Search

Straw incorporation is crucial to soil organic carbon (SOC) sequestration, thus improving soil fertility and mitigating climate change. The fate of straw C and the associated net SOC balance remain largely unexplored, particularly in soils subjected to long-term mineral and organic fertilization. To address this, soil (δ13C: –19‰) that had been continuously cropped with maize for 31 years and subjected to five long-term fertilization regimes, including (i) control (Unfertilized), (ii) mineral fertilizer (NPK) application, (iii) 200% NPK (2 × NPK) application, (iv) manure (M) application, and (v) NPK plus manure (NPKM) application, was incubated with or without addition of rice straw (δ13C: –29‰) for 70 days. Straw addition largely primed SOC mineralization. The priming effect (PE) was considerably higher in 2 × NPK (+122% of CO 2 from soil without straw addition) but lower in M (+43%) relative to the unfertilized soil (+82%), highlighting the importance of fertilization in controlling PE intensity. Fertilization increased the straw-derived microbial biomass C by 90–577% and straw-derived SOC by 34–68% compared to the unfertilized soil, primarily due to the increased abundance of Gram-negative bacteria and cellobiohydrolase activity. Straw-derived SOC was strongly positively correlated with straw-derived microbial biomass C, suggesting that dead microbial biomass (necromass) was a dominant precursor of SOC formation. Consequently, fertilization facilitated microbial utilization of straw C and its retention in soil, particularly in the M and NPKM fertilized soils. The amounts of straw-derived SOC overcompensated for the SOC losses by mineralization, resulting in net C sequestration which was highest in the NPK fertilized soil. Our study emphasizes that NPK fertilization decreases the intensity of the PE induced by straw addition and increases straw C incorporation into SOC, thus facilitating C sequestration in agricultural soils. • Fertilization regulated the intensity of priming effect induced by straw addition. • Fertilization increased straw C assimilated by microbial biomass and straw-derived SOC. • Straw-derived SOC was closely correlated with straw-derived microbial biomass C. • NPK fertilization decreased priming effect intensity and increased straw-derived SOC. • NPK fertilization facilitates the SOC sequestration after straw addition. [ABSTRACT FROM AUTHOR]

Long-term use of artificial fertiliser has a significant impact on soil organic carbon (SOC). We used physical–chemical fractionation methods to assess the impact of long-term (26 years) fertilisation in a maize cropping system developed on Brown Earth in Northeast China. Plot treatments consisted of control (CK); nitrogen (N) fertiliser (N2); low-level organic manure combined with inorganic N and phosphorus (P) fertiliser (M1N1P1); medium-level organic manure combined with inorganic N fertiliser (M2N2); and high-level organic manure combined with inorganic N and P fertiliser (M4N2P1). Our objectives were to (1) determine the contents of and variations in the SOC fractions; (2) explore the relationship between total SOC and its fractions. In treatments involving organic manure (M1N1P1, M2N2, and M4N2P1), total SOC and physically protected microaggregate (μagg) and μagg occluded particulate organic carbon (iPOC) contents increased by 9.9–58.9%, 1.3–34.7%, 29.5–127.9% relative to control, respectively. But there no significant differences ( P > 0.05) were detected for the chemically, physically–chemically, and physically–biochemically protected fractions among the M1N1P1, M2N2, and M4N2P1 treatments. Regression analysis revealed that there was a linear positive correlation between SOC and the unprotected coarse particulate organic carbon (cPOC), physically protected μagg, and iPOC fractions ( P < 0.05). However, physically–chemically, and physically–biochemically protected fractions responded negatively to SOC content. The highest rate of C accumulation among the SOC fractions occurred in the cPOC fraction, which accounted for as much as 32% of C accumulation as total SOC increased, suggesting that cPOC may be the most sensitive fraction to fertiliser application. We found that treatments had no effect on C levels in H-μsilt and NH-μsilt, indicating that the microaggregated silt C-fractions may have reached a steady state in terms of C saturation in the Brown Earth of Northeast China. [ABSTRACT FROM AUTHOR]

