Slower Decomposition Rates Research Articles

Enhancing Nitrocellulose Stability: Unveiling the Thermal Properties and Kinetic Degradation Mechanisms With Some Innovative Hybrid Stabilizers

ABSTRACTNitrocellulose (NC) is a highly energetic material used in various military and civilian applications. Nevertheless, the inherent instability of NC poses safety and storage lifetimes challenges. To address this issue, traditional stabilizers have been used to improve the thermal stability of NC. In this study, we investigate the effectiveness of novel hybrid stabilizers in enhancing the thermal stability of NC. We have prepared a series of NC samples supplemented with different hybrid stabilizers, including combinations Of 2‐nitrodiphenylamine (2‐NDPA) along with cobalt (Co), nickel (Ni), and manganese (Mn) ion‐exchanged sodium mordenite (NaMOR) zeolite. The prepared samples underwent structural characterizations to study their chemical compatibility and chemical structures. Furthermore, their thermal behavior were assessed using a range of analytical techniques, including C80 microcalorimetry, thermogravimetric analysis (TGA), and standardized tests like the methyl violet (MV), vacuum stability, and Bergmann–Junk (B&J) protocols. Experimental results confirmed the good compatibility between the hybrid stabilizer components and NC matrix. Results from TGA and C80 microcalorimetry demonstrated that combining 2‐NDPA with the ion‐exchange NaMOR has a synergistic effect. This combination not only enhances the stability of NC but also reduces its rate of degradation compared to using 2‐NDPA alone. Additionally, accelerated thermal aging tests emphasized the effectiveness of the hybrid stabilizer systems, demonstrating their ability to scavenge nitroxide radicals and mitigate the harmful effects of free radicals produced during the pyrolysis of NC. Thermo‐kinetic results clearly indicated a significant increase in activation energy (Ea) and the pre‐exponential factor (log(A)) after the addition of the designed stabilizers. Compared to pristine NC, the Ea increased by a substantial margin of 37–74 kJ/mol, whereas the log(A) rose by 4.2–8.3 s−1, indicating enhanced thermal stability and a slower rate of decomposition. This research highlights the potential of hybrid stabilizers as a viable alternative to traditional stabilizers for NC, paving the way for the development of safer and more effective nitrate ester‐based energetic materials (NEEMs).

Decomposition and nutrient release from shoot of legumes cover crops

The cover crops can reduce soil exposure and erosion while enhancing nutrient cycling for crops. Effective implementation requires understanding how cover crops decompose and release nutrients to align with crop demand. This research assessed the decomposition rates and nutrient release of various legume residues commonly used as green manure or cover crops in agricultural systems. The study took place in a nutrient-deficient Red-Yellow Ultisol, using a split-plot design with different legume cover crop species: Crotalaria juncea, Crotalaria spectabilis, Cajanus cajan, Cajanus cajan (L.) Millsp), Dolichos lablab, Canavalia ensiformis and Mucuna aterrima as the main plots and six evaluation periods: 0, 30, 60, 90, 120, and 150 days after incorporation (DAI) as the subplots. Initial mass losses were observed in the first 60 days, followed by a slower decline over the study period. The order of nutrient accumulation in biomass was found to be: K > N > P > Ca > Mg. The Dolichos lablab species had the slowest decomposition rate, with a half-life of 43 days, while Cajanus cajan had the fastest, with a half-life of 65 days. Potassium reached its maximum by 30 DAI, indicating a rapid transfer to the soil. Nitrogen, P, and K contents decreased during different vegetative phases, highlighting the importance of proper timing for legume management. Hemp, Crotalaria spectabilis, Dolichos lablab, and Canavalia ensiformis were suitable for short-cycle vegetables due to rapid nutrient availability. Conversely, Cajanus spp., and Mucuna aterrima were better for extended soil coverage and slow nutrient release.

Phenotypic Profiling of Selected Cellulolytic Strains to Develop a Crop Residue-Decomposing Bacterial Consortium.

