Changes In Carbon Content Research Articles

Influence of soil moisture availability on dissolved organic matter properties and microbial carbon content in Poa pratensis L. rhizosphere

The goal of the work was to assess changes in microbial carbon content and the properties of dissolved organic matter (DOM) of the Poa pratensis L. rhizopshere in response to the effects of soil drying and waterlogging. The vegetation experiment without plants and with dense sowing in vegetative vessels on Haplic Chernozem surfacewas used in the work. The properties of dissolved organic matter were evaluated based on the study of water-extractable organic matter (WEOM), in which the optical properties were assessed by UV-Vis spectrophotometry and spectrofluorimetry. Soil microbial carbon content was assessed by fumigation method. It has been shown that microbial carbon content in the bulk Chernozem does not depend on soil moisture, while in the rhizosphere it increases with drying and decreases with optimal and excess moisture. Soil moisture greatly affects WEOM properties of the bulk Chernozem, whereas the rhizosphere properties are influenced by the activity of the plant. Despite the lower microbial biomass compared to the bulk soil, the microbiome of P. pratensis L. rhizosphere is capable of more intense transformation of soil organic matter. The dynamic properties of P. pratensis L. rhizosphere ensure its more active and sustainable functioning compared to bulk soil.

Combined effects of carbon content and heat treatment on the high-temperature tensile performance of modified IN738 alloy processed by laser powder bed fusion

Laser powder bed fusion (LPBF) is an advanced manufacturing technology used in processing nickel-based superalloys, notably for aero-engine components. One such material, the LPBF-fabricated IN738 superalloy, is prone to significant cracking issues. This study found that a change in carbon content (the optimal content of which was also determined) effectively mitigated the cracking. This study has systematically investigated the impact of different heat treatments on microstructural alterations and high-temperature tensile properties. The addition of 0.55 wt.% of graphite proved effective in entirely inhibiting cracking in LPBF-fabricated IN738 specimens. Pre-alloyed IN738-M powder with the optimal carbon content was then produced and processed via LPBF to assess its formability. The as-built specimen revealed the presence of continuous carbides along the subgrain boundaries. Heat treatment promoted the transformation of substructured grains into recrystallised grains, accompanied by the precipitations of carbides and the γ' phase; their morphologies were strongly determined by the solution treatment temperature. Differential scanning calorimetry measurements were employed to elucidate the differing microstructural states following distinct heat-treatment regimens. Under a 900°C testing condition, stress-relieved (SR) specimens were found to exhibit superior performance, demonstrating an ultimate tensile stress (UTS) value of 843.6 MPa, a yield strength (YS) of 807.3 MPa and an elongation of 8.54%. Notably, SR specimens also exhibited the highest UTS and YS values at 1000°C, measuring 380.0 MPa and 346.5 MPa, respectively. This study’s findings will furnish valuable insights for researchers who aim to enhance the high-temperature tensile performance of LPBF-fabricated nickel-based superalloys.

Characteristics and Drivers of Soil Carbon, Nitrogen, and Phosphorus Ecological Stoichiometry at the Heavy Degradation Stage of the Alpine Meadow

An in-depth understanding of the soil nutrient status and balance relationship can help the effective recovery and management of alpine degraded meadows. In order to study the balance relationship among soil carbon, nitrogen, and phosphorus nutrients during the heavy degradation stage of meadows, field sampling and investigation, indoor analysis, and mathematical statistics were used to explore the characteristics and driving factors of changes in soil carbon, nitrogen, and phosphorus content, storage, and ecological stoichiometry during the heavy degradation stage of alpine meadows in the Sanjiangyuan region. The results showed that in the heavy degradation stage, miscellaneous grass plants occupied absolute dominance, soil C∶N∶P was approximately 32.83∶3.87∶0.67, and there was certain nitrogen limitation. The coefficients of variation of soil carbon, nitrogen, and phosphorus content were in the following order： organic carbon （1.09） > total nitrogen （0.63） > total phosphorus （0.29）. The organic carbon content and the carbon and nitrogen ratio showed a significant linear decreasing trend with the increase in the grassland degradation index （GDI）, while the total phosphorus content and organic carbon storage showed a significant non-linear change, in which the total phosphorus content showed a significant gentle U-shaped distribution, and the organic carbon storage decreased more gently at the beginning of the heavy degradation stage and then decreased sharply when the GDI was 57.9. The results of Mantel correlation analysis showed that the soil carbon to nitrogen ratio, carbon to phosphorus ratio, and nitrogen to phosphorus ratio showed significant correlation with organic carbon content and storage and total nitrogen storage. The results of structural equation modeling indicated that soil water content had direct effects as well as indirect through vegetation factors, soil carbon, nitrogen, and phosphorus ecological stoichiometry ratios, and soil water content and vegetation factors （height, cover, and biomass） were key environmental factors affecting soil ecological stoichiometry. The research results can provide scientific basis and practical guidance for the restoration of heavily degraded grassland in alpine meadows.

