Organic Carbon Accumulation Research Articles

Assessment of the Change in Soil Properties and Aggregates Formation of Freshly Restored Texturally Different Marginally Salt-Affected Soils Under Various Soil Amelioration Strategies

ABSTRACT Climate change and salt-affected soils detrimentally affect crop production in arid regions. Reclaiming these soils for crops and carbon sequestration can mitigate climate change and enhance food security. A laboratory-scale experiment was conducted on a wheat-maize crop rotation system for three consecutive years to check the effectiveness of organic amendments in reclaiming marginally salt-affected soils, improving soil health, sequestering carbon, and improving food grain production. This study included five treatments namely control (T1), gypsum alone at 100% gypsum requirements (G100), and its combinations with different organic amendments and 50% gypsum requirements (farm manure (FYM+G50), poultry manure (PM+G50), and green manure (GM+G50)) were used. Results indicated that sandy clay loam textured soil showed highest potential for its properties improvement after 45 days, i.e., EC decreased up to 3.9 dS m−1, pH 7.9 and, SOC increase up to 0.25%. After the fallow period, three consecutive years of crop production study indicated up to 39 and 70% increase in wheat and maize yields, respectively, compared to inorganic fertilizer alone. Maximum soil aggregation was noted in treatment with gypsum and farmyard manure application in loam soils (50%). The maximum soil organic carbon accumulation over the whole experiment was recorded in farmyard manure application in combination with gypsum (0.44 g kg−1) in both loam and sandy clay loam soil, while 0.31 g kg−1 in the clay loam soil. Based on the results, it was concluded that reclaiming marginally salt-affected soils enhances food crop production and incorporating manures improves soil through aggregation and carbon sequestration, mitigating climate change.

The Effect of Long-Term Crop Rotations for the Soil Carbon Sequestration Rate Potential and Cereal Yield

Depending on the type of agricultural use and applied crop rotation, soil organic carbon accumulation may depend, which can lead to less CO2 fixation in the global carbon cycle. Less is known about organic carbon emissions in different crop production systems (cereals, grasses) using different agrotechnologies. There is a lack of more detailed studies on the influence of carbon content in the soil on plant productivity, as well as the links between the physical properties of the soil and the absorption, viability, and emission of greenhouse gases (GHG) from mineral fertilizers. The aim of this study is to estimate the long-term effect of soil organic carbon sequestration potential in different crop rotations. The greatest potential for organic carbon sequestration is Norfolk-type crop rotation, where crops that reduce soil fertility are replaced by crops that increase soil fertility every year. Soil carbon sequestration potential was significantly higher (46.72%) compared with continuous black fallow and significantly higher from 27.70 to 14.19% compared with field with row crops and cereal crop rotations, respectively, intensive crop rotation saturated with intermediate crops. In terms of carbon sequestration, it is most effective to keep perennial grasses for one year while the soil is still full of undecomposed cereal straw from the previous crop. Black fallow without manure fertilization, compared to crop rotation, reduces the amount of organic carbon in the soil up to two times, the carbon management index by 2–5 times, and poses the greatest risk to the potential of carbon sequestration in agriculture.

Toward soil carbon storage: The influence of parent material and vegetation on profile-scale microbial community structure and necromass accumulation

