Carbon sequestration

The role of subsurface geomechanics in the green energy transition

The global energy landscape is currently experiencing a significant shift towards non-hydrocarbon, sustainable energy sources, often referred to as 'green energy'. This transition is being driven by the urgent need to address the problem of global warming caused by greenhouse gases, most of which are generated by the burning of fossil fuels. This article provides an overview of the role that subsurface geomechanics will play in this transition, focusing on green energy technologies such as carbon sequestration, geothermal energy production, hydrogen storage and nuclear waste disposal. The article starts with a review of geomechanical properties and structures that will be relevant to the green energy transition, such as in situ stresses, elastic moduli, strength properties, permeability, faults and fractures. This is followed by introductions to the four green energy technologies mentioned above. The next section focuses on the specific geomechanical challenges associated with each of these technologies, such as surface subsidence, induced seismicity and fluid and contaminant leakage. Gaps in existing knowledge, and potential pitfalls to be avoided, are highlighted. The article concludes with a brief discussion of public perception of environmental risks associated with subsurface energy technologies. It is concluded that geomechanics will play a key role in each of these emerging subsurface energy technologies, and the knowledge and tools that have mainly been developed in the context of fossil fuel exploitation will be key to these developments.

Dual carbon sequestration with photosynthetic living materials

Natural ecosystems efficiently sequester CO2 but containing and controlling living systems remains challenging. Here, we engineer a photosynthetic living material for dual CO2 sequestration that leverages biomass production and insoluble carbonate formation via microbially induced carbonate precipitation (MICP). To achieve this, we immobilize photosynthetic microorganisms within a printable polymeric network. Digital design and fabrication of the living structures ensure sufficient light access and nutrient supply to encapsulated cyanobacteria, enabling long-term culture for over a year. We showcase that photosynthetic living materials are able to sequester 2.2 ± 0.9 mg of CO2 per gram of hydrogel material over 30 days and 26 ± 7 mg of CO2 over 400 days. These findings highlight the potential of photosynthetic living materials for scalable, low-maintenance carbon sequestration with applications in carbon-neutral infrastructure and CO2 mitigation.

Variability analysis of soil organic carbon content across land use types and its digital mapping using machine learning and deep learning algorithms

Soil organic carbon (SOC) plays a crucial role in carbon cycle management and soil fertility. Understanding the spatial variations in SOC content is vital for supporting sustainable soil resource management. In this study, we analyzed the variability in SOC content across eleven different types of land use in the mining basin of Provence in southeastern France. We modelled this variability spatially using machine and deep learning regression. Four algorithms were tested: random forest (RF), support vector machine (SVM), extreme gradient boosting (XGBoost), and deep neural networks (DNNs). These integrated 162 soil samples and 21 environmental covariates, including climatic parameters, lithology, topographical features, land cover, remote sensing data, and soil physicochemical parameters. The results clearly show a large variability in SOC content across land use types, with forests revealing the highest values (mean of 69.3 g/kg) and arable land the lowest (mean of 8.9 g/kg). The Pearson correlation coefficients (R) indicate that land cover, topography, lithology, environmental indices, and clay content are the main factors influencing the SOC content. The XGBoost model generated the best result (R2 = 0.73), closely followed by RF (R2 = 0.68) and DNN (R2 = 0.60), while SVM showed the weakest performance (R2 = 0.36). XGBoost and RF remain the best options for obtaining reliable results with a limited number of soil samples and reduced calculation time. The results of this study provide vital insights for managing soil organic carbon in southeastern France and for climate change mitigation in sustainable land management.

Mineral Carbonation for Carbon Sequestration: A Case for MCP and MICP

Mineral carbonation is a prominent method for carbon sequestration. Atmospheric carbon dioxide (CO2) is trapped as mineral carbonate precipitates, which are geochemically, geologically, and thermodynamically stable. Carbonate rocks can originate from biogenic or abiogenic origin, whereby the former refers to the breakdown of biofragments and the latter precipitation out of water. Carbonates can also be formed through biologically controlled mechanisms (BCMs), biologically mediated mechanisms (BMMs), and biologically induced mechanisms (BIMs). Microbial carbonate precipitation (MCP) is a BMM occurring through the interaction of organics (extracellular polymeric substances (EPS), cell wall, etc.) and soluble cations facilitating indirect precipitation of carbonate minerals. Microbially induced carbonate precipitation (MICP) is a BIM occurring via different metabolic pathways. Enzyme-driven pathways (carbonic anhydrase (CA) and/or urease), specifically, are promising for the high conversion to calcium carbonate (CaCO3) precipitation, trapping large quantities of gaseous CO2. These carbonate precipitates can trap CO2 via mineral trapping, solubility trapping, and formation trapping and aid in CO2 leakage reduction in geologic carbon sequestration. Additional experimental research is required to assess the feasibility of MICP for carbon sequestration at large scale for long-term stability of precipitates. Laboratory-scale evaluation can provide preliminary data on preferable metabolic pathways for different materials and their capacity for carbonate precipitation via atmospheric CO2 versus injected CO2.

Accurate Force Field for Carbon Dioxide-Silica Interactions Based on Density Functional Theory

Fluid-silica interfaces are ubiquitous in chemistry, occurring in both natural geochemical environments and practical applications ranging from separations to catalysis. Simulations of these interfaces have been, and continue to be, a significant avenue for understanding their behavior. A constraining factor, however, is the availability of accurate force fields. Most simulations use traditional "mixing rules" to determine nonbonded dispersion interactions, an approach that has not been critically examined. Here, we present Lennard-Jones parameters for the interaction of carbon dioxide with silica interfaces that are optimized to reproduce density functional theory (DFT)-based binding energies. The modeling is based on the recently developed silica-DDEC force field, whose atomic charges are consistent with DFT calculations. Standard mixing rules are found to predict weaker CO2 binding to silica than that obtained from DFT, an effect corrected by the optimized parameters given here. This behavior extends to other silica force fields (Clayff and Gulmen-Thompson), and the present Lennard-Jones parameters improve their performance as well. The effects of improved Lennard-Jones parameters on the structural and dynamical properties of condensed CO2 in silica slit pores are also examined.

Subtropical forest floor CO2 emission at the Kaziranga National Park in Northeast India

This study investigates the seasonal and diurnal variations of soil CO2 flux (Fc) and the impact of meteorological variables on its dynamics. The study took place in the subtropical forest ecosystem of Kaziranga National Park (KNP), from November 2019 to March 2020. The highest Fc (6.24 gC m-2 day-1) was observed in the pre-monsoon season (March), and the lowest (0.85 gC m-2 day-1) in winter (February), with the mean value of 2.19 ± 0.84 gC m-2 day-1. Fc is primarily influenced by changes in air temperature (Tair), soil temperature (Tsoil), solar radiation (Rg), vapor pressure deficit (VPD), and photosynthetically active radiation (PAR). This is evident from the strong positive correlations of Fc with Tair, Tsoil, Rg, VPD, and PAR (correlation coefficients being 0.75, 0.67, 0.37, 0.59, and 0.37, respectively; all significant at 99% level) indicating their critical role in driving soil respiration. Conversely, relative humidity (RH) and atmospheric pressure (Pair) negatively affect Fc. Soil moisture (SoilM) influenced Fc to some extent, but its effect was less pronounced compared to Tair, Tsoil, and Rg. Diurnal variations revealed higher Fc during the daytime (between 10:00 and 14:00 IST) and the lowest in the night-time (between 05:30 and 07:00 IST). These findings underline the strong seasonal and diurnal controls of environmental factors on soil respiration enhancing our understanding of carbon dynamics in subtropical forest ecosystems.

Soil carbon stocks of regenerating Icelandic native birch woodlands: Effects of space and time

Icelandic native ecosystems and soils have been severely degraded since settlement in the 9th century. Today, barren landscapes occupy about 45 % of the land surface and only 1.5 % is covered by native birch woodlands versus 20-40 % in pre-settlement times. Iceland's soils are mainly Andisols, among the most carbon-rich soil orders owing to their unique colloidal characteristics. Hence, there is tremendous potential to sequester soil carbon in degraded soils through revegetation activities. The restoration of birch woodlands is considered a national priority, which may significantly impact the nation's carbon budget. The objective of this study was to determine soil carbon concentrations and stocks across chronosequences (0 to 60+ years) of birch woodlands under diverse geographical conditions comprised of ten study areas across Iceland. The highest carbon stocks were found in old birch woodlands with a mean of 7.4 kg C m-2 in the top 30 cm soils, which is unusually high compared to other Nordic deciduous woodlands. We attribute this to andic soil properties that effectively stabilize and sequester soil organic matter. Calculated soil carbon accumulation rates were 0.01 kg m-2 yr-1 for the first 30 years of birch woodland establishment and 0.04-0.07 kg m-2 yr-1 in mature woodlands (30-60 years old). These accumulation rates, if applied to large-scale birch woodland restoration plans, would amount to 20 % of the current total CO2 emissions of Iceland (not counting LULUCF). Importantly, we found a significant impact of dust deposition (up to 1 mm yr-1) on soil carbon stocks, contributing to carbon burial (∼26 g m-2 yr-1) in areas close to dust hotspots. Birch restoration further stabilizes soils from erosion and the above-ground biomass serves as an efficient dust collector. This study documents the potential of birch restoration as a highly effective strategy to address soil degradation and promote soil carbon sequestration across Iceland.