Polyunsaturated triacylglycerol accumulation mainly attributes to turnover of de novo-synthesized membrane lipids in stress-induced starchless Chlamydomonas.

Assembly of PUFA-attached TAGs is intimately correlated to turnover of newly formed membrane lipids in starch-deficient Chlamydomonas exposed to high light and nitrogen stress under air-aerated mixotrophic conditions. Triacylglycerols (TAGs) rich in polyunsaturated fatty acids (PUFAs) in microalgae have attracted extensive attention due to its promising application in nutraceuticals and other high-value compounds. Previous studies revealed that PUFAs accumulated in TAG primarily derived from the dominant membrane lipids, monogalactosyldiacylglycerolipid, digalactosyldiacylglycerol and diacylglycerol-N,N,N-trimethylhomoserine (DGTS), in the model alga Chlamydomonas reinhardtii. However, their respective contribution to PUFA-attached TAG integration has not been clearly deciphered, particularly in starchless Chlamydomonas that hyper-accumulates TAG. In this study, the starchless C. reinhardtii BAFJ5 was mixotrophically cultivated in photobioreactors aerated with air (0.04% CO2), and we monitored the dynamic changes in growth, cellular carbon and nitrogen content, photosynthetic activity, biochemical compositions, and glycerolipid remodeling under high light and nitrogen starvation conditions. The results indicated that multiple PUFAs continually accumulated in total lipids and TAG, and the primary distributors of these PUFAs gradually shifted from membrane lipids to TAG in stress-induced BAFJ5. The stoichiometry analyses showed that the PUFA-attached TAG assembly attributed to turnover of not only the major glycerolipids, but also the phospholipids, phosphatidylethanolamine (PE) and phosphatidylglycerol. Specifically, the augmented C16:3n3 and C18:3n3 in TAG mainly originated from de novo-synthesized galactolipids, while the cumulative C18:3n6 and C18:4n3 in TAG were intimately correlated with conversion of the newly formed DGTS and PE. These findings emphasized significance of PUFA-attached TAG formation dependent on turnover of de novo assembled membrane lipids in starch-deficient Chlamydomonas, beneficial for enhanced production of value-added lipids in microalgae.

Prediction of mechanical properties of rolled steel based on dual-attention multiscale convolutional neural network

The mechanical properties of carbon steel sheet directly depend on the chemical composition and process parameters of the steel. There is a complex nonlinear relationship between chemical composition, process parameters, and mechanical properties, and the establishment of a model with the ability to automatically distinguish the importance of different parameters, and to have good prediction accuracy and generalisation in different data sets is one of the important issues in the field of carbon steel mechanical properties prediction. In this paper, we proposed a multi-scale convolutional network model based on dual-attention mechanism (DAM-MSDSC), where the dual-attention module mines from features and channels at the same time, making the model focus on the important features. The multiscale feature fusion module effectively improves the model prediction accuracy by mining features from the output of the middle layer of the network to obtain features containing multiscale fusion features. In hot-rolled steel, for the two parameters of carbon content and temperature, it is confirmed that the change of carbon content has a greater impact on TS, while FTT and CT have a greater impact on YS. Through comparative experiments on different datasets, the proposed model had the best prediction performance, in which the correct rates of YS, TS, and EL are 98 %, 98.7 %, and 99.4 %, respectively, in cold rolled steel, and 97.8 %, 98.6 %, and 99.2 %, respectively, in hot rolled steel.

