Crop-Specific Responses to Cold Stress and Priming: Insights from Chlorophyll Fluorescence and Spectral Reflectance Analysis in Maize and Soybean

This study aimed to investigate the impact of cold stress and priming on photosynthesis in the early development of maize and soybean, crops with diverse photosynthetic pathways. The main objectives were to determine the effect of cold stress on chlorophyll a fluorescence parameters and spectral reflectance indices, to determine the effect of cold stress priming and possible stress memory and to determine the relationship between different parameters used in determining the stress response. Fourteen maize inbred lines and twelve soybean cultivars were subjected to control, cold stress, and priming followed by cold stress in a walk-in growth chamber. Measurements were conducted using a portable fluorometer and a handheld reflectance instrument. Cold stress induced an overall downregulation of PSII-related specific energy fluxes and efficiencies, the inactivation of RCs resulting in higher energy dissipation, and electron transport chain impairment in both crops. Spectral reflectance indices suggested cold stress resulted in pigment differences between crops. The effect of priming was more pronounced in maize than in soybean with mostly a cumulatively negative effect. However, priming stabilized the electron trapping efficiency and upregulated the electron transfer system in maize, indicating an adaptive response. Overall, this comprehensive analysis provides insights into the complex physiological responses of maize and soybean to cold stress, emphasizing the need for further genotype-specific cold stress response and priming effect research.

Mycorrhizal fungi modify decomposition: a meta-analysis

It has been proposed that ectomycorrhizal fungi can reduce decomposition while arbuscular mycorrhizal fungi may enhance it. These phenomena are known as the 'Gadgil effect' and 'priming effect', respectively. However, it is unclear which one predominates globally. We evaluated whether mycorrhizal fungi decrease or increase decomposition, and identified conditions that mediate this effect. We obtained decomposition data from 43 studies (97 trials) conducted in field or laboratory settings that controlled the access of mycorrhizal fungi to substrates colonized by saprotrophs. Across studies, mycorrhizal fungi promoted decomposition of different substrates by 6.7% overall by favoring the priming effect over the Gadgil effect. However, we observed significant variation among studies. The substrate C : N ratio and absolute latitude influenced the effect of mycorrhizal fungi on decomposition and contributed to the variation. Specifically, mycorrhizal fungi increased decomposition at low substrate C : N and absolute latitude, but there was no discernable effect at high values. Unexpectedly, the effect of mycorrhizal fungi was not influenced by the mycorrhizal type. Our findings challenge previous assumptions about the universality of the Gadgil effect but highlight the potential of mycorrhizal fungi to negatively influence soil carbon storage by promoting the priming effect.

Differences in patient-reported and clinical characteristics by age group in adults with type 2 diabetes

BACKGROUND

The global burden of type 2 diabetes (T2D) is growing, and the age of onset is widening, resulting in increasing numbers of young adults and elderly patients with T2D. Age-specific diabetes care needs have yet to be fully explored.

AIMS

This study examined (1) differences in patient-reported and clinical characteristics by age group and (2) the effect of age on two proxy measures assessing psychological health and self-care adherence after adjusting for potential mediators.

METHODS

A cross-sectional, correlational design was used. Adults with type 2 diabetes (T2D) were recruited from a university hospital in Korea between 2019 and 2020. Participants were divided into four groups based on years of age (40s and younger group [n = 27]; 50s group [n = 47]; 60s group [n = 54]; and 70s and older group [n = 48]) to compare patient-reported and clinical characteristics. Chi-square tests, ANOVA, Kruskal-Wallis tests, and logistic regression analysis were performed to assess group differences and effect of age on psychological health and self-care adherence.

RESULTS

Of 178 participants, two-thirds were men (n = 114; 64.41%). The mean ages in the 40s and younger, 50s, 60s, and 70s and older groups were 39.4, 54.7, 63.9, and 76.0 years, respectively. There were significant differences in patient-reported and clinical characteristics by age group. The youngest group reported the poorest psychological health and self-care behaviors. Although the oldest group showed the poorest physical functioning, this group also showed the highest self-care adherence and the best psychological health. Regarding clinical characteristics, traditional diabetes-related blood test results showed no significant group differences.

LINKING EVIDENCE TO ACTION

Age-specific diabetes care needs were identified in adults with T2D. Interventions to improve psychological health and priming effects of behavioral adherence need to be developed. Furthermore, meticulous investigation to detect potential complications early is essential in adults with T2D.

