Global changes in soil organic carbon and implications for land degradation neutrality and climate stability

Tele-connection of embodied carbon emissions from industries in China's trade: A complex network analysis

Regions can meet their development demands through trade, with the attendant environmental costs being shifted to other regions, and carbon emissions emitted from different industries could be transferred over long distances through the increasingly diversified trade network. However, it remains unclear how regional trade leads to the tele-connection and transfer of embodied carbon emissions form industries, and what is the structure and characteristics of the transfer. Thus, multiregional input‒output models and complex network analysis are employed to reveal the tele-connection of carbon emissions from industries in China. The results show that embodied carbon emissions from trade increased by 869.47 million tons during in five years, with North China being the largest outflow area, while the coastal regions being the inflow areas. Moreover, the secondary industry is the highest source of embodied carbon emissions, accounting for 96.68 % of the volume, and the transfer of carbon emissions mainly occurs in North and East China. In carbon emissions networks, North China holds a controlling position, as analysed by degree and strength. The first 23.3%-30% of nodes carry about 62.6%-72.4% of the entire carbon emissions flow, and the network conforms to scale-free features. Centrality further reveals that northern and coastal areas occupy core positions, with interregional carbon flows dominating the critical pathways in the network. The number of clusters evolved from three to four communities during 2012-2017 in the network, demonstrating that the carbon flow network is developing towards multipolarity and modularity. This study underscores the urgency of mitigating carbon emissions in industrial trade by identifying key nodes and cluster structures in emission networks.

A unifying modelling of multiple land degradation pathways in Europe

Land degradation is a complex socio-environmental threat, which generally occurs as multiple concurrent pathways that remain largely unexplored in Europe. Here we present an unprecedented analysis of land multi-degradation in 40 continental countries, using twelve dataset-based processes that were modelled as land degradation convergence and combination pathways in Europe's agricultural (and arable) environments. Using a Land Multi-degradation Index, we find that up to 27%, 35% and 22% of continental agricultural (~2 million km2) and arable (~1.1 million km2) lands are currently threatened by one, two, and three drivers of degradation, while 10-11% of pan-European agricultural/arable landscapes are cumulatively affected by four and at least five concurrent processes. We also explore the complex pattern of spatially interacting processes, emphasizing the major combinations of land degradation pathways across continental and national boundaries. Our results will enable policymakers to develop knowledge-based strategies for land degradation mitigation and other critical European sustainable development goals.

High levels of soil calcium and clay facilitate the recovery and stability of organic carbon: Insights from different land uses in the karst of China

Soil organic carbon (SOC) is a crucial medium of the global carbon cycle and is profoundly affected by multiple factors, such as climate and management practices. However, interactions between different SOC fractions and land-use change have remained largely unexplored in karst ecosystems with widespread rock outcrops. Owing to the inherent heterogeneity and divergent response of SOC to land-use change, soil samples with close depth were collected from four typical land-use types (cropland, grassland, shrubland, and forestland) in the karst rocky desertification area of China. The aim of this study was to explore the responses of SOC dynamics to land-use types and underlying mechanism. The results showed that land-use type significantly affected SOC contents and its fractions. Compared with cropland, the other three land uses increased the total organic carbon (TOC), microbial biomass carbon (MBC), and non-labile organic carbon (NLOC) contents by 6.11-129.44%, 32.58-173.73%, and 90.98-347.00%, respectively; this demonstrated that a decrease in both labile and recalcitrant carbon resulted in SOC depletion under agricultural land use. Readily oxidized organic carbon (ROC) ranged from 42 to 69%, accounting for almost half of the TOC in the 0-40-cm soil layer. Cropland soil showed significantly higher ROC:TOC ratios than other land-use types. These results indicated that long-term vegetation restoration decreased SOC activity and improved SOC stability. Greater levels of soil exchangeable calcium (ECa) and clay contents were likely responsible for higher stabilization and then accumulation of SOC after vegetation restoration. The carbon pool index (CPI) rather than the carbon pool management index (CPMI) exhibited consistent variation trend with soil TOC contents among land-use types. Thus, further study is needed to validate the CPMI in evaluating land use effects on soil quality in karst ecosystems. Our findings suggest that land-use patterns characterized by grass or forest could be an effective approach for SOC-sequestration potential and ensure the sustainable use of soil resources in the karst area.

Response of soil CO2 emissions and water-carbon use efficiency of winter wheat to different straw returning methods and irrigation scenarios

BACKGROUND

The shortage of water resources and the increase of greenhouse gas emissions from soil seriously restrict the sustainable development of agriculture. Under the premise of ensuring a stable yield of winter wheat through a reasonable irrigation scenario, identifying a suitable straw returning method will have a positive effect on agricultural carbon sequestration and emission reduction in North China Plain.