Influence of inhomogeneities in chemical composition and porosity of sintered steel on development of martensitic transformation

The article is devoted to the study of martensitic transformation in porous sintered steels. When analyzing the process of development of marten­sitic transformation in porous sintered steel, the influence of two factors was assessed: depletion of carbon in the near-surface layers of pores and a change in the energy balance due to relaxation of transformation stresses on free surfaces of the pores. The martensitic transformation was studied in porous steel with a carbon content of 1.56 wt. % obtained after pressing and sintering of a mixture of PZhRV iron powders and GK-3 graphite in hydrogen atmosphere at 1200 °C. Gas carburizing at 1100 °C and homogenization helped to achieve the specified carbon content. The samples were quenched in a sodium chloride solution at a temperature of 27 °C. Pre-cooling was used from temperatures Ast to 800 °C at a rate of 62 °C/s. X-ray microanaly­sis of carbon distribution was carried out using the installation CAMECA Microsonde M.S. 46 with a probe diameter of two microns. The martensite plates predominantly formed on the pores’ surfaces and their cross section had shape close to rhomboidal. The data obtained on the morphology of α′-phase crystals growing from pores and the study by X-ray spectral microanalysis of carbon distribution along the largest martensite plates convince us of the absence of any significant changes in carbon content and, as a consequence, their influence on development of martensitic transformation in the area of pores is not the leader. For sintered porous steels, an irremovable factor in the increase in temperature is the presence of porosity, in contrast to a removable factor – inhomogeneity of the chemical composition, which is caused by incompleteness of the alloy homogenization processes, both during sintering and during the austenitization process that precedes quenching.

Changes in biomass and organic carbon content during the growth period of dominant seaweed in the intertidal zone of Gouqi Island, China

Changes in biomass and organic carbon content during the growth period of dominant seaweed in the intertidal zone of Gouqi Island, China

Coupled Vis-NIR spectroscopy with chemometrics strategy for soil organic carbon prediction in the Agro-pastoral Transitional zone of northwest China

Rapidly and accurately grasp the change of soil organic carbon content in farmland, which is of great significance in guiding the timely and effective mastery of farmland soil fertility and improvement of soil physical properties. In this study, an ASD FieldSpec 4 spectrometer was used to collect spectral reflectance data on 128 agricultural soil samples taken from Jingbian County, Yulin City, Shaanxi Province, China. Firstly, descriptive statistics of the SOC in the study area were performed, and secondly, after 10 spectral transformations were performed, the correlation analysis and the Boruta algorithm were used to extract the characteristic wavebands of soil organic carbon, respectively, in order to reduce the redundancy of the data. Finally, by comparing the accuracies of different strategies, we constructed a spectral prediction model of soil organic carbon in farmland of the Northwest Agricultural and Animal Husbandry Intertwined Zone that integrates the optimal preprocessing, feature selection strategy and modelling method. The results indicate that: 1) The mean SOC content of the farmland in the study area was low and at the nutrient deficient level, with the standard errors and coefficients of variation for the modelling and validation sets were 1.596 g kg−1, 1.457 g kg−1, 54 % and 52 %, respectively; 2) The shape and trend of spectral special curves with different SOC contents show consistency, and the SOC content is negatively correlated with spectral reflectance; 3) CA selects more feature bands, but the feature bands are more homogeneous, while the Boruta algorithm can effectively remove irrelevant variables and improve the SOC feature selection effect; 4) The SOC prediction model based on Boruta-FD-RF can be better for soil organic carbon estimation, with R2 of 0.899 and 0.748 for the training set and validation set, respectively, RMSE of 1.432 g kg−1 and 1.967 g kg−1, and RPD of 2.557 and 1.647, respectively. The results show that the SOC model established by integrating optimal spectral pre-processing, feature selection strategy and chemometrics strategy has obvious improvement in prediction accuracy and stability, and this study provides an important reference for the fast and accurate estimation of SOC content in farmland of Agro-pastoral Transitional zone in northwest China.

Molecular Composition of Humic Acids of Different Aged Fallow Lands and Soils of Different Types of Use in Northwest of Russia

