Soil Organic Carbon Transformation Research Articles

The Oasisization Process Promotes the Transformation of Soil Organic Carbon into Soil Inorganic Carbon

The dynamic fluctuations in the soil organic carbon (SOC) stock, a fundamental part of the terrestrial ecosystem’s carbon stock, are critical to preserving the global carbon balance. Oases in arid areas serve as critical interfaces between oasis ecosystems and deserts, with land use changes within these oases being key factors affecting soil organic carbon turnover. However, the response of the soil SOC-CO2-SIC (soil inorganic carbon) micro-carbon cycle to oasis processes and their underlying mechanisms remains unclear. Five land-use types in the Alar reclamation area—cotton field (CF), orchard (OR), forest land (FL), waste land (WL), and sandy land (SL)—were chosen as this study’s research subjects. Using stable carbon isotope technology, the transformation process of SOC in the varieties of land-use types from 0 to 100 cm was quantitatively analyzed. The results showed the following: (1) The SOC of diverse land-use types decreased with the increase in soil depth. There were also significant differences in SIC-δ13C values among the different land-use types. The PC(%) (0.73 g kg−1) of waste land was greatly higher than that of other land-use types (p < 0.05) (factor analysis of variance). (2) The CO2 fixation in cotton fields, orchards, forest lands, and waste land primarily originates from soil respiration, whereas, in sandy lands, it predominantly derives from atmospheric sources. (3) The redundancy analysis (RDA) results display that the primary influencing factors in the transfer of SOC to SIC are soil water content, pH, and microbial biomass carbon. Our research demonstrates that changes in land use patterns, as influenced by oasis processes, exert a significant impact on the conversion from SOC to SIC. This finding holds substantial significance for ecological land use management practices and carbon sequestration predictions in arid regions, particularly in the context of climate change.

Effect of long-term straw return on organic matter transformation by hydroxyl radical during paddy soil oxygenation

The generation of hydroxyl radicals (OH) mediated by Fe(II) has drawn increasing amounts of attention due to its significant role in the transformation of soil organic carbon (SOM) during redox fluctuations in paddy soil. This study further examined the effect of long-term (since 1984) straw return on Fe(II) on driving OH formation and SOM transformation upon paddy soils oxygenation. We found that long-term straw return could inhibit the OH and CO2 production in abiotic processes. The OH production decreased from 190.4 to 133.4 µM as the straw return amount increased from 0 to 19.16 t·hm−2·year−1. Moreover, 14.7–38.6 % of the CO2 production was associated with OH during oxygenation. By combining radical quenching and OM extraction, we determined that straw return could increase O2 reduction to H2O2 through a two-electron transfer pathway. Based on chemical extraction, Mössbauer spectra and multilinear regression model, we demonstrated that straw return resulted in more active Fe(II) species that controls the OH production. The results of 3DEEMs and FT-ICR MS showed that oxidative transformation can be accomplished by the introduction of OH to aromatic structures or olefins through ring opening and hydroxylation mechanisms. And OM at high straw return concentrations was likely oxidized by OH into bioavailable aliphatic compounds. Therefore, this study highlights the underappreciating effects of long-term straw return on Fe(II) oxidation in driving OH generation and SOM transformation in paddy soil redox fluctuation events.

Spatial soil heterogeneity rather than the invasion of Spartina alterniflora drives soil bacterial community assembly in an Eastern Chinese intertidal zone along an estuary coastline

The invasion of Spartina alterniflora (S. alterniflora) significantly influences the stability and transformation of soil organic carbon in coastal ecosystems. However, the impact of this invasion on the assembly of soil bacterial communities along estuary coastlines and soil profiles remains unclear. This study involved collecting soil samples from different environments (areas covered with S. alterniflora vs. barren flats) along the coastline of an estuary. The samples were taken at different depths (0–20 cm, 20–40 cm, 40–60 cm, 60–80 cm, 80–100 cm) within a 1-meter soil profile in the intertidal area of Xiaoyangkou Estuary in Jiangsu, China. The invasion of S. alterniflora had a notable impact on soil SOM (soil organic matter), DOC (dissolved organic carbon), POC (particulate organic carbon), and MAOC (mineral-associated organic carbon). Concurrently, the soil layer primarily influenced the levels of soil DOC and MAOC. The dominant bacterial communities inside the soil consisted of Proteobacteria (27.4–50.2 %), Bacteroidota (5.2–23.3 %), and Desulfobacterota (9.5–19.8 %), which participates in several elemental cycles, such as the carbon, nitrogen, sulfur, and phosphorus cycles. The changes in the patterns and functions of bacterial communities related to carbon cycling were mostly associated with the estuary shoreline, rather than being influenced by the invasion of S. alterniflora or variations in soil depths. Soil total carbon (TC) and SOM displayed a greater influence than other soil organic fractions on the distribution of the bacterial community. Furthermore, elements such as As, Cr, and Zn also exerted a significant impact on the assembly of soil bacterial communities. Our research findings suggest that the influence of S. alterniflora invasion on the composition and functioning of soil bacterial communities is contingent upon the specific features of the area. These characteristics, in turn, control the stability of soil carbon and the transformation of various types of soil carbon.