RESULTS

Straw burying (SR) and straw mulching (SM) were adopted based on traditional tillage under in the winter wheat growing season of 2020-2021 and 2021-2022. Three irrigation scenarios were used for each straw returning method: no irrigation (I0), irrigation 60 mm at jointing stage (I1), and irrigation of 60 mm each at the jointing and heading stages (I2). Soil moisture, soil respiration rate, cumulative soil CO2 emissions, yield, water use efficiency (WUE) and soil CO2 emission efficiency (CEE) were mainly studied. The results showed that, compared to SM, SR improved the utilization of soil water and enhanced soil carbon sequestration. SR reduced soil respiration rate and cumulative soil CO2 emissions in two winter wheat growing seasons, and increased yield by increasing spike numbers. In addition, with an increase in the amount of irrigation, soil CO2 emissions and yield increased. Under SR-I1 treatment, WUE and CEE were the highest. SR-I1 increases crop yields at the same time as reducing soil CO2 emissions.

CONCLUSION

The combination of SR and irrigation 60 mm at jointing stage is a suitable straw returning irrigation scenario, which can improve water use and reduce soil CO2 emission in NCP. © 2023 Society of Chemical Industry.

Seaweed and a biocontrol agent and their effects on the growth and production of Brassica juncea: a sustainable approach

Chemical fertilizers are crucial for increasing agricultural growth and productivity, but inorganic fertilizers can negatively impact agricultural systems. To address this issue, sustainable techniques like organic farming are being developed, which improve soil quality and nutritional status while preserving human safety. In the Botanical Garden, of Department of Botany at the University of Delhi, India, experiments on Brassica juncea were carried out over a three-year period in six micro plots, each measuring 10 square meters. Vermicompost (V), Sargassum johnstoni (S), NPK (N), Trichoderma viride (T), and Sargassum + Trichoderma viride were five distinct organic combinations that were used to replenish the garden soil (ST). The aim of the study was to assess the effects of organic fertilizers and compare the results with commercially available chemical fertilizers (NPK) on Brassica growth and yield. The study found that soil modified with seaweed fertilizers significantly improved the morphological, reproductive, and biochemical properties of plants. Sargassum + Trichoderma soil amendment led to early flowering and fruiting, better-quality produce, and a low incidence of fungal infection and aphid infestation. This study reveals a new cost-effective method for crop development and production sustainability, benefiting both farmers and environmentalists.

Land degradation neutrality (LDN) in Rajasthan, Western India: a combined approach of pressure-state-response model and MODIS data products

Land degradation has become a key concern worldwide due to changes in meteorological variables and human-caused activities. This study primarily focuses on the rate, impact, and pattern of land degradation in western India. In this instance, we evaluated the effectiveness of land degradation neutrality (LDN) between 2000 and 2020 using an integrative approach based on a PSR (pressure-state-response) model developed by the OECD-UNEP under the UNCCD framework. Here, we mainly used MODIS products (e.g., NDVI, PET, LULC, and NPP). Also, soil organic carbon (SOC) and climatic variables (e.g. precipitation, aridity index and soil moisture) were taken into account. These indicators were analysed using the Google Earth Engine (GEE) code editor platform, and post-processing was done through Q-GIS software. The analysed parameters indicate that the NDVI and NPP values are + 0.20 to + 0.3 and 4.27 × 109 to 7.74 × 109 kg Cm-2, respectively. However, overall precipitation and soil moisture depicted a positive trend, and the aridity index adeptly followed a negative trend. Hence, the land degradation rate has increased in the north-western region besides the Aravalli range and neutrality work in the southwest part of the study area. The overall land degradation trend is negative over the last two decades. Therefore, this study anticipates the policymakers and government bodies to understand about land degradation of western India.

Molecular composition and possible transformations of labile soil organic matter fractions in Mediterranean arable soils: Relevance and implications

With the increased global interest in sequestering carbon in soil, it is necessary to understand the composition of different pools of soil organic matter (SOM) that cycle over suitably short timeframes. To explore in detail the chemical composition of agroecologically relevant yet distinct fractions of SOM, the light fraction of SOM (LFOM), the 53-μm particulate organic matter (POM), and the mobile humic acid (MHA) fractions were sequentially extracted from agricultural soils and characterized using both ¹³C cross polarization magic angle spinning nuclear magnetic resonance (CPMAS NMR) spectroscopy and also Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). The NMR results showed a decrease in the O-alkyl C region assigned to carbohydrates (51-110 ppm) and an increase in the aromatic region (111-161 ppm) proceeding from the LFOM to the POM and then to the MHA fraction. Similarly, based on the thousands of molecular formulae assigned to the peaks detected by FT-ICR-MS, condensed hydrocarbons were dominant only in the MHA, while aliphatic formulae were abundant in the POM and LFOM fractions. The molecular formulae of the LFOM and POM were mainly grouped in the high H/C lipid-like and aliphatic space, whereas a portion of the MHA compounds showed an extremely high (17-33, average of 25) double bond equivalent (DBE) values, corresponding to low H/C values of 0.3-0.6, representative of condensed hydrocarbons. The labile components appeared most pronounced in the POM (93% of formulae have H/C ≥ 1.5) similar to the LFOM (89% of formulae have H/C ≥ 1.5) but in contrast to the MHA (74% of formulae have H/C ≥ 1.5). The presence of both labile and recalcitrant components in the MHA fraction suggests that the stability and persistence of soil organic matter is influenced by a complex interaction of physical, chemical, and biological factors in soil. Understanding the composition and distribution of different SOM fractions can provide valuable insights into the processes that govern carbon cycling in soils, which can help inform strategies for sustainable land management and climate change mitigation.