Ara h 2 was purified from peanuts that were thermally treated by various processes, including boiling, glycation, frying and roasting. The allergenicity of Ara h 2 in Balb/c mice and the influence of thermal processing on the structural characteristics, and binding capacity of three core antigenic epitopes were studied. The results demonstrated that boiling, glycation and frying induced the down-regulation of the allergenicity of Ara h 2 in Balb/c mice, the collapse of its tertiary/secondary structure, and a reduction in the core epitope binding capacity; roasting showed a comparable allergenicity and the weakest inhibitory effect on core epitope binding capacity. These results indicate that thermal processing causes alteration of the protein structure and core epitopes of Ara h 2, and may affect its allergenicity. [ABSTRACT FROM AUTHOR]

Cationic polyacrylates have efficient reverse demulsification performance and air flotation performance, which make them potentially viable for application in offshore oil fields. However, study of the relationship between their structure and performance is still lacking. In this paper, four compounds (benzyl chloride, 3-chloro-1-propanol, 3-chloro-1,2-propanediol and 3-chloro-2-hydroxytrimethylammonium chloride) were used to modify the copolymer of acrylate and tertiary amine monomer, and four cationic polyacrylates (CP-1, CP-2, CP-3 and CP-4) with different cationic unit structures were prepared. The hydrophilicity of the cationic units in these four cationic polyacrylates increased successively. The relationship between the cationic unit structure, interface properties and produced water treatment performance of products was studied. The results showed that CP-1 had the highest air flotation efficiency because it had the largest adsorption capacity on the surface of bubble and the strongest attractive force between oil droplets, while CP-2 had the highest reverse demulsification efficiency because it had the largest adsorption capacity on the surface of oil droplet and the strongest ability to reduce the elastic modulus of the O/W interface. The research results can provide a reference for chemical agent selection in the treatment of oilfield produced water. • Four cationic polyacrylates with different cationic units were prepared. • 5 mg/L CP-1 had the highest flotation efficiency of 81.3% among four polyacrylates. • 5 mg/L CP-2 had the highest reverse demulsification efficiency of 56.0%. [ABSTRACT FROM AUTHOR]

The availability of soil phosphorus (P) is one of the key factors that regulate crop productivity. Fertilization practices with P fertilizers carry a high risk of non-point environmental pollution due to water run-off and leaching. The present work discusses data from a 29-year (1982–2011) fertilization experiment with wheat–soybean rotation. Its aim was to quantify and evaluate the dynamic of soil P availability in relation to P accumulation, crop yield, and environmental safety in northern China. This study included six treatments with four field replicates: CK (no fertilizer), NPK (mineral fertilizers), 1/2SNPK (mineral fertilizers plus 50% wheat straw return), SNPK (mineral fertilizers plus 100% wheat straw return), PMNPK (mineral fertilizers plus pig manure), and CMNPK (mineral fertilizers plus cattle manure). Continual additional application of farmyard manure (i.e., PMNPK and CMNPK) produced significantly ( P < 0.01) better soil total P and Olsen-P than NPK treatment, and both factors showed increasing trends. However, straw incorporation (i.e., 1/2SNPK and SNPK) had no effect on soil P or Olsen-P. There were significant positive correlations between P budget and increase in Olsen-P and total P. These correlations indicated that, with each 100 kg ha −1 of P budget, there were about 1.0–1.1 and 22.5–26.0 mg kg −1 increases in Olsen-P and total P for the straw incorporation treatments, whereas there were 5.7–5.9 and 26.5–30.8 mg kg −1 increases in Olsen-P and total P for use of manure. Average P activation coefficients for soil Olsen-P in the PMNPK and CMNPK treatments increased sharply by 87.2% and 121.3% compared to the NPK treatment ( P < 0.01). Two segment regression analyses indicated there to be observable changes in the relationships between Olsen-P and relative crop yield, and in Olsen-P and soluble-P, indicating critical Olsen-P levels of 11 mg kg −1 for crop yield, and 18 mg kg −1 for soluble P, respectively. In conclusion, much more P is available in the soil under long-term farmyard manure than crop straw incorporation when the amount of P accumulation is uniform. Long-term, continuous, excessive use of farmyard manure to increase crop yield is not sustainable and has a high risk of P environmental pollution. The incorporation of crop straw is a recommended means of managing which decreases the risk of P environmental pollution without compromising crop productivity of vertisol soil in northern China. [ABSTRACT FROM AUTHOR]