Features of Soil Organic Carbon Transformations in the Southern Area of the East European Plain

Features of Soil Organic Carbon Transformations in the Southern Area of the East European Plain

Progress on the Effect of Nitrogen on Transformation of Soil Organic Carbon

Carbon and nitrogen are the essential elements constituting living organisms and are closely coupled during biogeochemical cycles. Due to the atmospheric nitrogen deposition and increased agricultural nitrogen fertilizer input, the effect of nitrogen on the sequestration of soil organic carbon (SOC) is controversial. To facilitate a comprehensive understanding of this issue, the progress of recent studies on the different SOC stabilization mechanisms is reviewed. Based on the differences in the stability and fate mechanisms of particulate organic carbon (POC) and mineral-associated organic carbon (MAOC), nitrogen input can increase POC input and inhibit microbial decomposition of POC by increasing terrestrial biomass, changing the quality of litter and promoting the formation of aggregates. N input reduces the chemical stability of MAOC by altering the chemical bonding of mineral–organic complexes. This study has promising implications for understanding the effect of N on SOC transformation by different stabilization mechanisms to promote soil carbon sequestration.

Salinity Effects on Microbial Derived-C of Coastal Wetland Soils in the Yellow River Delta

Microorganisms play a crucial role in regulating the turnover and transformation of soil organic carbon (SOC), whereas microbial contribution to SOC formation and storage is still unclear in coastal wetlands. In this study, we collected topsoil (0–20 cm) with 7 salinity concentrations and explored the shifts in microbial residues [represented by amino sugar (AS)] and their contribution to the SOC pool of coastal wetlands in the Yellow River delta. The gradually increasing soil salinity reduced soil water content (SWC), SOC, and soil nitrogen (N), especially in high salinity soils of coastal wetlands. Total ASs and their ratio to SOC, respectively, decreased by 90.56 and 66.35% from low salinity to high salinity soils, indicating that coastal wetlands with high salinity restrained microbial residue accumulation and microbial residue-C retention in the SOC pool. Together with redundancy analysis and path analysis, we found that SWC, pH, SOC, soil N, and glucosamine/muramic arid were positively associated with the ratio of ASs to SOC. The higher available soil resource (i.e., water, C substrate, and nutrient) increased microbial residue accumulation, promoting microbial derived-C contribution to SOC in low salinity coastal wetlands. The greatly decreased microbial residue contribution to SOC might be ascribed to microbial stress strategy and low available C substrate in coastal wetlands with high salinity concentration. Additionally, the gradually increasing salinity reduced fungal residue contribution to SOC but did not change bacterial residue contribution to SOC. These findings indicated that changed fungal residues would substantially influence SOC storage. Our study elucidates microbial contribution to SOC pool through residue reservoir in coastal wetlands and pushes microbial metabolites to a new application in global wetland SOC cycling.

Effect of long-term fertilization on bacterial community in a sandy loam soil and its relation to organic carbon accumulation

Fertilization can affect the transformation of soil organic carbon (SOC) and soil microbial community composition. However, thus far, how SOC accumulation in association with bacterial community is still unclear. We collected arable soils (aquic inceptisol) from a long-term fertilization experiment (20 years) including compost (CM), inorganic nitrogen + phosphorus + potassium (NPK), half compost N plus half inorganic fertilizer N (HCM), NP, NK, PK, and untreated (Control). We investigated the relationship between the SOC accumulation rate and bacterial community composition measured by high-throughput sequencing. The highest SOC accumulation rate was observed in the compost treatments. Furthermore, compost and balanced NPK treatments increased soil carbohydrate content significantly (P < 0.05), while no such enhancement was observed following NK and PK application. Compared with the Control, fertilization substantially reduced the effective diffusion coefficient of oxygen in soil. Meanwhile, fertilization lowered the relative abundance (RA) of Bacteroidetes but increased the RA of Proteobacteria. Compost application increased the RA of Firmicutes, while inorganic fertilizers reduced it. The RA of Proteobacteria and Firmicutes were significantly and positively correlated with the SOC and carbohydrate content and the SOC accumulation rate (P < 0.05). SOC accumulation was also accompanied with the reduction in the effective diffusion coefficient of oxygen in soil. Our results indicated that poor aeration may induce a shift in the microbial community composition and a transition from aerobic to anaerobic degradation of SOC, thereby favoring SOC accumulation.