Post-agrogenic transformation of fallow soils leads to changes in soil carbon content, the molecular composition of humic substances, and rates of organic matter stabilization, which can affect climate change on the planet. In this regard, we analyzed the molecular composition of humic acids isolated from natural and fallow soils in the southern Taiga zone of northwest Russia. Different-aged soils on fallow lands represent a model of soil transformation in time, and data on the transformation of soil humic acid molecular composition make a significant contribution to the understanding of soil organic matter stabilization aspect issues. In this case, the molecular structure of humic acids isolated from natural and fallow soils in northwest Russia was analyzed. To study the molecular composition of HAs, the elemental composition was analyzed, and 13C (CP/MAS) NMR spectroscopy of HAs isolated from different aged abandoned soils and soils of different types of use was carried out. The obtained data showed that with the increasing age of soils in the fallow state, there is an increase in the carbon content of humic acids as well as a decrease in nitrogen content. As a result of the increasing age of soils in the fallow state, there are dynamics in the content of aromatic structural fragments in humic acids: 34% for 40 years old, 28% for 80 years old, and 31% for 120 years old. This is due to changes in the precursors of humification and the further transformation of plant residues in the soil. Re-involved fallow land soils lead to an increase in the content of aromatic structural fragments in the composition of HA in relation to HA extracted from mature soils. The lowest content of aromatic structural fragments was observed in the humic acids of 130-year-old agricultural soil, which is associated with the long-term application of organic fertilizers.

In-situ online detection of carbon during combustion via laser-induced breakdown spectroscopy

The combustion of fossil fuels is primarily responsible for disrupting the carbon cycle equilibrium by releasing greenhouse gases (GHGs). Therefore, detecting GHG emissions from fossil fuels is extremely important. In this study, utilizing laser-induced breakdown spectroscopy (LIBS), a new method for real-time in-situ detection of carbon fluctuations during combustion has been developed. The combustion of fossil fuels is emulated through the controlled burning of candles within a confined area, and the elemental content of the surrounding air during this process is analyzed. Fluctuations in the intensity of CN spectral lines were tracked to reveal changes in carbon concentration. The backpropagation neural network (BPNN) is used to identify and verify local air with different carbon concentrations, and the predictions are accurate. In conclusion, the integration of BPNN and LIBS for the purpose of identifying variations in carbon content during combustion provides an effective method for environmental management.

Organic amendments increased Chinese milk vetch symbiotic nitrogen fixation by enriching Mesorhizobium in rhizosphere.

Symbiotic nitrogen fixation of Chinese milk vetch (Astragalus sinicus L.) can fix nitrogen from the atmosphere and serve as an organic nitrogen source in agricultural ecosystems. Exogenous organic material application is a common practice of affecting symbiotic nitrogen fixation; however, the results of the regulation activities remain under discussion. Studies on the impact of organic amendments on symbiotic nitrogen fixation have focused on dissolved organic carbon content changes, whereas the impact on dissolved organic carbon composition and the underlying mechanism remain unclear. In situ pot experiments were carried out using soils from a 40-year-old field experiment platform to investigate symbiotic nitrogen fixation rate trends, dissolved organic carbon concentration and component, and diazotroph community structure in roots and in rhizosphere soils following long-term application of different exogenous organic substrates, i.e., green manure, green manure and pig manure, and green manure and rice straw. Remarkable increases in rate were observed in and when compared with that in green manure treatment, with the greatest enhancement observed in the treatment. Moreover, organic amendments, particularly pig manure application, altered diazotroph community composition in rhizosphere soils, therefore increasing the abundance of the host-specific genus Mesorhizobium. Furthermore, organic amendments influence the diazotroph communities through two primary mechanisms. Firstly, the components of dissolved organic carbon promote an increase in available iron, facilitated by the presence of humus substrates. Secondly, the elevated content of dissolved organic carbon and available iron expands the niche breadth of Mesorhizobium within the rhizosphere. Consequently, these alterations result in a modified diazotroph community within the rhizosphere, which in turn influences Mesorhizobium nodulation in the root and symbiotic nitrogen fixation rate. The results of the present study enhance our understanding of the impact of organic amendments on symbiotic nitrogen fixation and the underlying mechanism, highlighting the key role of dissolved organic carbon composition on diazotroph community composition in the rhizosphere.

A dataset for soil organic carbon in agricultural systems for the Southeast Asia region

The determination of changes in soil organic carbon (SOC) content under different cropping systems is necessary for policy development oriented towards soil conservation, C sequestration, and future C credit markets. The aim of this study was to generate an open SOC dataset resulting from a systematic literature search related to the agricultural systems for Southeast Asia. The dataset has 209 articles and 4341 observations on soils of cropping systems in this region from articles published between 1987 and 2023. This dataset included different management practices, land uses, soil sampling depth, and length of SOC content assessment. In addition, inherent features of crop production reported in the experiments were included in the dataset. This dataset can be applied to quantify and compare the impact of different land uses or management practices on SOC content, providing foundational knowledge towards identifying sustainable practices. Lastly, it is a useful guide for future regional SOC sequestration policies and the development of C credit markets.