Abstract: Using first-principles calculations, the structural phase transition between the zinc-blende (ZB) and the rocksalt (RS) phases and the thermodynamic properties of indium phosphide (InP) are investigated by means of the pseudo-potential plane-waves method. The calculations are performed within the generalized gradient approximation (GGA) to density functional theory with the Perdew-Burke and Ernzerhof (PBE) exchange-correlation functional. On the basis of the third-order Birch–Murnaghan equation of states, the transition pressure P t =10GPa between the ZB and RS phases of InP is determined. The calculated values are in excellent agreement with experiments and similar theoretical calculations. From the theoretical calculations, the relationship of the relative volume V/V 0, the Debye temperature Θ and the heat capacity C V with the pressure P and temperature T is also successfully obtained. [ABSTRACT FROM AUTHOR]

The incorporation of crop straw with fertilization is beneficial for soil carbon sequestration and cropland fertility improvement. Yet, relatively little is known about how fertilization regulates the emissions of the greenhouse gas nitrous oxide (N 2 O) in response to straw incorporation, particularly in soils subjected to long-term fertilization regimes. Herein, the arable soil subjected to a 31-year history of five inorganic or organic fertilizer regimes (unfertilized; chemical fertilizer application, NPK; 200% NPK application, 2 × NPK; manure application, M; NPK plus manure application, NPKM) was incubated with and without rice straw to evaluate how historical fertilization influences the impact of straw addition on N 2 O emissions. The results showed that compared to the unfertilized treatment, historical fertilization strongly increased N 2 O emissions by 0.48- to 34-fold, resulting from increased contents of hot water-extracted organic carbon (HWEOC), NO 3 −, and available phosphorus (Olsen-P). Straw addition had little impact on N 2 O emission from the unfertilized and NPK treatments, primarily due to Olsen-P limitation. In contrast, straw addition increased N 2 O emissions by 102–316% from the 2 × NPK, M, and NPKM treatments as compared to the corresponding straw-unamended treatments. These results indicated that N 2 O emissions in response to straw addition were largely regulated by historical fertilization. The N 2 O emissions were closely associated with the depletion of NO 3 − and decoupled from change in NH 4 + content, suggesting that NO 3 − was the main substrate for N 2 O production upon straw addition. The stoichiometric ratios of HWEOC to mineral N and mineral N to Olsen-P were key factors affecting N 2 O emissions, underscoring the importance of resource stoichiometry in regulating N 2 O emissions. In conclusion, historical fertilization largely regulated the impacts of crop straw incorporation on N 2 O emissions via shifts in NO 3 − depletion and the stoichiometry of HWEOC, mineral N, and Olsen-P. Image 1 • Historical fertilization regulated the response of N 2 O emission to straw addition. • The magnitude of N 2 O emissions was closely linked to the depletion of soil nitrate. • The availability and stoichiometry of soil C, N and P were key factors affecting N 2 O emission. [ABSTRACT FROM AUTHOR]

Here, we report the development of a real-time PCR assay using a TaqMan minor groove binder (MGB, Genecore, NCBI: AF249896.1, 806-820) probe and primer sets designed to recognize the α-lactalbumin gene from the cow (Bos taurus). We evaluated the efficacy of this assay for detecting and quantifying cow α-lactalbumin in commercial foods. Our results demonstrated that the developed method was highly sensitive and showed high specificity for cow milk, with consistent detection of 0.05 ng of bovine DNA. We tested 42 commercial food samples with or without cow milk listed as an ingredient by using the developed assay. Among the 42 samples, 26 products that listed milk as an ingredient and 3 products might contain milk showed positive signals, whereas the other 9 products that did not contain milk and 4 products that might contain milk tested negative. Therefore, this method could be widely used for the detection of cow milk allergens in food. [ABSTRACT FROM AUTHOR]