Intercropping and N application enhance soil dissolved organic carbon concentration with complicated chemical composition

Soil dissolved organic carbon (DOC) plays a critical role in migration and transformation of soil organic carbon. For revealing effects of intercropping and N application on dynamics of DOC concentration and chemical structure, a multi-year located field experiment with cropping patterns (maize monocropping and maize-potato intercropping) subjected to four N levels (0 kg ha−1, 125 kg ha−1, 250 kg ha−1, 375 kg ha−1) was conducted. The results showed that N application raised DOC concentration while DOC accumulation, had a quadratic relationship with N application rate during the entire growth period of maize. At the same N level, intercropping increased the concentration and accumulation of DOC compared with monocropping. Meanwhile N application promoted the contents of amines and aromatic compounds and average molecular weight of DOC molecules, which reached the highest value at rate of 125 kg N ha-1. Compared with monocropping at the same N level, there was a tendency to increase the content of amines and aromatic compounds and the average molecular weight of DOC in intercropping, thus improving the degree of humification and aromatization of soil DOC. Soil temperature, water content and NH4+-N were the main factors mediating DOC concentration, while DOC concentration and soil temperature significantly affected the chemical structure of DOC. The structural equation model showed intercropping and N application elevated soil DOC concentration by increasing soil temperature, litter and root biomass, and the improvement of DOC concentration and soil temperature further enhanced the average molecular weight of DOC, resulting in accumulation of DOC.

林冠氮添加和林下植被去除对杉木林土壤有机碳组分的影响

为探讨氮添加和林下植被管理对杉木人工林土壤有机碳组分的影响，以福建沙县官庄国有林场杉木人工林为对象，设置对照（CK）、林冠氮添加（CN）、林下植被去除（UR）、林冠氮添加和林下植被去除（CNUR）4个处理的野外控制实验，研究林冠氮添加和林下植被去除对土壤总有机碳、惰性有机碳、易氧化有机碳、颗粒有机碳、微生物生物量碳和水溶性有机碳的影响。结果表明：5年CN添加处理显著降低易氧化有机碳（10—20 cm）和微生物生物量碳（20—40 cm）含量，增加表层土壤颗粒有机碳占总有机碳的比例。UR处理对土壤有机碳组分的作用不显著，而CNUR处理显著降低表层土壤水溶性有机碳含量及其比例。土壤各有机碳组分均与土壤含水量、可溶性有机氮、微生物生物量氮和铵态氮呈显著正相关。研究表明，土壤活性有机碳比惰性有机碳对林冠氮添加（5年）的响应更敏感，且表现为中下层土壤响应大于表层土壤，短期氮添加能促进土壤活性有机碳的分解，而林下植被去除在短时间内可能通过改变土壤含水量和可利用氮减缓有机碳的分解与转化，从而补偿由于氮添加引起的土壤活性有机碳下降，未来需要通过长期氮添加实验进一步研究土壤有机碳动态变化的响应机制。;Increased nitrogen (N) deposition due to anthropogenic activities has been recognized to have important effects on forest carbon dynamic and plant diversity. However, most N manipulative experiments from the understory have suggested that external N addition can influence soil organic carbon pool, very little is known about the effects of canopy N addition on soil organic carbon fractions. To investigate these effects, a field experiment was carried out with four different treatments including control (CK), canopy N addition (CN, 25 kg N hm^-2a^-1, understory removal (UR), and canopy N addition plus understory removal (CNUR, 25 kg N hm^-2a^-1) in a Chinese fir plantation at Shaxian State Forest Farm, Fujian Province. The experiment was started in June 2014 and was a random block design with four replicates. After 5-years treatment, soil samples were collected by a stainlessness core (3.5 cm diameter, 60 cm length) and separated into three depths of 0-10 cm, 10-20 cm, and 20-40 cm. Then, total organic carbon (TOC), recalcitrant organic carbon (ROC), readily oxidizable organic carbon (ROOC), particular organic carbon (POC), microbial biomass carbon (MBC), and water-soluble organic carbon (WSOC) were determined. The results showed that soil TOC and ROC contents in the CN treatment had no significant changes, but the contents of soil ROOC at the 10-20 cm layer and MBC at the 20-40 cm layer, and the proportion of WSOC to TOC in surface soil layer significantly decreased and increased, respectively, compared to CK treatment. Moreover, single UR treatment did not influence soil organic carbon components, while CNUR treatment significantly decreased soil WSOC contents and proportions to TOC. Pearson analysis showed that both soil labile and recalcitrant organic carbons were positively correlated with soil moisture, water-soluble organic nitrogen, microbial biomass nitrogen, and ammonium nitrogen. These results indicated that soil labile organic carbon (LOC) was more sensitive to the short-term CN (5 years) compared to ROC, and the responses of subsoil (10-40 cm) were larger than top soil (0-10 cm). CN could promote soil LOC decomposition and consequently have a negative effect on the accumulation of soil organic carbon. However, UR was likely to offset the decrease of soil LOC induced by CN in the short time since UR would change the soil water and available nitrogen to decline the decomposition and transformation of soil organic carbon. All these findings suggest that the effects of CN and UR on soil organic carbon fractions and dynamics are complex, which requires a much longer-term manipulative experiment to understand the responding mechanism of soil carbon dynamics in the future.

