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Human activities have significantly accelerated emissions of each carbon dioxide and biologically reactive nitrogen into the atmosphere. As nitrogen availability frequently limits forest productivity, it has long been anticipated that anthropogenic nitrogen deposition ought to stimulate carbon sequestration in forests. The present study aimed to understand the effects of nitrogen addition on the growth of the Syzygium cumini in ambient (408 ppm) and elevated (450 ppm, 500 ppm, 550 ppm and 600 ppm) carbon dioxide conditions. The addition of nitrogen in the form of potassium nitrate in different levels (0, 3, 6, 12, & 24 g N m−2) was used in this study. The responses of the plant in terms of growth (shoot length, leaf length and leaf width) were examined. Multiple regression equation was used for the model fit to determine the carbon content. The carbon content was found to be higher in all ambient and elevated CO2 conditions at the nitrogen addition level of 24 g N m−2.

The “Grain-for-Green” project on the Loess Plateau is the largest revegetation program in the world. However, revegetation-induced land use changes can influence both water and carbon cycles, and the diverse consequences were not well understood. Therefore, the reasonability and sustainability of revegetation measures are in question. This study quantifies the impacts of revegetation-induced land use conversions on the water and carbon cycles in a typical watershed on the Loess Plateau and identifies suitable areas where revegetation of forest or grassland could benefit both soil and water conservation and carbon sequestration. We used a coupled hydro-biogeochemical model to simulate the changes of a few key components in terms of water and carbon by designing a variety of hypothetical land use conversion scenarios derived from revegetation policy. Compared to the baseline condition (land use in 2000), both sediment yield and water yield decreased substantially when replacing steep cropland with forest or grassland. Converting cropland with slopes >25°, 15°, and 6° to forest (CTF) would enhance the carbon sequestration with a negligible negative effect on soil water content, while replacing cropland with grassland (CTG) would result in a decline in net primary production but with a substantial increase in soil water content (3.8%–14.9%). Compared to the baseline, the soil organic carbon would increase by 0.9%–3.2% in CTF and keep relatively stable in CTG. Through testing a variety of hypothetical revegetation scenarios, we identified potential priority areas for CTF and CTG, where revegetation may be appropriate and potentially beneficial to conserving soil and water and enhancing carbon sequestration. Our study highlights the challenges in future water and carbon coupling management under revegetation policy, and our quantitative results and identification of potential areas for revegetation could provide information to policy makers for seeking optimal management on the Loess Plateau.

Given that cultivated land serves as a strategic resource to ensure national food security, blind emphasis on improvement of food production capacity can lead to soil overutilization and impair other soil functions. Therefore, we took Heilongjiang province as an example to conduct a multi-functional evaluation of soil at the provincial scale. A combination of soil, climate, topography, land use, and remote sensing data were used to evaluate the functions of primary productivity, provision and cycling of nutrients, provision of functional and intrinsic biodiversity, water purification and regulation, and carbon sequestration and regulation of cultivated land in 2018. We designed a soil function discriminant matrix, constructed the supply-demand ratio, and evaluated the current status of supply and demand of soil functions. Soil functions demonstrated a distribution pattern of high grade in the northeast and low grade in the southwest, mostly in second-level areas. The actual supply of primary productivity functions in 71.32% of the region cannot meet the current needs of the population. The dominant function of soil in 34.89% of the area is water purification and regulation, and most of the cultivated land belongs to the functional balance region. The results presented herein provide a theoretical basis for optimization of land patterns and improvement of cultivated land use management on a large scale, and is of great significance to the sustainable use of black soil resources and improvement of comprehensive benefits.

Land management is one of the most important factors affecting the protection and carbon sequestration of natural ecosystems. If the ecosystem is maintained naturally, it will have suitable vegetation and soil stability. One of the important factors that affects land management is livestock grazing. In order to evaluate the impact of exclosure rangeland on carbon sequestration (CS) in salty rangelands, the study was carried out in Inchehboroun rangelands of Golestan province, Iran. The main purpose of current research was to evaluate the effectiveness of management of salt rangeland on CS by topsoil and halophytes species. For this purpose, 40 plots (with 2 m2 area) were located along 8 transects of 100 m in exclosure rangeland (ER) and grazing rangeland (GR) sites. The sampling method was randomized-systematic. In the area sampled, plant biomass was estimated. In addition, the content of above ground and underground biomass carbon, litter carbon, and soil organic carbon were determined for both ER and GR. The difference between the means was compared using Duncan test and t-test at P

Salinization of freshwater ecosystems impacts carbon cycling, a particular concern for coastal wetlands, which are important agents of carbon sequestration. Previous experimental work using salt additions as a proxy for sea level rise, reveals widely divergent effects of salt on soil carbon processes. We performed a laboratory salt addition experiment on two different types of wetland soils (Ponzer muck and Hyde loam, both poorly drained organic soils) from the Coastal Plain of North Carolina. We used a commercial aquarium salt mix to make treatment solutions of 0, 2.5 and 10 ppt salinity and independently manipulated solution pH (5.5, 7.2, 8.8) for a full factorial experimental design. Our goal was to identify the effects of increasing ionic strength and increasing soil solution pH on soil carbon solubility and turnover. Microbial respiration and dissolved organic carbon solubility were depressed by marine salts, while pH manipulation alone had minimal effect. The addition of marine salts substantially reduced rates of carbon mineralization, reduced carbon solubility, and preferentially reduced the abundance of phenolic and aromatic organic molecules in solution. In the more acidic Ponzer muck, where salt additions dropped the pH from > 5 to

As president of the Climate Change Conference of the Parties, Chile has advocated for developing ambitious commitments to mitigate greenhouse gas emissions to achieve carbon-neutrality by 2050. However, Chile's motivations and ambitious push to reach carbon-neutrality are complicated by a backdrop of severe drought, climate change impacts (i.e., wildfires, tree mortality), and the use of industrial plantations as a mitigation strategy. This has become more evident as widespread and severe wildfires have impacted large areas of industrial plantations, transforming the land-use, land-use change, and forestry sector from a carbon sink to a net carbon source. Consequently, Chile must diversify its climate actions to achieve carbon-neutrality. Nature-based solutions, including wetlands-peatlands and oceans, represent alternative climate actions that can be implemented to tackle greenhouse gas emissions at a national level. Diversification, however, must guarantee Chile's long-term carbon sequestration capacity without compromising the ecological functionality of biodiverse tree-less habitats and native forest ecosystems.

Understanding interactions between complex human and natural systems involved in urban carbon cycling is important when balancing the dual goals of urban development to accommodate a growing population, while also achieving urban carbon neutrality. This study develops a systems breakdown accounting method to assess the urbancarbon cycle. The method facilitates greater understanding of the complex interactions within and between systems involved in this cycle, in order to identify ways in which humans can adapt their interactions to reduce netgreenhouse gas emissionsfrom urban regions. Testing the systems breakdown accounting method in Stockholm County, Sweden, we find that it provides new insights into the carbon interactions with urban green-blue areas in the region. Results show how Stockholm County can reduce its emissions and achieve its goal of local carbon net-neutrality, if the green areas protect itscarbon sequestrationpotential and maintain it to offset projected remaining active emissions. Results also show that the inland surface waters and innerarchipelagowaters within Stockholm County are a considerable source of greenhouse gases to the atmosphere. A better understanding of these water emissions is necessary to formulate effective planning and policy measures that can reduce urban emissions. The insights gained from this study can also be applied in other regions. In particular, water bodies could play a significant role in the urban carbon cycle and using this knowledge for more complete carbon accounting, and a better understanding of green-blue interactions could help to reduce net urban emissions in many places. Available at:https://www.sciencedirect.com/science/article/pii/S2213305421000199#ack0005

The value of terrestrial carbon sequestration in urban areas, due to lack of vegetation as a carbon sink, is rarely studied. In fact, urban areas have high carbon emission values, which must be minimised. On the other hand, the value of carbon sequestration in urban areas is very dynamic due to natural factors from the environment and non-natural factors from anthropogenic activities. The main objectives of this study are to identify the carbon dioxide sequestration in urban areas, especially in tropical climates, and to determine the dynamics of carbon sequestration in urban areas for a year. The results show that carbon sequestration in tropical urban areas has a significant value compared with urban areas in temperate climates. This condition happens because there are still green open spaces in gardens and agricultural lands. The value of carbon sequestration in this tropical urban area experiences monthly dynamics caused by rainfall variation and anthropogenic activities, such as land conversion and plant type conversion in agricultural lands.