Soil microbial communities play a crucial role in the accumulation and stabilization of soil organic carbon (SOC) through complex processes involving plant residue transformation and mineral interactions. These processes are influenced by plant inputs and modulated by soil properties that are mostly determined by the parent material. However, our understanding is limited regarding the manner in which vegetation and parent material affect microbial community structure, necromass accumulation, and their subsequent impact on SOC storage. To bridge this knowledge gap, we conducted an in-depth investigation focusing on the top-down influence of vegetation type and the bottom-up effect of parent material on microbial-mediated carbon transformation across soil profiles in a tropical region. Our study encompassed 42 sites on three parent materials (basalt, granite, and marine sediments) and four vegetation types (rubber, banana, areca plantations and uncultivated grassland). Soil samples were collected at 0–20, 20–40, 40–80, and 80–100 cm depth. Microbial community structure and necromass were quantified using microbial biomarkers of phospholipid fatty acids and amino sugars, respectively. In rubber plantations, we observed a trend toward higher microbial biomass that, though not significant when compared to other vegetation types, transformed to a significantly higher accumulation of microbial necromass. This increase in microbial necromass was linked to the accumulation of SOC facilitated by the presence of clay size minerals in clayey soils developed from basalt. In particular, basaltic soils were dominated by bacteria, which facilitated the accumulation of bacterial necromass that significantly bolstered its contribution to SOC. In contrast, in sandier soils developed from granite and marine sediments, fungal communities and necromass dominated due to the propensity of fungi for coarser soil environments. Overall, the main impact of vegetation on microbial communities and necromass accumulation was primarily demonstrated for the topsoil. Differences in soil texture arising from different parent materials exert significant effects on the fungal-to bacterial-biomass and necromass ratios, consequently influencing the contribution of fungal and bacterial necromass carbon to SOC across soil profiles. Our study underscores the pivotal role of parent material in governing tropical profile-scale soil carbon storage by shaping the structure of microbial communities and influencing the retention of microbial necromass.

The After-Effect of Organic Fertilizer Varies among Climate Conditions in China: A Meta-Analysis

Organic fertilizer is utilized to improve the organic carbon levels in arable soils, which is helpful for soil quality improvement and crop yield increase. However, the after-effect of organic fertilizer varies among regions with different temperature and precipitation conditions, and the extent of the impact remains unknown. This study aimed to investigate the impact of varying temperature and rainfall conditions on the accumulation of soil organic carbon after organic fertilizer application. A meta-analysis of 168 peer-reviewed studies published between 2005 and 2022 involving a total of 464 trials was conducted. The following was discovered: (1) In the major grain-producing areas of China, there was a significant positive correlation (p < 0.01) between latitude and soil organic carbon content. Meanwhile, temperature and precipitation had a significant negative correlation (p < 0.01) with soil organic carbon content. (2) The increase in temperature inhibited the increase in soil organic carbon storage. The improvement effect of organic fertilizer application in the low-temperature areas was significantly increased by 60.93% compared with the mid-temperature areas, and by 69.85% compared with the high-temperature areas. The average annual precipitation affected the after-effect of organic fertilizer as follows: 400–800 mm > 400 mm > more than 800 mm. (3) The influence of climatic conditions on the after-effect of organic fertilizer was more significant depending on the specific tillage practice. To increase organic fertilizer use efficiency and eliminate greenhouse gas emissions, liquid organic fertilizers with abundant trace nutrients and amino acids, which take advantage of releasing nutrients more swiftly and have a better fertilization effect, could be an alternative to traditional organic fertilizers.

How does exotic Spartina alterniflora affect the contribution of iron-bound organic carbon to soil organic carbon in salt marshes?

Iron-bound organic carbon (OC-FeR) is important for the stability of soil organic carbon (SOC) in salt marshes, and the Spartina alterniflora invasion reshaped local salt marshes and changed the SOC pool. To evaluate the effects of S. alterniflora invasion on the contribution of OC-FeR to SOC, we determined the OC-FeR content and soil characteristics in the 0–50 cm soil profile along the vegetation sequence, including mudflats (MF), S. alterniflora marshes established in 2003 (SA03) and 1989 (SA89), the ecotone of S. alterniflora and Phragmites australis (SE), S. salsa marsh (SS), and P. australis marsh (PA). The SOC content was 6.55–17.5 mg g−1 in the S. alterniflora marshes. Reactive iron oxides (Fed, Feo, Fep) accumulated significantly in the S. alterniflora and P. australis salt marshes. PA and S. alterniflora marshes had higher DOC contents of 0.28–0.77 mg g−1. The OC-FeR content in the 0–50 cm soil profile in these ecosystems ranged from 0.3 to 3.29 mg g−1, with a contribution to the SOC content (fOC-FeR) of approximately 11 %, which was highest in SA03 (16.3 % ~ 18.8 %), followed by SA89, SE, and PA. In addition, the molar ratios of OC-FeR to Fed were <1, indicating that the iron oxides were associated with SOC through sorption more than coprecipitation. According to the structural equation model, SOC, DOC and iron oxides were the direct driving factors of OC-FeR formation, while the vegetation zone indirectly functioned by regulating organic C inputs, iron oxide formation, and pH. This study suggested that S. alterniflora invasion promotes iron-bound organic carbon accumulation by increasing organic C inputs and regulating iron oxide formation in salt marshes, but such promotion will degenerate with development duration.