Wetlands function as carbon sink: Evaluation of few floodplains of middle Assam, northeast India in the perspective of climate change

Floodplain wetlands are biologically rich and productive ecosystems that can capture carbon (C) from the atmosphere through macrophytes and phytoplanktons and hold it in soil for a long time thus playing a critical role in mitigating climate change. The Assam state of India has about 1392 floodplain wetlands engulfing around 100,000 ha area in the Brahmaputra and Barak River basin. In the present study, five different wetlands in the middle Assam viz., 47-Morakolong, Jaliguti, Charan, Chatla, and Urmal were chosen for the estimation of C capture and its storage in soil. The net primary planktonic productivity (NPP) of Chatla was much higher (300mgC/m3/hr) than other wetlands where it ranged around 100-150 mgC/m3/hr. Macrophyte coverage was highest (80%) in Chatla followed by Urmal (50%) and 30% in others. Total organic carbon (TOC) content in water was also significantly higher in Chatla than in others. The C content at different depths of the soil (upper 15 and 15-30 cm) of the wetlands varied widely from 1.3 to 7% and in absolute terms, the total C accumulated in top 30 cm varied from 12.65 to 76.95 MgC/ha. The amount of C in upper 30 cm of corresponding upland sites was estimated to be 8.8-33.62 MgC/ha. Thus, wetlands are superior in terms of C accumulation and storage in their soil compared to the corresponding upland sites. If properly managed, the wetlands can be very effective in capturing and storing C and offset GHG emission and global warming to a great extent.

Distinct microbiomes underlie divergent responses of methane emissions from diverse wetland soils to oxygen shifts

Hydrological shifts in wetlands, a globally important methane (CH4) source, are critical constraints on CH4 emissions and carbon-climate feedbacks. A limited understanding of how hydrologically driven oxygen (O2) variability affects microbial CH4 cycling in diverse wetlands makes wetland CH4 emissions uncertain. Transient O2 exposure significantly stimulated anoxic CH4 production in incubations of Sphagnum peat from a temperate bog by enriching for polyphenol oxidizers and polysaccharide degraders, enhancing substrate flow toward methanogenesis under subsequent anoxic conditions. To assess whether shifts in soil microbiome structure and function operate similarly across wetland types, here we examined the sensitivity of different wetland soils to transient oxygenation. In slurry incubations of Sphagnum peat from a minerotrophic fen, and sediments from a freshwater marsh and saltmarsh, we examined temporal shifts in microbiomes coupled with geochemical characterization of slurries and incubation headspaces. Oxygenation did not affect microbiome structure and anoxic CH4 production in mineral-rich fen-origin peat and freshwater marsh soils. Key taxa linked to O2-stimulated CH4 production in the bog-origin peat were notably rare in the fen-origin peat, supporting microbiome structure as a primary determinant of wetland response to O2 shifts. In contrast to freshwater wetland experiments, saltmarsh geochemistry-particularly pH-and microbiome structure were persistently and significantly altered postoxygenation, albeit with no significant impact on greenhouse gas emissions. These divergent responses suggest wetlands may be differentially resistant to O2 fluctuations. With climate change driving greater O2 variability in wetlands, our results inform mechanisms of wetland resistance and highlight microbiome structure as a potential resiliency biomarker.

Inclusive Indian Central Himalayan soil carbon estimates underscores significant inorganic carbon contribution and temporal dynamics: Implications for carbon sequestration

Soil carbon estimates in the Indian Himalayan region-a global climate change hotspot-primarily rely on the lossy wet oxidation method and predominantly focus on soil organic carbon (SOC), neglecting the soil inorganic carbon (SIC) component. Sensitive and holistic soil carbon estimates are crucial for effective policy planning. By incorporating eight major Central Himalayan forest types along a 3000 m elevational gradient, we report that the acidic Himalayan soil (surface soil pH: 4.74-6.84) of the selected forest types hold up to 31% of the total soil carbon stock as SIC stock. Using soil carbon and soil organic matter assays based on elemental analyzer and the loss-on-ignition method, we established that these Himalayan soils store less than 50% of SOC in SOM, challenging the use of universal factors in the region. The amount of SOC in SOM also showed temporal variability. The machine learning Random Forest algorithm highlighted the influence of SOM and climate variables in regulating the distribution of SOC, microbial biomass carbon, and key carbon cycling soil enzymes. The vertical distribution of SOC was more uniform than that of SIC. We found higher activity of soil carbon-cycling enzymes (dehydrogenase, beta-glucosidase, and phenol oxidase) in the forest types. Sensitive and higher soil carbon estimates substantiate a lower microbial quotient (0.17-1.23 %) than the regional trend. Notably, we explained how seasonal and temporal changes in soil carbon estimations hinder a constant positive soil carbon flux. Meanwhile, the mean surface SOC flux (4.63 Mg C ha-1 yr-1) and SIC flux (1.68 Mg C ha-1 yr-1) indicate that the Himalayan soils have significant potential for carbon sequestration. In conclusion, our research indicates substantial soil organic and inorganic carbon storage in major Central Himalayan forest types, with negative anthropogenic activities posing a clear and present threat to the soil carbon stocks.

European croplands under climate change: Carbon input changes required to increase projected soil organic carbon stocks

Increasing soil organic carbon (SOC) stocks in agricultural systems is a pivotal strategy for promoting soil health and mitigating climate change. Global initiatives have set ambitious targets, aspiring to achieve an annual SOC stock increase of 4 ‰. In the European Union, the recently approved Nature Restoration Law aims to increase SOC stock trends in the top 30 cm of cropland mineral soils. However, current monitoring and reporting practices in some countries rely on simplistic SOC models with default parameters, which may not provide reliable predictions. In this paper, we study the feasibility of a 4 ‰ target in European croplands (i.e., an aspirational target proposed by The international "4 per 1000" Initiative), through estimations of required C input changes. To ensure robust predictions, we propose a novel calibration approach that links model parameters to pedo-climatic variables via statistical relationships from 16 long-term experiments. The effectiveness of the method is evaluated for three SOC models across 4281 sites from the European LUCAS soil survey. Our findings demonstrate that the statistical calibration of the multi-model ensemble improves the accuracy of 2015 and 2018 SOC stock predictions, compared to default parameterization. This improvement was however mainly due to the substantial enhancement of one of the models. According to the weighted multi-model mean, median C input changes to reach a 4 ‰ target for Northern, Central, and Southern Europe stand at 1.85, 1.20, and 0.13 Mg C ha-1 yr-1 under RCP 2.6, and 2.21, 1.26, and -0.10 Mg C ha-1 yr-1 under RCP 6.0, respectively. To achieve the aspirational 4 ‰ target, estimated C input change requirements exceed the predicted changes in net primary productivity under RCP 2.6 and RCP 6.0. This emphasizes the importance of strategic land-use and land-management interventions to enhance SOC stocks.

Ecological and vegetation responses in a humid region in southern China during a historic drought

Climate change has triggered more frequent drought occurrence, which can have devastating impacts on the ecosystem functions. Studies on vegetation behavior during droughts have mainly focused on arid/semi-arid regions, yet the ecological and vegetation responses during drought in humid regions remain unclear. Here we systematically evaluated the evolution of the historic drought occurred in the humid Pearl River Basin in 2021 and quantified the vegetation responses using a multitude of vegetation indicators. Analyses showed that the East River Basin and North River Basin were the most severely hit by drought, which enhanced surface temperature and evapotranspiration, and caused soil moisture and terrestrial water storage deficits. Mean vegetation response time was shorter based on solar-induced fluorescence (SIF, 2.7 months) and the water use efficiency (WUE, 2.8 months), followed by the gross primary productivity (GPP, 3.2 months), and longer using the normalized difference vegetation index (NDVI, 4.2 months) and the vegetation optical depth (VOD, 5.0 months). By contrast, over 90% of the ecosystems recovered to their normal states within 3 months using all indicators. The results implied that the NDVI lacks sensitivity to changes in water stress in humid regions, and revealed that vegetation in humid regions may respond slowly and recover rapidly under droughts, which may relate to the water availability that enhances the resistance and resilience of the ecosystems.

Long-term biochar and soil organic carbon stability - Evidence from field experiments in Germany

Organic soil amendments (OSA) with long residence times, such as biochar, have a high potential for soil organic carbon (SOC) sequestration. The highly aromatic structure of biochar reduces microbial decomposition and explains the slow turnover of biochar, indicating long persistence in soils and thus potential SOC sequestration. However, there is a lack of data on biochar-induced SOC sequestration in the long-term and under field conditions. We sampled two long-term field experiments in Germany, where biochar was applied 12 and 14 years ago. Both locations differ in soil characteristics and in the types and amounts of biochar and other OSA. Amendments containing compost and 31.5 Mg ha-1 of biochar on a loamy soil led to a SOC stock increase of 38 Mg ha-1 after OSA addition. The additional increase is due to non-biochar co-amendments such as compost or biogas digestate. After eleven years, this SOC stock increase was still stable. High biochar amount additions of 40 Mg ha-1 combined with biogas digestate, compost or synthetic fertilizer on a sandy soil led to an increase of SOC stocks of 61 Mg ha-1; 38 Mg ha-1 dissipated in the following four years most likely due to lacking physical protection of the coarse soil material, and after nine years the biochar-amended soils showed only slightly higher SOC stocks (+7 Mg ha-1) than the control. Black carbon stocks on the same soil increased in the short- and mid-term and decreased almost to the original stock levels after nine years. Our results indicate that in most cases the long-term effect on SOC and black carbon stocks is controlled by biochar quality and amount, while non-biochar co-amendments can be neglected. This study proves that SOC sequestration through the use of biochar is possible, especially in loamy soils, while non-biochar OSA cannot sequester SOC in the long term.