Study on the characterization and thermal conversion behavior of sequential extraction products from medium temperature coal pitch

To achieve the high value-added clean utilization of medium temperature coal pitch (MTP), five fractions were separated from MTP by the sequential extraction method using n-heptane, n-butanol, toluene, tetrahydrofuran and quinoline as solvents. Briefly, the extracts were analysed using proximate analysis, elemental analysis, fourier infrared spectrum (FTIR), ultraviolet visible spectrum (UV–vis), fluorescence spectrum, and thermogravimetric analysis (TGA) to investigate their structural parameters, aromatic condensation degree and pyrolysis properties. Meanwhile, Raman spectrum, X-ray diffraction (XRD), and polarizing microscope were used to quantitatively analyze the microstructures of thermal conversion products of the extracts. This allowed for investigation of the thermal conversion mechanism and determination of the thermal conversion behavior. In fact, the chain index (CH3/CH2), aromatic index (Iar), aromatic condensation degree and thermal stability of the extracts increase gradually with deeper extraction. Extracts with high aromatic condensation degree are more favorable for the formation of mesocarbon microbeads (MCMBs). However, overly aromatic condensation degree will lead to excessive coalescence of MCMBs. The ideal carbon microcrystalline content increases with higher temperatures during the thermal conversion of the same fraction. But the change of amorphous carbon content has no obvious regularity. The results of this work will provide theoretical and experimental support for the selection of precursors for carbon/graphite materials.

Decomposition of Hemp Residues in Soil as Facilitated by Different Nitrogen Sources

Improving soil health across agroecosystems has continued to receive attention around the globe, with an emphasis on sustainable organic inputs from agricultural practice. It is well known that different organic materials, such as composts, manure and cereal straws, positively affect soil carbon. The changing agricultural practices have continuously led to new and improved plants in farming. One of these innovative plants is industrial hemp. With the increasing cultivation of industrial hemp globally, the problem of the disposal of hemp residues has been encountered. However, the rich carbon content found in hemp residues in soil is anticipated to enhance the soil quality and address the challenge of effectively utilizing hemp straw. In this study, we conducted a two-way experimental trial to evaluate the decomposition of hemp residues using placement methods (residues incorporated into the soil or left on the soil surface) and nitrogen sources as additives. Different nitrogen additives (nitrogen fertilizer pellets, liquid nitrogen, organic fertilizers, and the preparation “Bioversio”) were selected to accelerate the decomposition of hemp residues. The results showed that the mineralization rates were faster in the residues incorporated in the soil, with a mass loss of over 54% compared to the treatments left on the soil. The influence of additives on the decomposition rates was statistically significant. Additionally, there was a significant increase in the N content in the soil, while the change in carbon content in the soil was not statistically significant. These research results reinforce nitrogen fertilizers’ positive role in accelerating hemp residue decomposition in soil. Furthermore, our findings will help contribute to the effective and sustainable utilization of hemp residues as a bioresource material to improve soil health.

Effects of Continuous Annual Crop Rotation and Fallow on Soil Aggregate Stability and Organic Carbon

In order to explore the effects of continuous annual crop rotation and fallow on aggregate stability and organic carbon content in red soil, the red soil in sloping farmland was taken as the research object, and the water-stable aggregates and organic carbon content were determined using the wet sieve method and potassium dichromate-concentrated sulfuric acid external heating method, respectively. The changes in soil aggregate stability and organic carbon content under the four treatments of maize-vetch-maize rotation (M-V-M), maize-pea-maize rotation (M-P-M), maize-fallow-maize (M-F-M), and annual fallow (F-F-F) from 2020 to 2022 and the relationships between them were analyzed. The results showed that in 2021 and 2022, the contents of > 2 mm aggregates treated with F-F-F, M-V-M, and M-P-M were significantly increased by 67.01%-100.92%, 29.71%-33.67%, and 29.68%-38.07%, respectively, compared with that treated with M-F-M. In 2021 and 2022, the stability parameters of F-F-F and M-V-M were significantly higher than those of M-F-M (P < 0.05). The content of > 2 mm aggregates, geometric mean diameter (GMD), and mean weight diameter (MWD) under the M-V-M treatment and R0.25 (> 0.25 mm aggregate contents), MWD and > 2 mm aggregate contents under the F-F-F treatment increased with the increase in fallow years, whereas the content of 1-2 mm and < 0.25 mm under the F-F-F treatment decreased with the increase in fallow years. Both green manure rotation and fallow treatment could increase the SOC content, and the SOC content of F-F-F and M-V-M treatment increased with the extension in age. Correlation analysis showed that SOC content was significantly positively correlated with R0.25 and GMD under all treatments. R0.25 and GMD under the F-F-F treatment and GMD and MWD under M-V-M were significantly positively correlated with SOC content. The results showed that continuous annual crop rotation and fallow was beneficial to improve the content of soil macro-aggregates, aggregate stability, and SOC content, which could provide theoretical basis for the implementation of reasonable continuous annual crop rotation and fallow patterns and soil erosion control in red soil areas of sloping farmland in southern China.