Agricultural land abandonment promotes soil aggregation and aggregate-associated organic carbon accumulation: a global meta-analysis

Agricultural land abandonment promotes soil aggregation and aggregate-associated organic carbon accumulation: a global meta-analysis

Ridge with no-tillage facilitates microbial N2 fixation associated with methane oxidation in rice soil

Aerobic methane-oxidizing bacteria (MOB) play a crucial role in mitigating the greenhouse gas methane emission, particularly prevalent in flooded wetlands. The implementation of ridge with no-tillage practices within a rice-rape rotation system proves effective in overcoming the restrictive redox conditions associated with waterlogging. This approach enhances capillary water availability from furrows, especially during periods of low rainfall, thereby supporting plant growth on the ridges. However, the microbe-mediated accumulation of soil organic carbon and nitrogen remains insufficiently understood under this agricultural practice, particularly concerning methane oxidation, which holds ecological and agricultural significance in the rice fields. In this study, the ridge and ditch soils from a 28-year-old ridge with no-tillage rice field experiment were utilized for incubation with 13C-CH4 and 15NN2 to estimate the methane-oxidizing and N2-fixing potentials. Our findings reveal a significantly higher net production of fresh soil organic carbon in the ridge compared to the ditch soil during methane oxidation, with values of 626 and 543 μg 13C g−1 dry weight soil, respectively. Additionally, the fixed 15N exhibited a twofold increase in the ridge soil (14.1 μg 15N g−1 dry weight soil) compared to the ditch soil. Interestingly, the result of DNA-based stable isotope probing indicated no significant differences in active MOB and N2 fixers between ridge and ditch soils. Both Methylocystis-like type II and Methylosarcina/Methylomonas-like type I MOB catalyzed methane into organic biomass carbon pools. Soil N2-fixing activity was associated with the 15N-labeling of methane oxidizers and non-MOB, such as methanol oxidizers (Hyphomicrobium) and conventional N2 fixers (Burkholderia). Methane oxidation also fostered microbial interactions, as evidenced by co-occurrence patterns. These results underscore the dual role of microbial methane oxidation – not only as a recognized sink for the potent greenhouse gas methane but also as a source of soil organic carbon and bioavailable nitrogen. This emphasizes the pivotal role of microbial methane metabolism in contributing to soil carbon and nitrogen accumulation in ridge with no-tillage systems.

Increased light intensity enhances photosynthesis and biochemical components of red macroalga of commercial importance, Kappaphycus alvarezii, in response to ocean acidification

The concentration of atmospheric carbon dioxide (CO2) has increased drastically over the past several decades, resulting in the pH of the ocean decreasing by 0.44 ± 0.005 units, known as ocean acidification (OA). The Kappaphycus alvarezii (Rhodophyta, Solieriaceae), is a commercially and ecologically important red macroalga with significant CO2 absorption potential from seawater. The K. alvarezii also experienced light variations from self-shading and varied cultivation depths. Thus, the aim of present study was to investigate the effects of two pCO2 levels (450 and 1200 ppmv) and three light intensities (50, 100, and 150 μmol photons·m−2·s−1) on photosynthesis and the biochemical components in K. alvarezii. The results of the present study showed that a light intensity of 50 μmol photons·m−2·s−1 was optimal for K. alvarezii photosynthesis with 0.663 ± 0.030 of Fv/Fm and 0.672 ± 0.025 of Fv’/Fm’. Phycoerythrin contents at two pCO2 levels decreased significantly with an increase in light intensity by 57.14–87.76%, while phycocyanin contents only decreased from 0.0069 ± 0.001 mg g−1 FW to 0.0047 ± 0.001 mg g−1 FW with an increase in light intensity at 1200 ppmv of pCO2. Moreover, moderate increases in light intensity and pCO2 had certain positive effects on the physiological performance of K. alvarezii, specifically in terms of increasing soluble carbohydrate production. Although OA and high light levels promoted total organic carbon accumulation (21.730 ± 0.205% DW) in K. alvarezii, they had a negative impact on total nitrogen accumulation (0.600 ± 0.017% DW).