Key Role of Vegetation Cover in Alleviating Microplastic-Enhanced Carbon Emissions

Microplastics (MPs) are considered to influence fundamental biogeochemical processes, but the effects of plant residue-MP interactions on soil carbon turnover in urban greenspaces are virtually unknown. Here, an 84-day incubation experiment was constructed using four types of single-vegetation-covered soils (6 years), showing that polystyrene MP (PSMP) pollution caused an unexpectedly large increase in soil CO2 emissions. The additional CO2 originating from highly bioavailable active dissolved organic matter molecules (<380 °C, predominantly polysaccharides) was converted from persistent carbon (380-650 °C, predominantly aromatic compounds) rather than PSMP derivatives. However, the priming effect of PSMP derivatives was weakened in plant-driven soils (resistivity: shrub > tree > grass). This can be explained from two perspectives: (1) Plant residue-driven humification processes reduced the percentage of bioavailable active dissolved organic matter derived from the priming effects of PSMPs. (2) Plant residues accelerated bacterial community succession (dominated by plant residue types) but slowed fungal community demise (retained carbon turnover-related functional taxa), enabling specific enrichment of glycolysis, the citric acid cycle and the pentose phosphate pathway. These results provide a necessary theoretical basis to understand the role of plant residues in reducing PSMP harm at the ecological level and refresh knowledge about the importance of biodiversity for ecosystem stability.

Internal representations of the canonical real-world distance of objects

In the real world, every object has its canonical distance from observers. For example, airplanes are usually far away from us, whereas eyeglasses are close to us. Do we have an internal representation of the canonical real-world distance of objects in our cognitive system? If we do, does the canonical distance influence the perceived size of an object? Here, we conducted two experiments to address these questions. In Experiment 1, we first asked participants to rate the canonical distance of objects. Participants gave consistent ratings to each object. Then, pairs of object images were presented one by one in a trial, and participants were asked to rate the distance of the second object (i.e., a priming paradigm). We found that the rating of the perceived distance of the target object was modulated by the canonical real-world distance of the prime. In Experiment 2, participants were asked to judge the perceived size of canonically near or far objects that were presented at the converging end (i.e., far location) or the opening end (i.e., near location) of a background image with converging lines. We found that regardless of the presentation location, participants perceived the canonically near object as smaller than the canonically far object even though their retinal and real-world sizes were matched. In all, our results suggest that we have an internal representation of the canonical real-world distance of objects, which affects the perceived distance of subsequent objects and the perceived size of the objects themselves.

Carbon emissions and priming effects derived from crop residues and their responses to nitrogen inputs

Crop residue-derived carbon (C) emissions and priming effects (PE) in cropland soils can influence the global C cycle. However, their corresponding generality, driving factors, and responses to nitrogen (N) inputs are poorly understood. As a result, the total C emissions and net C balance also remain mysterious. To address the above knowledge gaps, a meta-analysis of 1123 observations, taken from 51 studies world-wide, has been completed. The results showed that within 360 days, emission ratios of crop residues C (ER) ranged from 0.22% to 61.80%, and crop residues generally induced positive PE (+71.76%). Comparatively, the contribution of crop residue-derived C emissions (52.82%) to total C emissions was generally higher than that of PE (12.08%), emphasizing the importance of reducing ER. The ER and PE differed among crop types, and both were low in the case of rice, which was attributed to its saturated water conditions. The ER and PE also varied with soil properties, as PE decreased with increasing C addition ratio in soils where soil organic carbon (SOC) was less than 10‰; in contrast, the opposite phenomenon was observed in soils with SOC exceeding 10‰. Moreover, N inputs increased ER and PE by 8.31% and 3.78%, respectively, which was predominantly attributed to (NH4 )2 SO4 . The increased PE was verified to be dominated by microbial stoichiometric decomposition. In summary, after incorporating crop residues, the total C emissions and relative net C balance in the cropland soils ranged from 0.03 to 23.47 mg C g-1 soil and 0.21 to 0.97 mg C g-1 residue-C g-1 soil, respectively, suggesting a significant impact on C cycle. These results clarify the value of incorporating crop residues into croplands to regulate global SOC dynamics and help to establish while managing site-specific crop return systems that facilitate C sequestration.