Slow decomposition rates of cereal crop residues can lead to agronomic challenges, such as nutrient immobilization, delayed soil warming, and increased pest pressures. In this regard, microbial inoculation with efficient strains offers a viable and eco-friendly solution to accelerating the decomposition process of crop residues. However, this solution often focuses mostly on selecting microorganisms based on the appropriate enzymic capabilities and neglects the metabolic versatility required to utilize both structural and non-structural components of residues. Therefore, this study aimed to address these limitations by assessing the metabolic profiles of five previously identified cellulolytic bacterial strains, including Bacillus pumilus 1G17, Micromonospora chalcea 1G49, Bacillus mobilis 5G17, Streptomyces canus 1TG5, and Streptomyces achromogenes 3TG21 using Biolog Phenotype Microarray analysis. Moreover, this study evaluated the impact of wheat straw inoculation with single strains and a bacterial consortium on soil organic carbon and nitrogen content in a pot experiment. Results revealed that, beyond the core subset of 12 carbon sources, the strains exhibited diverse metabolic capacities in utilizing 106 carbon sources. All strains demonstrated effective straw biomass degradation compared to the negative control, with significant differences detected only in oil seed rape straw biodegradation estimations. Furthermore, wheat straw inoculated with a bacterial consortium showed a significant increase in soil organic carbon content after 180 days in the pot experiment. Overall, these findings underscore the critical role of metabolic profiling in gaining a deeper understanding of microbial capabilities and addressing the complexities of residue composition and environmental variability.

Effects of anecic Amynthas aspergillum on the proportion and depth of straw-derived carbon input into soil

Straw mulching significantly affects the soil organic carbon (OC) pool, but its positive effect on soil OC is limited by the slow decomposition rate and shallow depth. Increasing the conversion rate of straw-derived carbon (C) to soil OC and the depth affected are important for enhancing soil carbon storage and mitigating global climate change. Anecic earthworms feed on surface organic residues and dwell underground; and thus, they can carry surface straw directly underground. However, previous studies have focused on European earthworms, and it is still unclear how Chinese widely distributed earthworms, such as the anecic Amynthas aspergillum, affect the conversion rate of straw-derived C into soil OC and the depth affected, and whether these effects are related to soil properties. Using 13C tracing technology, we established treatments with and without A. aspergillum in soil with added straw to examine how A. aspergillum regulate the distribution of straw-derived OC in soil profiles during incubation for 31 days. Soil samples from the plow layer (PL) and plow pan layer (PP) of subtropical corn land were used in this study to represent two soils of different properties. Visible earthworm casts were not observed on the surface soil. A. aspergillum significantly increased the loss of surface straw by 86.1 % and 43.1 % in the PL and PP soils, respectively (p < 0.05). The conversion rate of straw-derived C into soil OC was 21.8 ± 0.5 % in the presence of earthworms in the PL soils, which was significantly greater than that without earthworms (7.9 ± 0.5 %, p < 0.05). The conversion rates were 8.0 % and 12.8 % in the absence and presence of earthworms, respectively, in the PP soils. The A. aspergillum increased the soil depth affected by straw-derived C input in the profiles of both the PL (to 10–20 cm) and PP soils (to 5–10 cm) compared with the treatments without earthworms (0–5 cm). Thus, anecic A. aspergillum promoted the decomposition of straw, enhanced the conversion of straw-derived C into soil OC and depth affected, and the effects of A. aspergillum were greater in the fertile soils. The underground casting behavior of A. aspergillum, may enhance the effects of incorporation of surface straw-derived C in deep soils. We suggest that earthworm regulation combined with straw return could be considered in sustainable agriculture.

Preparation of polyvinyl alcohol/carboxymethyl cellulose sodium/chitosan paper-based antimicrobial indicator cards using mixed anthocyanin with stability-colorimetric sensitivity: Monitoring freshness of carp