The contribution of microbial necromass to soil organic carbon and influencing factors along a variation of habitats in alpine ecosystems

A growing consensus is reached that microbes contributes to regulating the formation and accumulation of soil organic carbon (SOC). Nevertheless, less is known about the role of soil microbes (necromass, biomass) in SOC accumulation in different habitat conditions in alpine ecosystems. To address this knowledge gap, the composition and distribution of amino sugars (ASs) and phospholipid fatty acids (PLFAs) as biomarkers of microbial necromass and biomass were investigated in forest, meadow and wetland soil profile (0–40 cm) of Mount Segrila, Tibet, China, as well the contribution of bacterial and fungal necromass to SOC. The results revealed that microbial necromass carbon contributed 45.15 %, 72.51 % and 78.08 % on average to SOC in 0–40 cm forest, meadow and wetland soils, respectively, and decreased with microbial biomass. Fungal necromass contributed more to SOC in these habitats than bacterial necromass. Microbial necromass increased with microbial biomass and both of them decreased with soil depth in all habitats. The necromass accumulation coefficient was significantly correlated with microbial necromass and biomass, affected by habitat and soil moisture. Structural equation model indicated that soil abiotic factors indirectly mediated the accumulation of SOC through microbial necromass and biomass. This study revealed that different habitats and soil depths control considerably soil physicochemical properties and microbial community, finally influencing SOC accumulation in alpine ecosystems, which emphasized the influence of abiotic factors on microbial necromass and biomass for SOC accumulation in alpine ecosystems.

CARBON STOCK, RATES OF CARBON ACCUMULATION AND DISTRIBUTION OF PARTICLES IN A LAKE OF THE ANAVILHANAS ARCHIPELAGO, NEGRO RIVER - AMAZON DURING THE LAST 1900 YEARS

Recent studies show that, despite great variability, the lake systems of the Amazon Basin have presented significant results in the accumulation and storage of organic carbon (TOC). However, the demonstration in the region is still limited and lacks more data to better estimate this non-carbon component of the region. The objective of this article was to estimate the carbon stock, the carbon accumulation rates and characterize the granulometric distribution of an Amazonian lake located in the Anavilhanas Archipelago, in the Lower Negro River region. Data were carried out using the 14C method and analyses of density, granulometry and TOC rate sof samples of a sediment core 1 meter deep. The results have shown that, during the period of 1900 cal years BP, Lake Boto presented two isolated peaks of sand particle sedimentation possibly related to major hydrodynamic events. Generally, well-defined characteristics of a lacustrine environment with sedimentation of fine silt and clay particles predominate. The sedimentation rate was 0.03 cm.year-¹ between approximately 1900 to 850 cal years BP and 0.07 cm.year-¹ in the last 850 cal years BP. It is estimated that Lake Boto has a stock of approximately 231,000 tons of TOC accumulated during the entire period. The stock of TOC is not significant as it is estimated for the soils of the Amazon. The results are an important indication of the role of the Anavilhanas Archipelago as a TOC sink.

Metabolism Regimes in Regulated Rivers of the Illinois River Basin, USA

Metabolism estimates organic carbon accumulation by primary productivity and removal by respiration. In rivers it is relevant to assessing trophic status and threats to river health such as hypoxia as well as greenhouse gas fluxes. We estimated metabolism in 17 rivers of the Illinois River basin (IRB) for a total of 15,176 days, or an average of 2.5 years per site. Daily estimates of gross primary productivity (GPP), ecosystem respiration (ER), net ecosystem productivity (NEP), and the air-water gas exchange rate constant (K600) are reported, along with ancillary data such as river temperature and saturated dissolved oxygen concentration, barometric pressure, and river depth and discharge. Workflows for metabolism estimation and quality assurance are described including a new method for estimating river depth. IRB rivers are dominantly heterotrophic; however, autotrophy was common in river locations coinciding with reported harmful algal blooms (HABs) events. Metabolism of these regulated Midwestern U.S. rivers can help assess the causes and consequences of excessive algal blooms in rivers and their role in river ecological health.