Plateau zokor (Eospalax baileyi) is a native subterranean rodent living in alpine rangeland on the Qinghai–Tibet Plateau. The zokors excavate soil in their tunnels and push it out to form the zokor mound, which is secondary bare land on the ground. In the alpine rangeland ecosystem, the bare lands emit greenhouse gases and reduce carbon sequestration. However, little is known about the greenhouse gas emissions from the zokor mounds with bare soil. In this study, we used a gas analyzer in situ combined with a closed static chamber to monitor the emissions of CO2 and CH4 from new mounds, seminew mounds, old mounds, and the pasture without mounds. The biomass bacteria, fungi, and actinomycetes in the 0- to 20-cm soil layer of the mounds and the pasture without mounds were simultaneously investigated. To explore the source of the CO2 and CH4 emissions, we compared the differences of CO2 and CH4 flux in the zokors’ active tunnels, tunnel-free soil, and mound-free pasture. The results showed that 1) the highest flux of CO2 and CH4 emissions in the same month was from new mounds, followed by seminew mounds, old mounds, and the pasture without mounds; 2) CO2 and CH4 emissions from the different mounds in 4 mo were significantly influenced by months and mound types, although there was no significant interaction between these factors; and 3) the flux of CO2 and CH4 emissions from the zokor mounds were significantly positively correlated with their total biomass of microbes and the flux of CO2 and CH4 inside the zokor active tunnels. The CO2 and CH4 inside the zokor active tunnels had more contributions to CO2 and CH4 emissions from the zokor mounds than the soil microbes’ biomass in the mounds.

We synthesized 20 years of research to explain the interrelated processes that determine soil and plant responses to biochar. The properties of biochar and its effects within agricultural ecosystems largely depend on feedstock and pyrolysis conditions. We describe three stages of reactions of biochar in soil: dissolution (1–3 weeks); reactive surface development (1–6 months); and aging (beyond 6 months). As biochar ages, it is incorporated into soil aggregates, protecting the biochar carbon and promoting the stabilization of rhizodeposits and microbial products. Biochar carbon persists in soil for hundreds to thousands of years. By increasing pH, porosity, and water availability, biochars can create favorable conditions for root development and microbial functions. Biochars can catalyze biotic and abiotic reactions, particularly in the rhizosphere, that increase nutrient supply and uptake by plants, reduce phytotoxins, stimulate plant development, and increase resilience to disease and environmental stressors. Meta-analyses found that, on average, biochars increase P availability by a factor of 4.6; decrease plant tissue concentration of heavy metals by 17%–39%; build soil organic carbon through negative priming by 3.8% (range −21% to +20%); and reduce non-CO greenhouse gas emissions from soil by 12%–50%. Meta-analyses show average crop yield increases of 10%–42% with biochar addition, with greatest increases in low-nutrient P-sorbing acidic soils (common in the tropics), and in sandy soils in drylands due to increase in nutrient retention and water holding capacity. Studies report a wide range of plant responses to biochars due to the diversity of biochars and contexts in which biochars have been applied. Crop yields increase strongly if site-specific soil constraints and nutrient and water limitations are mitigated by appropriate biochar formulations. Biochars can be tailored to address site constraints through feedstock selection, by modifying pyrolysis conditions, through pre- or post-production treatments, or co-application with organic or mineral fertilizers. We demonstrate how, when used wisely, biochar mitigates climate change and supports food security and the circular economy., Program of Competitive Growth of Kazan Federal University and the “RUDN University program 5-100” La Trobe University. Grant Number: LTU SFWE RFA 2000004349

A number of processes for post-production treatment of “raw” biochars, including leaching, aeration, grinding or sieving to reduce particle size, and chemical or steam activation, have been suggested as means to enhance biochar effectiveness in agriculture, forestry, and environmental restoration. Here, I review studies on post-production processing methods and their effects on biochar physio-chemical properties and present a meta-analysis of plant growth and yield responses to post-processed vs. “raw” biochars. Data from 23 studies provide a total of 112 comparisons of responses to processed vs. unprocessed biochars, and 103 comparisons allowing assessment of effects relative to biochar particle size; additional 8 published studies involving 32 comparisons provide data on effects of biochar leachates. Overall, post-processed biochars resulted in significantly increased average plant growth responses 14% above those observed with unprocessed biochar. This overall effect was driven by plant growth responses to reduced biochar particle size, and heating/aeration treatments. The assessment of biochar effects by particle size indicates a peak at a particle size of 0.5–1.0 mm. Biochar leachate treatments showed very high heterogeneity among studies and no average growth benefit. I conclude that physiochemical post-processing of biochar offers substantial additional agronomic benefits compared to the use of unprocessed biochar. Further research on post-production treatments effects will be important for biochar utilization to maximize benefits to carbon sequestration and system productivity in agriculture, forestry, and environmental restoration. Supplementary Information The online version contains supplementary material available at 10.1007/s42773-021-00115-0.

While being major greenhouse gas (GHG) emitters, cities also suffer some of the most severe climate change impacts. Urban forests have gained increasing recognition as nature-based solutions to climate change via the various benefits they provide, such as carbon sequestration and temperature regulation. Many cities have developed climate change and/or urban forest policies to enhance climate resilience and support urban livability. However, it is still unclear whether these policies consider and address potential alignment between climate action and urban forest planning and management. This study explored whether and to what extent urban forest and climate change policies are mutually supportive and reinforcing, by conducting a review of climate change and urban forest policies in the largest 20 Canadian cities. Results suggest significant gaps and discrepancies between these policies, across and within study cities, indicating potential weaknesses related to stakeholder/actor engagement, policy integration, departmental collaboration and communication, and cohesive management priorities and practices. Only three (15 %) of the cities have developed climate change and urban forest policies that align to some extent. Furthermore, despite some commonalities, most cities defined their urban forests differently, highlighting locally-specific understanding and needs in addition to a lack of cohesion across Canadian municipalities concerning urban forest planning and management. Across most cities, both types of policies included general and locally-relevant information related to impacts of climate change. However, gaps and inconsistencies found between and within many municipalities’ policies may present a major barrier to effective policy implementation and mutually-reinforcing management actions. Areas for improvement are suggested for policy planning and implementation to ensure alignment between urban forest and climate change policies, which should also prove useful for municipalities outside of the study scope.

International audience; Given the prospects of low short- term emissions reduction, carbon removals (CDRs) are expected to play an important role in achieving ambitious mitigation targets in future scenarios of integrated assessment models (IAMs), particularly Bioenergy with Carbon Capture and Storage (BECCS). In this paper, we explore the IAMC 1.5 data-base to depict the characteristics of the two main CDR options present in mitigation scenarios: BECCS and afforestation/reforestation. We apply a linear mixed- effect model to capture the specific regional and cross- IAM effects. Results reveal that the distribution of BECCS and afforestation deployment differs across IAMs and regions and, to a second extent, time. BECCS is preferred in the scenarios not for its ability to expand energy use but actually because it appears as an alternative to afforestation, which is associated with a decrease in energy use. However, the regional distribution of CDR deployment does not show a common pattern across scenarios and IAMs. Therefore, a more comprehensive investigation is needed before it can support policy proposals.