The trend of changes in soil organic carbon content in Poland over recent years

The article analyzes soil organic carbon (SOC) content of in Poland from 2015 to 2021. The research aims to determine SOC levels and their dependence on soil agronomic categories and drought intensity. Soil samples from 1011 farms across 8 Polish voivodships were collected for analysis, all from the same agricultural plots. SOC determination was conducted using the Tiurin method. The results indicate a low SOC content nationwide (0.85-2.35%). Heavy soils exhibited higher SOC accumulation compared to light soils. Moreover, significant drought impact led to decreased SOC content in affected regions. Scientific evidence underscores a declining trend in organic carbon stock within agricultural soils, attributed to natural soil changes and unsustainable management practices. This decline is concerning given the crucial role of SOC in soil health, quality, and crop productivity. Therefore, it is imperative to monitor and address areas with low SOC levels to enhance SOC abundance. Furthermore, when used as a whole-cell biocatalyst in a low-cost upflow MFC, the Morganella morganii-rich SF11 consortium demonstrated the highest voltage and power density of 964.93±1.86 mV and 0.56±0.00 W/m3, respectively. These results suggest that the SF11 bacterial consortium has the potential for use in ceramic separator MFCs for the removal of penicillin and electricity generation.

Grape Skin Composting Process to Recycle Food Waste: Kinetics and Optimization.

Within the various approaches to organic waste handling, composting has been recognized as an acceptable method to valorize organic waste. Composting is an aerobic technique of microbial disruption of organic matter which results with compost as a final product. To guarantee the quality of the compost, key process factors (like the moisture content, temperature, pH, and carbon-to-nitrogen ratio) must be maintained. In order to optimize the process, nine composting trials using grape skins were conducted in the present study under various initial moisture content and air flow rate conditions over the course of 30 days. The processes were monitored through physicochemical variables and microbiological activity. Also, the kinetics of the organic matter degradation and microbial growth were investigated. Although the thermophile phase was only achieved in experiments 3 and 8, the important variables proved the efficiency of all nine composting processes. The organic carbon content and C/N ratio decreased after the 30 days of composting processes and a great color change was noticed too. The values for the germination index for all experiments were above 80%, which means that the final products are non-toxic for plants. Also, the greatest change in organic carbon content in was evident in experiment 3; it decreased from 71.57 to 57.31%. And consequently, the rate of degradation for that experiment was the highest, at 0.0093 1/day. Furthermore, the response surface methodology was used to identify optimal operating conditions for grape skin composting and the obtained conditions were 58.15% for the initial moisture content and 1.0625 L/min for the air flow rate.