Soil organic carbon transformation and dynamics of microorganisms under different organic amendments

Organic amendments (OAs) application is a practical strategy to improve soil organic carbon (SOC) in agriculture. The present study evaluated the impact of different OAs on the transformation of carbon and the dynamics of microorganisms in a 77-day incubation experiment. The OA treatments applied included wheat straw (U + WS), pig manure (U + PM), compost (U + CP), and improved compost (U + IC), and the no amendment group was the CK. After incubation, the SOC increased significantly in the U + WS group, but the other OA treatments had no significant effect relative to the CK. Among the OA treatments, U + CP and U + IC had lower CO2-C cumulative mineralization and the highest humification of dissolved organic carbon (DOC). U + PM had the lowest SOC content and the lowest aromatization of DOC. Redundancy analyses (RDA) showed that the CO2-C cumulative mineralization directly influenced the DOC, extracted organic carbon (EOC) and microbial biomass carbon (MBC) in all treatments. Proteobacteria positively correlated with SOC and MBC, Bacteroidetes were significantly related to DOC, and Gemmatimonadetes had a significant negative relationship with CO2-C cumulative mineralization. These results showed that U + CP and U + IC were more conducive to carbon sequestration, and U + PM was the most unfavourable during the incubation. Wheat straw played an important role in the steady improvement of the SOC.

Sediment deposition changes the relationship between soil organic and inorganic carbon: Evidence from the Chinese Loess Plateau

Soil erosion has a significant impact on the distribution and sequestration of soil carbon, affecting the global C cycle. Although the transport and transformation of soil organic carbon (SOC) during the erosion process have been widely studied, there is still a lack of understanding of the impacts of soil erosion on soil inorganic carbon (SIC) and its relationships with SOC. In this study, 62 erosional sites (including 16 gullies, 17 grasslands, 16 forestlands and 13 croplands) and 35 depositional sites (check dams) on the Chinese Loess Plateau were selected. Partial least squares regression (PLSR) was carried out to explore the main influential factors of SIC variation. The results showed that, compared with erosional sites, the mean SOC and SIC content in depositional sites (0–25 cm) increased by 24.4 % and 15.4 %, respectively. Both SOC and SIC contents in depositional sites exhibited a decreasing tendency with depth. SIC was significantly negatively correlated with SOC (R2 = 0.25, P < 0.01) across all erosional sites (0–25 cm). In contrast, SIC was significantly positively correlated with SOC in all depositional layers beneath 100 cm (P < 0.05), and R2 increased from 0.23 (100–200 cm) to 0.68 (300–400 cm) and then decreased to 0.46 (500–600 cm). Sediment transport and deposition converted the negative relationship between SOC and SIC in the erosional sites to a positive relationship in deep depositional soil. The PLSR analysis suggested that SOC had an important (VIP > 1) positive impact on predicting SIC in depositional sites, which indicated that SOC increase contributed to enhancing SIC accumulation under the depositional conditions in the semi-arid region. We believe that the influencing mechanism of soil erosion on the relationship between SOC and SIC revealed in this study will contribute to understanding the soil C cycle.

Effects of litter removal and nitrogen addition on carbon and nitrogen in different soil fractions in a subtropical broad-leaved forest.