Fertilization affects soil microbial community by altering soil organic carbon (C) and nutrients availability. However, it remains unclear how changes in stoichiometric C, N, and P ratios resulting from fertilization affect microbial community. We investigated a 26-year field experiment receiving inorganic fertilizers (N, NP, PK, and NPK), organic N combination (with manure and straw), natural recovery (fallow), and no fertilizer (control). The aim of this study was to explore the responses of microbial community to C: N:P stoichiometry in soil and microbial biomass of topsoil (0–20 cm) and subsoil (20–40 cm). Results showed that compared to control treatment, organic application increased the ratio of fungi to bacteria (F:B) in topsoil and gram-negative bacteria to gram-positive bacteria (G−:G+) in subsoil. However, application of inorganic decreased both the F: B and G−:G+ ratio in topsoil. Increasing soil C, N and P availability resulted from inorganic fertilizers and organic combination fertilization caused stoichiometric imbalance between soil and microbial biomass. As a result, the F:B and G−:G+ ratio were positively related to C:N imbalance but negatively associated with N:P imbalance in topsoil. Redundancy analysis (RDA) showed that main factors regulating microbial community were pH, C:P and N:P imbalances in topsoil, whereas TDN, N:P imbalance, DOC and soil C:N in subsoil. Furthermore, C:P and N:P imbalance explained 16.4% in topsoil, and N:P imbalance explained 22.0% in subsoil of microbial community variation. These results reveal the shifts of soil microbial community are driven by changes in soil pH and C, N and P stoichiometric imbalance from long-term fertilization. [Display omitted] • Long-term organic combination enhanced soil C, N, and P pool and availability. • Soil microbial community was linked to stoichiometric C, N, and P imbalances. • F:B and G−:G+ ratios were regulated by N limitation in topsoil but P limitation in subsoil. • Driving factors on microbial community differed from topsoil to subsoil. [ABSTRACT FROM AUTHOR]

Abstract: Relatively few studies have compared invasibility and species invasiveness among microhabitats within communities, synchronously. We surveyed the abundance and performance of non-native Alternanthera philoxeroides (Mart.) Griseb. (alligator weed), its co-occurring native congener, Alternanthera sessilis (L.) DC. (sessile joyweed), and other species in a wetland community along a riparian zone in southeast China to test the hypotheses that: i) degree of invasion differs between different types of microhabitats within the community; and ii) microhabitat types that differ in invasibility also differ in soil resource availability or in sediment characteristics likely to affect resource availability; iii) phenotypic plasticity of A. philoxeroides may play a key role in its adaptation to diverse habitats as can be concluded from its extremely low genetic diversity in China. The study riparian zone comprises different types of microhabitats including wet abandoned field, swamp, marsh dunes and gravel dunes. Consistent with these hypotheses, cover of A. philoxeroides was high in abandoned fields (73±2.9%) and swamps (94±1.3%), which had high soil nutrients and water availability. On the contrary, cover of native A. sessilis was relatively high in marsh dunes and grave dunes, which had coarse gravel surfaces, low soil nutrients and low water availability. A. philoxeroides showed greater morphological plasticity in response to habitat variation. In abiotically harsh habitats, stems had limited growth, and were prostrate with weak adventitious roots at nodes, forming thin, scattered patches. In the two richer habitats, the highly branched plants spread over the water or soil surface, supporting dense stronger leaf-bearing stems which grew vertically. The growth pattern of A. sessilis among microhabitats did not exhibit significant variations. These results suggest that morphological plasticity and microhabitat types with high soil resources may facilitate invasions of A. philoxeroides. [Copyright &y& Elsevier]

Abnormal expression of specific microRNAs (miRNAs) is associated with the occurrence, development and prognosis of many diseases. In this study, a miRNA detection method based on exponential amplification reaction (EXPAR) and triplex DNA mediated aggregation of gold nanoparticles (AuNPs) was established. Specifically, one class of AuNPs is conjugated with an EXPAR probe, on which there is a complementary sequence of the target miRNA. The EXPAR reaction is triggered and duplex DNA is formed on the surface of AuNPs when the target miRNA exists. Then, single DNA probe on another class of AuNPs interacts with the duplex DNA to form triplex DNA, leading to the aggregation of the two classes of AuNPs, which could be quantified by UV–vis. The proposed method is highly selective and can afford a detection limit of 0.23 fM. Notably, all the ingredients needed for the analysis can pre-add to a tube and only 30 min is needed for the whole detection process. The method is simple, fast and with considerable selectivity and accuracy, so a great potential for this method is expected to meet the need of point-of-care testing of miRNA. Image 1 • A highly sensitive microRNA (miRNA) colorimetric detection method is established. • It is based on exponential amplification reaction and triplex DNA mediated aggregation of gold nanoparticles. • The method is highly selective and can afford a detection limit of 0.23 fM. • All the ingredients can pre-add to a tube and only 30 min is needed for the whole detection process. • A great potential for this method is expected to meet the need of point-of-care testing of miRNA. [ABSTRACT FROM AUTHOR]