Deciphering Biotic and Abiotic Mechanisms Underlying Straw Decomposition and Soil Organic Carbon Priming in Agriculture Soils Receiving Long-Term Fertilizers

Straw-related carbon (C) dynamics are central for C accrual in agro-ecosystems and should be assessed by investigating their decomposition and soil organic carbon (SOC) priming effects. Our understanding of biotic and abiotic mechanisms underpinning these two C processes, however, is still not sufficiently profound. Soils that had received organic and mineral fertilizers for 26 years were sampled for a 28 day incubation experiment to assess 13C-labeled straw decomposition and SOC priming effects. On the basis of analyzing physicochemical properties, fungal taxonomic (MiSeq sequencing) and functional (metagenomics) guilds, we quantified the contributions of biotic and abiotic attributes to straw decomposition and SOC priming. Here, we propose two distinct mechanisms underlying straw decomposition and SOC priming in agriculture soils: (i) accelerated straw mineralization in manure-treated soils was mainly driven by biotic forces, while (ii) larger SOC priming in NPK-amended soils was through abiotic regulation.

Accelerated organic matter decomposition in thermokarst lakes upon carbon and phosphorus inputs

Mineralization of dissolved organic matter (DOM) in thermokarst lakes plays a non-negligible role in the permafrost carbon (C) cycle, but remains poorly understood due to its complex interactions with external C and nutrient inputs (i.e., aquatic priming and nutrient effects). Based on large-scale lake sampling and laboratory incubations, in combination with 13 C-stable-isotope labeling, optical spectroscopy, and high-throughput sequencing, we examined large-scale patterns and dominant drivers of priming and nutrient effects of DOM biodegradation across 30 thermokarst lakes along a 1100-km transect on the Tibetan Plateau. We observed that labile C and phosphorus (P) rather than nitrogen (N) inputs stimulated DOM biodegradation, with the priming and P effects being 172% and 451% over unamended control, respectively. We also detected significant interactive effects of labile C and nutrient supply on DOM biodegradation, with the combined labile C and nutrient additions inducing stronger microbial mineralization than C or nutrient treatment alone, illustrating that microbial activity in alpine thermokarst lakes is co-limited by both C and nutrients. We further found that the aquatic priming was mainly driven by DOM quality, with the priming intensity increasing with DOM recalcitrance, reflecting the limitation of external C as energy sources for microbial activity. Greater priming intensity was also associated with higher community-level ribosomal RNA gene operon (rrn) copy number and bacterial diversity as well as increased background soluble reactive P concentration. In contrast, the P effect decreased with DOM recalcitrance as well as with background soluble reactive P and ammonium concentrations, revealing the declining importance of P availability in mediating DOM biodegradation with enhanced C limitation but reduced nutrient limitation. Overall, the stimulation of external C and P inputs on DOM biodegradation in thermokarst lakes would amplify C-climate feedback in this alpine permafrost region.

Unraveling the roles of coastal bacterial consortia in degradation of various lignocellulosic substrates

Lignocellulose, as the most abundant natural organic carbon on earth, plays a key role in regulating the global carbon cycle, but there have been only few studies in marine ecosystems. Little information is available about the extant lignin-degrading bacteria in coastal wetlands, limiting our understanding of their ecological roles and traits in lignocellulose degradation. We utilized in situ lignocellulose enrichment experiments coupled with 16S rRNA amplicon and shotgun metagenomics sequencing to identify and characterize bacterial consortia attributed to different lignin/lignocellulosic substrates in the southern-east intertidal zone of East China Sea. We found the consortia enriched on woody lignocellulose showed higher diversity than those on herbaceous substrate. This also revealed substrate-dependent taxonomic groups. A time-dissimilarity pattern with increased alpha diversity over time was observed. Additionally, this study identified a comprehensive set of genes associated with lignin degradation potential, containing 23 gene families involved in lignin depolymerization, and 371 gene families involved in aerobic/anaerobic lignin-derived aromatic compound pathways, challenging the traditional view of lignin recalcitrance within marine ecosystems. In contrast to similar cellulase genes among the lignocellulose substrates, significantly different ligninolytic gene groups were observed between consortia under woody and herbaceous substrates. Importantly, we not only observed synergistic degradation of lignin and hemi-/cellulose, but also pinpointed the potential biological actors at the levels of taxa and functional genes, which indicated that the alternation of aerobic and anaerobic catabolism could facilitate lignocellulose degradation. Our study advances the understanding of coastal bacterial community assembly and metabolic potential for lignocellulose substrates. IMPORTANCE It is essential for the global carbon cycle that microorganisms drive lignocellulose transformation, due to its high abundance. Previous studies were primarily constrained to terrestrial ecosystems, with limited information about the role of microbes in marine ecosystems. Through in situ lignocellulose enrichment experiment coupled with high-throughput sequencing, this study demonstrated different impacts that substrates and exposure times had on long-term bacterial community assembly and pinpointed comprehensive, yet versatile, potential decomposers at the levels of taxa and functional genes in response to different lignocellulose substrates. Moreover, the links between ligninolytic functional traits and taxonomic groups of substrate-specific populations were revealed. It showed that the synergistic effect of lignin and hemi-/cellulose degradation could enhance lignocellulose degradation under alternation of aerobic and anaerobic conditions. This study provides valuable taxonomic and genomic insights into coastal bacterial consortia for lignocellulose degradation.

