Carbon To Nitrogen Ratio Research Articles

Differences in the composition, source, and stability of suspended particulate matter and sediment organic matter in Hulun Lake, China.

The occurrence, migration, transformation, and stability of sediment (SOM) and suspended particulate (SPOM) organic matters have important effects on the environmental behaviors of carbon, nitrogen, phosphorus, and other pollutants in a water environment. The content, composition, fluorescence characteristics, source, and stability of SOM and SPOM in Hulun Lake, a typical lake in cold and arid region of China, were compared by sequential extraction, three-dimensional fluorescence spectroscopy, parallel factor technique, carbon-nitrogen ratio, and stable carbon isotope. Contents of SOM and SPOM in north and west were higher than those in east and south. The average content of SPOM (24.70 ± 4.63g/kg) was slightly higher than that of SOM (23.04 ± 10.27g/kg), but the difference was not significant. Humin was the dominant component in SOM and SPOM, accounting for 73.7% and 61.2%, respectively. Humus was the main fluorescence component of water-extractable organic matter in SOM and SPOM, accounting for 79.9% and 70.4%, respectively, of the total fluorescence intensity. SOM and SPOM were derived from terrestrial sources with a relative contribution rate of about 70%. SPOM was more influenced by autochthonous sources and had a significantly lower humification degree and stability than SOM. Effects of climate changes on migration, transformation, stability, and bioavailability of organic matters and endogenous pollutants closely related to organic matters in lakes of cold and arid regions should be paid attention in the future.

The Composition of Dissolved Organic Matter in Arable Lands: Does Soil Management Practice Matter?

Dissolved organic matter (DOM) is a key soil quality property, indicative of the organic matter stored in the soil, which may also be a function of temporal variation. This study examines whether DOM is a robust property of the soil, controlling fertility, or if it may change with time. Altogether eight sets of soil samples were collected in 2018 and 2019 from the cultivated topsoil (0–10 cm) of cropland and from a nearby grassland near Martonvásár, Hungary. The study sites were characterized by Chernozem soil and were part of a long-term experimental project comparing the effects of manure application and fertilization to the control under maize and wheat monocultures. DOM was extracted from the samples with distilled water. The dissolved organic carbon (DOC), total dissolved nitrogen (DN), biological index (BIX), fluorescence index (FI), humification index (HIX), carbon nitrogen (C/N) ratio and specific ultraviolet absorbance at 254 nm (SUVA254) index were studied in the arable soils, and the results showed that all the DOM samples were humified, suggesting relevant microbiological contributions to the decomposition of OM and its conversion into more complex molecules (FI = 1.2–1.5, BIX = ~0.5, and HIX = ~0.9). Temporal variations were detected only for the permanent grassland where higher DOM concentration was found in spring. This increased DOM content mainly originated from humified, solid phase associated, recalcitrant OM. In contrast, there were no differences among fertilization treatments and sampling dates under cropfield conditions. Moreover, climatic conditions were not proven as a general ruler of DOM properties. Therefore, momentary DOM alone is not necessarily the direct property of soil organic matter under cropfield conditions. The application of this measure needs further details of sampling conditions to achieve adequate comparability.

Organic materials with high C/N ratio: more beneficial to soil improvement and soil health.

In order to figure out the effect of organic fertilizers with different carbon-nitrogen (C/N) ratios on the soil improvement and the healthy cultivation, the pot experiment method was used to study effects on the physical and chemical properties and the bacterial community structure of sandy loam soil using five treatments of chemical fertilizer application with the C/N ratios of 15 (CN15), 20 (CN20), 25 (CN25), 30 (CN30) and the control (CK) respectively. Results show that the organic materials with different C/N ratios significantly improve the soil porosity and water content, which all show a linear change rule with the C/N ratio. It can also significantly increase the soil total carbon, total nitrogen, soil C/N ratio, soil microbial biomass carbon, microbial biomass nitrogen and microbial biomass C/N ratio. Among them, CN30 significantly increases the soil total carbon and C/N ratio, which are 5.34-24.13% and 8.87-30.15% respectively compared with other treatments. It can be also found that the dominant flora (at the phylum level) of each treatment are Actinobacteria, Proteobacteria and Chlorobi. The CN30 treatment presents the most obvious improvement in the diversity and richness of the soil bacterial community and is more conducive to the growth and reproduction of Proteobacteria and Firmicutes. The correlation analysis shows that Ctotal/Ntotal and Cmic/Nmic are the most important environmental factors affecting the soil physical and chemical properties and their correlation with the bacterial communities. The higher C/N ratio of organic materials results in a more significant improvement of the soil physical and chemical properties. This study provides a new theoretical basis for the soil health cultivation technology.