As an effective field management practice for better crop productivity, fertilization showed profound impacts on soil health by altering soil chemical, physical, and biological processes. But, how soil health and related ecosystem multifunctionality (EMF) respond to long-term fertilization remains unclear. In this study, based on a 29-year field experiment, we evaluated soil health and EMF under chemical fertilization versus manure application. Long-term manure application maintained soil pH, significantly increased water-stable aggregate, total and available nutrients, microbial biomass and community (bacteria, fungi, and actinomycetes, etc.), and enzyme activities compared with treatments under chemical fertilizers. Edaphic factors of soil organic carbon (SOC), available phosphorous (AP), fungi, cation exchange capacity, and clay content were identified as key indicators of soil health evaluation by network analysis. The soil health indices (SHIs) of chemical fertilizer treatments were 39–52% lower than that of natural vegetation recovery, with carbon and nutrient cycling, soil biodiversity maintenance, and productivity at low ecosystem function levels. Manure application enhanced soil health by 150–196% compared to unfertilized control by improving SOC, P availability, and sustaining ecosystem functions with carbon and nutrient cycling, soil biodiversity maintenance, buffering and filtering capacity, and productivity at relatively high ecosystem function levels. The individual functions of carbon and nutrient cycling, physical structure stability, and productivity illustrated sensitive responses to the increase in soil health, while inherent soil functions of buffering and filtering capacity and soil biodiversity maintenance were only correlated with high soil health. Manuring improved soil functions and soil health simultaneously, indicating a synergistic relationship. Our findings highlight the significance of manure application to improve soil health and sustain functions in intensive agricultural systems. • SOC, AP, fungi, clay content, and CEC were identified as key indicators. • Natural vegetation recovery improved SHI compared with chemical fertilization. • Manuring improved soil health by sustaining soil multifunction at high levels. • Soil functions had diverse responses to soil health shifts. [ABSTRACT FROM AUTHOR]

Understanding drivers of straw decomposition is essential for adopting appropriate management practice to improve soil fertility and promote carbon (C) sequestration in agricultural systems. However, predicting straw decomposition and characteristics is difficult because of the interactions between many factors related to straw properties, soil properties, and climate, especially under future climate change conditions. This study investigated the driving factors of straw decomposition of six types of crop straw including wheat, maize, rice, soybean, rape, and other straw by synthesizing 1642 paired data from 98 published papers at spatial and temporal scales across China. All the data derived from the field experiments using little bags over twelve years. Overall, despite large differences in climatic and soil properties, the remaining straw carbon (C, %) could be accurately represented by a three-exponent equation with thermal time (accumulative temperature). The lignin/nitrogen and lignin/phosphorus ratios of straw can be used to define the size of labile, intermediate, and recalcitrant C pool. The remaining C for an individual type of straw in the mild-temperature zone was higher than that in the warm-temperature and subtropical zone within one calendar year. The remaining straw C after one thermal year was 40.28%, 37.97%, 37.77%, 34.71%, 30.87%, and 27.99% for rice, soybean, rape, wheat, maize, and other straw, respectively. Soil available nitrogen and phosphorus influenced the remaining straw C at different decomposition stages. For one calendar year, the total amount of remaining straw C was estimated to be 29.41 Tg and future temperature increase of 2 °C could reduce the remaining straw C by 1.78 Tg. These findings confirmed the long-term straw decomposition could be mainly driven by temperature and straw quality, and quantitatively predicted by thermal time with the three-exponent equation for a wide array of straw types at spatial and temporal scales in agro-ecosystems of China. [ABSTRACT FROM AUTHOR]