In this study, an anthocyanin solution with both high stability and sensitivity was successfully prepared through a blending method, and the optimal ratio was determined. Ultraviolet-visible spectroscopy analysis demonstrated that an increase in the proportion of black bean peel anthocyanins resulted in a deeper color and a more pronounced color change effect. Moreover, the stability of the blended anthocyanins was markedly enhanced with an increase in the proportion of purple cabbage anthocyanins, resulting in a slower decomposition rate under light, temperature, oxidation, and varying pH conditions. The blended anthocyanins, employed as a pH indicator, were utilized to prepare an antibacterial indicator card. It was observed that the mechanical properties of the coated paper remained unaltered by the ratio of the mixed pigments. The mixed pigments enhanced the stability of the antibacterial indicator card with respect to environmental fluctuations while facilitating more rapid and sensitive color transitions in the presence of ammonia and under disparate pH conditions. The application of indicator cards with five different anthocyanin ratios to fish resulted in a shelf life extension of 1–2 days compared to the control group and enabled real-time monitoring of fish freshness. A comprehensive evaluation demonstrated that the optimal indicator performance was attained when the mass ratio of black bean peel anthocyanins to purple cabbage anthocyanins was 1:1.

Defect Engineering of Ultrasmall TiO2 Nanoparticles Enables Highly Efficient Photocatalysts for Solar H2 Production from Woody Biomass.

The conversion of woody biomass to H2 through photocatalysis provides a sustainable strategy to generate renewable hydrogen fuel but was limited by the slow decomposition rate of woody biomass. Here, we fabricate ultrasmall TiO2 nanoparticles with tunable concentration of oxygen vacancy defects (VO-TiO2) as highly efficient photocatalysts for photocatalytic conversion of woody biomass to H2. Owing to the positive role of oxygen vacancy in reducing energy barrier for the generation of •OH which was the critical species to oxidize woody biomass, the obtained VO-TiO2 achieves rapid photocatalytic conversion of α-cellulose and poplar wood chip to H2 in the presence of Pt nanoclusters as the cocatalyst. As expected, the highest H2 generation rate in α-cellulose and poplar wood chip system respectively achieve 1146 and 59 μmol h-1 g-1, and an apparent quantum yield of 4.89% at 380 nm was obtained in α-cellulose aqueous solution.

Nitrogen Deposition Reduces the Rate of Leaf Litter Decomposition: A Global Study

The litter decomposition of plant leaves is a vital process in carbon (C) and nitrogen (N) cycling in global terrestrial ecosystems. However, previous assessments of the key determinants of the N deposition effects of litter decomposition have been more controversial. In this meta-analysis, we compared the overall effects of N addition on the litter decomposition rates, litter nutrient content (C and N), and litter constituent (lignin and cellulose) residual rates using a log response ratio approach. Our results showed that exogenous N addition increased the N content and inhibited lignin degradation in litter. N deposition decreased the leaf litter decomposition rate by increasing the lignin and N residues and decreasing the litter C content and soil pH. The analysis also concluded that the initial litter C/N ratio, lignin content, and soil pH were main factors in mediating the effect of N deposition on litter decomposition rate. Overall, the results of this study indicate that N deposition can slow decomposition rates by inhibiting N release and lignin degradation of litter. Notably, these results emphasize that the effect of N deposition on litter decomposition mainly depends on the endogenous quality of the litter and soil pH in the decomposition environment.

Study on Pyrolysis Characteristics of Phosphate Tailings under H2O Atmosphere.

The pyrolysis separation of calcium and magnesium from phosphate tailings is an important process due to its high-value resource utilization. In this paper, aiming to address the problems of high energy consumption, a slow decomposition rate and the low activity of decomposition products in the high-temperature pyrolysis of phosphate tailings, the medium-temperature pyrolysis of phosphate tailings under a H2O atmosphere was carried out, and the phase reconstruction and activation of pyrolysis process were discussed. The results showed that compared with N2, air and CO2 atmospheres, the pyrolysis process of phosphate tailings in a H2O atmosphere was changed from two stages to one stage, the starting decomposition temperature was reduced to 500 °C and the decomposition time was shortened to 30 min. The order of the influence of each factor on the pyrolysis of phosphate tailings was temperature > H2O pressure > holding time. Under the optimized pyrolysis conditions, the yield of CaMg(CO3)2 decomposition of phosphate tailings into MgO and CaO was 97.3% and 98.1%, respectively, and the reactivity of MgO was 31.6%. The distribution of Ca and Mg elements in the phosphate tailings after pyrolysis showed a negative correlation, and both of them no longer formed associated compounds; Ca mainly existed in the form of Ca(OH)2, Ca5(PO4)3F, CaSiO3 and CaF2, and Mg mainly existed in the form of MgO, MgF2 and Mg(OH)2.