Vascular epiphyte populations with higher leaf nutrient concentrations showed weaker resilience to an extreme drought in a montane cloud forest.

Leaf stoichiometry can characterize plant ecological strategies and correlate with plant responses to climate change. The role of vascular epiphytes in the ecosystem processes of tropical and subtropical forest ecosystems cannot be ignored. Vascular epiphytes are very vulnerable to climate change, however, the relationship between the response of epiphytes to climate change and leaf stoichiometry is not well understood. We present data for 19 vascular epiphyte species that were collected during four consecutive censuses (in 2005, 2010, 2015, and 2020) over 15 years in a subtropical montane cloud forest. We assessed the relationships between the population dynamics and leaf stoichiometry of these vascular epiphytes. Experiencing an extreme drought, 14 of the 19 epiphyte species showed an obvious decrease in the number of individuals, and all species showed negative growth in the number of populations. Subsequently, the total number of individuals gradually recovered, increasing from 7,195 in 2010 to 10,121 in 2015, then to 13,667 in 2020. The increase in the number of vascular epiphyte individuals from 2010 to 2015 was significantly negatively correlated with leaf nitrogen and phosphorus concentration, and was significantly positively correlated with the leaf carbon-nitrogen ratio. Vascular epiphyte populations with higher leaf nutrient concentrations exhibited weaker resilience to the extreme drought, which demonstrated that a resource-conservative strategy was advantageous for the recovery of epiphyte populations. Our findings suggest that ecological stoichiometry can be a useful framework for forecasting the dynamics of vascular epiphyte populations in response to climate change.

Effects of phylogeny, traits, and seasonality on invertebrate herbivory damage in a meadow community

Invertebrate herbivory affects the composition of meadow communities by differentially decreasing the fitness of individual species. The ability of individual species to resist herbivore pressure depends on their traits, which are often phylogenetically structured, and changes seasonally. We conducted a field study assessing invertebrate herbivory damage of 17 selected plant species in an oligotrophic wet meadow, aiming to assess the effect of functional traits, specifically leaf dry matter content (LDMC), carbon content (C), nitrogen content (N), carbon-nitrogen ratio (C:N), specific leaf area (SLA), and plant height on invertebrate herbivory damage, while taking into account seasonal dynamics of herbivory and phylogenetic relationships of studied species. Herbivory damage was different among individual species, with the biggest distinction between monocots and dicots. Herbivory was best predicted by LDMC, season, and interaction of height with season. After filtering the effect of common evolutionary history from the model, the effect of C, height, and interaction of C with season became significant. LDMC was the best trait predictor in both models. Unique relative contributions of phylogeny and traits to the model explained variability were 15.4% and 33.9%, respectively (with phylogeny using 3 and traits 6 df), with their substantial overlap (35.7%) emphasizing that traits are considerably phylogenetically structured. The effect of seasonality was rather minor (15%). In this study, we point out to the strong interplay between traits, evolutionary history, and seasonal changes influencing herbivory damage and stress the importance of phylogenetic context when evaluating the effect of plant characteristics in plant-herbivore interactions.

Sugarcane Bagasse as Carbon Source and Filler to Enhance the Treatment of Low C/N Wastewater by Aerobic Denitrification Flora

Sugarcane bagasse as a biomass solid waste has good prospects as a carbon source for biological wastewater treatment. However, it has rarely been investigated for aerobic denitrification (AD). Herein, we investigated its carbon release performance and constructed a bagasse-loaded sequencing batch biofilm reactor (SBBR) to investigate the feasibility of sugarcane bagasse as a carbon source and filler for AD bacteria to treat wastewater with low carbon–nitrogen ratios (C/N). Results showed that chemical oxygen demand (COD) leaching from sugarcane bagasse was 418.07 ± 17.05 mg/g; high-temperature and high-pressure operation had no significant effect on the carbon release performance of the bagasse. A shake-flask experiment revealed that adding sugarcane bagasse significantly enhanced the AD flora denitrification effect in low C/N wastewater; the removal process of NO3−–N by AD flora followed first-order kinetics. In the SBBR inoculated with AD flora, biofilm formation on the bagasse surface was evident; the NO3−–N removal rate reached 20.20 ± 4.27% after 28 operation cycles, which was significantly higher than that of the control sequencing batch reactor during the same period, and the effluent COD stabilized below 50 mg/L. The results provide a reference for AD application in the practical wastewater treatment and biomass resource utilization of sugarcane bagasse.