Enhancement of Soil Organic Carbon, Water Use Efficiency and Maize Yield (Zea mays L.) in Sandy Soil through Organic Amendment (Grass Peat) Incorporation

The efficient use of organic amendment (OM) is considered an economic, environmental and sustainable practice to improve soil quality, especially the accumulation of organic carbon (C) and water use efficiency (WUE) in dryland agriculture. However, the effect of different OM on soil nutrients, organic carbon fractions, water content and maize yield is unclear in arid and semi-arid regions with sandy soil. Field experiments with four OM, grass peat (GP), biochar (BC), organic fertilizer (OF) and maize straw (MS), were conducted with an equivalent amount of C input on the southeastern edge of Mu Us Sandy Land in China. Results indicated that the soil nutrients and labile organic carbon (DOC, MBC, KMnO4-C and POC) concentrations were higher under OM (GP, BC, OF and MS) treatments than in CK in the 0–0.10 m soil layers. GP treatment remarkably improved carbon pool index values (1.63, 2.51 and 2.24, respectively) in all layers compared to CK (1.00). At maturity stages of maize, the soil water content (SWC) under GP and OF treatments (11.3–13.4%) was remarkably higher than that in CK treatment (around 10.0%). Yield and WUE were remarkably greater in GP and OF treatments compared to CK. The results proved that GP amendment is superior for barren sandy soil than BC, OF and MS treatments in improving soil nutrients, organic carbon sequestration, WUE and crop yield in China.

Effects of Different Modifiers on Aggregates and Organic Carbon in Acidic Purple Soil

The aim of this study was to examine the effects of different modifiers on the changes in aggregates and organic carbon in acidic purple soil， providing a scientific basis for the remediation of acidic purple soil. Using purple soil as the research object， a total of six treatments were set up， including no fertilization （CK）， single fertilization （F）， fertilization with lime （SF）， fertilization with organic fertilizer （OM）， fertilization with biochar （BF）， and fertilization with distiller's grains ash （JZ）. We compared the composition of aggregates in acidic purple soil under the application of different modifiers， as well as the distribution pattern of organic carbon in aggregates of different particle sizes. Combined with the stability indicators of aggregates， we sought to clarify the impact of different modifiers on the structure of aggregates in acidic purple soil. The results showed that fertilization significantly increased the soil pH， with the JZ treatment being the most effective. Fertilization significantly increased soil organic matter content， with the OM treatment showing the largest increase. The BF and OM treatments significantly reduced soil bulk density， whereas the SF and BF treatments significantly increased soil moisture content （P &lt; 0.05）. All treatments used &lt; 0.25 mm aggregates as the dominant particle size. Fertilization could significantly increase the content of large aggregates （aggregate structure units with diameter &gt; 0.25 mm）. At the same time， fertilization treatments significantly increased the soil geometric mean diameter （GMD）， average weight diameter （MWD）， and R0.25 value （ &gt; 0.25 mm aggregate content） and reduced the fractal cone number （D） and aggregate destruction rate （PAD） values （P &lt; 0.05）. Fertilization also promoted the aggregation and stability of soil aggregates， with the OM treatment having the greatest effect. Compared with that in the CK treatment， fertilization could significantly increase soil organic carbon content by 31.71%-209.67%， with the OM treatment showing the most significant change. Different treatments of soil organic carbon were mainly distributed in large aggregates. Compared with that in the CK treatment， each treatment significantly increased the contribution rate of organic carbon in large aggregates by 19.34%-47.76%， with the OM treatment having the most significant effect （P &lt; 0.05）. In general， chemical fertilizer combined with organic fertilizer could promote the formation of large aggregates in acidic purple soil， improve the stability of soil aggregates， and increase the content of soil organic carbon， which is an effective measure to improve the soil structure and improve the quality of acidic purple soil.