Manure amendments have been generally considered to enhance soil nutrient supply, thus improving soil fertility and crop productivity, especially in subtropical area. However, the underlying mechanisms of manure application effects on soil nitrogen (N) supply capacity and N transformation processes remain uncertain. Here, 15N isotope pool dilution techniques were used to determine the gross rates of N mineralization, ammonium (NH 4 +) immobilization and nitrification in red soil subjected to three decades of long-term fertilization regimes. Results showed that compared to treatments without manure, manure application alone or combined with chemical fertilizers significantly increased gross N mineralization rates by 4.55−8.31 folds, resulting from increased N-acquiring enzyme activity and decreased microbial N use efficiency (NUE). The decreased microbial NUE in the manure application treatments was due to alleviated imbalance of C:N between soil and microbial biomass. Gross NH 4 + immobilization rates were 7.35−11.34 folds higher in the treatments amended with manure (1.51−2.23 mg N kg−1 d−1) relative to without manure, attributed to increased microbial biomass and bacterial abundance. Compared to chemical fertilizers application, manure application decreased gross nitrification rates by 38−55%, due to the decline in NH 4 + availability via enhanced NH 4 + immobilization. The significantly lower ratio of gross nitrification to NH 4 + immobilization in the treatments with manure suggested that manure amendments could potentially mitigate the risk of soil N losses. Overall, long-term manuring has the potential to improve soil N supply and retention capacities by enhancing gross N mineralization and NH 4 + immobilization accompanying with decreased gross nitrification. • Manuring increased gross N mineralization rate via decreased microbial NUE. • Manuring facilitated gross NH 4 + immobilization, due to increased microbial biomass. • Gross nitrification rate was positively related to NH 4 + content and AOA abundance. • Manuring decreased ratio of gross nitrification to NH 4 + immobilization rates. [ABSTRACT FROM AUTHOR]

Reclamation has been widely used to alleviate the degradation of cultivated upland and support the increasing grain demand. However, the response of soil ecosystem functioning and soil health to the reclamation of coastal wetlands remains unclear. A reclaimed soil chronosequence over 1000 years in Hangzhou Bay, China, was analyzed to assess two key approaches to evaluate soil health. We used the minimum data set along with the soil quality index (SQI) area and the sensitivity–resistance approaches. The physicochemical properties of the reclaimed soils changed drastically at the initial stage (during the first 60 years) but only marginally thereafter. Owing to continuous freshwater irrigation, plant cultivation, fertilization, and desalination, from natural tidal flats converted to vegetable fields, the SQI and soil multifunctional index increased along the reclamation chronosequence. The soil properties sensitive to the reclamation of coastal wetlands (electrical conductivity, exchangeable potassium, and enzyme activities) explained most of the variation in the SQI area, followed by the resistance indicators. This suggests that small changes in the sensitivity indicators might have considerable impacts on the improvement of soil quality. The most resistant properties with the slowest changes included pH and physical characteristics—water content, bulk density, and aggregate size classes. The quality indicators identified for reclaimed soils in Hangzhou Bay based on the SQI area and sensitivity–resistance approaches can be useful for soil health evaluation for soils affected by natural and anthropogenic factors. These approaches and indicators can be effectively used to evaluate soil quality and develop sustainable agriculture. [Display omitted] • Soil quality indexes (SQI) were used and analyzed in a chronosequence of tidal flat reclamation. • SQI area and sensitivity–resistance approaches were useful for soil health evaluation. • Tidal flat reclamation increased soil quality and multifunctionality in Hangzhou Bay. • Sensitive parameters explained more variability of SQI area index than resistant soil properties. [ABSTRACT FROM AUTHOR]