Tailings dam failures can cause devastation to the environment, loss of human life, and require expensive remediation. A promising approach for de-risking brucite-bearing ultramafic tailings is in situ cementation via carbon dioxide (CO2) mineralization, which also sequesters this greenhouse gas within carbonate minerals. In cylindrical test experiments, brucite [Mg(OH)2] carbonation was accelerated by coupling organic and inorganic carbon cycling. Waste organics generated CO2 concentrations similar to that of flue gas (up to 19%). The abundance of brucite (2-10 wt %) had the greatest influence on tailings cementation as evidenced by the increase in total inorganic carbon (TIC; +0.17-0.84%). Brucite consumption ranged from 64-84% of its initial abundance and was mainly influenced by water availability. Higher moisture contents (e.g., 80% saturation) and finer grain sizes (e.g., clay-silt) that allowed for a better distribution of water resulted in greater brucite carbonation. Furthermore, pore clogging and surface passivation by Mg-carbonates may have slowed brucite carbonation over the 10 weeks. Unconfined compressive strengths ranged from 0.4-6.9 MPa and would be sufficient in most scenarios to adequately stabilize tailings. Our study demonstrates the potential for stabilizing brucite-bearing mine tailings through in situ cementation while sequestering CO2.

This work aims to study the structural and residual trapping mechanisms on the Deccan traps topography to elucidate the possible implementation of CO2 geological sequestration. This study provides an insight into a selection of stairsteps landscape from Deccan traps in the Saurashtra region, Gujarat, India. Various parameters affect the efficiency of the structural and residual trapping mechanisms. Thus, the parametric study is conducted on the modeled synthetic geological domain by considering the suitable injection points for varying injection rates and petrophysical properties. The outcomes of this study will provide insights into the dependencies of structural and residual trapping on the Deccan traps surface topography and injection rates. It can also establish a protocol for selecting the optimal injection points with the desired injection rate for the safe and efficient implementation of CO2 sequestration. The simulation results of this study have shown the dependencies of structural and residual trapping on the geological domain parameters.

The increasing interest in bio-based construction materials has resulted in the emergence of the concept of “buildings as a carbon sink”. Quantifying and comparing the effects of carbon sequestration and storage in buildings from a life cycle perspective involves the evaluation of flows and processes taking place at different timescales and across ecological, technological, and economic domains. This scoping review sheds light on the heterogeneous body of approaches and results from relevant scientific literature of the past decade: 180 articles were reviewed following a systematic search and relevance-checking process. Contributions are evaluated based on the scale of interest (material, building, building stock), the sequestration mechanism (photosynthesis, carbonation) and the accounting methodology adopted to quantify global warming. The majority of works taking a life cycle perspective adopt static methods, with only a few accounting for dynamic effects over time, although more recent studies do tend to recognise the need for dynamic life cycle assessment. A characterisation of current and future carbon storage in the global building stock is still needed, and substantial work remains to be done to validate the theory of buildings as a carbon sink to mitigate the effects of climate change. Reports on carbon stored in durable construction products and buildings mostly find cumulative effects that are less than emissions from fossil fuel use in a single year (ranging from negligible to 175%). Furthermore, net gains in storage in the built environment can be offset by net losses in forest carbon, and the benefits of substitution with wood are sometimes overstated. Further adoption of bio-based construction materials can – at best – only make a substantial contribution to climate change mitigation in the context of rapid global progress in decarbonisation.

In the twentieth century, climate change has become one of the most severe environmental threats in the world. Carbon sequestration and storage by natural forests are considered as one of the most vital ecosystem services that reduce atmospheric CO2 which accelerates climate change. Therefore modeling the spatial distribution of carbon storage is necessary when combating climate change. Although the Uva province in Sri Lanka consists of more than ~ 50% of such forests and scrublands, the spatial distribution and quantification of carbon storage are rarely studied. Thus, the prime objective of the current study was to model and estimate the carbon storage of the Uva province in Sri Lanka using the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST 3.7.0) carbon storage and sequestration modeling software. The model summarized results into a raster output of the spatial distribution of carbon storage. The results revealed that with a land area of 850,000 hectares, the study area currently stores 9663.5 million tons of carbon whereas carbon storage varies within different land use land cover (LULC) types. The LULC types with rich vegetation had a higher amount of carbon stored on a per hectare basis and vice-versa. Natural forests obtained the largest carbon stored with 6863.6 million tons which comprise ~ 71% of the total carbon stock in the area. However, this study highlights the importance of natural forests for carbon storage whereas these outcomes could be effectively used in the preparation of environmental management plans, making environmental policies, and establishing country development plans conducted by the government and other organizations.

Background and aims Forest management towards increased carbon (C) sequestration has repeatedly been suggested as a “natural climate solution”. We evaluated the potential of altered management to increase C sequestration in boreal Pinus sylvestris forest plantations. Methods At 29 forest sites, distributed along a 1300 km latitudinal gradient in Sweden, we studied interactive effects of fertilization and thinning on accumulation of C in standing biomass and the organic horizon over a 40 year period. Results Abstention from thinning increased the total C stock by 50% on average. The increase was significant (14% on average) even when C in the removed timber was included in the total ecosystem C pool. Fertilization of thinned stands increased stocks similarly regardless of including (11%) or excluding (12%) removed biomass, and fertilization combined with abstention from thinning had a synergistic effect on C stocks that generated an increase of 79% (35% when removed timber was included in the C stock). A positive effect of fertilization on C stocks was observed along the entire gradient but was greater in relative terms at high latitudes. Fertilization also reduced soil respiration rates. Conclusion Taken together, our results suggest that changed forest management practices have major potential to increase the C sink of boreal forests. Although promising, these benefits should be evaluated against the undesired effects that such management can have on economic revenue, timber quality, biodiversity and delivery of other ecosystem services.

An increasingly urbanized world is one of the most prominent examples of global environmental change. Across the globe, urban parks are designed and managed in a similar way, resulting in visually pleasing expansions of lawn interspersed with individually planted trees of varying appearances and functional traits. These large urban greenspaces have the capacity to provide various ecosystem services, including those associated with soil physicochemical properties. Our aim was to explore whether soil properties in urban parks diverge underneath vegetation producing labile or recalcitrant litter, and whether the impact is affected by climatic zone (from a boreal to temperate to tropical city). We also compared these properties to those in (semi)natural forests outside the cities to assess the influence of urbanization on plant-trait effects. We showed that vegetation type affected percentage soil organic matter (OM), total carbon (C) and total nitrogen (N), but inconsistently across climatic zones. Plant-trait effects were particularly weak in old parks in the boreal and temperate zones, whereas in young parks in these zones, soils underneath the two tree types accumulated significantly more OM, C and N compared to lawns. Within climatic zones, anthropogenic drivers dominated natural ones, with consistently lower values of organic-matter-related soil properties under trees producing labile or recalcitrant litter in parks compared to forests. The dominating effect of urbanization is also reflected in its ability to homogenize soil properties in parks across the three cities, especially in lawn soils and soils under trees irrespective of functional trait. Our study demonstrates that soil functions that relate to carbon and nitrogen dynamics-even in old urban greenspaces where plant-soil interactions have a long history-clearly diverged from those in natural ecosystems, implying a long-lasting influence of anthropogenic drivers on soil ecosystem services.