Carbon and Nitrogen Stocks in Agricultural Soils under Different Natural Conditions and Management in Slovakia

Soil is a natural capital which supplies valuable ecosystem services including carbon and nitrogen storage. Agroecosystems play an important role in soil organic carbon (SOC) and soil total nitrogen (NT) accumulation. The aim of this study was to analyse SOC stock (SOCS) and NT stock (NTS) in relation to land use (arable land-AL, permanent grasslands-PG), management, soil depth, and selected soil properties of six soil subtypes (Rendzic Leptosol—LPrz, Dystric Cambisol—CMdy, Stagnic Cambisol—CMst, Haplic Fluvisol—FLha, Gleyic Fluvisol—FLgl, Haplic Chernozem—CHha) which are the most widespread in Slovakia. SOCS for a 50 cm deep soil profile ranged from 161 t.ha−1 in CHha to 59 t.ha−1 in FLgl in grasslands, and in arable lands from 111 t.ha−1 in CHha to 38 t.ha−1 in CMst. In grasslands, FLs and CMst showed the significantly lowest SOCS and NTS in comparison to CMdy, LPrz, and CHha. The mean soil NT content in arable land and grasslands was 2.21 g.kg−1 and 2.82 g.kg−1, respectively. ANOVA showed that soil subtype, land use, and site have significantly affected SOCS but not NTS. The correlation analysis revealed correlations between SOCS and NTS. SOCS was also correlated with C:N, pH, P, and K. This study should help to encourage practices to maintain soil C and soil properties and to ensure the sustainability of the functions of many soil types in Slovakia.

Assessment of Particulate Matter, Heavy Metals, and Carbon Deposition Capacities of Urban Tree Species in Tehran, Iran

Air pollution is a pressing environmental concern in urban areas, with particulate matter (PM) posing serious health and environmental threats. Urban greening has emerged as a potential solution to capture and retain PM. This study assesses the PM deposition capacity of five common tree species: Morus alba (M. alba), Ailanthus altissima (A. altissima), Platanus orientalis (P. orientalis), Robinia pseudoacacia (R. pseudoacacia), and Ulmus minor (U. minor) in two highly polluted sites in Tehran, Iran. Additionally, this study investigates the accumulation of heavy metals (Ni, Fe, Cd, and Pb), Organic Carbon (OC), Elemental Carbon (EC), and Total Carbon (TC) on the leaves of these tree species. The results demonstrate species-specific differences in PM deposition capacity, with U. minor and M. alba showing high PM retention. A. altissima exhibits strong capability in adsorbing PM 0.1–2.5, while U. minor demonstrates greater retention of PM &gt; 2.5. Moreover, the deposition of heavy metals varies among species, with R. pseudoacacia and A. altissima capturing higher levels. This study highlights the significance of appropriate tree utilization in urban environments against air pollution in order to make the air healthier in major cities. Awareness of the different tree species capacities leads urban planners and policymakers to make intelligent decisions about urban greening initiatives to improve air quality and overall well-being.

Optimized Nitrogen Fertilization Promoted Soil Organic Carbon Accumulation by Increasing Microbial Necromass Carbon in Potato Continuous Cropping Field