Degradation kinetics of PLA compounds with castor oil

AbstractPoly (lactic acid) (PLA) compounds with castor oil (CO) and epoxidized castor oil (ECO) were produced via formic acid, with levels of 5% CO, 3 and 5% ECO. The contribution of this study lies in the detailed analysis of thermal degradation and degradation kinetics of PLA/CO and PLA/ECO. Chemical changes were evidenced by Fourier transform infrared (FTIR), thermal stability, and degradation kinetics were investigated by thermogravimetric analysis (TGA), using Friedman (FR), Ozawa–Flynn–Wall (OFW), Kissinger–Akahira–Sunose (KAS) and Vyazovkin (VZ) models. Results showed changes in FTIR spectra for PLA/CO and PLA/ECO. For PLA/5%CO and PLA/3%ECO, lower energy bonds formation were observed, resulting in modifications in the involved molecules and presence of CH type bonds in PLA/5%ECO. TGA analysis showed that PLA presented greater thermal stability compared with PLA/CO and PLA/ECO, with T5% = 306°C. The compounds 5% CO, 3 and 5% ECO exhibited lower degradation temperatures (298, 300, and 296°C), compared with PLA, as well as slower decomposition rates. Kinetic modeling using KAS and OFW models proved to be incapable of describing the degradation kinetics of PLA and its compounds. However, FR and VZ were considered adequate, with discrepancies varying between 7% to −4% and 9% to −3%, which showed higher (215, 185, 210, 189 KJ/mol) at α = 0.3 for PLA.

Wastewater Treatment Utilizing Industrial Waste Fly Ash as a Low-Cost Adsorbent for Heavy Metal Removal: Literature Review

Wastewater discharges from industrial processes typically include elevated concentrations of contaminants, which largely consist of potentially harmful chemicals such as heavy metals. These contaminants are characterized by their slow rate of decomposition. Hence, the removal of these metallic ions from effluents poses a challenge. Among different treatments, the adsorption approach has considerable potential due to its ability to effectively eliminate both soluble and insoluble pollutants from effluent, even at lower levels of concentration. Of various wastes, fly ash (FA) material has been the subject of attention because it is abundant, has favorable qualities, and contains a high percentage of minerals. This review investigates multiple facets, with a specific focus on the application of FA, an industrial byproduct, as an adsorbent in removing heavy metals. A comprehensive examination was conducted on a range of concerns pertaining to the pollution caused by metallic ions, including the underlying causes, levels of contamination, health implications of heavy metals, and removal methods. Multiple factors were found to affect the adsorption process. Of all the factors, the pH value considerably influences the elimination of heavy metals. An acidic pH range of 2.5–4.5 was found to be optimal for achieving the highest possible elimination of As(V), Cu(II), Hg(II), and Cr(VI). The latter elimination rate reached 89% at the optimal pH level. Most heavy metals’ adsorption isotherms conformed to the Langmuir or Freundlich models, while the pseudo-second-order kinetics provided a satisfactory match for their removal. Using a raw FA, adsorption capacities were achieved in the removal of metallic ions, Ni(II), Pb(II), and Cr(VI), that ranged from 14.0 to 23.9 mg g−1. Meanwhile, the FA-zeolite showed a remarkable capacity to adsorb ions Mn(II), Ni(II), Cd(II), Cu(II), and Pb(II), with values ranging from about 31 to 66 mg g−1. The cost analysis showed that the treatment of FA is economically advantageous and may result in significant cost reductions in comparison to commercial adsorbents. In summary, FA is an inexpensive waste material with potential for water treatment applications and several other purposes due to its excellent chemical and mineralogical composition.