Sensitivity analysis of parameters for carbon sequestration: Symbolic regression models based on open porous media reservoir simulators predictions

Open Porous Media (OPM) Flow is an open-source reservoir simulator used for solving subsurface porous media flow problems. Focus is placed here on carbon sequestration and the modeling of fluid flow within underground porous reservoirs. In this study, a sensitivity analysis of some input parameters for carbon sequestration is performed using six different uncertain parameters. An ensemble of model realizations is simulated using OPM Flow, and the model output is then calculated based on the values of the six input parameters mentioned above. CO2 injection is simulated for a period of 15 years, while the post-injection migration of CO2 in the saline storage aquifer is simulated for a subsequent period of 200 years, leading to a final analysis after 215 years. The input parameter values are generated using the quasi-Monte Carlo (QMC) method in the region of interest, following specified patterns suitable for analysis. The optimal convergence rate for quasi-Monte Carlo is observed. The aim of this study is to identify important input parameters contributing significantly to the model output, which is accomplished using sensitivity analysis and verified through symbolic regression modeling based on machine learning. Global sensitivity analysis using the Sobol sequence identifies input parameter 3, 'Permeability of shale between sand layers,' as having the most influence on the model output 'Secondary Trapped CO2.' All regression models, including the simplest and least accurate ones, incorporate parameter 3, confirming its significance. These approximations are valid within the designated area of interest for the input parameters and are easily interpretable for human experts. Sensitivity analysis of the developed time-dependent carbon sequestration model shows that the significance of each physical parameter changes over time: Sand porosity is more significant than shale permeability for roughly the first 120 years. Consequently, the presented results show that simulation timescales of at least 200 years are necessary for carbon sequestration evaluation.

Microbial and mineral interactions decouple litter quality from soil organic matter formation

Current understanding of soil carbon dynamics suggests that plant litter quality and soil mineralogy control the formation of mineral-associated soil organic carbon (SOC). Due to more efficient microbial anabolism, high-quality litter may produce more microbial residues for stabilisation on mineral surfaces. To test these fundamental concepts, we manipulate soil mineralogy using pristine minerals, characterise microbial communities and use stable isotopes to measure decomposition of low- and high-quality litter and mineral stabilisation of litter-C. We find that high-quality litter leads to less (not more) efficient formation of mineral-associated SOC due to soil microbial community shifts which lower carbon use efficiency. Low-quality litter enhances loss of pre-existing SOC resulting in no effect of litter quality on total mineral-associated SOC. However, mineral-associated SOC formation is primarily controlled by soil mineralogy. These findings refute the hypothesis that high-quality plant litters form mineral-associated SOC most efficiently and advance our understanding of how mineralogy and litter-microbial interactions regulate SOC formation.

Effects of environmental changes on soil respiration in arid, cold, temperate, and tropical zones

Soil respiration (Rs) is projected to be substantially affected by climate change, impacting the storage, equilibrium, and movement of terrestrial carbon (C). However, uncertainties surrounding the responses of Rs to climate change and soil nitrogen (N) enrichment are linked to mechanisms specific to diverse climate zones. A comprehensive meta-analysis was conducted to address this, evaluating the global effects of warming, increased precipitation, and N enrichment on Rs across various climate zones and ecosystems. Data from 123 studies, encompassing a total of 10,377 worldwide observations, were synthesized for this purpose. Annual Rs were modeled and their uncertainties were associated with a 1-km2 resolution global Rs database spanning from 1961 to 2022. Calibrating Rs using ensemble machine learning (EML) and employing 10-fold cross-validation, 13 environmental covariates were utilized. The meta-analysis findings revealed an upsurge in Rs rates in response to warming, with tropical, arid, and temperate climate zones exhibiting increases of 12 %, 13 %, and 16 %, respectively. Furthermore, increased precipitation led to stimulated Rs rates of 11 % and 9 % in tropical and temperate zones, respectively, while N deposition affected Rs in cold (+6 %) and tropical (+5 %) climate zones. The machine learning technique estimated the global soil respiration to range from 91 to 171 Pg C yr-1, with an average Rs of 700 ± 300 g C m-2 yr-1. The values ranged between 314 and 2500 g C m-2 yr-1, with the lowest and highest values observed in cold and tropical zones, respectively. Spatial variation in Rs was most pronounced in low-latitude areas, particularly in tropical rainforests and monsoon zones. Temperature, precipitation, and N deposition were identified as crucial environmental factors exerting significant influences on Rs rates worldwide. These factors underscore the interconnectedness between climate and ecosystem processes, therefore requiring explicit considerations of different climate zones when assessing responses of Rs to global change.

Present trends, sustainable strategies and energy potentials of crop residue management in India: A review

India generating huge amount of agricultural waste, especially crop residues. In India, around 141 MT of crop residue is generated each year, in which 92 MT burned due to inadequate sustainable management practices, which results in rise in emissions of particulate matter as well as quality of air pollution. Burning crop residues raises mortality rates and substantially decreases crop production while posing a major risk of threatening the environment, condition of the soil, human health, and air quality. Proper crop residue management is crucial because it is rich is nutrient contents and could potentially be used to value-added products. Proper crop residue management helps in improvement in soil organic matter, increases the physical, chemical and biological properties of soil which leads to increase the production and productivity. The short planting season following the previous crop's harvest, insufficient agricultural equipment, a manpower shortage, and declining acceptance of crop residue as feed are just a few of the major causes of residue burning. This major goal of this study is to pinpoint the primary causes of this illicit activity, damaging effect of crop residue burning on the environment, and the appropriate handling of agricultural leftover for animal feed. In addition, the septs plan to keep agricultural residue on the farm by using both conventional and reduced tillage techniques, turning it into biofuels like biochar and bio-oil, mulching, composting, and briquette production. Moreover, Indian government has taken several efforts to address this issue, including programs and laws that support sustainable management practices like shifting agricultural waste into energy, providing 50-80 % subsidies under various policies and schemes to purchase crop residue management machineries. The crop residues machinery used for retention of crop residue into soil is one easy and simple method for crop residue management. This paper includes history of crop residue management, crop residue management techniques, various conversion technologies to generate energy from crop residue, generation of biogas, compost and production of briquette and biodiesels and several households uses. Moreover, different machines which help to manage the crop residues retained in soils in agricultural field used after harvest and way forward are also discussed.

Effects of understory intercropping with salt-tolerant legumes on soil organic carbon pool in coastal saline-alkali land

Phytoremediation through understory intercropping with salt-tolerant legumes (forest-green manure composite patterns) efficiently and sustainably enhances saline-alkali soils, while significantly improving the stability of monoculture forest ecosystems and the efficacy of soil upgrades. However, exactly how forest-green manure patterns regulate the dynamics of the soil organic carbon (SOC) pool and related mechanisms remain unclear. For this study, a pure forest was used as the control, and three leguminous herbaceous plants (M. sativa, S. cannabina, and C. pallida) were intercropped under two forest stand types (T. hybrid 'Zhongshanshan' and C. illinoensis). The variable characteristics and control factors of SOC and its components under different patterns were elucidated by analyzing the soil physical and chemical properties, enzyme activities, and microbial communities. The results revealed that the composite pattern improved soil salinization and increased the activities of β-1,4-glucosidase, polyphenol oxidase, peroxidase (PER), invertase (INV), and urease, as well as the carbon pool management index and the proportion of active organic carbon. At the T. hybrid 'Zhongshanshan' experimental site, planting M. sativa effectively increased the total carbon (TC) content. The ammonium nitrogen, soil moisture content, total phosphorus, alkaline phosphatase, PER, and polyphenol oxidase were the primary driving factors that affected the SOC pool. At the C. illinoensis experimental site, S. cannabina planting was observed to increase the TC content, with the TC, exchangeable Na+, β-1,4-N-acetylglucosaminidase, and INV being the main driving factors that impacted the SOC pool. The composite pattern can indirectly influence the SOC pool by altering the soil properties to regulate the microbial community. Further, it was found that soil inorganic carbon (SIC) was the main contributor to increasing the soil carbon pool following the short-term planting of legumes; thus, there may have been a transfer process that occurred from the SOC to SIC. Our study suggests that the forest-green manure pattern has more positive effects on improving soil quality and the carbon pool in saline-alkali land.

Stoichiometric theory in aquatic carbon sequestration under elevated carbon dioxide

Global climate change projections indicate that the atmospheric concentration of carbon dioxide will increase twofold by the end of this century. However, how the elevated carbon dioxide affects aquatic carbon sequestration and species composition within aquatic microbial communities remains inconclusive. To address this knowledge gap, we formulate a bacteria-algae interaction model to characterize the effects of elevated carbon dioxide on aquatic ecosystems and rigorously derive the thresholds determining the persistence and extinction of algae or bacteria. We explore the impacts of abiotic factors, such as light intensity, nutrient concentration, inorganic carbon concentration and water depth, on algae and bacteria dynamics. The main findings indicate that the elevated atmospheric carbon dioxide will increase algae biomass and thus facilitate carbon sequestration. On the other hand, the elevated atmospheric carbon dioxide will reduce bacterial biomass, and excessive carbon dioxide concentrations can even destroy bacterial communities. Numerical simulations indicate that eutrophication and intensified light intensity can reduce aquatic carbon sequestration, while elevated atmospheric carbon dioxide levels can mitigate eutrophication. Furthermore, higher algae respiration and death rates are detrimental to carbon sequestration, whereas the increased bacterial respiration rates promote carbon sequestration.