The form and distribution of organic carbon in soil affect its stability and storage, and nitrogen (N) fertilization can affect the transformation and accumulation of soil organic carbon (SOC), whereas how the N fertilizer rate affects SOC storage by regulating its fractions in a potato continuous cropping system is unknown. A 6-year field experiment was conducted to study the effect of different N fertilizer rates (NE (Nutrient Expert) –N, NE–1/2N, NE, and NE+1/2N) on the changes in SOC and its fractions in a potato continuous cropping system in North China. Soil NO3−-N gradually increased with increasing N fertilizer rates, whereas the N fertilizer rate had less effect on NH4+-N. Compared with the NE−N treatment, the increasing N fertilization increased the SOC and its components, whereas these C fractions did not continue to increase or began to decrease after N fertilization exceeded the rate applied in the NE treatment. While the increase in mineral-associated organic C (MAOC; 16.1–17.2% and 26.1–52.7% in the 0–20 cm and 20–40 cm layers, respectively) was greater than that of particulate organic C (POC; 3.7–7.4% and 11.5–16.4% in the 0–20 cm and 20–40 cm layers, respectively), the increase in bacterial necromass C (BNC; 9.2–21.8% and 28.9–40.4% in the 0–20 cm and 20–40 cm layers, respectively) was greater than that of fungal necromass C (FNC; 6.2–10.1% and 7.1–24.9% in the 0–20 cm and 20–40 cm layers, respectively). Furthermore, the increase in FNC was greater than that of BNC in the 20–40 cm layer of the same treatment. SOC was significantly and positively correlated with MAOC and FNC, and the correlation between SOC and both MNC and FNC was more significant in the 20–40 cm layer than in the 0–20 cm layer. Overall, in the potato continuous cropping system in North China, N fertilization improved SOC storage by increasing MNC to form MAOC, and optimizing N fertilization based on the NE system could better balance the increase and mineralization loss of SOC to achieve high SOC sequestration.

Characteristics of soil organic carbon fractions in four vegetation communities of an inland salt marsh

BackgroundThe study of soil organic carbon characteristics and its relationship with soil environment and vegetation types is of great significance to the evaluation of soil carbon sink provided by inland salt marshes. This paper reports the characteristics of soil organic carbon fractions in 0–50 cm soil layers at four vegetation communities of the Qinwangchuan salt marsh.Results(1) The soil organic carbon content of Phragmites australis community (9.60 ± 0.32 g/kg) was found to be higher than that of Salicornia europae (7.75 ± 0.18 g/kg) and Tamarix ramosissima (4.96 ± 0.18 g/kg) and Suaeda corniculata community (4.55 ± 0.11 g/kg). (2) The soil dissolved organic carbon, particulate organic carbon and soil microbial biomass carbon in 0–50 cm soil layer of Phragmites australis community were higher, which were 0.46 ± 0.01 g/kg, 2.81 ± 0.06 g/kg and 0.31 ± 0.01 g/kg, respectively. (3) Soil organic carbon was positively correlated with dissolved organic carbon, particulate organic carbon, and microbial biomass carbon, and negatively correlated with easily oxidized organic carbon. (4) Above-ground biomass has a strong direct positive effect on soil organic carbon, total nitrogen and pH have a strong direct positive effect on microbial biomass carbon content, pH and average density have a strong direct negative effect on easily oxidized organic carbon, and particulate organic carbon.ConclusionsThe interaction between plant community characteristics and soil factors is an important driving factor for soil organic carbon accumulation in inland salt marshes.

Role of genes encoding microbial carbohydrate-active enzymes in the accumulation and dynamics of organic carbon in subtropical forest soils

Microbial anabolism and catabolism regulate the accumulation and dynamics of soil organic carbon (SOC). However, very little attention has been paid to the role of microbial functional traits in the accumulation and dynamics of SOC in forest soils. In this study, nine forest soils were selected at three altitudes (600 m, 1200 m, and 1500 m) and three soil depths (0–15 cm, 15–30 cm, and 30–45 cm) located in Jiugong Mountain. Vertical traits of functional genes encoding microbial carbohydrate-active enzymes (CAZymes) were observed using metagenomic sequencing. Soil amino sugars were used as biomarkers to indicate microbial residue carbon (MRC). The results showed that GH1 (β-glucosidase: 147.49 TPM) and GH3 (β-glucosidase: 109.09 TPM) were the dominant genes for plant residue decomposition, and their abundance increased with soil depth and peaked in the deep soil at 600 m (GH1: 147.89 TPM; GH3: 109.59 TPM). The highest abundance of CAZymes for fungal and bacterial residue decomposition were GH18 (chitinase: 30.81 TPM) and GH23 (lysozyme: 58.02 TPM), respectively. The abundance of GH18 increased with soil depth, while GH23 showed the opposite trend. Moreover, MRC accumulation was significantly positively correlated with CAZymes involved in the degradation of hemicellulose (r = 0.577, p = 0.002). Compared with the soil before incubation, MRC in the topsoil at the low and middle altitudes after incubation increased by 4 % and 8 %, respectively, while MRC in the soils at 1500 m tended to decrease (p > 0.05). The mineralization capacity of SOC at 1500 m was significantly higher than that at 1200 m and 600 m (p < 0.05). Our results suggested that microbial function for degrading plant residue components, especially hemicellulose and lignin, contributed greatly to SOC accumulation and dynamics. These results were vital for understanding the roles of microbial functional traits in C cycling in forest.