Biochar application and enhanced weathering are negative emission technologies (NETs) with the potential for large-scale deployment for the removal of CO2 from the atmosphere. Biochar is a solid product of pyrolysis that can permanently store carbon when applied in soil due to its chemical recalcitrance. Enhanced weathering is based on the acceleration of the natural reaction of moisture, CO2, and alkaline minerals. Both of these NETs rely on the application of pulverized material to different types of terrestrial sinks, which can include marginal and agricultural land. These two NETs can be used separately or concurrently, depending on local sink conditions. In some cases, simultaneous application of biochar and mineral powder to soil has the advantage of attaining additional beneficial effects of soil amendment. Although recent papers have reported the development of process integration models for optimizing carbon management networks based on either biochar application or enhanced weathering, none have reported models integrating these two NETs in the same system. To address this gap, a fuzzy mixed-integer linear programming model is developed that integrates biochar application and enhanced weathering for large-scale carbon sequestration. Fuzzy set theory provides a well-tested framework for integration of both subjectivity and uncertainty into mathematical programming. The model determines the optimal allocation of biochar and/or alkaline minerals from each source to each sink, while considering the application limits and CO2 sequestration potential. An illustrative case study is solved that clearly demonstrates the application of the model. The case study shows interesting results that can guide how the full sustainable potential of these two technologies can be utilized in a carbon management network.

Riverine floodplain soils are important reservoirs of organic carbon (OC) in terrestrial ecosystems because of their high biomass productivity and OC input via flood events. Substantial knowledge of the riverine floodplain soil OC distribution and its impacting variables are significant for predicting carbon sequestration and emission. This study aimed at (1) predicting SOC in riverine floodplain soils using the multiple linear regression (MLR), M5P, and random forest (RF) models, (2) comparing the model performances, and (3) revealing the significant variables controlling the spatial dynamic of riverine floodplain soils OC. In this study, 4227 topsoil samples (0–20 cm) from the Yangtze riverine floodplain were collected and analyzed for soil organic carbon (SOC) and other properties. We identified the key variables impacting SOC and predicted the SOC spatial distribution based on three predictive models (i.e., MLR, M5P, and RF), measured soil attributes, and land-use data. The study results indicated that total soil sulfur and nitrogen concentrations were the most important variables affecting the SOC distribution, followed by soil geochemical variables (e.g., Al2O3, Na2O, CaO, and Fe2O3), and alkalinity conditions. The M5P and RF models showed higher accuracy in predicting SOC compared with the MLR model. Although RF outperformed M5P in SOC prediction, RF was limited in revealing the relationships between SOC and environmental variables, restricting its interpretability. The land-use analysis highlighted that paddy soils were more conducive to maintaining high SOC concentration than upland soils. We recommend using the RF and M5P models to efficiently predict the SOC distribution in riverine floodplain soils as RF could produce higher prediction accuracy and M5P can detect the splitting process and identify relevant thresholds for the regression. Paddy management is crucial for SOC sequestration and grain production. Therefore, it is recommended as an efficient approach to enhance soil fertility, mitigate climate change, and ensure food security.

Plant functional traits shape many ecosystem processes, including carbon sequestration in vegetation and soil. The shifts of trait-based indices can reflect changes in plant resource-use strategies during successional processes. The aim of this study was to determine how plant functional diversity affects carbon sequestration during secondary succession in semi-arid grassland, and how the limiting environmental factor (that is, soil water) affects these processes. We investigated 16 plots at three sites with different stand ages and climate conditions in the semi-arid area of the Loess Plateau, China. We measured the key plant functional traits: plant height; leaf dry matter content (LDMC); specific leaf area (SLA); leaf carbon (LC), nitrogen (LN), and phosphorus contents (LP); and ecosystem carbon components: aboveground biomass (AGB); root biomass (RB); and soil organic carbon stock (SOC). The community weighted mean (CWM) of LDMC increased and SLA and LN decreased with stand age at a wetter site, indicating that plants’ resource-use strategy might shift from acquisition to conservation during succession. The exception of the shifting of CWM_SLA deviated from the general trend during succession can be attributed to the appearance of slow-growing species in the early successional stage at a drier site. The structural equation models (SEM) showed that stand age, soil water content (SWC) and functional diversity indices accounted for 55.7%, 53.2%, and 56.5% of variations in AGB, RB, and SOC during succession, respectively. The interplays of stand age and SWC were regulated by functional diversity indices, especially the CWMs of plant height and SLA, functional variance (FDvar) of plant height and functional evenness (FEve). Carbon stocks accumulated faster at wetter sites. Our results indicate that the mass ratio and niche complementary hypotheses are not contradictory in explaining relationships between community functional diversity and ecosystem carbon stocks during the restoration of semi-arid grasslands, and that SWC affects the progress of succession and carbon sequestration.

Increased levels of global atmospheric carbon dioxide (CO2) and further consequences of climate change derived more research efforts to emphasize the actual role of the ecosystems of higher significance in this task. Mangrove ecosystem received a great interest in the demonstration of its potential to sequester atmospheric CO2. Sampling process from the sediment of mangrove ecosystem extended some 600 km along the Egyptian western coast of Red Sea, starting from Abu Monquar Island (27.216250° N, 33.876288° E) at the north near Hurghada to Sharm El-Madfa’a (22.895165° N, 35.717757° E) near the Egyptian–Sudanese frontiers. This work compares the pure population of Avicennia marina (Forssk.) Vierh. and Rhizophora mucronata, Lam. as well as the mixed population of both species. Mean values of dry bulk density (DBD) were 1.2 ± 0.02, g cm−3 for pure A. marina, 0.8 ± 0.06 g cm−3 for pure R. mucronata, and 0.7 ± 0.04 g cm−3 for mixed sites. In addition, the values of mean soil organic carbon (SOC) were 10.2, 51.7 and 89.0 g C kg−1 for pure A. marina, pure R. mucronata and mixed sites, respectively. On the other hand, the mean values of soil organic carbon pool (SOCP) were 258.0, 604.7 and 1049.3 Mg C ha−1 for pure A. marina, pure R. mucronata and mixed sites of both species, respectively. The carbon sequestration potential (CSP) of pure A. marina, pure R. mucronata, and mixed sites of both species were 0.8, 2.2, 3.4 Mg C ha−1 year−1, respectively.

In recent decades, global warming and nitrogen (N) deposition have been increasing obviously, which have led to some strong responses in terrestrial ecosystems, especially the carbon (C) cycle. The boreal forest occupies an important position in the global C cycle with its huge C storage. However, the impact of global change such as N deposition on boreal forest ecosystem C cycle has been not very clear. In order to solve this problem, the field experiment of N addition in a boreal forest has been built in the Greater Khingan Mountains of Northeast China since 2011. Four N addition gradients (0, 25, 50, 75 kg N ha−1 year−1) were set up to study the response of above- and belowground C pool to N addition. The results showed that the total forest C sequestration of low-, medium- and high-N treatments was 104.4 ± 5.9, 20.2 ± 2.7 and 5.3 ± 0.4 g C/g N, respectively. Aboveground trees were the largest C pool, followed by soil, roots and floor C pool. Low-N increased the input of C by promoting photosynthesis. Trees of Larix gmelini increased the investment in the belowground root system and increased the belowground C pool. High-N reduced the inter-annual litter biomass and decreased litter C:N that accelerated the decomposition of litter, resulting in a reduction in the floor C pool. Low-N increased total soil respiration, while medium- and high-N inhibited heterotrophic respiration and then increased soil C sequestration. The estimation of forest C pool provides valuable data for improving the C dynamic characteristics of boreal forest ecosystem and is of great significance for us to understand the impact of climate change on the global C cycle.