The increasing nitrogen deposition due to human activities has impacted forest ecosystems to a large extent. The organic carbon and nitrogen released from decomposing litters play an important role in the formation, stability and transformation of soil organic carbon and nitrogen. We collected soil samples from a subtropical evergreen broadleaved forest experiment with nitrogen deposition [control (0), LN (75 kg·hm-2·a-1), HN (150 kg·hm-2·a-1)] and litter control (litter retained and litter removal) for eight years. After extracted by solution of K2SO4, Na2B4O7, Na4P2O7, NaOH, H2SO4, Na2S2O4 and HF step by step, carbon and nitrogen in each extraction was analyzed. The results showed that overall most of soil carbon and nitrogen existed in the Humin fraction, accounting for 33.5% of the total carbon and 33.3% of the total nitrogen. The soluble total carbon and nitrogen extracted by Na2B4O7 solution was the highest, followed by NaOH and Na4P2O7 solution. The soluble total carbon, soluble total nitrogen and soluble organic nitrogen of soil extracted by three reagents accounted for 46.2%, 47.9%, and 76.5% of the total extractions, respectively. In addition, nitrogen addition significantly increased carbon and nitrogen content in Na2S2O4 and Humin fractions. Litter removal reduced carbon content in Na2B4O7, H2SO4, Na2S2O4 and Humin fractions, and nitrogen content in NaOH, HF and Humin fractions. The nitrogen content in the K2SO4 extraction was significantly increased by both litter remained and nitrogen addition. Our results demonstrated that litter and nitrogen added could mutually affect carbon and nitrogen concentration of soil fractions with different chemical stability, with consequences on the process of soil carbon and nitrogen.

Inorganic Nitrogen Addition Affects Soil Respiration and Belowground Organic Carbon Fraction for a Pinus tabuliformis Forest

The capability of forest ecosystems to sequester carbon from the atmosphere largely depends on the interaction of soil organic matter and nitrogen, and thus, this process will be greatly influenced by nitrogen deposition under the future scenario of global change. To clarify this interaction, the current study explored the variations in soil carbon fraction and soil respiration with different levels of nitrogen deposition. NH4NO3 was added at concentrations of 0, 50, 100, 200, and 400 kg N ha−1 year−1 separately on twenty 100 m2 plots in a Pinus tabuliformis Carr forest in northern China. Soil samples were analyzed for their nutrient content and biophysical properties two years after nitrogen application, and the soil respiration rate was measured every month during the study period. Seasonal variation and nitrogen addition significantly affected soil respiration rate. On average, nitrogen addition significantly reduced the annual soil respiration rate by 23.74%. Fine root biomass significantly decreased by an average of 43.55% in nitrogen treatment plots compared to the control plot. However, the average proportions of autumn and winter soil respiration rates out of the annual cumulative soil respiration rate greatly increased from 23.57% and 11.04% to 25.90% and 12.18%, respectively. The soil microbial biomass carbon content in the control plot was 342.39 mg kg−1, 23.50% higher than the average value in nitrogen treatment plots. The soil dissolved organic carbon was reduced by 22.60%, on average, following nitrogen addition. Significant correlations were detected between fine root biomass and the annual cumulative soil respiration rate, soil microbial biomass carbon content, and soil dissolved organic carbon content. This demonstrates that nitrogen addition affects soil organic carbon transformation and carbon emission, mainly by depressing fine root production.

Effect of polymer materials on soil structure and organic carbon under drip irrigation

Polymer materials have broad potential applications for saving water and increasing crop yields in irrigated agricultural systems. However, little is known about how polymers affect the distribution and transformation of soil organic carbon. The purpose of this study is to evaluate the effects of humic acid (H) (an alkali extract of cottonseed meal), modified polymer (P) (a mixture of anionic polyacrylamide, polyvinyl alcohol, and manganese sulfate), and composite polymer (HP) (a 1:1 mixture of H and P) applied with drip irrigation on soil aggregate stability and organic carbon stability. The results demonstrated that the H and P treatments significantly increased soil aggregate stability and organic carbon content, compared with the HP treatment. Compared with the controls for corpped soils (CK) and uncorpped soils (CK-NP), the DR0.25 (>0.25 mm soil mechanical-stable aggregate), W-MWD (mean weight diameter of water stable aggregate), and W-GMD (geometric mean diameter of water stable aggregate) of the H treatment increased by 3.9%, 33.1%, and 23.2%, respectively (p < 0.05); the WR0.25 (>0.25 mm soil water stable aggregate), W-MWD, and W-GMD of the H-NP treatment (H treatment for uncorpped soils) increased by 44.7%, 38.0%, and 37.6%, respectively (p < 0.05); the WR0.25 and W-GMD of the P treatment increased by 29.8% and 26.8%, respectively (p < 0.05); and the W-GMD of the P-NP treatment (P treatment for uncorpped soils) increased by 16.5% (p < 0.05). Although the HP treatment also increased the organic carbon content of soil aggregates, it was less effective for improving soil aggregate stability. During the first 20 days of incubation, the mineralisation rate of the CK was the highest. Then, the mineralisation rates for the H and HP treatments increased more rapidly than that of the CK (p < 0.05), with increases of 27.6% and 54.4%, respectively. Results from field experiments (soil microbial biomass carbon content) supported this result. Compared with the CK, the H and P treatments rapidly increased soil labile organic carbon (LOC). The LOC content for the H treatment was 28.9% and 21.6% higher than that of the CK after 30 and 90 days, respectively (p < 0.05), whereas the LOC content for the P treatment was 32.8% and 20.2% higher than that of the CK after 60 and 90 days, respectively (p < 0.05). Redundancy analyses revealed that cultivation vs fallow treatments affected how polymer materials transform soil organic carbon. Cultivation allowed humic acid to improve soil aggregate mechanical-stability, promoting microbial decomposition of carbon and increasing organic carbon content. Modified polymer improved soil aggregate water-stability and reduced aggregate destruction, increasing the proportion of soil organic carbon that can be easily oxidised.