Optimal nitrogen (N) management is critical for efficient crop production and agricultural pollution control. Approximate 210–220 kg ha−1 N fertilizer was applied in millions of small plots through broadcasting way in China, resulting in over and loss of N fertilizers. However, it is difficult to implement advanced management practices on smallholder farms due to a lack of knowledge. Here, using 35,502 on-farm fertilization experiments, we demonstrated that smallholders in China could actually produce more grain with less N fertilizer use only through optimizing N application rate. The yields of wheat, maize and rice were shown to increase between 10% and 19% while N application rates were reduced by 15–19%. These changes resulted in an increase in N use efficiency (NUE) by 32–46% and a reduction in N surplus by 40% without actually changing farmers' operational practices. By reducing N application rates in line with official recommendations would not only save fertilizer cost while increasing crop yield, but also at the same time reduce environmental N pollution in China. Beyond of optimizing N application rate, improved management practices were required to produce more grain with less pollution, which would need about 11.8 billion US dollars for the implementation and reducing N loss reduction by 1.75 million tons to the environment. [Display omitted] • Optimizing N fertilizer rate was estimated based on 35,502 field experiments nationally. • Optimizing N rate increased NUE by 32–46% with 40% lower N surplus. • Environmental N loss was predicted to be reduced by 5.06 million t by optimizing N rate. • Best management strategies could result in 1.75 million tons N loss reduction. [ABSTRACT FROM AUTHOR]

Highlights: [•] We compared mating systems of two Scirpus species. [•] S. mariqueter is a completely self-compatible species despite protogynous flowers. [•] S. planiculmis is a primarily outcrossing species, but possessing a low level of self-compatibility. [•] Asymmetrical gene flow can occur from S. planiculmis to S. mariqueter. [ABSTRACT FROM AUTHOR]

Abstract: Scirpus × mariqueter Tang & F.T. Wang (CYPERACEAE) is a pioneer plant of the tidal zone of estuaries of East Asia. Amplified fragment length polymorphisms (AFLP) were used to infer the relationship between S. × mariqueter and its putative progenitors, Scirpus planiculmis F. Schmidt and Scirpus triqueter L. The genetic distance between S. × mariqueter and S. triqueter was much higher than that between S. × mariqueter and S. planiculmis, and samples of S. × mariqueter and those of S. planiculmis did not form a monophyletic group, while the S. triqueter group formed a distinct monophyletic group. However, we also detected an apparent clustering of individuals of S. × mariqueter and S. planiculmis separately. Our results disprove the hybrid origin of S. × mariqueter and rather suggest that it is more closely related to S. planiculmis. [Copyright &y& Elsevier]

Labile carbon (C) inputs affect the soil carbon:nitrogen (C:N) ratio and microbial stoichiometric homeostasis, which control the intensity and direction of the priming effect (PE). Here, we clarified how soil microorganisms regulate enzyme production and PE to maintain the C:N stoichiometric balance. Specifically, we conducted an incubation experiment by adding 13C-labeled glucose to four long-term fertilized paddy soils: no fertilization; fertilization with mineral nitrogen, phosphorus, and potassium (NPK); NPK combined with straw; and NPK with manure (NPKM). After glucose addition, the dissolved organic carbon-to-ammonium (DOC:NH 4 +) ratio (24–39) initially increased, but subsequently decreased after day 2 following glucose exhaustion. In parallel, the microbial C:N imbalance [(DOC:NH 4 +):(microbial biomass C:microbial biomass N)] rapidly decreased from day 2 (4.6–7.2) to day 20 (<0.5). Thus, microorganisms became C limited after 20 days of incubation. Excess C, resulting from glucose addition, increased N-hydrolase (chitinase) production and N mining from soil organic matter (SOM) through positive PEs. However, C hydrolase (β -1,4-glucosidase and β-xylosidase) activity increased, while that of N hydrolase (chitinase) decreased, following glucose exhaustion. Consequently, the C:N microbial biomass ratio increased as the DOC:NH 4 + ratio decreased, leading to negative PEs. NPKM-fertilized soil had the largest cumulative PE (2.3% of soil organic carbon) because it had the highest microbial biomass and iron (Fe) reduction rate. Thus, this increased N mining from SOM maintained the microbial C:N stoichiometric balance. We concluded that soil microorganisms regulate C- and N-hydrolase production to control the intensity and direction of PE, maintaining the C:N stoichiometric balance in response to labile C inputs. [Display omitted] • Glucose input into paddy soil increased DOC:NH 4 + ratio and microbial biomass (MB). • High C availability increased activity of N-hydrolases and priming effect (PE). • Decreased MB and N-hydrolase activity induced negative PE with labile C exhaustion. • Highest cumulative PE observed in combined NPK and chicken manure fertilized soil. • C and N hydrolase production is key for regulating C:N stoichiometry of MB and PE. [ABSTRACT FROM AUTHOR]