Biochar can affect CO2 emission and C sequestration from soils, but little is known about the effects of its re-application and interaction with easily accessible substrates. Since most agricultural soils are continuously reworked, understanding the mechanics of CO2 evolution as affected by soil amendments and their combinations may have important lessons for the global effort to combat climate change. In this study carried out in a controlled environment, we tested the short-term effects of biochar, and its re-application at different rates, on the production of CO2 emission and C accumulation in samples of arable soils. We used a loamy Haplic Luvisol as the substrate and added varying amounts of biochar and sources of easily accessible N and C. We observed CO2 evolution for 20 days at optimal temperature and moisture conditions. We found that in the control treatment with no biochar, the total potential respiration after the addition of (NH4)2SO4 (N) and glucose (G) was increased compared to basal respiration. The addition of biochar reduced CO2 emission in the control, N- and G-stimulated treatments by 12–22, 13‒24 and 2‒21%, respectively. Conversely, the application of biochar increased CO2 emission in the combined NG treatment. Application of biochar at a higher rate, as well as its re-application, increased soil organic carbon content and reduced emission of CO2 into the atmosphere.

Geological carbon dioxide sequestration in deep saline aquifers can play a key role in the successful mitigation of greenhouse gas emissions. Several conditions have been identified that affect the solubility of CO2 in water, including temperature, pressure, pH, and salinity. At similar conditions, the solubility in bulk fluids differs from the solubility in confined porous media. We conducted equilibrium molecular dynamics (MD) simulations to investigate the solubility of CO2 in water confined in slit-shaped calcite pores. We studied the effects of brine (NaCl and MgCl2). Compared to bulk water/brine, the solubility of CO2 is lower in calcite pores and decreases as the pores narrow. Adsorption energy calculations were performed to compare our results to CO2 solubility in water-filled silica pores. These results indicate that narrower calcite pores are less attractive for the adsorption of CO2. In addition, the simulation results suggest that the difference in the positions where the ions adsorb also affects whether salts increase or decrease the solubility of CO2 in confined water. Confinement and ions also reduce the mobility of CO2 in water. These observations contribute to the design of long-term CO2 sequestration strategies as they provide boundary constraints for the amount of CO2 that can dissolve in hydrated pores, as well as the timing of CO2 transport in such systems.

Soil organic carbon (SOC) plays a key role in improving soil quality and optimizing crop yield. Yet little is known about the fate of macroaggregates (>0.25 mm) under long-term fertilization and their relative importance in SOC sequestration in reclaimed calcareous soil. Therefore, the effects of mineral fertilizers and organic manure on the mechanisms of organic carbon (OC) stabilization in macroaggregates were investigated in this study. Four treatments were used: unfertilized control (CK), mineral fertilizer (NPK), compost chicken manure alone (M), and mineral fertilizers plus manure (MNPK). Samples from the 0–20 cm layer of soil receiving 11-year-long fertilization were separated into four fractions based on the macroaggregates present (unprotected coarse and fine particulate organic matter, cPOM and fPOM; physically protected intra-microaggregate POM, iPOM; and biochemically protected mineral associated OM, MOM) by the physical fractionation method. Compared with the control, the long-term application of NPK had little effect on SOC content, total nitrogen (TN) content, and OC and TN contents of macroaggregate fractions. In contrast, incorporation of organic manure (MNPK) significantly increased SOC (45.7%) and TN (24.3%) contents. Application of MNPK increased OC contents within macroaggregate-extracted fractions of cPOM (292.2%), fPOM (136.0%) and iPOM (124.0%), and TN contents within cPOM (607.1%), fPOM (242.5%) and iPOM (127.6%), but not the mineral associated organic carbon (MOM-C) and nitrogen (MOM-N) contents. Unprotected C fractions were more strongly and positively correlated with SOC increase than protected C fractions, especially for cPOM-C, indicating that SOC sequestration mainly occurred via cPOM-C in the studied calcareous soil. In conclusion, MNPK increased the quantity and stability of SOC by increasing the contents of cPOM-C and cPOM-N, suggesting that this management practice (MNPK) is an effective strategy to develop sustainable agriculture.

As fluids are injected into a reservoir, the pore fluid pressure changes in space and time. These changes induce a mechanical response to the reservoir fractures, which in turn induces changes in stress and deformation to the surrounding rock. The changes in stress and associated deformation comprise the geomechanical response of the reservoir to the injection. This response can result in slip along faults and potentially the loss of fluid containment within a reservoir as a result of cap-rock failure. It is important to recognize that the slip along faults does not occur only due to the changes in pore pressure at the fault location; it can also be a response to poroelastic changes in stress located away from the region where pore pressure itself changes. Our goal here is to briefly describe some of the concepts of geomechanics and the coupled flow-geomechanical response of the reservoir to fluid injection. We will illustrate some of the concepts with modeling examples that help build our intuition for understanding and predicting possible responses of reservoirs to injection. It is essential to understand and apply these concepts to properly use geomechanical modeling to design geophysical acquisition geometries and to properly interpret the geophysical data acquired during fluid injection.

The conservation of ecosystems and their biodiversity has numerous co-benefits, both for local societies and for humankind worldwide. While the co-benefit of climate change mitigation through so called blue carbon storage in coastal ecosystems has raised increasing interest in mangroves, the relevance of multifaceted biodiversity as a driver of carbon storage remains unclear. Sediment salinity, taxonomic diversity, functional diversity and functional distinctiveness together explain 69%, 69%, 27% and 61% of the variation in above- and belowground plant biomass carbon, sediment organic carbon and total ecosystem carbon storage, respectively, in the Sundarbans Reserved Forest. Functional distinctiveness had the strongest explanatory power for carbon storage, indicating that blue carbon in mangroves is driven by the functional composition of diverse tree assemblages. Protecting and restoring mangrove biodiversity with site-specific dominant species and other species of contrasting functional traits would have the co-benefit of maximizing their capacity for climate change mitigation through increased carbon storage., Conserving mangrove biodiversity has numerous co-benefits, including climate change-mitigation. Here the authors demonstrate that blue carbon storage in mangroves can be best sustained by combining site-specific dominant species with other species with contrasting functional traits.

Tropical forests are a global biodiversity centre providing enormous ecosystem services to the humankind. The present study was undertakento examine and analyze the phytosociology and regeneration status of tree species in 39 permanent preservation plots spread across 22 different forest sub-types in Madhya Pradesh, India. A total of 975 quadrats were laid with a sampling intensity of 2.42% of the total area under study. 109 tree species were recorded. Density range varied from 516 individuals/hectare (ind/ha) in southern tropical dry deciduous forests to 3,412 ind/ha in dry grassland forests. Most of the forest sub-types showed log normal distribution owing to relatively high species richness, diversity and evenness, but a low dominance. Out of 62,228 live stems recorded, 68.52% were poles followed by saplings (26.39%), young trees (5.01%) and mature trees (0.08%). The result also showed high seedling density in each forest sub-type ranging from 1,040 ind/ha to 51,124 ind/ha, indicating a healthy population of mature reproducing adults. The diameter distribution in all the forest sub-types showed negative slope and followed the classic inverse J-shaped curve frequently observed in natural forests. Most of the forest sub-types in these preservation plots are regenerating successfully owing to the absolute protection given to the studied sites. It is recommended to study carbon sequestration in these permanent preservation plots over atime, which will inform climate policymakers about the true potential of Indian tropical forests as carbon sink.

