Carbon Pools Research Articles

How Can Land Use Management in Traditional Cultural Landscapes Become a Policy Instrument for Soil Organic Carbon Sequestration and Climate Change Mitigation? A Transylvanian Case Study

Changes in land use from high-nature-value grasslands to arable fields reduce the organic carbon stock in soil, increasing atmospheric carbon concentrations. Maintaining grasslands through traditional agricultural techniques can mitigate climate change by transferring atmospheric carbon to the soil. Benefits of soil organic carbon sequestration include improved soil properties and enhanced ecosystem services and biodiversity. With Romania’s ratification of the Paris Agreement, it is crucial to review climate-related agricultural policies and incentivize carbon sequestration practices in organic soils. This paper presents a soil carbon study in Transylvania’s Târnava Mare region, Romania, known for its preserved cultural landscapes. Soil samples were taken at a depth of 60 cm to assess organic carbon pools under grassland and arable land management across three soil classes: Cernisoils, Hidrisoils, and Luvisoils. Several statistical tests were applied to evaluate the most significant drivers of soil organic carbon sequestration including land use, soil class, and soil depth. The results indicate that land management has the largest impact, with grasslands storing 45% more carbon than arable land on average. This finding should be integrated into national climate action plans, prioritizing the preservation of grasslands and sustainable agricultural practices to support soil organic carbon sequestration.

The Process of Soil Carbon Sequestration in Different Ecological Zones of Qingtu Lake in the Arid–Semi-Arid Region of Western China

As a vital component of the global carbon pool, soils in arid and semi-arid regions play a significant role in carbon sequestration. In the context of global warming, increasing temperatures and moisture levels promote the transformation of barren land into wetlands, enhancing carbon sinks. However, the overdevelopment of oases and excessive extraction of groundwater lead to the opposite effect, reducing carbon sequestration. This study examines two soil types—meadow soil (MS) and swamp soil (SS)—from Qingtu Lake, an arid lake in western China. It analyzes the sources of soil inorganic carbon, the composition and origin of dissolved organic matter (DOM), and the relationships between microbes, soil organic carbon (SOC), soil inorganic carbon (SIC), mineral composition, and soil texture. The results indicate that inorganic carbon in the study area consists of both primary carbonate minerals and secondary pedogenic carbonates. The DOM primarily consists of two components, both identified as terrestrial humic substances. In meadow soils, bacterial activity drives the weathering of plagioclase, which releases Ca2+ necessary for the formation of pedogenic carbonates. Plagioclase also provides colonization sites for microbes and, along with microbial activity, participates in the soil carbon cycle. Within the soil community, bacteria appear to play a more critical role than fungi. In contrast, microbial contributions to the carbon cycle in swamp soils are weaker, with minerals predominantly interacting with organic carbon to form mineral-associated organic matter, thus promoting the soil carbon cycle. These findings have important implications for understanding soil carbon sinks under different micro-ecological conditions in arid and semi-arid regions. Through targeted human intervention, it is possible to enhance carbon sequestration in these areas, contributing to the mitigation of global climate change.

Carbon Budgeting of a Long-term Rice-rice Cropping Sequence in the Typic ustipsamments of Kerala, India

A judicious management practice to improve the soil's organic carbon level and soil fertility is essential for agricultural and environmental sustainability. The present study was undertaken to assess the long-term effect of various management practices on soil carbon dynamics and agricultural sustainability by computation of indices like carbon pool index (CPI), carbon lability index (CLI), carbon management index (CMI), critical carbon input and carbon budgeting. CMI has been used as a more sensitive indicator to evaluate capacity of a management practice to promote soil quality. Sensitivity index was used to determine the degree of changes in each carbon fraction due to management practices. The study was carried out in a permanent manurial trial plot started in 1964 under a long term rice-rice cropping sequence in Kerala. Based on the results obtained, integrated application of NPK fertilizers along with FYM showed significantly higher carbon indices, increased soil carbon fractions, and carbon sequestration compared to other management practices. The study revealed that applying organics coupled with inorganic fertilizers will manage the SOC level and result in enhanced soil fertility, productivity, and agricultural sustainability.