The impact of green roofs' composition on its overall life cycle

Green roof systems have been developed to improve the environmental, economic, and social aspects of sustainability. Selecting the appropriate version of the green roof composition plays an important role in the life cycle assessment of a green roof. In this study, 10 compositions of an intensive green roof for moderate zone and 4 green roof compositions for different climatic conditions were designed and comprehensively assessed in terms of their environmental and economic impacts within the "Cradle-to-Cradle" system boundary. The assessment was carried out over a 50-year period for a moderate climate zone. The results showed that asphalt strips and concrete slab produced the highest total emissions. It was found that most greenhouse gases emissions were released in the operational energy consumption phase and in the production phase. The energy consumption phase (48.78%) for automatic irrigation and maintenance caused the highest Global Warming Potential (GWP) value (758.39 kg CO2e) in the worst variant, which also caused the highest life cycle cost (878.47€). On the contrary, in the best variant, planting more vegetation and lower maintenance and irrigation requirements led to a reduction in GWP (445.0 kg CO2e), but in terms of cost (506.6€) this composition didn't represent the best variant. The Global Warming Potential Biogenic (GWP-bio) compared to the Global Warming Potential Total (GWP-total) represents a proportion ranging from 0.8% to 78% depending on the proposed vegetation. Overall higher biogenic carbon values (up to 1525 kg CO2e) were observed for the proposed tall vegetation of Magnolia, Red Mulberry, Hawthorne, Cherry, and Crab-apple Tree. Based on the results of the multicriteria analysis, which included core environmental & economic parameters, biogenic carbon emission levels, the outcome of this paper proposed optimal green roof composition. Optimal intensive green roof composition was subjected to a sensitivity analysis to determine the impact of changing climatic conditions on CO2 emissions and life cycle costs. The results of the sensitivity analysis show that the optimal variant of the green roof can be implemented in the cold and subtropical zone with regard to CO2 emissions, but not with regard to life cycle costs.

Soil Carbon Dioxide Emissions and Carbon Sequestration with Implementation of Alley Cropping in a Mediterranean Citrus Orchard

Agroecological ecosystems produce significant carbon dioxide fluxes; however, the equilibrium of their carbon sequestration, as well as emission rates, faces considerable uncertainties. Therefore, sustainable cropping practices represent a unique opportunity for carbon sequestration, compensating greenhouse gas emissions. In this research, we evaluated the short-term effect of different management practices in alleys (tillage, no tillage, alley cropping with Rosmarinus officinalis and Thymus hyemalis on soil properties, carbon sequestration, and CO2 emissions in a grapefruit orchard under semiarid climate). For two years every four months, soil sampling campaigns were performed, soil CO2 emissions were measured, and rhizosphere soils were sampled at the end of the experimental period. The results show that alley cropping with Thymus and Rosmarinus contributed to improve soil fertility, increasing soil organic carbon (SOC), total nitrogen, cation exchange capacity, and nutrients. The CO2 emission rates followed the soil temperature/moisture pattern. Tillage did not contribute to higher overall CO2 emissions, and there were no decreased SOC contents. In contrast, alley crops increased CO2 emission rates, especially Rosmarinus; however, the bigger root system and biomass of Rosmarinus contributed to soil carbon sequestration at a greater rate than Thymus. Therefore, Rosmarinus is positioned as a better option than Thymus to be used as an alley crop, although long-term monitoring is required to evaluate if the reported short-term benefits are maintained over time.

Recent advances on greenhouse gas emissions from wetlands: Mechanism, global warming potential, and environmental drivers

Greenhouse gas (GHG) emissions from wetlands have exacerbated global warming, attracting worldwide attention. However, the research process and development trends in this field remain unknown. Herein, 1865 papers related to wetlands GHG emissions published from January 2000 to December 2023 were selected, and CiteSpace and VOSviewer were used for bibliometric analysis to visually analyze the publications distribution, research authors, organizations and countries, core journal and keywords, and discussed the research progress, trends and hotspots in the fields. Over the past 24 years, the research has gone through three phases: the "embryonic" stage (2000-2006), the accumulation stage (2007-2014), and the acceleration stage (2015-2023). China has played a pivotal role in this domain, publishing the most papers and working closely with the United States, United Kingdom, Canada, Germany, and Australia. In addition, this study synthesized 311 field observations from 123 publications to analyze the variability in GHG emissions and their driving factors in four different types of natural wetlands. The results suggested that the average carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) fluxes in different wetlands were significantly different. River wetlands exhibited the highest GHG fluxes, while marsh wetlands demonstrated greater global warming potential (GWP). The average CO2, CH4 and N2O fluxes were 60.41 mg m-2·h-1, 2.52 mg m-2·h-1 and 0.05 mg m-2·h-1, respectively. The GWP of Chinese natural wetlands was estimated as 648.72 Tg·CO2-eq·yr-1, and CH4 contributed the largest warming effect, accounting for 57.43%. Correlation analysis showed that geographical location, climate factors, and soil conditions collectively regulated GHG emissions from wetlands. The findings provide a new perspective on sustainable wetland management and reducing GHG emissions.

Drought risk in Moldova under global warming and possible crop adaptation strategies

This study analyzes the relationship between drought processes and crop yields in Moldova, together with the effects of possible future climate change on crops. The severity of drought is analyzed over time in Moldova using the Standard Precipitation Index, the Standardized Precipitation Evapotranspiration Index, and their relationship with crop yields. In addition, rainfall variability and its relationship with crop yields are examined using spectral analysis and squared wavelet coherence. Observed station data (1950-2020 and 1850-2020), ERA5 reanalysis data (1950-2020), and climate model simulations (period 1970-2100) are used. Crop yield data (maize, sunflower, grape), data from experimental plots (wheat), and the Enhanced Vegetation Index from Moderate Resolution Imaging Spectroradiometer satellites were also used. Results show that although the severity of meteorological droughts has decreased in the last 170 years, the impact of precipitation deficits on different crop yields has increased, concurrent with a sharp increase in temperature, which negatively affected crop yields. Annual crops are now more vulnerable to natural rainfall variability and, in years characterized by rainfall deficits, the possibility of reductions in crop yield increases due to sharp increases in temperature. Projections reveal a pessimistic outlook in the absence of adaptation, highlighting the urgency of developing new agricultural management strategies.

A systematic analysis and review of soil organic carbon stocks in urban greenspaces

Urban greenspaces typically refer to urban wetland, urban forest and urban turfgrass. They play a critical role in carbon sequestration by absorbing carbon from the atmosphere; however, their capacity to retain and store carbon in the form of soil organic carbon (SOC) varies significantly. This study provides a systematic analysis and review on the capacity of different urban greenspace types in retaining and storing SOC in 30 cm soil depth on a global scale. Data came from 78 publications on the subject of SOC stocks, covering different countries and climate zones. Overall, urban greenspace types exerted significant influences on the spatial pattern of SOC stocks, with the highest value of 18.86 ± 11.57 kg m-2 (mean ± standard deviation) in urban wetland, followed by urban forest (6.50 ± 3.65 kg m-2), while the lowest mean value of 4.24 ± 3.28 kg m-2 was recorded in urban turfgrass soil. Soil organic carbon stocks in each urban greenspace type were significantly affected by climate zones, management/environmental settings, and selected soil properties (i.e. soil bulk density, pH and clay content). Furthermore, our analysis showed a significantly negative correlation between SOC stocks and human footprint in urban wetland, but a significantly positive relationship in urban forest and urban turfgrass. A positive correlation between SOC stocks and human footprint indicates that increased human activity and development can enhance SOC stocks through effective management and green infrastructure. Conversely, a negative correlation suggests that improper management of human activities can degrade SOC stocks. This highlights the need for sustainable practices to maintain or enhance SOC accumulation in urban greenspaces.

Soil fungal community has higher network stability than bacterial community in response to warming and nitrogen addition in a subtropical primary forest

Global change factors are known to strongly affect soil microbial community function and composition. However, as of yet, the effects of warming and increased anthropogenic nitrogen deposition on soil microbial network complexity and stability are still unclear. Here, we examined the effects of experimental warming (3°C above ambient soil temperature) and nitrogen addition (5 g N m-2 year-1) on the complexity and stability of the soil microbial network in a subtropical primary forest. Compared to the control, warming increased |negative cohesion|:positive cohesion by 7% and decreased network vulnerability by 5%; nitrogen addition decreased |negative cohesion|:positive cohesion by 10% and increased network vulnerability by 11%. Warming and decreased soil moisture acted as strong filtering factors that led to higher bacterial network stability. Nitrogen addition reduced bacterial network stability by inhibiting soil respiration and increasing resource availability. Neither warming nor nitrogen addition changed fungal network complexity and stability. These findings suggest that the fungal community is more tolerant than the bacterial community to climate warming and nitrogen addition. The link between bacterial network stability and microbial community functional potential was significantly impacted by nitrogen addition and warming, while the response of soil microbial network stability to climate warming and nitrogen deposition may be independent of its complexity. Our findings demonstrate that changes in microbial network structure are crucial to ecosystem management and to predict the ecological consequences of global change in the future.

IMPORTANCE

Soil microbes play a very important role in maintaining the function and health of forest ecosystems. Unfortunately, global change factors are profoundly affecting soil microbial structure and function. In this study, we found that climate warming promoted bacterial network stability and nitrogen deposition decreased bacterial network stability. Changes in bacterial network stability had strong effects on bacterial community functional potentials linked to metabolism, nitrogen cycling, and carbon cycling, which would change the biogeochemical cycle in primary forests.