The fall of phyllodes from Acacia aneura F.Muell. ex Benth. (mulga) in central Australia was studied over 22 months from mid-1958 at four locations within a livestock reserve north of Alice Springs in the Northern Territory, in order to identify rainfall or seasonal triggers. Phyllode fall increased by at least an order of magnitude for short periods following rain of 15–20 mm or more on a ‘mature’ mulga site and similar trends were apparent for ‘young’ and ‘desert form’ mulga on the same site, and on a second, independent, ‘mature’ site. When rates of phyllode fall were high after substantial rain, at both ‘mature’ locations, ~30% of nitrogen and ~50% of phosphorus were withdrawn before abscission, suggesting that mulga was markedly conservative of these nutrients. Conversely, under dry conditions, when phyllode fall was relatively low (

Alnus acuminata Kunth. (alnus) is widely used in agroforestry systems across the globe and is believed to provide multiple ecosystem services; however, evidence is lacking in agroforestry literature to support the perceived benefits, particularly in Rwanda. To understand carbon sequestration potential and other benefits of alnus, a household survey, tree inventory and destructive sampling were conducted in north-western Rwanda. Over 75% of the respondents had alnus trees in their farms. The trees provide stakes for climbing beans, firewood and timber. They also improve soil fertility and control soil erosion. Farmers had between 130 and 161 alnus trees per hectare with an average height of 7.7 ± 0.59 m and diameter at breast height of 16.3 ± 1.39 cm. The largest biomass proportion was found in stems (70.5%) while branches and leaves stock about 16.5 and 13% of the total biomass, respectively. At farm level, aboveground biomass of alnus trees was estimated to be 27.2 ± 0.7 Mg ha−1 representing 13.6 Mg of carbon (C) per hectare. Biomass carbon increased with tree size, from 7.1 ± 0.2 Mg C ha−1 in 3 years old trees to 34.4 ± 2.2 Mg C ha−1 in 10 years old trees. The converse was observed with elevation; biomass carbon decreased with increasing elevation from 21.4 ± 1.29 Mg C ha−1 at low (2011–2110 m) to 9.6 ± 0.75 Mg C ha−1 in the high elevation (> 2510 m). In conclusion, alnus agroforestry significantly contributes to carbon sequestration, although the magnitude of these benefits varies with tree age and elevation. Planting alnus trees on farms can meet local needs for stakes for climbing beans, wood and soil fertility improvement, as well as the global need for regulation of climate change.

Climate change is driving the impetus for carbon sequestration. Compared to other countries, little is known about C sequestration after grassland conversion to plantation forestry in South Africa. To this aim 27 sites were studied in the Weatherley catchment in the north eastern part of the Eastern Cape Province. About half of this 160 ha grassed catchment was planted to Pinus elliottii, Pinus patula, and Eucalyptus nitens. Soil organic carbon was measured in detail at the 27 sites before and eight years after afforestation, and augmented with litter and above-ground biomass measurements. The total C stocks for the different tree species and grassland areas were lowest for the grassland area (43.6 Mg C ha−1) and highest for the Pinus patula and Eucalyptus nitens areas (90.0 and 91.6 Mg C ha−1 respectively). In general, the afforested catchment aboveground C stocks contributed about a third to the total C stocks. Afforested soils in the poorly drained class had the lowest total C stocks (69.6 Mg C ha−1) compared to the freely drained soil group, which had 87.7 Mg C ha−1. Poorly and freely drained soil conditions therefore seemed to restrain tree growth while C sequestration was promoted on moderately drained soils. Afforestation contributed a total gain of 2 187 Mg C to the catchment, at a rate of 273 Mg C a−1 or 3.59 Mg C ha−1 a−1 for the afforested area only. The C sequestration rate by the plantation forest system was therefore 2.6 times that of the grassland system.

Abstract Mineral carbonation is a potentially attractive sequestration technology for the permanent safe disposal and immobilization of CO2. In this technology, CO2 is chemically reacted with calcium, sodium, and magnesium containing materials to form thermodynamically stable and environmentally harmless minerals, usually carbonates. In our research, mechanical activation of red mud was carried out in order to enhance its reactivity by means of mechanochemical reactions (surface activation), and its sequestration behaviour was investigated using carbon dioxide gas at 25 °C temperature and at high pressure (5 bar) in an autoclave. The reacted red mud was characterized by Fourier-transformed infrared spectrometer, scanning electron microscopy, X-ray diffraction, laser particle size analyzer, BET specific surface area measurement, and pH measurement. It was found that mechanical activation improved the CO2 sequestration ability by 1.7 wt% of red mud, as demonstrated by the above investigations. The pH of red mud slurry can be lowered by reacting it with carbon dioxide. During our measurements, the pH of the suspension decreased from 10 to 6.81. Furthermore, the carbonation process can be successfully used to decrease the amount of harmful PM10 (particles with a diameter of 10 μm or less) and PM2.5 (particles with a diameter of 2.5 μm or less) fraction. The proportion of 10 μm particles can be reduced by 40% and that of 2.5 μm by 20%. Graphic Abstract

Eucalyptus plantations at higher elevations in Sri Lanka are being confronted by a conflict between their industrial need maintenance and ecological need conservation. Increasing carbon sequestrati...

Natural grasslands represent the second largest ecosystem in Turkey. However, the impact of varying nitrogen (N) fertilization rates on overall soil health indicators have not been reported in the country. A 2-year study was conducted in the Kahramnmaras Plateau region in Turkey to evaluate the impacts of seven N application rates [i.e., 0 (N0), 50 (N50), 100 (N100), 150 (N150), 200 (N200), 250 (N250), and 350 (N350) kg N ha−1] on physical, chemical, and biological parameters of soil health. Nitrogen addition decreased bulk density by 8–12%, and increased aggregate stability by 3–5% and EC up to 110%. Application of ≥ 100 kg N ha−1 increased soil porosity up to 6.7%. Soil pH and C:N ratios were not affected by N addition. The lowest plant available water occurred with the N0 and N50 treatments, decreasing around 24% and 17% compared to N300. Soil organic carbon, total nitrogen, and C and N stocks increased with increasing N addition. Application of N300 rates increased C stocks between 4 and 34%, and N stocks between 15 and 22% compared to all other treatments. Compared to control, N250 increased microbial biomass carbon by 349% and nitrogen by 250%. Microbial respiration in the N250 and the N300 treatments was 97% and 129% greater than control. Addition of N fertilization for a first time in a grassland ecosystem with a previous history of long-term overgrazing, even at low rates, positively impacted several parameters of soil health, a positive impact that could ensure a greater sustainability of these fragil systems over the long-term.

Kelp forests provide many important ecosystem services to people, including mitigating storm damage, cycling nutrients, and providing commercially-harvestable resources. However, kelp forests’ ability to sequester carbon dioxide, and therefore help regulate the climate, has until recently, been overlooked in assessments of the beneficial services they provide. In this study we incorporate updated knowledge on the potential of kelp to sequester ‘blue carbon’, and use the extensive kelp forests of the Falkland Islands as a case study to assess the value of kelp forest to society through multiple associated ecosystem services. Our analysis shows kelp forests provide a highly valuable range of direct and indirect services, which if managed correctly, will continue to benefit people, both now and in the future. The total estimated value of the Falkland Islands’ kelp system is currently equivalent to ~ £2.69 billion per year (or £3.24 million km-2 year-1). However, the true value of the kelp forest surrounding the Falkland Islands is likely to be higher still, given that our estimate does not account for elements such as associated scientific research, tourism, and cultural services, due to the necessary data currently being unavailable. Similarly, the full value of these highly biodiverse ecosystems in supplying habitat and food to a large range of associated species is crucial, yet extremely difficult to fully quantify. This study illustrates the importance of maintaining kelp ecosystems in a healthy state to ensure they continue to supply valuable ecological processes, functional roles, and ecosystem services, including their overlooked role as significant long-term carbon sinks.