Priming effect stimulates carbon release from thawed permafrost

Climate warming leads to widespread permafrost thaw with a fraction of the thawed permafrost carbon (C) being released as carbon dioxide (CO₂ ), thus triggering a positive permafrost C-climate feedback. However, large uncertainty exists in the size of this model-projected feedback, partly owing to the limited understanding of permafrost CO₂ release through the priming effect (i.e., the stimulation of soil organic matter decomposition by external C inputs) upon thaw. By combining permafrost sampling from 24 sites on the Tibetan Plateau and laboratory incubation, we detected an overall positive priming effect (an increase in soil C decomposition by up to 31%) upon permafrost thaw, which increased with permafrost C density (C storage per area). We then assessed the magnitude of thawed permafrost C under future climate scenarios by coupling increases in active layer thickness over half a century with spatial and vertical distributions of soil C density. The thawed C stocks in the top 3 m of soils from the present (2000-2015) to the future period (2061-2080) were estimated at 1.0 (95% confidence interval (CI): 0.8-1.2) and 1.3 (95% CI: 1.0-1.7) Pg (1 Pg = 10¹⁵  g) C under moderate and high Representative Concentration Pathway (RCP) scenarios 4.5 and 8.5, respectively. We further predicted permafrost priming effect potential (priming intensity under optimal conditions) based on the thawed C and the empirical relationship between the priming effect and permafrost C density. By the period 2061-2080, the regional priming potentials could be 8.8 (95% CI: 7.4-10.2) and 10.0 (95% CI: 8.3-11.6) Tg (1 Tg = 10¹²  g) C year^-1 under the RCP 4.5 and RCP 8.5 scenarios, respectively. This large CO₂ emission potential induced by the priming effect highlights the complex permafrost C dynamics upon thaw, potentially reinforcing permafrost C-climate feedback.

Nonlinear Effects Induced by Interactions among Functional Groups of Bacteria and Fungi Regulate the Priming Effect in Malagasy Soils

The priming effect (PE) occurs when fresh organic matter (FOM) supplied to soil alters the rate of decomposition of older soil organic matter (SOM). The PE can be generated by different mechanisms driven by interactions between microorganisms with different live strategies and decomposition abilities. Among those, stoichiometric decomposition results from FOM decomposition, which induces the decomposition of SOM by the release of exoenzymes by FOM-decomposers. Nutrient mining results from the co-metabolism of energy-rich FOM with nutrient-rich SOM by SOM-decomposers. While existing statistical approaches enable measurement of the effect of community composition (linear effect) on the PE, the effect of interactions among co-occurring populations (non-linear effect) is more difficult to grasp. We compare a non-linear, clustering approach with a strictly linear approach to separately and comprehensively capture all linear and non-linear effects induced by soil microbial populations on the PE and to identify the species involved. We used an already published data set, acquired from two climatic transects of Madagascar Highlands, in which the high-throughput sequencing of soil samples was applied parallel to the analysis of the potential capacity of microbial communities to generate PE following a ¹³C-labeled wheat straw input. The linear and clustering approaches highlight two different aspects of the effects of microbial biodiversity on SOM decomposition. The comparison of the results enabled identification of bacterial and fungal families, and combinations of families, inducing either a linear, a non-linear, or no effect on PE after incubation. Bacterial families mainly favoured a PE proportional to their relative abundances in soil (linear effect). Inversely, fungal families induced strong non-linear effects resulting from interactions among them and with bacteria. Our findings suggest that bacteria support stoichiometric decomposition in the first days of incubation, while fungi support mainly the nutrient mining of soil's organic matter several weeks after the beginning of incubation. Used together, the clustering and linear approaches therefore enable the estimation of the relative importance of linear effects related to microbial relative abundances, and non-linear effects related to interactions among microbial populations on soil properties. Both approaches also enable the identification of key microbial families that mainly regulate soil properties.