Understanding how corn-yellow melilot intercropping combined with straw return increased stable organic carbon pool in Mollisols by reducing the application of chemical fertilizer

Long-term cultivation with persistent use of chemical fertilizers causes a rapid decline in organic matter content of Mollisols. But practicing intercropping along with straw return instead of the use of chemical fertilizer have the potential to reverse the decline and improve soil organic carbon (SOC) content. A field experiment with five treatments at two sites of Songnen Plain of Northeast China included the following treatments (1) corn monoculture with no chemical fertilizers and no straw return (c), (2) corn monoculture with chemical fertilizers and no straw return (c + F), (3) corn-yellow melilot intercropping and straw return combined with full application of chemical fertilizers (c&m + S + F), (4) corn-yellow melilot intercropping and straw return combined with half dose of chemical fertilizers (c&m + S + F/2), and (5) corn-yellow melilot intercropping and straw return without chemical fertilizers (c&m + S). The results showed that c&m + S + F, c + F, and c&m + S + F/2 decreased specific gravity and c&m + S + F increased water content. The c&m + S + F, c&m + S + F/2, and c&m + S improved SOC with 18.7%, 7.95%, and 8.17% (P < 0.05), respectively. The c&m + S + F and c&m + S + F/2 increased mineral-associated organic carbon, humus organic carbon, and heavy fraction organic carbon content. These findings provide a method for utilizing intercropping and straw return to replace chemical fertilizers to improve SOC and stable organic carbon content to ameliorate soil quality.

The Role of Fertilization on Soil Carbon Sequestration in Bibliometric Analysis

The soil carbon pool is the largest and most dynamic carbon reservoir in terrestrial ecosystems. Fertilization, an important component of agricultural management, is a significant factor influencing soil carbon sequestration. This study analyzed literature from the Web of Science from 2008 to 2024 using CiteSpace. The results revealed a steady increase in publications on this topic, with a significant surge in the recent four years. The analysis highlighted key collaborations among countries, institutions, and authors, and identified main journal sources and seminal works in the research on the role of fertilization in soil carbon sequestrations. Keyword analysis indicated that current research hotspots include ‘soil organic carbon dynamics and organic matter decomposition’, ‘microbial community dynamics and carbon cycling’, and ‘agricultural management practices on carbon sequestration’. In the context of climate change, future research is likely to focus on enhancing sustainable agricultural practices, promoting biochar and resource utilization, and utilizing microbial communities to optimize soil carbon sequestration. This study provides a comprehensive overview of the role of fertilization in soil carbon sequestration, providing important insights for improving soil carbon sequestration strategies.

Data-driven effects of human activities and environmental factors on inland aquatic dissolved organic matter in China: Insights from machine learning

Aquatic DOM, a major carbon pool in inland waters, plays a key role in the global carbon cycle and is influenced by human activities and environmental factors. While watershed surveys have identified some drivers of aquatic DOM changes, national-scale knowledge remains limited. Spectral monitoring data from 721 aquatic DOMs in inland China were collected to predict and quantify the spectral properties of aquatic DOMs and the coupled effects of human activities and environmental factors by complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN), random forest (RF) and structural equation modeling (SEM). Our results show that the dataset is relatively evenly distributed in terms of flow regimes, and the data are adequately representative of various types of water in China. Although the performance of CEEMDAN is affected by the skewed distribution of data sampling points (453 and 449 for eastern regions and eutrophic waters, respectively), CEEMDAN effectively processes the spatial sequences of aquatic DOM spectra, which significantly improves the reliability of the machine learning model (by 13%–68%) and reduces the error (by 63%–92%). CEEMDAN-RF and SEM results indicate that longitude and latitude are the most important environmental factors affecting the spectral properties of aquatic DOM through temperature, light and land cover differences, reducing the biogenic properties of aquatic DOM. Unlike observations in small watersheds and estuaries, environmental factors of season, precipitation and salinity have weak effects on aquatic DOM. Furthermore, the biogenic character of aquatic DOM is enhanced by urban human activities, represented by urbanization, population, and impervious land fraction, which have long-lasting and strong impacts on aquatic DOM by driving water eutrophication and enhancing phytoplankton and microbial activity. Our study informs the prediction and quantification of coupled environmental and anthropogenic impacts on aquatic DOM at large scales.