Carbon storage in rare ecosystems relative to their encroaching forests in western Lower Michigan

Rising atmospheric carbon dioxide levels are impacting global temperatures, ecological systems, and human societies. Natural carbon sequestration through the conservation of soil and native ecosystems may slow or reduce the amount of CO2 in the atmosphere, and thus slow or mitigate the rate of global warming. Most of the research investigating carbon sequestration in natural systems occurs in forested ecosystems, however rare ecosystems such as coastal plain marshes and wet-mesic sand prairie collectively may serve as significant carbon sinks. Our objectives were to measure and assess the importance of carbon sequestration in three rare ecosystems (oak-pine barrens, coastal plain marsh, and wet-mesic sand prairie) in western Lower Michigan. We measured carbon in standing vegetation, dead organic matter, and soils within each ecosystem and adjacent encroaching forested areas. Driven by tree carbon, total carbon stocks in encroaching areas were greater than in intact rare ecosystems. Soil organic carbon was greater in all intact ecosystems, though only significantly so in coastal plain marsh. Principal components analysis explained 72% of the variation and revealed differences between intact ecosystems and their encroaching areas. Linear models using the ratio of red to green light reflectance successfully predicted SOC in intact coastal plain marsh and wet-mesic sand prairie. Our results infer the importance of these rare ecosystems in sequestering carbon in soils and support the need to establish federal or state management practices for the conservation of these systems.

Soil adsorption potential: Harnessing Earth's living skin for mitigating climate change and greenhouse gas dynamics

Soil adsorption, which could be seen as a crucial ecosystem service, plays a pivotal role in regulating environmental quality and climate dynamics. However, despite its significance, it is often undervalued within the realms of research and policy frameworks. This article delves into the multifaceted aspects of soil adsorption, incorporating insights from chemistry and material science, ecological perspectives, and recent advancements in the field. In exploring soil components and their adsorption capacities, the review highlights how organic and inorganic constituents orchestrate soil's aptitude for pollutant mitigation and nutrient retention/release. Innovative materials and technologies such as biochar are evaluated for their efficacy in enhancing these natural processes, drawing a link with the sustainability of agricultural systems. The symbiosis between soil microbial diversity and adsorption mechanisms is examined, emphasizing the potential for leveraging this interaction to bolster soil health and resilience. The impact of soil adsorption on global nutrient cycles and water quality underscores the environmental implications, portraying it as a sentinel in the face of escalating anthropogenic activities. The complex interplay between soil adsorption mechanisms and climate change is elaborated, identifying research gaps and advocating for future investigations to elucidate the dynamics underpinning this relation. Policy and socioeconomic aspects form a crucial counterpart to the scientific discourse, with the review assessing how effective governance, incentivization, and community engagement are essential for translating soil adsorption's functionality into tangible climate change mitigation and sustainable land-use strategies. Integrating these diverse but interconnected strata, the article presents a comprehensive overview that not only charts the current state of soil adsorption research but also casts a vision for its future trajectory. It calls for an integrated approach combining scientific inquiry, technological innovation, and proactive policy to leverage soil adsorption's full potential to address environmental challenges and catalyze a transition towards a more sustainable and resilient future.

Algal-bacterial consortium promotes carbon sink formation in saline environment

INTRODUCTION

The level of atmospheric CO2 has continuously been increasing and the resulting greenhouse effects are receiving attention globally. Carbon removal from the atmosphere occurs naturally in various ecosystems. Among them, saline environments contribute significantly to the global carbon cycle. Carbonate deposits in the sediments of salt lakes are omnipresent, and the biological effects, especially driven by halophilic microalgae and bacteria, on carbonate formation remain to be elucidated.

OBJECTIVES

The present study aims to characterize the carbonates formed in saline environments and demonstrate the mechanisms underlying biological-driven CO2 removal via microalgal-bacterial consortium.

METHODS

The carbonates naturally formed in saline environments were collected and analyzed. Two saline representative organisms, the photosynthetic microalga Dunaliella salina and its mutualistic halophilic bacteria Nesterenkonia sp. were isolated from the inhabiting saline environment and co-cultivated to study their biological effects on carbonates precipitation and isotopic composition. During this process, electrochemical parameters and Ca2+ flux, and expression of genes related to CaCO3 formation were analyzed. Genome sequencing and metagenomic analysis were conducted to provide molecular evidence.

RESULTS

The results showed that natural saline sediments are enriched with CaCO3 and enrichment of genes related to photosynthesis and ureolysis. The co-cultivation stimulated 54.54% increase in CaCO3 precipitation and significantly promoted the absorption of external CO2 by 49.63%. A pH gradient was formed between the bacteria and algae culture, creating 150.22 mV of electronic potential, which might promote Ca2+ movement toward D. salina cells. Based on the results of lab-scale induction and 13C analysis, a theoretical calculation indicates a non-negligible amount of 0.16 and 2.3 Tg C/year carbon sequestration in China and global saline lakes, respectively.

CONCLUSION

The combined effects of these two typical representative species have contributed to the carbon sequestration in saline environments, by promoting Ca2+ influx and increase of pH via microalgal and bacterial metabolic processes.

Identifying carbon sequestration's priority supply areas from the standpoint of ecosystem service flow: A case study for Northwestern China's Shiyang River Basin

Finding important supply areas helps maintain the ecological security of the region and promotes the creation of healthy ecosystems. By considering the ecosystem service flows (ESF), priority provisioning area studies can be approached from a new perspective. This study describes the real supply in terms of flows. The goal was to reveal the priority-ranked supply pattern of ecosystem carbon sequestration services (ECSS) in the Shiyang River Basin (SRB). First and foremost, soil respiration models and Carnegie-Ames-Stanford Approach (CASA) model were used to examine the supply of ECSS, and a combination of natural and human factors was used to determine the demand for ECSS. Second, Python was used to illustrate the ECSS flow trajectories and flows. Lastly, and utilized in conjunction with System Conservation Planning (SCP) to determine supply regions of importance. The results show that, first, the spatial distribution of ECSS supply and demand clearly demonstrates heterogeneity. This is reflected in the spatial characteristics of supply, which are "high in the south and low in the north," and demand, which is "high in the urban areas and low in the suburbs." Second, the middle and lower portions of the basin, where there is little precipitation and little vegetation, are home to the majority of the locations with poor carbon sequestration fluxes. These areas accounted for almost 60 % of the entire watershed area over time. Third, the first priority area of ECSS occupies 19.3 % of the basin's total area, while the second priority area occupies 21.46 %. For the major supply regions, strict ecological protection laws must be implemented going forward in order to ensure the ability to sustain ECSS supply. The long-term growth of SRB as well as ecological and environmental management can benefit from this research's foundational role in policymaking.

Enhanced home-field advantage in deep soil organic carbon decomposition: Insights from soil transplantation in subtropical forests

Climate change affects microbial community physiological strategies and thus regulates global soil organic carbon (SOC) decomposition. However, SOC decomposition by microorganisms, depending on home-field advantage (HFA, indicating a faster decomposition rate in 'Home' than 'Away' conditions) or environmental advantage (EA, indicating a faster decomposition rate in warmer-wetter environments than in colder-drier environments) remains unknown. Here, a soil transplantation experiment was conducted between warmer-wetter and colder-drier evergreen broadleaved forests in subtropical China. Specifically, soil samples were collected along a 60 cm soil profile, including 0-15, 15-30, 30-45, and 45-60 cm layers after one year of transplantation. SOC fractions, soil chemical properties, and microbial communities were evaluated to assess where there was an HFA of EA in SOC decomposition, along with an exploration of internal linkages. Significant HFAs were observed, particularly in the deep soils (30-60 cm) (P < 0.05), despite the lack of a significant EA along a soil profile, which was attributed to environmental changes affecting soil fungal communities and constraining SOC decomposition in 'Away' conditions. The soils transplanted from warmer-wetter to colder-drier environments changed the proportions of Mortiereltomycota or Basidiomycota fungal taxa in deep soils. Furthermore, the shift from colder-drier to warmer-wetter environments decreased fungal α-diversity and the proportion of fungal necromass carbon, ultimately inhibiting SOC decomposition in 'Away' conditions. However, neither HFAs nor EAs were significantly present in the topsoil (0-30 cm), possibly due to the broader adaptability of bacterial communities in these layers. These results suggest that the HFA of SOC decomposition in deep soils may mostly depend on the plasticity of fungal communities. Moreover, these results highlight the key roles of microbial communities in the SOC decomposition of subtropical forests, especially in deep soils that are easily ignored.

Long-term conservation tillage increase cotton rhizosphere sequestration of soil organic carbon by changing specific microbial CO2 fixation pathways in coastal saline soil

Coastal saline soil is an important reserve resource for arable land globally. Data from 10 years of continuous stubble return and subsoiling experiments have revealed that these two conservation tillage measures significantly improve cotton rhizosphere soil organic carbon sequestration in coastal saline soil. However, the contribution of microbial fixation of atmospheric carbon dioxide (CO2) has remained unclear. Here, metagenomics and metabolomics analyses were used to deeply explore the microbial CO2 fixation process in rhizosphere soil of coastal saline cotton fields under long-term stubble return and subsoiling. Metagenomics analysis showed that stubble return and subsoiling mainly optimized CO2 fixing microorganism (CFM) communities by increasing the abundance of Acidobacteria, Gemmatimonadetes, and Chloroflexi, and improving composition diversity. Conjoint metagenomics and metabolomics analyses investigated the effects of stubble return and subsoiling on the reverse tricarboxylic acid (rTCA) cycle. The conversion of citrate to oxaloacetate was inhibited in the citrate cleavage reaction of the rTCA cycle. More citrate was converted to acetyl-CoA, which enhanced the subsequent CO2 fixation process of acetyl-CoA conversion to pyruvate. In the rTCA cycle reductive carboxylation reaction from 2-oxoglutarate to isocitrate, synthesis of the oxalosuccinate intermediate product was inhibited, with strengthened CO2 fixation involving the direct conversion of 2-oxoglutarate to isocitrate. The collective results demonstrate that stubble return and subsoiling optimizes rhizosphere CFM communities by increasing microbial diversity, in turn increasing CO2 fixation by enhancing the utilization of rTCA and 3-hydroxypropionate/4-hydroxybutyrate cycles by CFMs. These events increase the microbial CO2 fixation in the cotton rhizosphere, thereby promoting the accumulation of microbial biomass, and ultimately improving rhizosphere soil organic carbon. This study clarifies the impact of conservation tillage measures on microbial CO2 fixation in cotton rhizosphere of coastal saline soil, and provides fundamental data for the improvement of carbon sequestration in saline soil in agricultural ecosystems.