The priming effect of repetitive transcranial magnetic stimulation on clinical response to electroconvulsive therapy in treatment-resistant depression: a randomized, double-blind, sham-controlled study

BACKGROUND

Electroconvulsive therapy (ECT) is one of the most effective treatments for treatment-resistant depression (TRD). However, due to response delay and cognitive impairment, ECT remains an imperfect treatment. Compared to ECT, repetitive transcranial magnetic stimulation (rTMS) is less effective at treating severe depression, but has the advantage of being quick, easy to use, and producing almost no side effects. In this study, our objective was to assess the priming effect of rTMS sessions before ECT on clinical response in patients with TRD.

METHODS

In this multicenter, randomized, double-blind, sham-controlled trial, 56 patients with TRD were assigned to active or sham rTMS before ECT treatment. Five sessions of active/sham neuronavigated rTMS were administered over the left dorsolateral prefrontal cortex (20 Hz, 90% resting motor threshold, 20 2 s trains with 60-s intervals, 800 pulses/session) before ECT (which was active for all patients) started. Any relative improvements were then compared between both groups after five ECT sessions, in order to assess the early response to treatment.

RESULTS

After ECT, the active rTMS group exhibited a significantly greater relative improvement than the sham group [43.4% (28.6%) v. 25.4% (17.2%)]. The responder rate in the active group was at least three times higher. Cognitive complaints, which were assessed using the Cognitive Failures Questionnaire, were higher in the sham rTMS group compared to the active rTMS group, but this difference was not corroborated by cognitive tests.

CONCLUSIONS

rTMS could be used to enhance the efficacy of ECT in patients with TRD. ClinicalTrials.gov: NCT02830399.

Effect of leaves damaged by Dendrolimus punctatus and insect frass on soil priming effect

Insect herbivory in the forest canopy leads to a large amount of damaged leaves and frass input to soil, with consequence on soil carbon cycle. However, the influence of damaged leaves and frass from insect canopy herbivory on the soil priming effect is unclear. We examined the effects of leaf litter, leaf damage caused by Dendrolimus punctatus, and insect frass on soil priming effect by using the ¹³C natural abundance technique. The results showed that the addition of leaf litter, damaged leaves, and frass significantly increased native soil organic carbon mineralization, producing a positive priming effect. Moreover, significant differences were observed among treatments. The accumulative priming effect induced by frass was the largest, followed by damaged leaves, and that of leaf litter was the smallest. The priming effect was positively correlated with total P, condensed tannin, total phenolic content, and the ratio of condensed tannin to P (condensed tannin/P), and negatively correlated with C/N, lignin/N, C/P, and lignin/P in the early stage of incubation. There was a significant negative correlation between the priming effect and lignin content in the later stage of incubation. Our results indicated that damaged leaves and frass increased the magnitude of positive priming effect, which was influenced by different factors at different incubation stages. Our results would strengthen the understanding in the effects of insect herbivory on soil carbon cycling in forests, and improve the accuracy of the assessment of its effects on forest carbon sink.

Degradation of Bio-Based and Biodegradable Plastic and Its Contribution to Soil Organic Carbon Stock

Expanding the use of environmentally friendly materials to protect the environment is one of the key factors in maintaining a sustainable ecological balance. Poly(butylene succinate-co-adipate) (PBSA) is considered among the most promising bio-based and biodegradable plastics for the future with a high number of applications in soil and agriculture. Therefore, the decomposition process of PBSA and its consequences for the carbon stored in soil require careful monitoring. For the first time, the stable isotope technique was applied in the current study to partitioning plastic- and soil-originated C in the CO₂ released during 80 days of PBSA decomposition in a Haplic Chernozem soil as dependent on nitrogen availability. The decomposition of the plastic was accompanied by the C loss from soil organic matter (SOM) through priming, which in turn was dependent on added N. Nitrogen facilitated PBSA decomposition and reduced the priming effect during the first 6 weeks of the experiment. During the 80 days of plastic decomposition, 30% and 49% of the released CO₂ were PBSA-derived, while the amount of SOM-derived CO₂ exceeded the corresponding controls by 100.2 and 132.3% in PBSA-amended soil without and with N fertilization, respectively. Finally, only 4.1% and 5.4% of the PBSA added into the soil was mineralized to CO₂, in the treatments without and with N amendment, respectively.