Multi-Scenario Simulation of Land Use and Assessment of Carbon Stocks in Terrestrial Ecosystems Based on SD-PLUS-InVEST Coupled Modeling in Nanjing City

In the context of achieving the goal of carbon neutrality, exploring the changes in land demand and ecological carbon stocks under future scenarios at the urban level is important for optimizing regional ecosystem services and developing a land-use structure consistent with sustainable development strategies. We propose a framework of a coupled system dynamics (SD) model, patch generation land-use simulation (PLUS) model, and integrated valuation of ecosystem services and trade-offs (InVEST) model to dynamically simulate the spatial and temporal changes of land use and land-cover change (LUCC) and ecosystem carbon stocks under the NDS (natural development scenario), EPS (ecological protection scenario), RES (rapid expansion scenario), and HDS (high-quality development scenario) in Nanjing from 2020 to 2040. From 2005 to 2020, the expansion rate of construction land in Nanjing reached 50.76%, a large amount of ecological land shifted to construction land, and the ecological carbon stock declined dramatically. Compared with 2020, the ecosystem carbon stocks of the EPS and HDS increased by 2.4 × 106 t and 1.5 × 106 t, respectively, with a sizable ecological effect. It has been calculated that forest and cultivated land are the two largest carbon pools in Nanjing, and the conservation of both is decisive for the future carbon stock. It is necessary to focus on enhancing the carbon stock of forest ecosystems while designating differentiated carbon sink enhancement plans based on the characteristics of other land types. Fully realizing the carbon sink potential of each ecological functional area will help Nanjing achieve its carbon neutrality goal. The results of the study not only reveal the challenges of ecological conservation in Nanjing but also provide useful guidance for enhancing the carbon stock of urban terrestrial ecosystems and formulating land-use planning in line with sustainable development strategies.

Enhancing soybean yield stability and soil health through long-term mulching strategies: Insights from a 13-year study

Sustainable agriculture systems incorporate important stabilizing mechanisms, such as mulching, for increasing yield and improving soil health. However, the synergistic effects of different long-term mulching practices on soybean yield stability and soil health remain unexplored. In this study, we conducted a 13-year long-term investigation to evaluate the impacts of various mulching methods—no mulching (CK), straw mulching (SM), plastic mulching (PM), and ridged and plastic mulching (RM)—over a 13-year period on soil nutrients, and soybean yield, stability, and sustainability. Our findings revealed that SM, PM, and RM treatments significantly increased the average yields by 28.02 %, 20.49 %, and 51.56 %, respectively. Moreover, SM and RM treatments significantly enhanced yield stability (SM +107.90 %, RM +98.82 %) and sustainability (SM +47.85 %, RM +37.14 %). Additionally, compared to CK, the SM treatment significantly increased the average soil organic carbon (SOC) and total nitrogen (STN) content by 16.78 % and 16.23 %, respectively. Meanwhile, mulching practices also improved soil reactive carbon and nitrogen pools. Compared to CK, plastic mulch reduced microbial biomass carbon (MBC) content (PM −8.85 %, RM −0.73 %) and soil ammonium nitrogen (AN) content (PM −8.19 %, RM −1.20 %), while increasing microbial biomass nitrogen (MBN) content (PM +8.73 %, RM +9.47 %). The SM treatment increased MBC, AN, and MBN contents by 0.24 %, 7.23 %, and 8.94 %, respectively. Additionally, SM and RM treatments significantly increased β-1,4-glucosidase (BG) activity (SM +98.74 %, RM +128.25 %) and decreased and β-1,4- n -acetamido-glucosidase (NAG) + 1-leucine aminopeptidase (LAP) (NAG + LAP) activity (SM −28.74 %, RM −25.33 %) compared to CK. Furthermore, SM, PM, and RM treatments significantly increased the Chao1 index by 35.30 %, 68.08 %, and 52.23 %, respectively, compared to CK. Finally, results of the Mantel test and random forest model indicated that the increases in yield and stability were due to improved soil temperature (ST), active carbon and nitrogen pools, enzyme activity, and diazotrophic bacterial diversity. In summary, our findings suggest that ridged and plastic mulching enhances soil nutrient effectiveness by maintaining soil moisture and regulating diazotrophic bacterial community structure, thereby increasing soybean yields. Conversely, straw mulching continuously supplies nutrients to the soil, enhancing soil quality and diazotrophic bacterial community structure, thus improving yield stability. Over all, our findings provides new insights into global long-term agricultural sustainability.