Impacts of Biochar and Straw Application on Soil Organic Carbon Transformation

To explore the effects of biochar and straw application on soil carbon constitution and transformation, an incubation experiment was conducted to study the characteristics of the release of carbon dioxide,as well as the changes in microbial biomass carbon and organic carbon in soil after applying biochar or straw only, or biochar plus straw. The results showed that the straw mineralization rate of organic carbon in soil was 21.50% at 2% application level, which was much higher than that of biochar (8.09%). With the same addition amount of biochar and straw at 4% level for 200 days incubation, the soil organic carbon content was 24.40 and 17.40 g·kg^-1,respectively. It suggested that the positive impact of biochar application on improving soil organic carbon was greater than that of straw. The application of biochar had protective function on soil original organic carbon. Biochar promoted the straw mineralization and resulted in positive interaction effect between biochar and straw on mineralization of soil organic carbon. The application of straw increased soil microbial biomass carbon (MBC) greatly, while biochar had less impact on MBC. The application of straw and biochar also increased soil microbial biomass carbon, but the interaction effect could be positive or negative, which was dependent on the incubation time or application rate.

Change in water extractable organic carbon and microbial PLFAs of biochar during incubation with an acidic paddy soil

Biochar has been considered to affect the transformation of soil organic carbon, soil microbial activity and diversity when applied to soil. However, the changes in chemical and biological properties of biochar itself in soil have not been fully determined. In this study, various biochar samples were obtained from three crop straws (rice, peanut and corn) and two wood chips (bamboo and pine), and incubated with an acidic paddy soil. We examined the changes of biochar water extractable organic carbon (WEOC) content and its ultraviolet (UV) absorbance at 280 nm during incubation period, and also investigated the microbial phospholipid fatty acids (PLFAs) profile of biochar after 75 days of incubation. The WEOC content of biochars decreased at the end of incubation, except for the biochar pyrolysed from bamboo chips at 400°C. An average reduction rate of 61.2% in WEOC concentration for straw biochars occurred within the first 15 days, while no significant change was observed for all biochars between day 15 and 45, and a slight increase in WEOC occurred for all biochars in the last 30 days. There was a positive relationship between biochar WEOC content and its UV absorbance properties. The microbial PLFAs concentrations of biochars varied from 15.56 to 60.35 nmol g–1, and there was a greater abundance in content and species for corn straw biochars than for the other types of biochars. General bacteria were the dominant microbial group that colonised biochar sample, while gram-positive bacterial and fungi were less in abundance. The chemical properties of fresh biochar were well correlated with total PLFAs concentrations, and significantly related to the composition of microbial community. We concluded that the WEOC component of most biochars change within such short-term application to soil, and the WEOC in combined with the pH and nutrient status of biochar, can alter the type and abundance of microorganisms that colonised biochar.

Relating microbial community structure to functioning in forest soil organic carbon transformation and turnover.