Legacy effects of long‐term autumn leaf litter removal slow decomposition rates and reduce soil carbon in suburban yards

Societal Impact StatementAs cities grow, it is essential to understand how landscape management decisions in urban spaces alter ecosystem function. This study demonstrates that the ubiquitous practice of long‐term leaf litter removal in suburbs, even in relatively small patches of a yard, reduces the soil's ability to cycle nutrients in plant litter and results in lower amounts of carbon stored in the soil. Even two years of retaining leaves where they previously were removed is insufficient to restore decomposition rates or carbon pools. This research is an important step in creating best practices for litter management to maintain essential ecosystem functions, like carbon sequestration, water holding capacity, and soil fertility.Summary Seasonal senesced leaf litter removal eliminates considerable organic material from suburban soils annually. We test if this disturbance alters decomposition and carbon cycles and depletes soils of organic matter over time, creating persistent legacy effects. We used a factorial experimental design to implement 1–2 years of current leaf litter manipulations (remove or retain fallen leaves) within historically raked and unraked areas in suburban Maryland yards. We then compared total organic soil carbon and decomposition using a standardized substrate decomposition methodology (Tea Bag Index) across treatment plots. Long‐term litter removal in suburban yards reduced decomposition rates by 17% and total soil organic carbon concentration by up to 24% compared to areas where leaf litter was retained in situ. In contrast, short‐term management changes (1–2 years) did not significantly impact decomposition rates or total organic soil carbon concentrations. Our findings suggest that long‐term suburban litter raking creates legacy effects that alter decomposition and carbon storage process trajectories that are not easily reversed. This is important in understanding urban ecosystem function and sustainable management.

Transforming Zeolite Tuff and Cigarette Waste into Eco-Friendly Ceramic Bricks for Sustainable Construction

The use of waste materials has gained attention as a sustainable approach in various industries. Cigarette waste, which is typically discarded as a non-recyclable material, poses a significant environmental challenge due to its toxicity and slow decomposition rate. However, by incorporating this waste into ceramic bricks, new approaches for waste management and resource utilization are explored. This research work provides a detailed evaluation of the possibility of utilizing natural zeolite tuff incorporated with cigarette waste to produce sustainable ceramic bricks. Uniform powders are produced by milling various combinations of zeolitic tuff and cigarette waste using a planetary ball mill. The substitution ratios ranged from 0% to 12% by weight of the zeolitic tuff, with increments of 2%. Ceramic discs were formed by dry pressing and then subjected to sintering at different heat treatment temperatures (950–1250 °C). The impact of the inclusion of cigarette waste on the microstructural and technical features of zeolite tuff-based ceramic bricks has been thoroughly investigated. The results of the experiments demonstrate that incorporating cigarette waste into the development of ceramic bricks leads to improved thermal insulation properties, with thermal conductivity ranging from 0.33 to 0.93 W/m·K. Additionally, these bricks exhibit a lighter weight in a range of 1.45 to 1.96 g/cm3. Although the inclusion of cigarette waste slightly reduces the compressive strength, with values ranging from 6.96 to 58.6 MPa, it still falls within the acceptable range specified by standards. The inclusion of cigarette waste into zeolite tuff is an innovative approach and sustainable practice for reducing energy consumption in buildings while simultaneously addressing the issue of waste disposal and pollution mitigation.

Ammoniated straw returning: A win-win strategy for increasing crop production and soil carbon sequestration

Increasing crop production and soil carbon sequestration is critical for sustainable agricultural development. Straw returning, a common agricultural practice, positively affects grain yield and soil organic carbon. Nevertheless, the slow decomposition rate and high carbon-to-nitrogen ratio of straw are significant obstacles to its effectiveness. Ammonifying straw using urea and calcium hydroxide may be a promising solution, whereas limited information is available on the impacts of ammoniated straw returning on crop production and soil carbon sequestration. Therefore, in a winter wheat-summer maize rotation system, we conducted an experiment with three straw returning treatments (T1, straw removal; T2, traditional straw returning; T3, ammoniated straw returning) to investigate their impacts on crop growth, grain yield and yield components, carbon inputs and outputs, and net ecosystem carbon budget (NECB). The results showed that T3 outperformed T2 regarding increasing leaf area index and aboveground biomass. Ear density and thousand kernel weight of winter wheat and hundred kernel weight of summer maize were ranked T1 < T2 < T3, with no significant differences between treatments for other grain yield components. Consequently, winter wheat, summer maize, and annual grain yields were the highest under T3, followed by T2 and T1. In comparison with T1, T2 and T3 increased annual total carbon inputs by 5463 and 7271 kg C ha–1, respectively, due to the increased carbon inputs from returned straw and net primary productivity. Annual carbon total outputs, primarily from aboveground biomass removal at harvest and carbon respiration, increased by 3305 kg C ha–1 under T2 and 4264 kg C ha–1 under T3, compared with T1. Balancing annual total carbon inputs and outputs, T1, T2, and T3 had annual NECB values of –1215, 944, and 1793 kg C ha–1, respectively. Therefore, the T1 agroecosystem acted as a carbon source, whereas the T2 and T3 agroecosystems, particularly T3, acted as a carbon sink on an annual scale. These results suggest that ammoniated straw returning may be a superior straw application practice for increasing crop production and soil carbon sequestration simultaneously.