Greenhouse gas emissions, carbon stocks and wheat productivity following biochar, compost and vermicompost amendments: comparison of non-saline and salt-affected soils

Understanding the impact of greenhouse gas (GHG) emissions and carbon stock is crucial for effective climate change assessment and agroecosystem management. However, little is known about the effects of organic amendments on GHG emissions and dynamic changes in carbon stocks in salt-affected soils. We conducted a pot experiment with four treatments including control (only fertilizers addition), biochar, vermicompost, and compost on non-saline and salt-affected soils, with the application on a carbon equivalent basis under wheat crop production. Our results revealed that the addition of vermicompost significantly increased soil organic carbon content by 18% in non-saline soil and 52% in salt-affected soil compared to the control leading to improvements in crop productivity i.e., plant dry biomass production by 57% in non-saline soil with vermicompost, while 56% with the same treatment in salt-affected soil. The grain yield was also noted 44 and 50% more with vermicompost treatment in non-saline and salt-affected soil, respectively. Chlorophyll contents were observed maximum with vermicompost in non-saline (24%), and salt-affected soils (22%) with same treatments. Photosynthetic rate (47% and 53%), stomatal conductance (60% and 12%), and relative water contents (38% and 27%) were also noted maximum with the same treatment in non-saline and salt-affected soils, respectively. However, the highest carbon dioxide emissions were observed in vermicompost- and compost-treated soils, leading to an increase in emissions of 46% in non-saline soil and 74% in salt-affected soil compared to the control. The compost treatment resulted in the highest nitrous oxide emissions, with an increase of 57% in non-saline soil and 62% in salt-affected soil compared to the control. In saline and non-saline soils treated with vermicompost, the global warming potential was recorded as 267% and 81% more than the control, respectively. All treatments, except biochar in non-saline soil, showed increased net GHG emissions due to organic amendment application. However, biochar reduced net emissions by 12% in non-saline soil. The application of organic amendments increased soil organic carbon content and crop yield in both non-saline and salt-affected soils. In conclusion, biochar is most effective among all tested organic amendments at increasing soil organic carbon content in both non-saline and salt-affected soils, which could have potential benefits for soil health and crop production.

SOC bioavailability significantly correlated with the microbial activity mediated by size fractionation and soil morphology in agricultural ecosystems

Despite the fact that physical and chemical processes have been widely proposed to explicate the stabilization mechanisms of soil organic carbon (SOC), thebioavailability of SOC linked to soil physical structure, microbial community structure, and functional genes remains poorly understood. This study aims to investigate the SOC division based on bioavailability differences formed by physical isolation, and to clarify the relationships of SOC bioavailability with soil elements, pore characteristics, and microbial activity. Results revealed that soil element abundances such as SOC, TN, and DOC ranked in the same order as the soil porosity as clay > silt ≥ coarse sand > fine sand in both top and sub soil. In contrast to silt and clay, which had reduced SOC bioavailability, fine sand and coarse sand had dramatically enhanced SOC bioavailability compared to the bulk soil. The bacterial and fungal community structure was significantly influenced by particle size, porosity, and soil elements. Copiotrophic bacteria and functional genes were more prevalent in fine sand than clay, which also contained more oligotrophic bacteria. The SOC bioavailability was positively correlated with abundances of functional genes, C degradation genes, and copiotrophic bacteria, but negatively correlated with abundances of soil elements, porosity, oligotrophic bacteria, and microbial biomass (p < 0.05). This indicated that the soil physical structure divided SOC into pools with varying levels of bioavailability, with sand fractions having more bioavailable organic carbon than finer fractions. Copiotrophic Proteobacteria and oligotrophic Acidobacteria, Firmicutes, and Gemmatimonadetes made up the majority of the bacteria linked to SOC mineralization. Additionally, the fungi Mortierellomycota and Mucoromycota, which are mostly involved in SOC mineralization, may have the potential for oligotrophic metabolism. Our results indicated that particle-size fractionation could influence the SOC bioavailability by restricting SOC accessibility and microbial activity, thus having a significant impact on sustaining soil organic carbon reserves in temperate agricultural ecosystems, and provided a new research direction for organic carbon stability.

Changes in inundation drive carbon dioxide and methane fluxes in a temperate wetland

Wetlands cycle carbon by being net sinks for carbon dioxide (CO2) and net sources of methane (CH4). Daily and seasonal temporal patterns, dissolved oxygen (DO) availability, inundation status (flooded or dry/partially flooded), water depth, and vegetation can affect the magnitude of carbon uptake or emissions, but the extent and interactive effects of these variables on carbon gas fluxes are poorly understood. We characterized the linkages between carbon fluxes and these environmental and temporal drivers at the Old Woman Creek National Estuarine Research Reserve (OWC), OH. We measured diurnal gas flux patterns in an upstream side channel (called the cove) using chamber measurements at six sites (three vegetated and three non-vegetated). We sampled hourly from 7 AM to 7 PM and monthly from July to October 2022. DO concentrations and water levels were measured monthly. Water inundation status had the most influential effect on carbon fluxes with flooded conditions supporting higher CH4 fluxes (0.39 μmol CH4 m-2 s-1; -1.23 μmol CO2 m-2 s-1) and drier conditions supporting higher CO2 fluxes (0.03 μmol CH4 m-2 s-1; 0.86 μmol CO2 m-2 s-1). When flooded, the wetland was a net CO2 sink; however, it became a source for both CH4 and CO2 when water levels were low. We compared chamber-based gas fluxes from the cove in flooded (July) and dry (August) months to fluxes measured with an eddy covariance tower whose footprint covers flooded portions of the wetland. The diurnal pattern of carbon fluxes at the tower did not vary with changing water levels but remained a CO2 sink and a CH4 source even when the cove where we performed the chamber measurements dried out. These results emphasize the role of inundation status on wetland carbon cycling and highlight the importance of fluctuating hydrologic patterns, especially hydrologic drawdowns, under changing climatic conditions.

Non-destructive real-time monitoring of underground root development with distributed fiber optic sensing

Crop genetic engineering for better root systems can offer practical solutions for food security and carbon sequestration; however, soil layers prevent the direct visualization of plant roots, thus posing a challenge to effective phenotyping. Here, we demonstrate an original device with a distributed fiber-optic sensor for fully automated, real-time monitoring of underground root development. We show that spatially encoding an optical fiber with a flexible and durable polymer film in a spiral pattern can significantly enhance sensor detection. After signal processing, the resulting device can detect the penetration of a submillimeter-diameter object in the soil, indicating more than a magnitude higher spatiotemporal resolution than previously reported with underground monitoring techniques. Additionally, we also developed computational models to visualize the roots of tuber crops and monocotyledons and then applied them to radish and rice to compare the results with those of X-ray computed tomography. The device's groundbreaking sensitivity and spatiotemporal resolution enable seamless and laborless phenotyping of root systems that are otherwise invisible underground.

Dynamic changes in soil organic carbon induced by long-term compost application under a wheat-maize double cropping system in North China

Soil organic carbon (SOC) plays a vital role in improving soil quality and alleviating global warming. Understanding the dynamic changes in SOC is crucial for its accumulation induced by compost application in agroecosystem. In this study, soil samples were collected from three treatments: high-rate bio-compost (BioMh), low-rate bio-compost (BioMl), and control (CK, no fertilization) during 2002-2020 in a wheat-maize double cropping system in North China. The soils were separated into three functional fractions, i.e., coarse particle organic matter (cPOM, >250 μm), microaggregates (μAgg, 53-250 μm) and mineral-associated organic matter (MAOM, < 53 μm), and the associated SOC contents were determined. During 1993-2002, SOC contents in bulk soil significantly increased with the duration in the BioMh and BioMl plots. However, there was no significant correlation between SOC content and duration during 2002-2020. These results suggested that compost application positively improved SOC sequestration, while the duration of SOC sequestration (i.e., the longevity of increased SOC with time) under compost inputs maintained only 9 years. Moreover, there was a significant increase in mean annual SOC contents in bulk soil with compost application rate during 2002-2020, indicating that carbon saturation did not occur. Additionally, the SOC contents in the cPOM fraction increased with time (p < 0.01), but the corresponding μAgg and MAOM associated SOC was insignificant (p > 0.05). The MAOM fraction exhibited no additional carbon accumulation with expanding compost application, confirming a hierarchical carbon saturation in these fractions. We concluded that soils under wheat-maize double cropping system in North China have greater potential to sequester C through additional compost inputs, despite showing hierarchical saturation behavior in the non-protected coarse particulate fraction.