Forest soils store vast amounts of terrestrial carbon, but we are still limited in mechanistic understanding on how soil organic carbon (SOC) stabilization or turnover is controlled by biotic and abiotic factors in forest ecosystems. We used phospholipid fatty acids (PLFAs) as biomarker to study soil microbial community structure and measured activities of five extracellular enzymes involved in the degradation of cellulose (i.e., β-1,4-glucosidase and cellobiohydrolase), chitin (i.e., β-1,4-N-acetylglucosaminidase), and lignin (i.e., phenol oxidase and peroxidase) as indicators of soil microbial functioning in carbon transformation or turnover across varying biotic and abiotic conditions in a typical temperate forest ecosystem in central China. Redundancy analysis (RDA) was performed to determine the interrelationship between individual PFLAs and biotic and abiotic site factors as well as the linkage between soil microbial structure and function. Path analysis was further conducted to examine the controls of site factors on soil microbial community structure and the regulatory pathway of changes in SOC relating to microbial community structure and function. We found that soil microbial community structure is strongly influenced by water, temperature, SOC, fine root mass, clay content, and C/N ratio in soils and that the relative abundance of Gram-negative bacteria, saprophytic fungi, and actinomycetes explained most of the variations in the specific activities of soil enzymes involved in SOC transformation or turnover. The abundance of soil bacterial communities is strongly linked with the extracellular enzymes involved in carbon transformation, whereas the abundance of saprophytic fungi is associated with activities of extracellular enzymes driving carbon oxidation. Findings in this study demonstrate the complex interactions and linkage among plant traits, microenvironment, and soil physiochemical properties in affecting SOC via microbial regulations.

Soil Organic Carbon Transformation and Related Properties in Urban Soil Under Impervious Surfaces

Installation of impervious surface in urban area prevents the exchange of material and energy between soil and other environmental counterparts, thereby resulting in negative effects on soil function and urban environment. Soil samples were collected at 0-20 cm depth in Nanjing City, China, in which seven sites were selected for urban open soils, and fourteen sites with similar parent material were selected for the impervious-covered soils, to examine the effect of impervious surface on soil properties and microbial activities, and to determine the most important soil properties associated with soil organic carbon (SOC) transformation in the urban soils covered by impervious surfaces. Soil organic carbon and water-soluble organic carbon (WSOC) concentrations, potential carbon (C) and nitrogen (N) mineralization rates, basal respiration, and physicochemical properties with respect to C transformation were measured. Installation of impervious surface severely affected soil physicochemical properties and microbial activities, e.g., it significantly decreased total N contents, potential C mineralization and basal respiration rate (P < 0.01), while increased pH, clay and Olsen-P concentrations. Soil organic carbon in the sealed soils at 0-20 cm was 2.35 kg m−2, which was significantly lower than the value of 4.52 kg m−2 in the open soils (P < 0.05). Canonical correlation analysis showed WSOC played a major role in determining SOC transformation in the impervious-covered soil, and it was highly correlated with total N content and potential C mineralization rate. These findings demonstrate that installation of impervious surface in urban area, which will result in decreases of SOC and total N concentrations and soil microbial activities, has certain negative consequences for soil fertility and long-term storage of SOC.

Changes of CO2 emission and labile organic carbon as influenced by rice straw and different water regimes

Crop residues under different water regimes can cause significant alterations in soil organic carbon fractions, and in turn, soil-atmospheric carbon dioxide (CO2) emissions. To evaluate the effect of rice straw application on CO2 emissions and labile organic carbon fractions under different water regimes, an incubation experiment was conducted for 90 days. Ten treatments were developed from the interaction between five water levels (100, 85, 70, 55, and 40 % of water-holding capacity (WHC)) with and without incorporation of rice straw. Peaks of CO2 fluxes were observed after 13 days of rice straw incorporation, which decreased gradually till the end of the incubation period. The incorporation of rice straw caused significant increases in CO2 fluxes by 2.77-2.83 times from the paddy soil. In the presence of rice straw, the highest CO2 fluxes were generally observed at W3 (70 % of WHC), whereas the lowest fluxes were occurred at W1 (100 % of WHC). Addition of rice straw under a range of water regimes markedly improved the transformation of soil organic carbon and labile organic carbon pools such as dissolved organic carbon, microbial biomass carbon, light fraction organic carbon, particulate organic carbon, and permanganate oxidizable carbon. The significant correla- tions between all labile soil organic carbon fractions and CO2 concentrations confirmed their important roles in the emission of CO2 from the paddy soil. In summary, the results suggest that light fraction organic carbon, particu- late organic carbon, and permanganate oxidizable carbon were more sensitive indicators for CO2 emissions and organic matter alterations as compared to other carbon fractions.