A soil-based approach on human taphonomy from five Portuguese public cemeteries

ABSTRACT Over the last decade, some Portuguese cemeteries have started to have issues with the lack of burial space, mainly due to the slow rate of cadaveric decomposition, hindering the reuse of soil graves as is common practice. To better understand the influence of soil on human taphonomy and help in cemetery management, the main goal of this research was to explore possible relationships between body decay and edaphic traits. A total of 217 soil samples were collected from graves of five public cemeteries and analysed for their soil organic matter content, moisture, pH, electrical conductivity, bulk density, texture, and colour. Five grave sampling areas were considered: the topsoil, above the coffin, and under the coffin in the head, pelvis and feet areas. Statistically significant differences have been found between the graves of skeletonized and incompletely skeletonized bodies for moisture above the coffin (p = 0.035) and for electrical conductivity in the topsoil (p = 0.014). Although the number of individuals (n = 56) studied might be considered low, this paper explores the possibility that soil itself might not be the main influencer on human taphonomy. A new perspective should be considered regarding the role played by intrinsic factors after death.

Chronic anthropogenic disturbance alters litter decomposition and nutrient concentrations and stocks across a Caatinga dry forest chronosequence

Litter decomposition plays a key role in the cycling and storage of nutrients in terrestrial ecosystems. However, very little is known about decomposition processes and their underlying drivers in tropical dry forests, particularly in human-modified landscapes. Here, we evaluate decomposition rates and nutrient concentrations and stocks in the litter of a Caatinga dry forest chronosequence, in northeast Brazil. Litter decomposition was monitored for a year across forest stands of varying ages and old-growth forests. The litter decomposition rate was highly variable across forest stands, although on average decomposition occurred slowly, with approximately 50% of the initial litter mass still present after one year. The decomposition rate is responsive to forest type and negatively affected by chronic disturbance. Litter nutrient concentration decreased along the decomposition process, exhibiting a nutrient-specific mineralization rate. Response to drivers was also nutrient specific, with precipitation and chronic disturbances playing prominent roles. Nutrient stocks in the remaining litter were higher in old-growth forests, and final stocks of certain nutrients also responded to multiple drivers. Our results suggest that the Caatinga dry forest experiences a slow rate of litter decomposition and mineralization, although rates exhibit considerable variability across forest stands and environmental conditions. Thus, chronic disturbance plays a role by either facilitating or reducing litter decomposition, mineralization rate, and the stocks transferred to the soil. Consequently, these factors have implications for nutrient availability, including goat consumption and subsequent loss of nutrients.

Ammoniated straw incorporation coupled with N management synergistically enhanced soil structure and crop productivity in a desert oasis farmland