Sorption/desorption of phenanthrene and ofloxacin by microbial-derived organic matter-mineral composites

IntroductionSoil organic matter plays an important role in the long-term “locking” of organic contaminants in soil environment. Recently, microbial-derived organic matter have been recognized as essential components of stabilized soil carbon pools. However, the contribution of microbial-derived organic matter to sorption of organic contaminants remains unclear.MethodsHere, we obtained microbial-derived organic matter-mineral composites by inoculating model soil (a mixture of hematite and quartz sand (FQ) or montmorillonite and quartz sand (MQ)) with natural soil microorganisms and different substrate-carbon (glycine (G), glucose (P), or 2, 6-Dimethoxyphenol (B)), which were named GF, PF, BF, GM, BM, and PM, respectively. Batch sorption/desorption experiments were conducted for phenanthrene (PHE) and ofloxacin (OFL) on the composites.Results and DiscussionThe composites cultured with 2,6-dimethoxyphenol had the highest carbon content (0.98% on FQ and 2.11% on MQ) of the three carbon substrates. The carbon content of the composites incubated with MQ (0.64%–2.11%) was higher than that with FQ (0.24%–0.98%), indicating that montmorillonite facilitated the accumulation of microbial-derived organic matter owing to its large specific surface area. The sorption of PHE by microbial-derived organic matter was mainly dominated by hydrophobic partitioning and π-π conjugation, whereas the sorption of OFL was mainly dominated by hydrophobic hydrogen bonding and π-π conjugation. The sorption of OFL onto the composites was more stable than that of PHE. Microbial-derived organic matter -mineral composites can reduce the risk of organic contaminant migration in soil, particularly ionic organic contaminants.

Effects of maize residue and biochar applications on soil δ13C and organic carbon sources in a subtropical paddy rice ecosystem

AbstractThis study investigates the utility of plant δ¹3C natural labeling in predicting the impacts of environmental shifts on carbon cycling within ecosystems, particularly focusing on paddy fields treated with maize (Zea mays L.) residues and biochar. Specifically, it examines how soil δ¹3C and the sources of soil organic carbon (SOC), respond in paddy fields (which cultivate C3 plants like rice) when amended with maize residues, maize biochar, and silica‐enriched biochar (derived from C4 plants). Conducted in the Fuzhou paddy fields, the experiment included control groups and treatment groups with maize residue (4 t ha⁻¹), maize biochar (4 t ha⁻¹), and silicon‐modified maize biochar (4 t ha⁻¹) during both the early and late rice growth periods. The results indicate that all soil treatments increased soil δ¹3C. The application of maize residues notably affected the δ¹3C of the upper soil profile (0–15 cm) differently from the deeper layers (15–30 cm), and it increased soil organic C more than biochar or silicon‐modified maize biochar. Soil available P (AP) and pH emerged as significant factors linking δ¹3C, influencing rice yield through changes in soil physicochemical properties. Unlike maize residues, which reduced rice yields, applications of biochar and silicon‐modified maize biochar increased rice yields. The latter, which was particularly effective in lowering SOC decomposition rates and addressing rice's silica needs, emerged as the preferred option. The study highlights maize biochar and silicon‐modified maize biochar as sustainable alternatives to maize residues for rice cultivation, enhancing soil fertility, carbon pool stability, and yields.

The Degradation of Polyethylene by Trichoderma and Its Impact on Soil Organic Carbon

Polyethylene mulching film, which is widely utilized in arid and semi-arid agriculture, leaves residual pollution. A novel approach to addressing this issue is microbial degradation. To screen the strains that degrade polyethylene efficiently and clarify the effect of degrading strains on the turnover of soil organic carbon, a polyethylene-degrading fungus PF2, identified as Trichoderma asperellum, was isolated from long-time polyethylene-covered soil. Strain PF2 induced surface damage and ether bonds, ketone groups and other active functional groups in polyethylene, with 4.15% weight loss after 30 days, where laccase plays a key role in the degradation of polyethylene. When applied to soil, the Trichoderma-to-soil weight ratios were the following: B1: 1:100; B2: 1:200; B3: 1:300 and B4: 1:400. Trichoderma asperellum significantly increased the cumulative CO2 mineralization and soil organic carbon mineralization in the B1 and B2 treatments compared with the control (B0). The treatments B1, B3 and B4 increased the stable organic carbon content in soil. An increase in the soil organic carbon content was observed with the application of Trichoderma asperellum, ranging from 27.87% to 58.38%. A positive correlation between CO2 emissions and soil organic carbon was observed, with the soil carbon pool management index (CPMI) being most correlated with active organic carbon. Trichoderma treatments improved the CPMI, with B3 showing the most favorable carbon retention value. Thus, Trichoderma asperellum not only degrades polyethylene but also contributes to carbon sequestration and soil fertility when applied appropriately.