Tropical peat swamp forests are waterlogged, acidic, anoxic and oligotrophic ecosystems. They are important terrestrial carbon pools that help mitigating global warming through carbon sequestration in peat. This study aimed at investigating putative roles of bacteria in the carbon and nitrogen cycles in North Selangor peat swamp forest, Malaysia. Whole-genome sequencing was performed on four bacterial isolates using Illumina NextSeq 500 to decipher their genetic information while Gen III Microplate (Biolog) was applied to verify carbon source utilization. The isolates were identified as Dyella sp. strain C9, Dyella sp. strain C11, Klebsiella sp. strain C31 and Paraburkholderia sp. strain C35. Both Dyella spp. and Paraburkholderia sp. strain C35 were likely novel species while Klebsiella sp. strain C31 was a different strain of the type species, Klebsiella pneumoniae. Both genomic and bioassay results suggested the involvement of the isolates in the degradation of lignocellulose, carbohydrates, sugar alcohols, organic acids and aromatic compounds. The isolates could potentially perform methanotrophy, which helps to mitigate methane emissions from tropical peatlands. In addition, the isolates also contained genes encoding enzymes for nitrite, nitrate and nitric oxide reduction, as well as dissimilatory nitrate reduction to ammonium, which retains the nitrogen in the ecosystems. The results generated insights into potential functions of bacteria in the energy production and nutrient cycling of tropical peatlands, which are essential for the sustainability of high biomass and biodiversity in these ecosystems.

Approximately one third of California is grazed by livestock, with most forage produced on annual rangelands, the common term for rangelands with a significant annual herbaceous component. Given the state's interest in mitigating climate change and growing public attention on grazing systems that enhance carbon sequestration, we investigate the impact of grazing management on soil carbon cycling on California annual rangelands, drawing on soil science, rangeland management, and policy analysis literature. We conclude that using managed grazing for augmenting soil organic carbon on California annual rangelands presents significant challenges. Challenges include the heterogeneity, biogeochemical characteristics, and nonequilibrium nature of California's Mediterranean region, where ecological site conditions, soil type and texture, and climate moderate carbon sequestration. Enduring unknowns in the science underlying soil carbon and the dearth of relevant California-based studies further obscure the potential climate change mitigation effects of grazing systems. Given this, grazing management on California annual rangelands should not be prioritized as a climate change mitigation strategy, unless it is for the purposes of data collection and research. Alternative climate change mitigation opportunities on these landscapes include preventing rangeland conversion and enhancing soil carbon stocks through the suite of range management practices known to augment soil organic carbon or prevent erosion, including marginal cropland restoration, riparian restoration, organic amendments, and silvopasture. In this review, we argue that single-purpose management is generally not fitting for the diverse portfolio of social-ecological services produced on California's vast and varied rangelands. When assessing the value of grazing systems for augmenting soil organic carbon, policymakers, landowners, and other decision makers should consider the potential impacts on the numerous ecosystem services supported by the landscape. The multidisciplinary method presented in this review provides a critical framework for evaluating the appropriateness of working lands carbon policies as Natural Climate Solutions for climate change mitigation are developed in California and other geographies.

The coal’s permeability plays a crucial role in coalbed methane (CBM) extraction and coal seam CO2 sequestration. An accurate understanding of permeability rebound and recovery is therefore essential. This study establishes an improved fully coupled gas migration model for CBM extraction. The permeability rebound and recovery times as well as rebound values are proposed to accurately quantify permeability evolution during CBM extraction. The evolution of these three parameters under the influence of different factors are evaluated in detail, such as initial gas pressure, the diffusion coefficient, and the permeability. The results show that the permeability rebound and recovery times increase along with initial gas pressure and the amount over time rises rapidly under high gas pressures. As the initial gas pressure increases, the permeability rebound value decreases. However, initial diffusion coefficient and permeability have a negative trend in permeability rebound, recovery time, and rebound value. These tendencies are particularly large for low initial permeabilities and diffusion coefficients, yet the change in rebound time is smaller than the one in recovery time. Finally, inspired by the relationship between permeability rebound and gas pressure change during CBM extraction, the evolution of coal seam permeability under different CO2 injection method is discussed. A stepwise increasing-pressure CO2 injection method is also proposed, which could effectively increase the volume of CO2 sequestered and reduce project costs. Therefore, our findings shall shed light on improving coal mine safety production and reducing greenhouse gas emission.

Soil carbon sequestration is seen as an effective means to draw down atmospheric CO2, but at the same time warming may accelerate the loss of extant soil carbon, so an accurate estimation of soil carbon stocks and their vulnerability to climate change is required. Here we demonstrate how separating soil carbon into particulate and mineral-associated organic matter (POM and MAOM, respectively) aids in the understanding of its vulnerability to climate change and identification of carbon sequestration strategies. By coupling European-wide databases with soil organic matter physical fractionation, we assessed the current geographical distribution of mineral topsoil carbon in POM and MAOM by land cover using a machine-learning approach. Further, using observed climate relationships, we projected the vulnerability of carbon in POM and MAOM to future climate change. Arable and coniferous forest soils contain the largest and most vulnerable carbon stocks when cumulated at the European scale. Although we show a lower carbon loss from mineral topsoils with climate change (2.5 ± 1.2 PgC by 2080) than those in some previous predictions, we urge the implementation of coniferous forest management practices that increase plant inputs to soils to offset POM losses, and the adoption of best management practices to avert the loss of and to build up both POM and MAOM in arable soils. Particulate and mineral-associated soil organic carbon have different climate sensitivity and distributions in Europe, according to analyses of measurements of soil carbon fractions from 352 topsoils.

In the context of climate change and the increase of the energy demand, there is a need for carbon sequestration methods and sustainable fuels. This can be done by cultivation of microalgae, an unicellular microscopic algae that converts carbon dioxide into high-value bioproducts and energy. Moreover, microalgae can be used to assess the health of ecosystems such as lakes. Here we review microalgae for biofuel, for wastewater treatment and as bioindicators. We discuss the impact of processes based on microalgae using life cycle assessment. We present co-cultivation of microalgae with other microbes, and we compare conventional processes with processes integrating auto-flocculation, in situ transesterification and excretion.

Deforestation and forest degradation are among the leading global concerns, as they could reduce the carbon sink and sequestration potential of the forest. The impoundment of Kenyir River, Hulu Terengganu, Malaysia, in 1985 due to the development of hydropower station has created a large area of water bodies following clearance of forested land. This study assessed the loss of forest carbon due to these activities within the period of 37 years, between 1972 and 2019. The study area consisted of Kenyir Lake catchment area, which consisted mainly of forests and the great Kenyir Lake. Remote sensing datasets have been used in this analysis. Satellite images from Landsat 1-5 MSS and Landsat 8 OLI/TRIS that were acquired between the years 1972 and 2019 were used to classify land uses in the entire landscape of Kenyir Lake catchment. Support vector machine (SVM) was adapted to generate the land-use classification map in the study area. The results show that the total study area includes 278,179 ha and forest covers dominated the area for before and after the impoundment of Kenyir Lake. The assessed loss of carbon between the years 1972 and 2019 was around 8.6 million Mg C with an annual rate of 0.36%. The main single cause attributing to the forest loss was due to clearing of forest for hydro-electric dam construction. However, the remaining forests surrounding the study area are still able to sequester carbon at a considerable rate and thus balance the carbon dynamics within the landscapes. The results highlight that carbon sequestration scenario in Kenyir Lake catchment area shows the potential of the carbon sink in the study area are acceptable with only 17% reduction of sequestration ability. The landscape of the study area is considered as highly vegetated area despite changes due to dam construction.

