in addressing current agricultural difficulties. This paper highlights the importance of valuing and integrating traditional indigenous practices as we strive towards agricultural sustainability and the achievement of the SDGs as discussed on G20 in India and how it helps us in achieving sustainable global economic growth.