Independent effects of tree diversity on aboveground and soil carbon pools after six years of experimental afforestation.

Planting diverse forests has been proposed as a means to increase long-term carbon (C) sequestration while providing many co-benefits. Positive tree diversity-productivity relationships are well established, suggesting more diverse forests will lead to greater aboveground C sequestration. However, the effects of tree diversity on belowground C storage have the potential to either complement or offset aboveground gains, especially during early stages of afforestation when potential exists for large losses in soil C due to soil decomposition. Thus, experimental tests of the effects of planted tree biodiversity on changes in whole-ecosystem C balance are needed. Here, we present changes in above- and belowground C pools 6 years after the initiation of the Forests and Biodiversity experiment (FAB1), consisting of high-density plots of one, two, five, or 12 tree species planted in a common garden. The trees included a diverse range of native species, including both needle-leaf conifer and broadleaf angiosperm species, and both ectomycorrhizal and arbuscular mycorrhizal species. We quantified the effects of species richness, phylogenetic diversity, and functional diversity on aboveground woody C, as well as on mineral soil C accumulation, fine root C, and soil aggregation. Surprisingly, changes in aboveground woody C pools were uncorrelated to changes in mineral soil C pools, suggesting that variation in soil C accumulation was not driven by the quantity of plant litter inputs. Aboveground woody C accumulation was strongly driven by species and functional identity; however, plots with higher species richness and functional diversity accumulated more C in aboveground wood than expected based on monocultures. We also found weak but significant effects of tree species richness, identity, and mycorrhizal type on soil C accumulation. To assess the role of the microbial community in mediating these effects, we further compared changes in soil C pools to phospholipid fatty acid (PLFA) profiles. Soil C pools and accumulation were more strongly correlated with specific microbial clades than with total microbial biomass or plant diversity. Our results highlight rapidly emerging and microbially mediated effects of tree biodiversity on soil C storage in the early years of afforestation that are independent of gains in aboveground woody biomass.

The conversion of biomass to biochar decreases soil organic and inorganic carbon-derived CO2 emissions under different water conditions in karst regions

Due to the unique geological background and climatic condition, karst soils in southwest China are mainly developed on carbonate rocks and accompanied by frequent dry-wet alternations. Therefore, the effects of biomass (BS) and biochar (BC) on the soil carbon pools (especially inorganic carbon) in karst regions are different from those in non-karst regions. In order to understand the responses of soil organic carbon (SOC) and soil inorganic carbon (SIC)-derived CO2 emissions to BS and BC amendments under different water conditions in karst regions, a microscopic study under dry-wet alternate (DW) and constant moisture (CM) conditions was established to investigate the stability of BC, BS, and their effects on SOC and SIC pools by isotope double-labeling methods. Results showed that the contribution rates of SOC and SIC to soil CO2 emissions were 51.55 %–99.52 %, 0.48 %–48.45 % and 60.55 %–97.72 %, 2.28 %–39.45 % under DW and CM conditions, respectively. Compared with the control, BS application under different water conditions increased SOC and SIC-derived CO2 emissions by 929.78˗1443.39 % and 169.69˗335.71 %, respectively. However, BC amendment significantly decreased SOC and SIC-derived CO2 emissions, especially in the DW condition. The mean residence time (the inverse of the decomposition rate) of BC in karst soils under different conditions ranged from 657 to 3105 years, which was much higher than those of BS (7˗18 years). Therefore, the conversion of BS to BC in karst regions enhances carbon sequestration due to its stability of recalcitrant carbon, the decrease of SOC and SIC- derived CO2 emissions. This study is helpful to understand the quantification of CO2 sources from calcareous soils and elucidate the environmental behaviors and carbon sequestration potentials of BC or BS amendments in karst regions.