Factors affecting soil invertebrate biodiversity in agroecosystems of the Po Plain area (Italy)

Soil is a fundamental component of the biosphere, whose properties and quality are affected by human activities, such as agriculture. Soil health is fundamental for different ecosystem services and soil biota has a crucial role in maintaining it. Elucidating how different crops and agricultural practices affect soil invertebrates communities is of relevance. In the present study, a DNA metabarcoding approach was adopted to evaluate the effects of different biotic and abiotic factors, including agricultural practices, on the composition and diversity of soil invertebrate communities of different agro-ecosystems (Po Plain-Italy). At this aim, the DNA markers and the more effective primers in retrieving soil metazoan communities were established. Bulk soil samples from different agro-ecosystems (i.e., cornfield, alfalfa, paddy fields, vineyard, stable meadow, woodland) were collected and, processed for obtaining 18S rRNA and coi sequences (raw reads analyzed using QIIME2 and R). Soil physical and chemical parameters were measured for each soil sample (e.g., pH, carbon-nitrogen ratio, texture, porosity) and metadata on farms management were retrieved. The most efficient primer pairs in recovering soil metazoans were M620F/M1260R for 18S rRNA, and mlCOIintF/jgHCO2198R for coi gene. Soil communities resulted dominated by Nematoda, Arthropoda, Annelida, Rotifera and Tardigrada. The most diverse invertebrate communities have been found in the soil of stable meadows and woodlands, while cornfields showed the lowest level of diversity. The diversity of soil invertebrate communities (Hill numbers) was positively correlated with the level of porosity and carbon-nitrogen ratio, while it was negatively correlated with the phosphate abundance. This pattern probably reflects the negative effect of excessive fertilization with phosphates on soil fauna, while the abundance of organic matter and microhabitats were found to enhance the presence of more complex communities. Other soil properties were correlated only with specific taxa (e.g., pH was negatively correlated with the diversity of Annelida and Rotifera).

Nitrogen removal characteristics of efficient heterotrophic nitrification-aerobic denitrification bacterium and application in biological deodorization

A heterotrophic nitrifying aerobic denitrifying (HN-AD) strain HY-1 with excellent capacity, identified as Paracoccus denitrificans, was isolated from activated sludge. HY-1 was capable of removing NH4+, NO2–, and NO3– with the corresponding rate of 17.33 mg-N L−1 h−1, 21.83 mg-N L−1 h−1, and 32.37 mg-N L−1 h−1, as well as the mixture of multiple nitrogen sources. Meanwhile, HY-1 could execute denitrification function under anaerobic conditions with a rate of 14.56 mg-N L−1 h−1. HY-1 required less energy investment, which exhibited average denitrification rate of 5.19 mg-N L−1 h−1 at carbon–nitrogen ratio was 1. After nitrification–denitrification metabolic pathway analysis, HY-1 was applied in a biological trickling filter reactor for compost deodorization. The results showed that adding of HY-1 greatly reduced the ionic concentration of NH4+ and NO3– in the circulating liquid without impairing the deodorization effect (NH3 removal rate＞98.07%). These findings extend the field of application of HN-AD and provide new insights for biological deodorization.

Rapid, Clean, and Sustainable Bioprocessing of Toxic Weeds into Benign Organic Fertilizer

A recent report in this journal from these authors, which shows that vermicomposting transforms a toxic weed such as lantana into a benign organic fertilizer, can be of practical utility only if processes can be developed for rapid, inexpensive, and sustainable vermicomposting of these weeds. This paper describes attempts leading to such a process for the vermicomposting of toxic and allelopathic weeds lantana (Lantana camara), parthenium (Parthenium hysterophorus), and ipomoea (Ipomoea carnea). For it, the ‘high-rate vermicomposting’ concept was employed due to which the weeds could be used for vermicomposting directly in each case without the need for pre-composting or any other form of pretreatment. The manure worm Eisenia fetida, which had been cultured on cowdung as feed and habitat, was slow to adapt to the weed-feed but survived and then began to thrive, in all the three weeds, enabling the weeds’ sustained and efficient vermicomposting throughout the 16 month’s uninterrupted operation of the vermireactors. In all cases the extent of vermicast production per unit time showed a rising trend, indicating that the rate of vermicomposting was set to rise further with time. The vermicomposting was found to accompany a 50 ± 10% loss of organic carbon of each weed with a 50 ± 10% increase in the concentration of total nitrogen as also the weed’s additional mineralization. The combined effect was a significant lowering of the carbon-nitrogen ratio, and enrichment of all major, medium, and trace nutrients in the vermicomposts relative to their parent substrates. The findings establish that sustained, direct, and rapid transformation to organic fertilizers of even toxic and allelopathic weeds can be accomplished with the high-rate vermicomposting paradigm.