Soil carbon-nutrient cycling, energetics, and carbon footprint in calcareous soils with adoption of long-term conservation tillage practices and cropping systems diversification

Calcareous soils, comprising vast areas in northern and eastern parts of India, are characterized by low soil organic carbon (SOC) with high free CaCO3 that results in low nutrient bioavailability with poor soil structure. Improvement of this soil can be achieved with conservation tillage with residue retention coupled with diversification of cropping system including legumes, and oilseeds in the system. Concerning all these, a long-term experiment was carried out in the calcareous soils having low organic carbon and high free CaCO3 (∼33 %) with varied tillage practices, viz. permanent bed with residue (PB), zero tillage with residue (ZT), and conventional tillage without residue (CT); and cropping systems viz. maize-wheat-greengram (MWGg), rice-maize (RM), and maize-mustard-greengram (MMuGg) during 2015-2021. From this study, it was observed that PB and ZT resulted in ∼25-30 % increment in SOC compared to the initial SOC, while CT showed a 4 % decrease in the SOC. Conservation tillage practices also resulted in better soil aggregation and favourable bulk density of the soil. Furthermore, PB and ZT practice exhibited 10-13 %; 15-18 %; 11-15 %; 40-60 %, 20-36 %, and 23-45 % increments in the soil available N, P, K, soil microbial biomass carbon, dehydrogenase activity, and urease activity, respectively over those under CT. Crop diversification with the inclusion of legume and oilseed crops (MMuGg, and MWGg) over cereal-dominated RM systems resulted in better soil health. Maize equivalent yield and energy use efficiency (%) were also found to be the maximum under PB, and ZT, in combination with the MMuGg system. ZT and PB also reduced the carbon footprint by 465 and 822 %, respectively over CT by elevating SOC sequestration. Hence, conservation tillage practices with residue retention coupled with diversification in maize-based cropping systems with mustard and greengram can improve soil health, system productivity, and energetics, and reduce the carbon footprint in calcareous soils.

Coastal distribution and driving factors for blue carbon fractions in the surface soil of a warm-temperate salt marsh in China

A better understanding of blue carbon (BC) sequestration can not only contribute to a better elucidation of global carbon cycle processes but can also lay the foundation for the incorporation of BC ecosystems into regional and global carbon offset schemes. In this study, the surface soils of seven plots along a landward to seaward distance gradient were analyzed for the concentrations and stocks of soil organic carbon (SOC), soil inorganic carbon (SIC), dissolved organic carbon (DOC), and dissolved inorganic carbon (DIC), as well as soil physical (bulk density, texture, moisture), chemical (pH, electrical conductivity), and microbiological (phospholipid fatty acid) properties in the coastal wetlands. Correlation, variation partition and random forest (RF) analyses were used to identify key variables correlating with BC fraction distribution patterns. The results suggested that SIC, DIC, and DOC, exhibited similar landward-increasing trends but the driving factors were distinct from each other. Based on correlation and RF analysis, both SIC and DIC were closely related to soil moisture and clay contents, but microbial indicators of arbuscular mycorrhizal fungi and actinomycete, were found to be associated with SIC, and abiotic properties played less important but still substantial roles in predicting DIC dynamics. In contrast with the other three investigated BC fractions, SOC showed a slight tendency toward enrichment in the seaward direction, and SIC was identified as the main driving factor. DOC showed no significant correlations with the other BC fractions, and its variation could not be explained well by the selected edaphic parameters. The soils in the YRD's tidal Suaeda salsa salt marshes showed a significant negative coupled SOC-SIC correlation, which was potentially related to divergent sedimentary processes and potential biotransformation between SOC and SIC. These results highlight the importance of integrating multiple BC fractions and their interactions into attempts to explore key mechanisms of BC cycling.

Unveiling the crucial role of soil microorganisms in carbon cycling: A review

Soil microorganisms, by actively participating in the decomposition and transformation of organic matter through diverse metabolic pathways, play a pivotal role in carbon cycling within soil systems and contribute to the stabilization of organic carbon, thereby influencing soil carbon storage and turnover. Investigating the processes, mechanisms, and driving factors of soil microbial carbon cycling is crucial for understanding the functionality of terrestrial carbon sinks and effectively addressing climate change. This review comprehensively discusses the role of soil microorganisms in soil carbon cycling from three perspectives: metabolic pathways, microbial communities, and environmental influences. It elucidates the roles of different microbial species in carbon cycling and highlights the impact of microbial interactions and environmental factors on carbon cycling. Through the synthesis of 2171 relevant papers in the Web of Science Core database, we elucidated the ecological community structure, activity, and assembly mechanisms of soil microorganisms crucial to the soil carbon cycle that have been widely analyzed. The integration of soil microbial carbon cycle and its driving factors are vital for accurately predicting and modeling biogeochemical cycles and effectively addressing the challenges posed by global climate change. Such integration is vital for accurately predicting and modeling biogeochemical cycles and effectively addressing the challenges posed by global climate change.

Meta-omics reveals role of photosynthesis in microbially induced carbonate precipitation at a CO2-rich geyser

Microbially induced carbonate precipitation (MICP) is a natural process with potential biotechnological applications to address both carbon sequestration and sustainable construction needs. However, our understanding of the microbial processes involved in MICP is limited to a few well-researched pathways such as ureolytic hydrolysis. To expand our knowledge of MICP, we conducted an omics-based study on sedimentary communities from travertine around the CO2-driven Crystal Geyser near Green River, Utah. Using metagenomics and metaproteomics, we identified the community members and potential metabolic pathways involved in MICP. We found variations in microbial community composition between the two sites we sampled, but Rhodobacterales were consistently the most abundant order, including both chemoheterotrophs and anoxygenic phototrophs. We also identified several highly abundant genera of Cyanobacteriales. The dominance of these community members across both sites and the abundant presence of photosynthesis-related proteins suggest that photosynthesis could play a role in MICP at Crystal Geyser. We also found abundant bacterial proteins involved in phosphorous starvation response at both sites suggesting that P-limitation shapes both composition and function of the microbial community driving MICP.

Organic matter stability and lability in terrestrial and aquatic ecosystems: A chemical and microbial perspective

Terrestrial and aquatic ecosystems have specific carbon fingerprints and sequestration potential, due to the intrinsic properties of the organic matter (OM), mineral content, environmental conditions, and microbial community composition and functions. A small variation in the OM pool can imbalance the carbon dynamics that ultimately affect the climate and functionality of each ecosystem, at regional and global scales. Here, we review the factors that continuously contribute to carbon stability and lability, with particular attention to the OM formation and nature, as well as the microbial activities that drive OM aggregation, degradation and eventually greenhouse gas emissions. We identified that in both aquatic and terrestrial ecosystems, microbial attributes (i.e., carbon metabolism, carbon use efficiency, necromass, enzymatic activities) play a pivotal role in transforming the carbon stock and yet they are far from being completely characterised and not often included in carbon estimations. Therefore, future research must focus on the integration of microbial components into carbon mapping and models, as well as on translating molecular-scaled studies into practical approaches. These strategies will improve carbon management and restoration across ecosystems and contribute to overcome current climate challenges.

Dual carbon sequestration with photosynthetic living materials

Natural ecosystems offer efficient pathways for carbon sequestration, serving as a resilient approach to remove CO2 from the atmosphere with minimal environmental impact. However, the control of living systems outside of their native environments is often challenging. Here, we engineered a photosynthetic living material for dual CO2 sequestration by immobilizing photosynthetic microorganisms within a printable polymeric network. The carbon concentrating mechanism of the cyanobacteria enabled accumulation of CO2 within the cell, resulting in biomass production. Additionally, the metabolic production of OH- ions in the surrounding medium created an environment for the formation of insoluble carbonates via microbially-induced calcium carbonate precipitation (MICP). Digital design and fabrication of the living material ensured sufficient access to light and nutrient transport of the encapsulated cyanobacteria, which were essential for long-term viability (more than one year) as well as efficient photosynthesis and carbon sequestration. The photosynthetic living materials sequestered approximately 2.5 mg of CO2 per gram of hydrogel material over 30 days via dual carbon sequestration, with 2.2 ± 0.9 mg stored as insoluble carbonates. Over an extended incubation period of 400 days, the living materials sequestered 26 ± 7 mg of CO2 per gram of hydrogel material in the form of stable minerals. These findings highlight the potential of photosynthetic living materials for scalable carbon sequestration, carbon-neutral infrastructure, and green building materials. The simplicity of maintenance, coupled with its scalability nature, suggests broad applications of photosynthetic living materials as a complementary strategy to mitigate CO2 emissions.

Modelling and testing forest ecosystems condition account

We developed an application model based on the System of Environmental Economic Accounting-Ecosystem Accounting (SEEA-EA) framework, endorsed by the United Nations Statistical Commission in 2021. This model enables mapping condition accounts for forest ecosystems using automated computation. We applied the model nationally in Spain between 2000 and 2015 to test its effectiveness. Our model follows five methodological steps to generate forest condition accounts: (i) definition and spatial delimitation of forest ecosystem types; (ii) selection of variables using the ecosystem condition typology encompassing physical, chemical, compositional, structural, functional, and landscape characteristics; (iii) establishment of reference levels, including lower (collapse) and upper (high ecosystem integrity) thresholds; (iv) aggregation of variables into condition index; and (v) calculation of a single condition index by rescaling the aggregated indicators between 0 and 1. The results obtained from the model provide valuable insights into the status and trends of individual condition indicators, as well as aggregated condition index values for forest ecosystems, in a spatially explicit manner. Overall, the condition of the forest ecosystems in Spain showed a slight increase, from 0.56 in 2000 to 0.58 in 2015. However, distinct trends were observed for each ecosystem type. For example, mixed Alpine and Macaronesia forests exhibited a significant improvement, while the continental Mediterranean coniferous forests did not show any change. This innovative approach to monitoring forest condition accounts has important potential applications in policy and decision-making processes. It can contribute to effective evidence-based nature conservation, ecosystem service management, and identifying restoration areas.