Potential Effect of Mangrove Ecosystem on Soil Carbon Sequestration and its Physico-Chemical Properties

The mangrove ecosystem is a natural wetland located in the Red Sea that extends 500 km on the Egyptian western coast. It has great potential to sequestrate soil organic carbon, reduce atmospheric CO2, and enhance soil hydro-physical properties. In this context, this research aims to characterise soil changes induced by mangrove growing. Both modelling and measurements herein were performed on five sampling areas at the Western Strand of the Red Sea (plus one control site - beach without plants). The locations (sites 1 and 2) of mangrove forest were in El-Gouna village with ages of 10 and 5 years, respectively, while (sites 3, 4, and 5) represent mangroves at Hurghada, Abu-Monquar Island, and Safaga, respectively. The mean values of measured soil organic carbon pool (SOCP) at the soil surface (0-90cm) revealed that the lowest values of the SOCP were at Hurghada with 8.81± 0.12 Mgha-1 and the highest values at Abu Monquar island with 59.75 ± 0.15 Mgha-1. At El Gouna 1, 2 and Safaga, the SOCP values were 14.48, 12.86, and 39.98 Mgha-1, respectively. In addition, the SOCP at the control site (beach without plants) was 6.62± 0.25 Mgha-1. Thus, the mangrove ecosystem has a great potential to sequestrate the soil's organic carbon and reduce atmospheric CO2. Soil bulk density (SBD) values varied at El-Gouna1, 2, and Hurghada from 1.63 to 1.75 g/cm³, while the lowest SBD values were observed at Abu-Monquar Island and Safaga with 1.31± 0.02, g/cm³ and 1.53 ± 0.05 g/cm³, respectively. SBD at the control site was 1.75± 0.05 g/cm³, which reflects the higher values. Morphological characteristics reveal that tree height results varied from 110-130 cm, 50-70 cm, 150-200 cm, 200-300 cm, and 200-270 cm for ElGouna1, ElGouna2, Hurghada, Abu-Manqar, and Safaga, respectively. Higher values of tree height, size index, and density are convenient, as are the lower values of SBD at Abu-Monquar and Safaga compared to other site locations. The soil-water HYDRUS-1D model revealed that the soil water storage capacity at Abu-Monquar was higher than the other samples. Thus, the joint use of modelling and measurements enabled deeper insight and a suitable characterisation of soil physicochemical changes induced by mangrove growth.

Variability in soil organic carbon pools in different land use systems in the north-eastern region of India

The current study was carried out during 2020 to 2022, at Horticulture Research Centre (HRC), Nagicherra, Agartala, Tripura to assess and compare the effects of various land use systems, including bamboo, tea, mango, lemon, rice-rice, wheat-millet, okra-onion and uncultivated soils, on soil organic carbon (SOC) dynamics. SOC is a critical component of terrestrial ecosystems, influencing soil health, fertility and carbon sequestration potential. The NEH region of India, Tripura characterized by its diverse agro-ecological zones and land use systems (LUS), presents a unique opportunity to investigate the various land use regimes' effects on SOC pools. Walkley and Black carbon (WBC) significantly vary among the selected LUS, ranging from 7.14–12.48 g/kg, with the maximum values in tea LUS. In 0–30 cm depth, very labile C (CVL) pools are very variable among the selected LUS (2.04–5.35 g/kg), which is the highest in tea and mango compared to the uncultivated system. The C pools in selected LUS indicated the deviation depth and land use pattern. Lability index (LI) varies from 1.50–1.63 and 1.40–1.74 in 0–30 cm and 30–60 cm depth, respectively. Carbon pool index (CPI) assessed highest in tea LUS, 1.78 and 2.1 from 0–30 and 30–60 cm, respectively. Carbon management index (CMI) was higher in selected LUS compared to uncultivated system.

Cadmium immobilization by mercapto-palygorskite in alkaline soil: Impacts on soil microbial communities and wheat rhizosphere metabolism

Weakly alkaline cadmium (Cd) contaminated soil in China has aroused great concern regarding its impact on food security and human health. Mercapto-modified palygorskite (MP) has exhibited good potential to minimize Cd accumulation in wheat, it is imperative to understand the underlying mechanisms within the soil-wheat-microbial system for sustainable development of agrochemicals. This study evaluated the effects of various MP dosages on soil Cd bioavailability, rhizosphere metabolomics, microbial community structure and wheat growth. The results indicated that MP (0.05–0.2 %) application significantly reduced Cd accumulation in wheat grains by 59.0–83.2 % (p < 0.05) and inhibited Cd translocation from root to grain. MP also promoted Mn oxide formation and redistributed the exchangeable Cd to Fe–Mn oxide-bound forms (44.2–109.6 %), thus lowering soil Cd bioavailability by 17.9–32.5 %. Additionally, MP reduced wheat rhizosphere organic acid levels, altered rhizosphere carbon and nitrogen pools, and stimulated the growth of Cd-tolerant Alternaria and Cladosporium, while inhibiting the growth of Fusarium. These findings highlight the potential of MP to modulate soil rhizosphere metabolism and microbial communities, offering a novel perspective on its environmental implications and supporting agrochemical sustainability.