AbstractStraw return is the simplest and the most economic method to improve soil structure. Slow decomposition rate limits straw return in sandy fields, which has becoming one of the obstacles in sandy land reclamation. Ammonification of straw before return accelerates straw decomposition, but it requires the use of extra N fertilizer, however, little is known about N fertilizer management in fields with ammoniated straw incorporation. So, a 3‐year field experiment was conducted with different proportions of N fertilizer aimed to maize straw ammonification and field broadcasting, and evaluated straw decomposition proportion, straw N release, soil organic carbon content, soil aggregates, soil water and N availability, and grain yield. Total N application rate was 300 kg per hectare, with five N input amounts for straw per hectare ammonification: 0 (SN0), 40 (SN40), 80 (SN80), 120 (SN120), and 160 (SN160) kg, and the rest of N broadcasted in soil during maize growing season. Ammonification accelerated straw decomposition and N release, and these effects showed no significant difference between SN80, SN120, and SN160. After straw decomposition for 150 days, the decomposition proportion was 62.1%, 53.0%, and 39.2% in SN80, SN40, and SN0, respectively. After 3 years of straw return, SN80 exhibited a significantly higher mean weight diameter of soil aggregates (35.6% higher), organic carbon content (18.4% higher), water‐holding capacity (17.4% higher), and soil water storage (17.2% higher) than SN0. Additionally, SN80 and SN120 showed the most significant effect on “N slow‐release” in soil. The above effects resulted with more available soil water and N used for crop growth, and increased grain yields (18.1% higher) and water use efficiency (18.6% higher) in SN80, compared with SN0. Hence, we conclude that a proper N allocation between straw and soil can synergistically enhance soil structure and crop productivity in sandy farmlands. This founding would provide scientific and technological support for straw return in sandy fields and is beneficial to sustainable development of oasis.

From Sphagnum to shrub: Increased acidity reduces peat bacterial diversity and keystone microbial taxa imply peatland degradation

AbstractPeatlands store one‐third of the Earth's carbon. Human activities and climate change‐induced peatland vegetation shift from Sphagnum to shrub may lead to peatland degradation. To understand the ecology and functions of these peatlands, we collected samples from 10 peatland mosaics dominated by Sphagnums, mixed plant communities of Sphagnums, and shrubs across south China. Through sequencing the plant rhizosphere microbiome and measuring peat properties, we explored the plant–soil interactions and identified the keystone microbial taxa in peatlands of three vegetation types. Results showed that peat pH decreased along with the plant community shift from Sphagnum to shrub, which may be due to the accumulation of sulfur and phenolics. Lower pH further reduced bacterial diversity in shrub peatlands as Acidobacteriota became predominant in the keystone taxa. Overall, microbiomes in shrub peatlands showed degraded properties, such as a less stable microbial community dominated by few keystone taxa and the loss of methane‐mitigating microbes. The keystone microbial taxa in Sphagnum peatlands included microbes that utilize insoluble organic substances, mono‐ and oligo‐saccharides. Most importantly, the methanotrophic microbes that oxidize methane only appeared in the keystone taxa of Sphagnum peatlands. Mixed plant community peatlands contained the highest concentrations of iron. Slow‐growing fungi and bacteria were in the keystone microbial taxa, indicating slow decomposition rates in these peatlands. Our study suggests that human activity and climate change‐induced peatland vegetation shift from Sphagnum to shrub leads to an unstable belowground community, indicating the degraded peatland, which may exacerbate in the future.

Ectomycorrhizal effects on decomposition are highly dependent on fungal traits, climate, and litter properties: A model-based assessment

It has been proposed that competition between ectomycorrhizal (ECM) fungi and free-living saprotrophs for resources like nitrogen (N) slows decomposition and increases the soil carbon storage in ECM ecosystems compared to arbuscular (AM) ecosystems. However, empirical evidence for the generality of such ECM effects is equivocal, and confounding mechanisms have been proposed that affect the magnitude and direction of ECM effects on soil carbon. Here we conduct a theoretical modeling experiment, where we explicitly incorporate mycorrhizal processes into the Carbon, Organisms, Rhizosphere, and Protection in the Soil Environment (CORPSE) model. We use the model to explore the conditions under which ECM N acquisition processes can induce stronger saprotrophic N limitation and result in slower decomposition rates and greater soil organic carbon accumulation compared to AM processes. We found that the ECM fungi more strongly inhibited decomposition when litter inputs were N-depleted and relatively recalcitrant and when ECM fungi possessed a strong capacity to mine N from both recalcitrant soil organic matter and microbial necromass. Climate and seasonality also played a role as the ECM competition effect was strongest at low mean annual temperatures and when litterfall peaked seasonally. Priming effects driven by high root exudation rates in ECM-dominated systems could overwhelm the competition effect and reduce soil carbon under some circumstances. The ECM effect on decomposition in our simulations was highly context dependent. Based on our model results, we expect to see a strong ECM competition effect in temperate deciduous and boreal forests with relatively recalcitrant litter inputs, and with ECM fungi that produce oxidases and necromass-degrading enzymes. However, even a relatively strong ECM competition effect on decomposition only increased soil organic carbon accumulation by ∼10%.