Effect of temperature and the Carbon-Nitrogen (C/N) ratio on methane production through anaerobic co-digestion of cattle manure and Jatropha seed cake

Anaerobic digestion is a method of agricultural residue transformation used in bioenergy, making these activities energy efficient. However, it can be limited on a larger scale by the availability and diversity of organic residues related to carbon-nitrogen (C/N). Therefore, the anaerobic co-digestion of bovine manure and Jatropha seed cake (Jatropha curcas) were evaluated, with three different C/N ratios, under two conditions: mesophilic (30ºC) and thermophilic (50ºC). Biodigesters were mounted with three replicates for each C/N ratio. The highest production of CH4 was registered after 30 days of processing in the thermophilic condition (C/N 25:1) with 633.95 ± 5.59 mL of CH4 g-1 VS. In contrast, the lowest production was in the mesophilic condition (C/N 20:1) with 208.66 ± 2.61 mL of CH4 g-1 VS. The feasibility of co-digestion of agricultural residues in the production of CH4 as a possible bioenergetic alternative in short periods was demonstrated.

The successful integration of anammox to enhance the operational stability and nitrogen removal efficiency during municipal wastewater treatment

The anaerobic ammonium oxidation (anammox) process is a promising method for carbon reduction and energy conservation. However, the advantages of its application in municipal wastewater treatment have not been completely revealed. Stable nitrogen removal was successfully achieved in the anaerobic/aerobic/anoxic (AOA) process by directly integrating stable anammox. Over a 200 + day operating period, the abundance of anammox bacteria (3.1 ± 0.9 × 108 copies/gSS) and anammox activity (0.32 ± 0.07 mgN/(gSS·h)) remained high, despite a temperature decrease (27.8–17.2 °C) and fluctuating carbon-nitrogen (C/N) ratio (1.6–5.0). A stable nitrogen removal efficiency of 87.1 ± 2.5 % was successfully maintained, because the anammox activity compensated for the effect of low temperatures and low C/N ratios on the nitrification and denitrification. Further analysis found that anammox accounted for 52.6 %-57.5 % of N2 production, and the rest was through nitrification–denitrification. The stable anammox reaction was mainly due to the limitation of oxygen and carbon sources and the stable supply of nitrite by endogenous denitrification. Overall, these findings confirmed that the stability and efficiency of nitrogen removal from municipal wastewater could be increased by integrating anammox under appropriate conditions.

Long-term nitrogen-addition-induced shifts in the ectomycorrhizal fungal community are associated with changes in fine root traits and soil properties in a mixed Pinus koraiensis forest

Nitrogen (N) deposition has marked effects on the structure and function of global forest ecosystems. Many forest tree species rely upon a symbiotic association with ectomycorrhizal (ECM) fungi to enhance nutrient acquisition, which affects nutrient and carbon (C) dynamics in forest ecosystems. A better understanding of the characteristics of ECM fungal diversity and composition and their primary determinants under N deposition will help us to identify the mechanisms underlying N-induced effects on forest nutrient and C cycling. In the present study, we explored the effects of long-term N addition (10 years) on the diversity and community composition of ECM fungi identified from fine roots of Corylus mandshurica, Pinus koraiensis and Tilia amurensis in a mixed temperate forest on Changbai Mountain in north-eastern China. We observed that N addition decreased the Shannon and Simpson indices of the ECM fungal community colonizing C. mandshurica and T. amurensis. Neither the Chao1 index nor the observed species richness of the ECM fungal community colonizing the three species was impacted by N addition. Nitrogen addition significantly decreased the fine root and stele diameter of C. mandshurica, and it significantly decreased the cortical thickness of fine roots of both P. koraiensis and T. amurensis. Nitrogen addition had a consistently negative effect on the mycorrhizal colonization of fine roots, but it did not affect the branching intensity of fine roots of the three tree species. Nitrogen addition altered the ECM fungal community composition, which was closely associated with fine root traits, such as mycorrhizal colonization, and edaphic factors, such as soil pH, soil total N concentration and soil CN ratio. An altered ECM fungal community composition was accompanied by shifts in the nutrient acquisition ability, as characterized by exploration types of ECM fungi. These findings have important implications for a better understanding of the effects of a changing ECM fungal community on the C and N cycling of forest ecosystems under increasing N deposition.