Effect of 9-year water and nitrogen additions on microbial necromass carbon content at different soil depths and its main influencing factors

Microbial necromass carbon (MNC) is a major source of soil organic carbon (SOC) pool, significantly influencing soil carbon sequestration. The effects of long-term water and nitrogen addition on MNC in soils at different depths, as well as their interactions, remain poorly understood. In this study, we examined the influence of water addition (+51.67 mm), nitrogen addition (25, 50, 100 kg N ha−1 yr−1), and their interactions on MNC accumulation at different soil depths in temperate grasslands. The addition of water and nitrogen over nine years has been observed to exhibit a decreasing trend in the MNC at different soil depths. Notably, MNC in the topsoil layer (0–10 cm) decreased significantly by 18.56 % under low nitrogen addition treatment, while MNC in the subsoil layer (40–60 cm) declined significantly by 27.19 % under high nitrogen addition treatment. Fungal microbial necromass carbon (FNC) contributed 3.25 times more to SOC than bacterial microbial necromass carbon (BNC). In the 0–10 cm soil layer, MNC is primarily governed by both microbial attributes and the physicochemical properties of the soil, in the 20–40 cm soil layer, the physicochemical properties of the soil predominantly control MNC, in the 40–60 cm layer, microbial characteristics exert a more significant influence on MNC. Collectively, our observations suggest that soil MNC decreased with the addition of water and nitrogen in the 0–60 cm soil slope, which could enable the accurate prediction of global change impacts on the accumulation of soil carbon, thus facilitating the implementation of strategies to augment soil carbon sequestration.

Soil Organic Carbon Research and Hotspot Analysis Based on Web of Science: A Bibliometric Analysis in CiteSpace

Soil carbon sequestration is an important process of the terrestrial carbon cycle, and even slight changes in soil carbon will trigger drastic variations in the global carbon pool. In this study, we used the CiteSpace software to analyze the development of research on soil organic carbon (SOC) and its current status from various perspectives, with the goal of revealing research hotspots and trends of SOC. A total of 3909 studies published between 2014 and 2023 were included in the analysis. Results show that China and the USA lead with a significant number of publications on SOC, which underscores their considerable interest in the subject. France and the USA exhibit a very high international influence in this field, with their intermediary centrality reaching up to 0.3 and 0.21, respectively. Among institutions, the Chinese Academy of Sciences is the largest contributor in terms of the number of publications, with a high centrality of 0.09, indicating this institution has built close collaboration and significant influence in this field. Kuzyakov Yakov achieved the highest publication record, with Lal Rattan sharing the second position. The hotspots in SOC can be summarized into the following aspects: conservation tillage, carbon sequestration, microbial biomass, and driving forces. The research focus has gradually shifted from macroscopic trends to explanations based on micro-level biological dynamics. Driving forces such as soil type, land use, and environmental conditions have a significant impact on the quantity, turnover, and spatiotemporal distribution of SOC. We highlighted that more attention should be paid to the mechanism of SOC transformation and stabilization, which is essential for developing more precise models of carbon cycling in the soil and for formulating effective strategies to maintain sustainable agriculture and mitigate climate change.

Spatiotemporal Evolution and Simulation Prediction of Ecosystem Carbon Storage in the Yellow River Basin Before and After the Grain for Green Project