Effect of different vegetation restoration on soil organic carbon dynamics and fractions in the Rainy Zone of Western China

Vegetation restoration on purple soil (Eutric Leptic Regosols) slopes aiming at reducing soil erosion in the Rainy Zone of Western China has significantly altered soil organic carbon (SOC) storage and distribution. A better understanding of the effects of different vegetation restoration types on SOC dynamics and fractions is critical in devising better policy to protect or enhance SOC stocks to improve soil quality and ecosystem function. In the present study, total, labile, and non-labile organic carbon (TOC, LC, and NLC), and carbon management index (CMI) of Cryptomeria fortunei (CF), mixed C. fortunei and Betula luminifera (MF), Neosinocalamus affinis (NA), and Camellia sinensis (CS) were compared with those of Zea mays field (ZM) on purple soil slopes in the Rainy Zone of Western China in order to develop more effective ways to implement vegetation restoration in the future. Different vegetation restoration types (CF, MF, NA and CS) increased TOC stock by 47.79%-118.31% and NLC stock by 56.61%-129.52% in the 0-50 cm soil layer compared with that of ZM. The direction and magnitude of changes in LC stock and CMI, however, depended strongly on the vegetation restoration type. Compared with ZM, CF had the largest increase of LC stock and CMI, whereas NA had the largest decrease of LC stock and CMI in the 0-50 cm soil layer. The LC:TOC ratio in four reforested species all declined significantly compared with that of ZM (p < 0.01), indicating decreased SOC activity after afforestation. The vegetation type and soil depth together explained more than 90% of the changes of TOC and its fractions in the plantations on purple soil slopes. Our study demonstrates that transforming the ZM into the CS is optimal to achieve the sustainable development goal, whereas transforming the ZM into the NA reduces the SOC activity and availability.

Spatio-Temporal Variation and Its Driving Forces of Soil Organic Carbon along an Urban-Rural Gradient: A Case Study of Beijing

Rapid urbanization has reshaped land cover and the ecological environment, potentially improving or deteriorating soil organic carbon (SOC). However, the response of SOC to urbanization has not yet been fully exploited. Herein, by using the land-use transfer matrix, the Sen & Mann-Kendall tests, the Hurst index, and a geographical and temporal weighted regression (GTWR) model, as well as an urban-rural gradient perspective, we assessed the dynamic response of SOC to Beijing's urbanization from 2001 to2015 and identified the main drivers. The results found that SOC stock decreased by 7651.50 t C during the study period. SOC density varied significantly along an urban-rural gradient, with high value areas mainly being located in remote mountainous rural areas and low value areas mainly being located in urban areas on the plains. There was an uneven variation in SOC density across the urban-rural gradient, with suburban areas (25-40 km away from urban cores) losing the most SOC density while urban areas and rural areas remained relatively unchanged. GTWR model revealed the spatio-temporal non-flat stability of various driving forces. Precipitation, the proportion of forest, the proportion of grassland, the population, distance to the urban center, the slope, and the silt content are the main factors related to SOC stock change. As a result, we suggest policy makers reconceptualize the uneven variation in the SOC between urban and rural areas, emphasize suburban areas as a target for controlling SOC loss, and take into consideration the spatial and temporal heterogeneity of the factors influencing SOC stock when evaluating policies.

Green Synthesis of Nanoparticles by Mushrooms: A Crucial Dimension for Sustainable Soil Management

Soil is the main component in the agroecosystem besides water, microbial communities, and cultivated plants. Several problems face soil, including soil pollution, erosion, salinization, and degradation on a global level. Many approaches have been applied to overcome these issues, such as phyto-, bio-, and nanoremediation through different soil management tools. Mushrooms can play a vital role in the soil through bio-nanoremediation, especially under the biological synthesis of nanoparticles, which could be used in the bioremediation process. This review focuses on the green synthesis of nanoparticles using mushrooms and the potential of bio-nanoremediation for polluted soils. The distinguished roles of mushrooms of soil improvement are considered a crucial dimension for sustainable soil management, which may include controlling soil erosion, improving soil aggregates, increasing soil organic matter content, enhancing the bioavailability of soil nutrients, and resorting to damaged and/or polluted soils. The field of bio-nanoremediation using mushrooms still requires further investigation, particularly regarding the sustainable management of soils.