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

The combustion of fossil fuels is intensifying global warming and destructing the ecosystem with negative human health impacts as well. Even so, other anthropogenic activities have unfortunately constituted pollution also to our environment, say, in the form of waste waters. Beside these, the existing technologies for waste water treatment have problems such as high costs, sludge disposal challenges, etc. Thus, it is now important to find economically viable and safe alternatives to decontaminate waste waters. Hence, low cost, renewable, easily accessible, and readily prepared biosorbents have become favourable alternatives to traditional counterpart for the elimination of pollutants from aqueous systems. Fortunately, these biosorbents also have requisite and comparable properties necessary for adsorption of pollutants. Many studies have been reported on the application of biosorbents for pollutants removal. However, this paper provides an overview of biosorbents preparation, properties, their applications in pollutants removal and related use. Biosorbents are usually used in raw or processed forms such as activated carbon (AC), biobar (BC), and charcoal (CC) for removal of pharmaceuticals, pesticides, organics, inorganics, mycotoxins, etc. from aqueous systems. Besides classical sorption of the pollutants, biosorbents have prospect of applications as electrodes in the microbial fuel cells, green packaging materials, energy storage devices, catalysts, soil remediation agent, carbon sequestration, etc. Hence, further concerted investigations should be exercised to develop feasibly best conditions for the preparations and modifications of biosorbents. In addition, mean pore size, pore size distribution, porosity, surface functionality, and zeta potential studies are necessary to be had about biosorbents, especially novel types. There is need for development of biosorbents for specific tasks. Another essential thing is to determine desorption studies of these novel biosorbents. Focus should also be directed on more economically viable and sustainable biosorbents to enhance their use. Again, it is suggested that more suitable biomasses be identified to enable successful preparation of efficient biosorbents. More so, biosorbents can be recycled after use to avoid littering and possible pollution.

Forests play a central role in the global carbon cycle. China's forests have a high carbon sequestration potential owing to their wide distribution, young age and relatively low carbon density. Forest biomass is an essential variable for assessing carbon sequestration capacity, thus determining the spatio-temporal changes of forest biomass is critical to the national carbon budget and to contribute to sustainable forest management. Based on Chinese forest inventory data (1999–2013), this study explored spatial patterns of forest biomass at a grid resolution of 1 km by applying a downscaling method and further analyzed spatio-temporal changes of biomass at different spatial scales. The main findings are: (1) the regression relationship between forest biomass and the associated influencing factors at a provincial scale can be applied to estimate biomass at a pixel scale by employing a downscaling method; (2) forest biomass had a distinct spatial pattern with the greatest biomass occurring in the major mountain ranges; (3) forest biomass changes had a notable spatial distribution pattern; increase (i.e., carbon sinks) occurred in east and southeast China, decreases (i.e., carbon sources) were observed in the northeast to southwest, with the largest biomass losses in the Hengduan Mountains, Southern Hainan and Northern Da Hinggan Mountains; and, (4) forest vegetation functioned as a carbon sink during 1999–2013 with a net increase in biomass of 3.71 Pg.

The response of peatlands to climate change can be highly variable. Through understanding past changes we can better predict the response of peatlands to future climate change. We use a multi-proxy approach to reconstruct the surface wetness and carbon accumulation of the Mukhrino mire (Western Siberia), describing the development of the mire since peat formation in the early Holocene, around 9360 cal. year BP. The mire started as a rich fen which initiated after paludification of a spruce forest (probably in response to a wetter climate), while the Mukhrino mire progressed to ombrotrophic bog conditions (8760 cal. year BP). This transition coincided with the intensive development of mires in Western Siberia and was associated with active carbon accumulation (31 g m(−2) year(−1)). The ecosystem underwent a change to a tree-covered state around 5860 cal. year BP, likely in response to warming and possible droughts and this accompanied low carbon accumulation (12 g m(2) year(−1)). If the future climate will be warmer and wetter, then regional mires are likely to remain a carbon sink, alternatively, a reversion to the wooded state with reduced carbon sink strength is possible. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13280-021-01545-7.

Biomass gasification generates a gas mixture (syngas) that constitutes a rich source of carbon and energy for the production of second-generation renewable fuels such as biomethane. However, the produced syngas composition (H2/CO/CO2) cannot be converted to natural gas grade biomethane due to stoichiometric limitations, and a waste stream of CO2 is released unexploited in the atmosphere. The present study introduces the concept of biomass gasification coupled to syngas biomethanation with in-situ exogenous H2 supply for the complete sequestration of the syngas carbon, the valorization of renewable excess electricity from wind and solar power and the production of biomethane satisfying the criteria for injection in the natural gas grid. Syngas biomethanation was executed by mixed microbial consortia in a trickle bed reactor at 37 °C and 60 °C. The assessment of the effects of the net inlet gas composition was performed according to a hereby proposed syngas quality index (SQI), which is based on the syngas content in compounds able to act as carbon and electron donors and the stoichiometry of methane production. The SQI of the stoichiometrically ideal syngas composition is 4. Values below 4 correspond to a stoichiometric carbon-moles excess while values above 4 correspond to a stoichiometric electron-moles excess. It was demonstrated that switching the SQI of the supplied syngas from 1.44 to 3.67 increased the CH4 content in the outlet of the reactor from 30 to 72%, accompanied by an at least 1.2-fold increase of the CH4 productivity. A SQI of 4.78 (> 4) resulted in a significant deterioration of the quality of the produced biomethane due to a high content (52–54%) of unconverted H2 and because of thermodynamic limitations on carboxydotrophic hydrogenogenesis in thermophilic conditions. Maximal carbon sequestration and production of natural gas grade biomethane was shown to be feasible at a SQI = 3.98 in thermophilic conditions. Graphic Abstract: [Figure not available: see fulltext.]

The need for sustainable production of renewable biofuel has been a global concern in the recent times. Overcoming the tailbacks of the first- and second-generation biofuels, third-generation biofuel using microalgae as feedstock has emerged as a plausible alternative. It has an added advantage of preventing any greenhouse gas (GHG) emissions with simultaneous carbon dioxide sequestration. Dewatering of microalgal culture is one of the many concerns regarding industrial-scale biofuel production. The small size of microalgae and dilute nature of its growth cultures creates huge operational cost during biomass separation, limiting economic feasibility of algae-based fuels. Considering the recovery efficiency, operation economics, technological feasibility and cost-effectiveness, bio-flocculation is a promising method of harvesting. Moreover, advantage of bio-flocculation over other conventional methods is that it does not incur the addition of any external chemical flocculants. This article reviews the current status of bio-flocculation technique for harvesting microalgae at industrial scale. The various microbial strains that can be prospective bioflocculants have been reviewed along with its application and advantages over chemical flocculants. Also, this article proposes that the primary focus of an appropriate harvesting technique should depend on the final utilization of the harvested biomass. This review article attempts to bring forth the beneficial aspects of microbial aided microalgal harvesting with a special attention on genetically modified self-flocculation microalgae.

Soil Organic Carbon (SOC) dynamics study in arable land use at different agro-ecological zones is important for recommendation of sustainable land use management practices against detrimental practices. This will provide insight on how to enhance SOC sequestration, improve soil quality and mitigate impact of climate change in different agro-ecological zones. This study was conducted at two agro-ecological zones of Nigeria; upland rainforest (Ado-Ekiti) and southern guinea savanna (Kabba) to evaluate SOC sequestration under arable land use. From the two agro-ecological zones, 1 ha (ha) of land was marked out, five soil samples were randomly collected at four different depths (0–15, 15–30, 30–45, and 45–60 cm) for SOC sequestration study. Higher SOC concentration and stock were observed at Ado-Ekiti site over Kabba site was due to best soil management practices like soil organic and inorganic fertilizers application and incorporation of crop residues. SOC concentration distribution varied greatly (%CV > 35%) and decreased with depth at the two agro-ecological zones. SOC stocks ranged from 6.59 t ha−1 to 24.97 t ha−1 and decreased with depth in similar trend with SOC concentration. Generally, at both sites, soil organic matter (SOM), total nitrogen (TN), available phosphorus (AP) decrease with increasing depth especially to 45 cm depth while soil pH increase with increasing depth. Both SOC concentration and stock were observed to have significant positive correlation (P