盐分和底物对黄河三角洲区土壤有机碳分解与转化的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 盐分和底物对黄河三角洲区土壤有机碳分解与转化的影响 DOI: 10.5846/stxb201206290914 作者: 作者单位: 滨州学院山东省黄河三角洲生态环境重点实验室 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（41101220，41101277）；山东省优秀中青年科学家奖励基金项目（BS2011HZ001）；山东省高校科研发展计划项目（J13LE58）；滨州学院国家级大学生创新训练计划项目（201210449127）；滨州学院博士基金项目（2008Y05） Effects of salinity and exogenous substrates on the decomposition and transformation of soil organic carbon in the Yellow River Delta Author: Affiliation: Shangdong Key laboratory of Eco-enviromental Science for Yellow River Delta, Binzhou University, Binzhou 256603, Shandong, China Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:土壤盐碱化能抑制微生物活性，影响土壤有机碳的分解与转化。以黄河三角洲盐碱耕地为研究对象，采用室内恒温培养法，设置3个NaCl盐分梯度（S1：0.1%；S2：0.5%；S3：0.9%），通过在土壤中添加不同底物（CK：不添加底物；N：添加氮；C：添加碳；C+N：添加碳+氮），研究该土壤释放CO2-C量、土壤微生物生物量碳（SMBC）、土壤微生物呼吸商（qCO2）及溶解性有机碳（DOC）对盐分和底物的响应。结果表明：在45 d的培养期内，CK、N处理中S1盐分土壤释放CO2-C量最高，S2和S3明显低于S1，降低幅度分别为18.3%-23.7%和24.3%-39.8%。C、C+N处理中3个盐分土壤释放CO2-C量差异较小，特别是在C+N处理中，3个盐分土壤释放CO2-C差异不显著。4个底物处理中，SMBC均在S1和S2盐分中含量较高，S3盐分最低。与CK相比，N处理并不能提高SMBC含量，C、C+N处理可明显提高SMBC，但S1和S2盐分土壤提高的幅度（80.4%-80.5%、58.0%-58.7%）明显高于S3（68.9%、49.7%）。4个底物处理中，qCO2均在S1盐分土壤中最高，C、C+N处理可明显提高qCO2。CK、N处理中3个盐分土壤DOC差异不显著，C、C+N处理中S3盐分土壤DOC较高。说明在无碳源输入条件下，增加盐分含量能明显抑制土壤释放CO2量。添加碳源后，盐分含量对土壤释放CO2的影响变小。微生物对碳源和盐分胁迫的响应较快，添加碳源能明显提高微生物数量及其活性。但较高盐分（含盐量 > 0.5%）可明显降低土壤微生物活性及对外源碳的利用率，导致较高盐分SMBC及qCO2较低而DOC较高。 Abstract:In the Yellow River Delta, nearly 50 percent of soils are saline and alkaline. Soil salinization can suppress microbial activity and thus affect the decomposition and transformation of soil organic carbon, while little information was found about the effects of salinity and exogenous C and N amendment on the decomposition and transformation of soil organic carbon in this area. A laboratory experiment was conducted to investigate the effects of soil salinity and exogenous substances on the turnover of organic carbon under conditions with 25℃ and 60% water holding capacity over 45 days. Three levels of salinity (S1: 0.1%; S2: 0.5%; S3: 0.9%) using NaCl (w/w) were imposed in the saline-alkaline cultivated soil in Yellow River Delta. Soil was amended with or without C (750 mg/kg) or inorganic N (30 mg/kg) as glucose or NH4Cl, and 4 treatments were established, including (Control: no substrates addition, N: NH4Cl addition, C: glucose addition, C+N: glucose and NH4Cl addition). The CO2-C emission, soil microbial biomass carbon (SMBC), dissolved organic carbon (DOC) and calculation of the respiratory quotient(qCO2)were determined. Without glucose addition, the cumulative amount of CO2-C emission was highest in S1 during the incubation, and it was decreased by 18.3%-23.7% and 24.3%-39.8% in S2 and S3 compared with S1, respectively. After glucose addition, the cumulative amount of CO2-C emission little changed among the three salinity soils, and especially it was no significant difference between the three salinity soils in C+N treatment. SMBC was higher in S1 and S2 than that in S3 under the four treatments with substrates addition. Addition of NH4Cl had no significant effect, but addition of glucose significantly increased SMBC, and SMBC increased by 80.4%-80.5% or 58.0%-58.7% in S1 and S2 in C or C+N treatment, and only 68.9% or 49.7% in S3. The qCO2 was significant higher in S1 than that in S2 and S3, and it was significantly improved with glucose addition. Compare with the control, DOC reminded unchanged in the N treatment, but it increased in S3 with glucose addition. It was suggested that the CO2 emission could be depressed with the increase of soil salinity without C addition, and soil salinity had little influence on CO2 emission after C addition. Microorganism was more sensitive to exogenous carbon and soil salinity. The size and the activity of microbial biomass would be improved with C addition, but higher salinity (>0.5%) could depress the microbial activity and the utilization of exogenous carbon, resulting in higher SMBC and qCO2 and lower DOC in higher salinity soil. 参考文献 相似文献 引证文献