Canopy gap impacts on soil organic carbon and nutrient dynamic: a meta-analysis

Key messageThe forest canopy gaps, formed by natural or anthropogenic factors, have been found to reduce soil carbon content and increase nutrient availability. The magnitudes of these effects have been observed to increase with gap age and size, and are largely influenced by changes in temperature, precipitation, and solar radiation.ContextLocal studies have illustrated the influence of canopy gaps on the spatial heterogeneity of soil carbon and nutrients, playing a pivotal role in driving forest regeneration and succession. Nevertheless, it remains largely unknown whether the response of soil carbon and nutrient content to gap formation is consistent across forest ecosystems at global scale.AimsThe aim of this paper is to assess the homogeneity of the observed responses of soil carbon and nutrients following gap formation among a wide array of forest ecosystems and climatic regions.MethodsWe performed a meta-analysis synthesizing 2127 pairwise observations from 52 published articles to quantify the changes in in soil physical, chemical, and microbial variables resulting from gap creation in natural forests and plantations spanning tropical to boreal regions.ResultsCanopy gaps resulted in significant decrease of soil organic carbon (Corg) and microbial carbon (Cmic). The concentrations of ammonium (NH4+), nitrate (NO3−), and available phosphorus (available P) increased following gap creation. These changes mainly occurred in the growing season and in the mineral soil layer, becoming more pronounced with increasing gap age and size. The change in Corg was negatively regulated by mean annual precipitation, and was associated with the changes in Nt and Nmic. The change in NH4+ was positively regulated by mean annual temperature, and was associated with the changes in available P and oxidoreductases (Ox-EEAs). The model explaining the change in soil carbon content exhibited a higher explanatory power than the one accounting for changes in soil nutrient availability.ConclusionThe results indicated that forest canopy gaps resulted in a reduction in soil carbon content and an increase in nutrient availability. These findings contribute to a better understanding of the role of small-scale disturbances as drivers of forest ecosystem succession.

Interactive effects of grassland utilization and climatic factors govern the plant diversity-soil C relationship in steppe of North China

The relationship between plant diversity and the ecosystem carbon pool is important for understanding the role of biodiversity in regulating ecosystem functions. However, it is not clear how the relationship between plant diversity and soil carbon content changes under different grassland use patterns. In a 3-year study from 2013 to 2015, we investigated plant diversity and soil total carbon (TC) content of grasslands in northern China under different grassland utilization methods (grazing, mowing, and enclosure) and climatic conditions. Shannon-Wiener and Species richness index of grassland were significantly decreased by grazing and mowing. Plant diversity was positively correlated with annual precipitation (AP) and negatively correlated with annual mean temperature (AMT). AP was the primary regulator of plant diversity. Grazing and mowing decreased TC levels in grasslands compared with enclosures, especially in topsoil (0–20 cm). The average TC content was decreased by 58 % and 36 % in the 0–10 cm soil layer, while it was decreased by 68 % and 39 % in 10–20 cm soil layer. TC was positively correlated with AP and negatively correlated with AMT. Principal component analysis (PCA) showed that plant diversity was positively correlated with soil TC, and the correlation decreased with an increase in the soil depth. Overall, this study provides a theoretical basis for predicting soil carbon storage in grasslands under human disturbances and climate change impacts.

Biological activity of soils in Ukraine depending on tillage options: A meta-analysis

Tillage is one of the major factors affecting soil biological activity, resulting in changes in soil organic carbon (SOC) content, providing for carbon sequestration and shifts in carbon dioxide emission from soils. Current climate change and aggravation of global warming through the increased emission of carbon dioxide are main driving forces for global transformation of agricultural practices in the direction of climate-smart agriculture (CSA), which requires the implementation of such crop cultivation practices that result in the minimization of SOC losses and carbon dioxide emissions. The magnitude and direction of different tillage practices affecting soil biological activity are different, therefore, the best tillage options should be chosen for implementation in national CSA systems to ensure achieving the global sustainability goals. This nationwide meta-analysis, conducted for tillage practices utilized in Ukrainian agriculture examines scientifically recorded effects of moldboard tillage depth, flat cutter and no-till options on soil respiration rates and cellulose decomposition intensity in dark-chestnut and chernozem soils of Ukraine. This meta-analysis enrolled 45 studies, which met the stipulated scientific quality criteria. Statistical processing was conducted through the standardized mean difference (SMD) model without subgroups at 95% confidence interval (CI). As a result, it was determined that there is subtle impact of moldboard tillage depth on soil biological activity, which is inconclusive and unclear. The similar results were obtained for the comparison between the tillage and no-till groups, where high heterogeneity of the dataset (I2 = 82.8%) resulted in low quality of evidence for the benefits of no-till in SOC sequestration. Besides, zero fail-safe numbers support the suggestion of low-quality evidence in favor of shallow plowing advantage over deep plowing, as well as no-till against tillage. As for the difference between the groups of moldboard and flat cutter tillage, it was established that there is strong enough evidence for the advantage of flat cutter tillage in terms of soil respiration rates and cellulose decomposition intensity reduction. Further studies in this direction are required to fill the gaps in current meta-analysis, especially in terms of no-till options and their effect on biological activity of Ukrainian soils in different cropping systems.