Potential impacts of seasonal and altitudinal changes on enzymatic peat decomposition in the High Andean Paramo region of Ecuador

The Andean Paramo is a vast ecosystem, characterized by distinct vegetational zones at several altitudinal levels with huge water storage and carbon fixation capacity within its peat-like andosols, due to a slow decomposition rate of organic matter. These characteristics become mutually related as enzymatic activities increase with temperature and are associated with oxygen penetration, restricting the activity of many hydrolytic enzymes according to the enzyme Latch Theory. This study describes the changing activity of sulfatase (Sulf), phosphatase (Phos), n-acetyl-glucosaminidase (N-Ac), cellobiohydrolase (Cellobio), β-glucosidase (β-Glu), and peroxidase (POX) on an altitudinal scale from 3600 to 4200 m, in rainy and dry seasons at 10 and 30 cm sampling depth, related to physical and chemical soil characteristics, like metals and organic elements. Linear fixed-effect models were established to analyze these environmental factors to determine distinct decomposition patterns. The data suggests a strong tendency towards decreasing enzyme activities at higher altitudes and in the dry season up to two-fold stronger activation for Sulf, Phos, Cellobio, and β-Glu. Especially the lowest altitude showed considerably stronger activity of N-Ac, β-Glu, and POX. Although sampling depth revealed significant differences for all hydrolases but Cellobio, it had minor effects on model outcomes. Further organic rather than physical or metal components of the soil explain the enzyme activity variations. Although the levels of phenols coincided mostly with the soil organic carbon content, there was no direct relation between hydrolases, POX activity, and phenolic substances. The outcome suggests that slight environmental changes with global warming might cause important changes in enzyme activities leading to increased organic matter decomposition at the borderline between the paramo region and downslope ecosystems. Expected extremer dry seasons could cause critical changes as aeration increases peat decomposition leading to a constant liberation of carbon stocks, which puts the paramo region and its ecosystem services in great danger.

Improvement of straw decomposition and rice growth through co-application of straw-decomposing inoculants and ammonium nitrogen fertilizer

BackgroundThe growth of rice is reduced by the slow decomposition of accumulated straw, which competes with rice for soil nitrogen nutrient. In recent year, straw-decomposing inoculants (SDIs) that can accelerate straw decomposition and ammonium nitrogen (N) fertilizer that can quickly generate available N is increasingly adopted in China. However, it is still unknown whether the N demand of straw decomposition and crop growth can be simultaneously met through the co-application of SDIs and ammonium N fertilizer.ResultsIn this study, we investigated the effect of the co-application of SDIs and ammonium bicarbonate on decomposition rate of wheat straw, rice growth and rice yield over two consecutive years in rice-wheat rotation system. Compound fertilizer (A0) was used as control. The ratios of ammonium bicarbonate addition were 20% (A2), 30% (A3) and 40% (A4), respectively, without SDIs or with SDIs (IA2, IA3, IA4). Our results revealed that without SDIs, compared with A0, straw decomposition rate, rice growth and yield were improved under A2; However, under A3, rice yield was decreased due to the slow decomposition rate of straw and limited growth of rice during late growth stage. Combining SDIs and N fertilizer increased straw decomposition rate, rice growth rate and yield more than that of N fertilizer alone, especially under IA3. Compared with A0, straw decomposition rate, tiller number, aboveground biomass, leaf area index, root length, and nitrogen use efficiency were significantly increased by 16%, 8%, 27%, 12%, 17%, and 15% under IA3. Consequently, the average rice yield of IA3 was increased to 10,856 kg/ha, which was 13% and 9% higher, respectively, than of A0 and A2.ConclusionOur results indicated that ammonium bicarbonate application alone carried a risk of nutrient deficiency during late growth stage and yield decline. Therefore, the co-application of SDIs and 30% ammonium N fertilizer substitution can be a favorable practice to simultaneously accelerate straw decomposition and increase rice crop growth.