Large herbivores on permafrost— a pilot study of grazing impacts on permafrost soil carbon storage in northeastern Siberia

The risk of carbon emissions from permafrost is linked to an increase in ground temperature and thus in particular to thermal insulation by vegetation, soil layers and snow cover. Ground insulation can be influenced by the presence of large herbivores browsing for food in both winter and summer. In this study, we examine the potential impact of large herbivore presence on the soil carbon storage in a thermokarst landscape in northeastern Siberia. Our aim in this pilot study is to conduct a first analysis on whether intensive large herbivore grazing may slow or even reverse permafrost thaw by affecting thermal insulation through modifying ground cover properties. As permafrost soil temperatures are important for organic matter decomposition, we hypothesize that herbivory disturbances lead to differences in ground-stored carbon. Therefore, we analyzed five sites with a total of three different herbivore grazing intensities on two landscape forms (drained thermokarst basin, Yedoma upland) in Pleistocene Park near Chersky. We measured maximum thaw depth, total organic carbon content, δ13C isotopes, carbon-nitrogen ratios, and sediment grain-size composition as well as ice and water content for each site. We found the thaw depth to be shallower and carbon storage to be higher in intensively grazed areas compared to extensively and non-grazed sites in the same thermokarst basin. First data show that intensive grazing leads to a more stable thermal ground regime and thus to increased carbon storage in the thermokarst deposits and active layer. However, the high carbon content found within the upper 20 cm on intensively grazed sites could also indicate higher carbon input rather than reduced decomposition, which requires further studies including investigations of the hydrology and general ground conditions existing prior to grazing introduction. We explain our findings by intensive animal trampling in winter and vegetation changes, which overcompensate summer ground warming. We conclude that grazing intensity—along with soil substrate and hydrologic conditions—might have a measurable influence on the carbon storage in permafrost soils. Hence the grazing effect should be further investigated for its potential as an actively manageable instrument to reduce net carbon emission from permafrost.

Phenological and physiological advantages of invasive annuals are strengthened by nitrogen enrichment

Abstract Anthropogenic nitrogen (N) deposition exerts profound influence on the composition and function of native ecosystems, commonly resulting in reduced plant richness and increases in nonnative plant invasion. Identifying differences in plant N responses and functional traits could help to explain the ongoing invasion and biological impoverishment of ecosystems subject to N deposition. We compared the growth, emergence phenology and functional traits of 30 native and invasive annual plant species under high and low N availability, with the goal of evaluating if invasives exhibit functionally dissimilar responses to N compared with the native species they displace. Invasives grew larger than natives, especially under increased N availability. Overall, invasives and natives did not differ in emergence phenology. However, these groups of species differed in relationships between growth and days to emergence, and N addition further strengthened these differences; invasives consistently grew larger than natives that emerged around the same time, whereas natives showed a strong negative effect of delayed emergence on plant growth. Relative N responses for measures of plant growth and allocation did not differ between native and invasive species, but invasives exhibited greater plasticity in physiological traits. This included significantly lower leaf N content, higher CN ratios and greater water‐use efficiency (WUE) in plants grown under high N. Invasives also showed functionally different patterns of growth and water use. Across species, invasives showed a positive relationship between shoot growth and WUE. Native species showed a trade‐off between root allocation and WUE, whereas invasives displayed high values for WUE even despite reduced root: shoot ratios under high N. Our results highlight the ability of invasives to rapidly accrue biomass, disproportionately benefit from early emergence and N addition and use water efficiently despite rapid growth. Natives, on the other hand, pay a higher cost for delayed emergence and may experience trade‐offs between growth and water use. The more pronounced functional differences between natives and invasives observed under high N likely play an important role in driving invasion and reduced species diversity under N enrichment. These differences could be used to inform successful management strategies for N‐impacted and water‐limited ecosystems. Read the free Plain Language Summary for this article on the Journal blog.