Litter decomposition is a vital component of carbon and nutrients cycling and energy flow within terrestrial ecosystems. Understanding the litter decomposition rate with a temperature change of 1 °C (k DD , degree days−1) is critical for quantifying the climate-carbon, nutrients, and energy cycle feedback and predicting the response of ecosystems to climate change. However, the spatial pattern of k DD is uncertain, given differences in litter quality and soil property responses to temperature. Therefore, our goal was to explore the spatial patterns and driving factors of the k DD with a synthesized dataset, which included 1370 individual studies from 253 publications and accumulated daily temperature of each site from 389 meteorological stations. The dataset covered forest, grassland, and cropland ecosystems. The k DD significantly decreased with increasing latitude and varied with climate variables, litter quality, soil properties, and experimental duration under different ecosystems. The averaged k DD in the forest, grassland, and cropland ecosystems were 1.30, 2.23, and 3.35 × 10−4 degree days−1, respectively. The k DD markedly decreased with the increase of experimental years. Climate variables [mean annual temperature (MAT) and precipitation (MAP)] accounted for 36.8% of the total variance in the k DD , followed by soil properties (e.g., soil sand content and pH; 28.1%); experimental duration (23.0%); and litter properties (e.g., nitrogen and lignin; 12.1%). MAT and MAP had substantially indirect effects on k DD via regulating soil and litter properties. Lignin directly and negatively affected k DD. Higher correlations between k DD and litter properties were maintained if the effects of climate, soil properties, and experimental duration were removed. Overall, our findings highlight that intrinsic (litter properties) and extrinsic (climatic and soil properties) variables directly and indirectly regulated the k DD at a regional scale, respectively, providing a framework for optimizing the ecosystem process model to global warming scenarios. Meantime, these results clarify the crucial role of environmental variables in regulating the k DD , potentially affecting the terrestrial carbon, nutrients, and energy-climate feedback. Image 1 • The highlights of the paper are as follows: • Litter decomposition rate significantly decreased with increasing latitude and experimental time. • A network of climate, soil properties, and litter properties determined litter decomposition rate. • Intrinsic and extrinsic variables directly and indirectly regulated litter decomposition rate. [ABSTRACT FROM AUTHOR]

Labile carbon (C) inputs strongly alter soil organic matter (SOM) turnover by priming, thus affecting soil C dynamics and soil fertility in the long term. The frequency of labile C inputs is expected to affect the intensity of priming effect. We evaluated the effects of single versus repeated additions of 13C-labeled glucose (with added 13C corresponding to 2% of soil organic C content) to five soils with increasing fertility level on the intensity of priming effect and soil C balance. Repeated glucose addition induced 61–108% greater C mineralization due to positive priming than the single addition in all soils. The intensity of priming effect declined with soil fertility level and mineral nitrogen (N) content, but increased with higher activities of N-acquisition enzymes (N-acetyl-glucosaminidase and leucine amino peptidase). Consequently, the decrease in N availability strongly increased the intensity of priming effect presumably by enhancing microbial N mining from SOM. Considering the C balance between SOM losses due to priming and glucose-C retention, glucose addition was responsible for net C losses in the low and moderate fertility soils (−14.0 to −0.30 mg C g−1 SOC after 14 weeks) but led to C gains in the high fertility soils (+0.44 to +4.36 mg C g−1 SOC). Greater retention of glucose-C was attributed to higher N availability and more intensive microbial growth, thus supporting microbial necromass formation and soil C sequestration. Compared to single addition, repeated glucose addition caused larger net C losses or lower C gains due to stronger SOM priming. In conclusion, the frequency of substrate addition and soil fertility are important regulators of SOM priming and the C balance. This knowledge should be informative to interpret soil C dynamics in response to labile C inputs in agroecosystems. • Positive SOM priming was much stronger after repeated versus single glucose addition. • The decrease in nitrogen availability increased the priming effect. • SOM priming declined with soil fertility level. • Increased soil fertility weakened SOM priming and increased glucose-C retention. • Increased soil fertility changed glucose-induced net soil C balance from negative to positive. [ABSTRACT FROM AUTHOR]