Spatial changes of soil structural properties and organic carbon storage of arable farmland at Umuahia, Abia State

Precision agriculture requires that spatial changes of soil structural properties and soil organic carbon (SOC) accumulation be established for effective soil management. A research was carried out to ascertain the spatial variation of soil structural properties and organic carbon accumulation of an arable farmland at Umuahia. The experiment was conducted by delineating the land into three (3) portions. Three auger and core soil samples each were randomly collected from each portion, and this gave nine (9) observational points which were georeferenced. The soil samples were prepared and analysed in a laboratory for determination of parameters. The data generated were analysed for spatial variation using a GIS software package. The highest SOC accumulation of 26.46 ton / ha was obtained at the extreme north and northwestern regions of the land, while the lowest SOC accumulation of 19.71 ton / ha was obtained at extreme southeastern region of the land. The entire central area to the north western portion of the land had lowest bulk density (BD) of 1.33 kg / m3, while the southward to the north eastern portions of the land had the highest BD of 1.37 kg / m3. The highest hydraulic conductivity of 4.75 cm / mins was observed at the south western portion. The southward and extreme north eastern portions of the land had the highest mean weight diameter (MWD) of 0.95 mm, while the lowest MWD of 0.75 mm was observed at the central areaand extended to the north western portions of the land. There were also spatial changes in the total porosity, and micro aggregate stability indices across the land area. Suitable agronomic practices need to be adopted within the various portions of the land in managing the soil.

Effects of simulated atmospheric nitrogen deposition on the bacterial community structure and diversity of four distinct biocolonization types on stone monuments: a case study of the Leshan Giant Buddha, a world heritage site

AbstractAtmospheric nitrogen deposition may affect the biodeterioration process of stone monuments through direct and indirect pathways, but relevant studies are lacking. Therefore, taking the biologically colonized rocks around the Leshan Giant Buddha (World Heritage - Mixed Property) as the research objects, we studied the effects of multiple nitrogen addition levels (0, 9, 18, 36, 72 kg N hm-2 a-1; N0, N1; N2 ; N3; N4) on the bacterial community structure and soil nutrients on the surfaces of stones with four biocolonization types, including naked rock (NR), and lichen (LR), bryophyte (BS) and vascular plant (VS) colonization, to investigate the potential effect of atmospheric nitrogen deposition on the rock weathering of the Leshan Giant Buddha. The results demonstrated that nitrogen addition impacted soil carbon, nitrogen and phosphorus nutrients, as well as bacterial community structure and composition, but the responses to nitrogen input varied among different colonization types. Nitrogen fertilization promoted the accumulation of total organic carbon and total nitrogen in NR and LR, and increased the content of total phosphorus in VS. Bacterial α-diversity decreased with nitrogen addition in NR but increased with nitrogen addition in VS. Nitrogen addition significantly (R &gt; 0.9, p &lt; 0.01) changed the bacterial community composition in the four biocolonization types, and the changes were dominated by species replacement (contributed to 60.98%, 76.32%, 67.27% and 72.14% for bacterial diversity in NR, LR, BS and VS, respectively). Total nitrogen, dissolved organic nitrogen, dissolved organic nitrogen and total phosphorus were the most important ecological factors affecting bacterial community structure in NR, LR, BS and VS, respectively. Nitrogen addition enriched different bacterial taxa in the four biocolonization types. The results of this study provide basic data for the protection of stone monuments and the formulation of sustainable development strategies under a changing climate.