Comparative study between compost and granular sludge inoculums as promising microbial consortia sources for biohydrogen production from food industry wastewater

This study performed a comparative analysis of anaerobic microbial communities from compost or granular sludge inoculum over the course of industrial substrate codigestion in order to identify the range of carbon-nitrogen ratios (20 to 50) that increase the biohydrogen production. The batch bioreactors were operated at pH = 5.5 ± 0.3 and 35 °C. Physicochemical characterization showed a pH < 4.0 after 32 h; a gradual decrease in organic matter was observed, reaching a maximum of 90% recovery. The highest biohydrogen yield was 72.9 ± 5.7 mL H2 g−1CODrem, which occurred after conducting fermentation with compost inoculum at a carbon–nitrogen ratio of 35. These fermentation processes were characterized by the proliferation of native populations from the substrate (Lactobacillus and Lactococcus) and the intrinsic inoculum conditions (Citrobacter spp. and Megasphaera elsdenii). A shift in the dominant biohydrogen-producing microbial population over time was observed mainly for reaction systems with high biohydrogen yields. Citrobacter spp., Kluyvera cryocrescens, and Rahnella spp. all proliferated during the codigestion processes facilitated by the compost inoculum samples, while Megasphaera elsdenii performed a similar function in the granular sludge inoculum bioreactors.

Responses of soil greenhouse gas emissions to land use conversion and reversion-A global meta-analysis.

Exploring the responses of greenhouse gas (GHG) emissions to land use conversion or reversion is significant for taking effective land use measures to alleviate global warming. A global meta-analysis was conducted to analyze the responses of carbon dioxide (CO2 ), methane (CH4 ), and nitrous oxide (N2 O) emissions to land use conversion or reversion, and determine their temporal evolution, driving factors, and potential mechanisms. Our results showed that CH4 and N2 O responded positively to land use conversion while CO2 responded negatively to the changes from natural herb and secondary forest to plantation. By comparison, CH4 responded negatively to land use reversion and N2 O also showed negative response to the reversion from agricultural land to forest. The conversion of land use weakened the function of natural forest and grassland as CH4 sink and the artificial nitrogen (N) addition for plantation increased N source for N2 O release from soil, while the reversion of land use could alleviate them to some degree. Besides, soil carbon would impact CO2 emission for a long time after land use conversion, and secondary forest reached the CH4 uptake level similar to that of primary forest after over 40 years. N2 O responses had negative relationships with time interval under the conversions from forest to plantation, secondary forest, and pasture. In addition, meta-regression indicated that CH4 had correlations with several environmental variables, and carbon-nitrogen ratio had contrary relationships with N2 O emission responses to land use conversion and reversion. And the importance of driving factors displayed that CO2 , CH4 , and N2 O response to land use conversion and reversion was easily affected by NH4 + and soil moisture, mean annual temperature and NO3 - , total nitrogen and mean annual temperature, respectively. This study would provide enlightenments for scientific land management and reduction of GHG emissions.

Using an innovative bivariate colour scheme to infer spatial links and patterns between prediction and uncertainty: an example based on an explainable soil CN ratio model

Using an innovative bivariate colour scheme to infer spatial links and patterns between prediction and uncertainty: an example based on an explainable soil CN ratio model

Mixed application of biochar, maize straw, and nitrogen can improve organic carbon fractions and available nutrients of a sandy soil