Under the background of "dual carbon", the impact of the implementation of the Grain for Green project on the carbon storage of the ecosystem in the Yellow River Basin must be explored, which can serve as an important reference for improving the policy implementation of the new round of the Grain for Green project and improving the carbon sink capacity of the ecosystem in the Yellow River Basin. In this study, 1990, before the implementation of the project, was selected as the starting year of the research period, and 2020, after the implementation of the two rounds of the project, was selected as the end year of the research period. Based on the ecosystem type data from 1990 to 2020, the InVEST model was used to calculate the soil carbon pool, underground carbon pool, below carbon pool, dead organic matter carbon pool, and total carbon storage of ecosystems in the Yellow River Basin and the area where the project was implemented from 1990 to 2020. The results showed that： ① From 1990 to 2020, the area of forest ecosystem in the Yellow River Basin expanded by 26 610.06 km2, and the area of farmland decreased by 46 849.06 km2 after the implementation of two rounds of the project. Spatially, the upper reaches of the Yellow River were dominated by grassland and other ecosystems； the middle reaches of the Yellow River were dominated by farmland, forest, and grassland ecosystems； and the lower reaches of the Yellow River were dominated by farmland ecosystems. ② From 1990 to 2020, the carbon storage in the project implementation area showed a fluctuating and increasing trend, and the total carbon storage reached a peak （219.47×108 t） in 2009 and decreased to 218.59×108 t in 2020 due to the decrease of grassland ecosystem from 2010 to 2020. Spatially, the high-value areas of carbon storage were distributed in Aba Tibetan and Qiang Autonomous Prefecture of Sichuan Province and the southern tip of Gansu Province in the upper reaches of the forest and grass accumulation and in the whole of Shanxi Province and the central and southern parts of Shaanxi Province in the middle reaches. Shangluo City in Shaanxi Province and Alxa League in Inner Mongolia Autonomous Region were prefecture-level cities with the highest and lowest average carbon density. ③ In 2035, the carbon storage loss of the natural development scenario was predicted to be 0.83×108 t, and the other three scenarios would increase this loss. Under the moderate farmland return scenario, the Yellow River Basin ecosystem had the strongest carbon sequestration capacity, and the predicted carbon storage would increase by 2.72×108 t compared with that in 2020, and the deep farmland return scenario was the comprehensive optimal scenario. Therefore, in the future, the Yellow River Basin could refer to the deep farmland return scenario to optimize and adjust the implementation plan of the Grain for Green project, and the predicted value of carbon storage can provide some data support for achieving the dual carbon goal.

The Responses of Soil Extracellular Enzyme Activities and Microbial Nutrients to the Interaction between Nitrogen and Phosphorus Additions and Apoplastic Litter in Broad-Leaved Korean Pine Forests in Northeast China

The impact of nitrogen and phosphorus deposition alternations, as well as apoplastic litter quality and quantity, on soil nutrient cycling and soil carbon pool processes in forest ecosystems is of considerable importance. Soil ecological enzyme chemistry is a powerful tool for elucidating the nutrient limitations of microbial growth and metabolic processes. In order to explore the responding mechanisms of soil ecological enzyme chemistry to the simultaneous changes in apoplast input and nitrogen and phosphorus deposition in temperate coniferous and broad-leaved mixed forests, an outdoor simulating experiment was conducted. The results demonstrate that the treatments involving apoplastic material and nitrogen and phosphorus additions had significantly impacted soil nutrient levels across different forest types. Apoplastic treatments and N-P additions had a significant effect on the soil total organic carbon (TOC), dissolved organic carbon (DOC), soil total soluble nitrogen (TSN), soil available phosphorus (SAP), soil total nitrogen (TN), soil total phosphorus (TP), and microbial biomass carbon (MBC). However, the effects on soil microbial biomass (MBN) and microbial biomass phosphorus (MBP) were insignificant. The apomictic treatments with N and P addition did not result in a statistically significant change in soil C-hydrolase activities (β-1,4-glucosidase BG, β-1,4-xylosidase BX, cellobiohydrolase CBH, phenol oxidase POX, and peroxidase PER), N-hydrolase activities (β-1,4-N-acetylglucosaminidase NAG and L-leucine aminopeptidase LAP), or P-hydrolase activities (Acid phosphatase AP). Although the apomictic treatments did not yield a significant overall impact on carbon hydrolase activity, they influenced the activity of specific enzymes, such as CBH, LAP, and PER, to varying degrees. The effects on BG, BX, CBH, AP, and C-hydrolase activities were significant for different stand types. The impact of apomictic treatments and N-P additions on soil nitrogen hydrolase activities was inconsequential with a minimal interactive effect. The highest correlation between PER, LAP, and N-hydrolase activities was observed in conjunction with elevated levels of nitrogen and phosphorus addition (N3L0, original litter treatment, and high amounts of N and P addition). These findings may provide a theoretical foundation for the management of ecosystem function in broad-leaved Korean pine forests.