Membrane Distillation-Crystallization for Sustainable Carbon Utilization and Storage

Anthropogenic greenhouse gas emissions from power plants can be limited using postcombustion carbon dioxide capture by amine-based solvents. However, sustainable strategies for the simultaneous utilization and storage of carbon dioxide are limited. In this study, membrane distillation-crystallization is used to facilitate the controllable production of carbonate minerals directly from carbon dioxide-loaded amine solutions and waste materials such as fly ash residues and waste brines from desalination. To identify the most suitable conditions for carbon mineralization, we vary the membrane type, operating conditions, and system configuration. Feed solutions with 30 wt % monoethanolamine are loaded with 5-15% CO2 and heated to 40-50 °C before being dosed with 0.18 M Ca2+ and Mg2+. Membranes with lower surface energy and greater roughness are found to more rapidly promote mineralization due to up to 20% greater vapor flux. Lower operating temperature improves membrane wetting tolerance by 96.2% but simultaneously reduces crystal growth rate by 48.3%. Sweeping gas membrane distillation demonstrates a 71.6% reduction in the mineralization rate and a marginal improvement (37.5%) on membrane wetting tolerance. Mineral identity and growth characteristics are presented, and the analysis is extended to explore the potential improvements for carbon mineralization as well as the feasibility of future implementation.

The effect of short-term plants cultivation on soil organic/inorganic carbon storage in newly formed soils

Studying total soil carbon (STC), which encompasses organic (SOC) and inorganic carbon (SIC), as well as investigating the influence of soil carbon on other soil properties, is crucial for effective global soil carbon management. This knowledge is invaluable for evaluating carbon sequestration, although its scope is currently limited. Boosting soil carbon sequestration, particularly in arid regions, has direct and indirect implications for achieving over four Sustainable Development Goals: mitigating hunger, extreme poverty, enhancing environmental preservation, and addressing global climate concerns. Research into changes within SOC and SIC across surface and subsurface soils was conducted on aeolian deposits. In this specific case study, two sites sharing similar climates and conditions were chosen as sources of wind-blown sediment parent material. The aim was to discern variations in SOC, SIC, and STC storage in surface and subsurface soils between Sistan and Baluchistan Province (with rapeseed and date orchard cultivation) and Kerman Province (with maize cultivation) in southeastern Iran. The findings highlighted an opposing pattern in SOC and storage concerning soil depth, unlike SIC. The average SOC content was higher in maize cultivation (0.2%) compared to date orchard and rapeseed cultivation (0.11%), attributed to the greater evolution of these arid soils (aridisols) in comparison to the other region (entisols). Conversely, SIC content in the three soil uses demonstrated minimal variation. The mean STC storage was greater in maize cultivation (60.35 Mg ha-1) than in date orchard (54.67 Mg ha-1) and rapeseed cultivation (53.42 Mg ha-1). Within the examined drylands, SIC, originating from aeolian deposits and soil processes, assumes a more prominent role in total carbon storage than SOC, particularly within subsurface soils. Notably, over 90% of total carbon storage exists in the form of inorganic carbon in soils.

Potential reuse of domestic organic residues as soil organic amendment in the current waste management system in Australia, China, and The Netherlands

Soil organic carbon (SOC) is essential for most soil functions. Changes in land use from natural land to cropland disrupt long-established SOC balances and reduce SOC levels. The intensive use of chemical fertilisers in modern agriculture accelerates the rate of SOC depletion. Domestic organic residues (DOR) are a valuable source of SOC replenishment with high carbon content. However, there is still a lack of knowledge and data regarding whether and to what extent DOR can contribute to replenishing SOC. This paper aims to unpack the potential of DOR as a SOC source. Total SOC demand and annual SOC loss are defined and calculated. The carbon flow within different DOR management systems is investigated in three countries (China, Australia, and The Netherlands). The results show that the total SOC demand is too large to be fulfilled by DOR in a short time. However, DOR still has a high potential as a source of SOC as it can mitigate the annual SOC loss by up to 100%. Achieving this 100% mitigation requires a shift to more circular management of DOR, in particular, more composting, and direct land application instead of landfilling and incineration (Australia and China), or a higher rate of source separation of DOR (The Netherlands). These findings form the basis for future research on DOR recycling as a SOC source.

Elevated CO2 along with inoculation of cyanobacterial biofilm or its partners differentially modulates C-N metabolism and quality of tomato beneficially

Diazotrophic cyanobacteria are known to influence nutrient availability in soil, however, their benefits under elevated CO2 environment, particularly on fruit quality attributes, is a less investigated aspect. Laboratory developed cyanobacterium-fungal biofilm (An-Tr), composed of Anabaena torulosa (An) as the matrix with the partner as Trichoderma viride (Tr), along with the individual partners were evaluated under ambient (aCO2-400 ± 50 ppm) and elevated (eCO2-700 ± 50 ppm) conditions, with and without tomato plants. An-Tr inoculation exhibited distinct and significantly higher values for most of the soil microbiological parameters, plant growth attributes and antioxidant/defense enzyme activities measured at 30 and 60 DAI (days after inoculation). Significant enhancement in soil nutrient availability, leaf chlorophyll, with 45-50% increase in the enzyme activities related to carbon and nitrogen assimilation, higher yields and better-quality parameters of tomato, with An-Tr biofilm or An inoculation, were recorded, particularly under eCO2 conditions. The fruits from An-Tr treatments under eCO2 exhibited a higher titrable acidity, along with more ascorbic acid, carotenoids and lycopene content, highlighting the superiority of this inoculant. Multivariate analyses revealed significant (p ≤ 0.05) interactions among cultures, DAI, and CO2 levels, illustrating that cyanobacterial inoculation can be advocated as a strategy to gainfully sequester eCO2. Significant improvement in yield and fruit quality along with 50% N savings, further attest to the promise of cyanobacterial inoculants for tomato crop in the climate change scenario.

Microbial growth under drought is confined to distinct taxa and modified by potential future climate conditions

Climate change increases the frequency and intensity of drought events, affecting soil functions including carbon sequestration and nutrient cycling, which are driven by growing microorganisms. Yet we know little about microbial responses to drought due to methodological limitations. Here, we estimate microbial growth rates in montane grassland soils exposed to ambient conditions, drought, and potential future climate conditions (i.e., soils exposed to 6 years of elevated temperatures and elevated CO2 levels). For this purpose, we combined 18O-water vapor equilibration with quantitative stable isotope probing (termed 'vapor-qSIP') to measure taxon-specific microbial growth in dry soils. In our experiments, drought caused >90% of bacterial and archaeal taxa to stop dividing and reduced the growth rates of persisting ones. Under drought, growing taxa accounted for only 4% of the total community as compared to 35% in the controls. Drought-tolerant communities were dominated by specialized members of the Actinobacteriota, particularly the genus Streptomyces. Six years of pre-exposure to future climate conditions (3 °C warming and + 300 ppm atmospheric CO2) alleviated drought effects on microbial growth, through more drought-tolerant taxa across major phyla, accounting for 9% of the total community. Our results provide insights into the response of active microbes to drought today and in a future climate, and highlight the importance of studying drought in combination with future climate conditions to capture interactive effects and improve predictions of future soil-climate feedbacks.

Biochemical Investigations of Five Recombinantly Expressed Tyrosinases Reveal Two Novel Mechanisms Impacting Carbon Storage in Wetland Ecosystems

Wetlands are globally distributed ecosystems characterized by predominantly anoxic soils, resulting from water-logging. Over the past millennia, low decomposition rates of organic matter led to the accumulation of 20-30% of the world's soil carbon pool in wetlands. Phenolic compounds are critically involved in stabilizing wetland carbon stores as they act as broad-scale inhibitors of hydrolytic enzymes. Tyrosinases are oxidoreductases capable of removing phenolic compounds in the presence of O2 by oxidizing them to the corresponding o-quinones. Herein, kinetic investigations (kcat and Km values) reveal that low-molecular-weight phenolic compounds naturally present within wetland ecosystems (including monophenols, diphenols, triphenols, and flavonoids) are accepted by five recombinantly expressed wetland tyrosinases (TYRs) as substrates. Investigations of the interactions between TYRs and wetland phenolics reveal two novel mechanisms that describe the global impact of TYRs on the wetland carbon cycle. First, it is shown that o-quinones (produced by TYRs from low-molecular-weight phenolic substrates) are capable of directly inactivating hydrolytic enzymes. Second, it is reported that o-quinones can interact with high-molecular-weight phenolic polymers (which inhibit hydrolytic enzymes) and remove them through precipitation. The balance between these two mechanisms will profoundly affect the fate of wetland carbon stocks, particularly in the wake of climate change.

Microbially mediated climate feedbacks from wetland ecosystems

Wetlands are crucial nodes in the carbon cycle, emitting approximately 20% of global CH4 while also sequestering 20%-30% of all soil carbon. Both greenhouse gas fluxes and carbon storage are driven by microbial communities in wetland soils. However, these key players are often overlooked or overly simplified in current global climate models. Here, we first integrate microbial metabolisms with biological, chemical, and physical processes occurring at scales from individual microbial cells to ecosystems. This conceptual scale-bridging framework guides the development of feedback loops describing how wetland-specific climate impacts (i.e., sea level rise in estuarine wetlands, droughts and floods in inland wetlands) will affect future climate trajectories. These feedback loops highlight knowledge gaps that need to be addressed to develop predictive models of future climates capturing microbial contributions. We propose a roadmap connecting environmental scientific disciplines to address these knowledge gaps and improve the representation of microbial processes in climate models. Together, this paves the way to understand how microbially mediated climate feedbacks from wetlands will impact future climate change.