Biochar with maize straw and nitrogen application may provide better crop growth conditions with respect to soil C/N, organic carbon fractions, and available nutrients than biochar applied alone. An incubation experiment was conducted in which biochar of maize straw pyrolyzed at 500 °C was applied with maize straw and nitrogen over 150 days. The treatments consisted of three rates of biochar applied at 0 (BC), 30 (BC3), and 60 g kg−1 (BC6), two rates (0 and 2 g kg−1) of maize straw (S), and two rates (0 and 0.1 g kg−1) of nitrogen (N) fertilizer (ammonium bicarbonate). The control (CK) was blank soil unfertilized with BC, N, and S. Sampling was done at 30, 60, and 150 days, respectively. The treatments of BC3 and BC6 significantly increased the content of soil total organic carbon by 840–1735%, oxidizable organic carbon (KMnO4–C) by 151–250%, dissolved organic carbon (DOC) by 221–976%, microbial biomass carbon (MBC) by 113–274%, available phosphorus (AP) by 969–4820%, and available potassium (AK) by 715–2413% in the sandy soil. Biochar reduced the ammonium nitrogen and nitrate nitrogen (NH4 +–N and NO3 −–N) contents, while it increased the carbon-nitrogen ratio (C/N) to 42. Nitrogen addition increased the contents of NH4 +–N by 395% and NO3 −–N by 661% compared with the CK after 30 days. Straw only affected the contents of DOC and MBC. The S + N treatment increased the content of MBC and available nitrogen compared with the CK. The contents of KMnO4–C, DOC, MBC, NH4 +–N, NO3 −–N, AP, and AK in the BC + N and BC + S treatments were higher than those in the BC treatments. The BC + N and BC + S treatments could decrease the high C/N that resulted from biochar alone. The contents of KMnO4–C, DOC, MBC, NH4 +–N, NO3 −–N, AP, and AK in the BC + S + N treatment were higher than those in the BC + S and BC + N treatments. Therefore, we recommend using BC6 + S + N to improve the organic carbon fractions and available nutrients in sandy soil. If straw is lacking in the field, BC6 + N is a suitable alternative.

Production, extraction, and quantification of laccase obtained from an optimized solid-state fermentation of corncob with white-rot fungi

Laccase is an enzyme capable of biotransforming synthetic pollutants. Its production by four white-rot fungi Trametes pubescens, Phanaerochaete chrysosporium, Pleurotus ostreatus, and Pleurotus pulmonarius was evaluated during 7, 10, and 13 days under solid-state fermentation onto the agricultural by-product corncob. Pleurotus ostreatus was selected to optimize the fermentation conditions through a central composite design. It was found that laccase production is maximized using malt extract as carbon source (18.2 g L−1), yeast extract as nitrogen source fitting carbon-nitrogen ratio at 5.15:1, tween 80 as inducer (0.17% v v−1), and a moisture content of 85.0%. Subsequently, several factorial designs allowed to select 50 mM sodium acetate buffer pH = 6.0 and pH = 4.0 as the best conditions to extract and quantify the enzyme, respectively. The optimization of these three stages allowed a 4.6-fold increase in enzyme activity with respect to the value reached at the beginning of the research.

An Ordovician ophiolitic complex in West Junggar, NW China: Implications for subduction initiation and oceanic arc evolution of the Paleo-Asian Ocean

As a key step of the Wilson cycle, subduction initiation is regarded as a start hallmark of the ocean-continent transformation. However, the crust-mantle interaction and crustal growth processes related to subduction initiation remain enigmatic. Here we report a newly recognized complete magmatic sequence containing three rock assemblages in the Hongguleleng ophiolitic complex (HOC) in West Junggar, NW China. Group I contains typical Mid-Oceanic Ridge (MOR)-derived rocks including abyssal peridotite, gabbro, plagiogranite, and basalt. Group II consists of forearc basalt (FAB) and boninitic gabbro and has a high continentality index (CI > 130), similar to the rock assemblages in the Mariana proto-arc. Group III composed of calc-alkaline andesite and arc tholeiite basaltic andesite exhibits middle CI values (50 < CI < 100), suggesting that they form in a transitional oceanic arc. Zircon U-Pb ages show that the N-MORB gabbro and plagiogranite samples are emplaced at 483–481 Ma, and the boninitic rocks, calc-alkaline andesites, and arc tholeiite basaltic andesites have the crystalline ages of 472–467 Ma, 456 Ma, and 452 Ma, respectively. An increasing trend of Ba/Th and V/Ti ratios from Group I to Group II suggests the addition of aqueous fluid and elevated oxidation in the mantle source during subduction initiation. However, it exhibits an uptrend in Th/Nb and (La/Sm)cn ratios but a downtrend in Ba/Th ratios from Group II to Group III, indicating a significant contribution of slab-derived sediments to the mantle during oceanic arc evolution. Combined with regional data, we consider that there developed an E-W–trending sub-ocean basin of the Paleo-Asian Ocean spanning northern West Junggar and East Kazakhstan during the Middle Cambrian–Ordovician. The MOR-type and forearc ophiolites in northern West Junggar as well as our results suggest that the ocean happened mid-ocean ridge spreading at ca. 512–478 Ma and subduction initiation at ca. 476–467 Ma, and developed a transitional oceanic arc at ca. 456–452 Ma.