Greenhouse Gas Emissions from Soils Amended with Cornstalk Biochar at Different Addition Ratios

Biochar addition has been recommended as a potential strategy for mitigating climate change. However, the number of studies simultaneously investigating the effects of biochar addition on CO₂, N₂O and CH₄ emissions and sequentially global warming potential (GWP) is limited, especially concerning its effect on native soil organic carbon (SOC) mineralization. An incubation experiment was conducted to investigate soil physicochemical properties, CO₂, N₂O and CH₄ emissions and GWP in the treatments with 0% (CK), 1% (BC1) and 4% (BC4) cornstalk biochar additions, and clarify the priming effect of biochar on native SOC mineralization by the ¹³C tracer technique. Generally, biochar addition increased soil pH, cation exchange capacity, SOC and total nitrogen, but decreased NH₄⁺-N and NO₃^--N. Compared with CK, BC1 and BC4 significantly reduced CO₂ emissions by 20.7% and 28.0%, and reduced N₂O emissions by 25.6% and 95.4%, respectively. However, BC1 significantly reduced CH₄ emission by 43.6%, and BC4 increased CH₄ emission by 19.3%. BC1 and BC4 significantly reduced the GWP by 20.8% and 29.3%, but there was no significant difference between them. Biochar addition had a negative priming effect on native SOC mineralization, which was the reason for the CO₂ emission reduction. The negative priming effect of biochar was attributed to the physical protection of native SOC by promoting microaggregate formation and preferentially using soluble organic carbon in biochar. The N₂O emission decrease was rooted in the reduction of nitrification and denitrification substrates by promoting the microbial assimilation of inorganic nitrogen. The inconsistency of CH₄ emissions was attributed to the different relative contributions of CH₄ production and oxidation under different biochar addition ratios. Our study suggests that 1% should be a more reasonable biochar addition ratio for mitigating greenhouse gas emissions in sandy loam, and emphasizes that it is necessary to furtherly investigate nitrogen primary transformation rates and the relative contributions of CH₄ production and oxidation by the ¹⁵N and ¹³C technique, which is helpful for comprehensively understanding the effect mechanisms of biochar addition on greenhouse gas emissions.

Rhizosphere effect of nanoscale zero-valent iron on mycorrhiza-dependent maize assimilation

Rhizosphere effect of nanoscale zero-valent iron (nZVI) is crucial but little reported. Maize seeds were dressed with four nZVI concentrations (0, 1.0, 1.5, 2 g kg^-1 ) and inoculated with arbuscular mycorrhizal fungus (AMF) (Funneliformis mosseae). The SEM images illuminated that excessive nZVI particles (2 g kg^-1 ) were agglomerated on the surface of hyphae and spore, causing severe deformation and inactivation of AMF symbionts and thereafter inhibiting water uptake in maize seedlings. This restrained the scavenging effects of enzymatic (superoxide dismutase, peroxidase) and non-enzymatic compounds (proline & malondialdehyde) on ROS, and leaf photoreduction activity and gas exchange ability (p < 0.05). Interestingly, the inoculation with AMF effectively alleviated above negative effects. In contrast, appropriate dose of nZVI, that is, ≤1.5 g kg^-1 , can be evenly distributed on the hyphae surface and form the ordered symbionts with AMF. This help massively to enhance hyphae growth and water and nutrient uptake. The enhanced mycorrhizal infection turned to promote rhizosphere symbiont activity and leaf Rubisco and Rubisco activase activity. Light compensation point was massively lowered, which increased photosynthetic carbon supply for AMF symbionts. Particularly, such priming effects were evidently enhanced by drought stress. Our findings provided a novel insight into functional role of nZVI in agriculture and AMF-led green production.

5300-Year-old soil carbon is less primed than young soil organic matter

Soils harbor more than three times as much carbon (C) as the atmosphere, a large fraction of which (stable organic matter) serves as the most important global C reservoir due to its long residence time. Litter and root inputs bring fresh organic matter (FOM) into the soil and accelerate the turnover of stable C pools, and this phenomenon is termed the "priming effect" (PE). Compared with knowledge about labile soil C pools, very little is known about the vulnerability of stable C to priming. Using two soils that substantially differed in age (500 and 5300 years before present) and in the degree of chemical recalcitrance and physical protection of soil organic matter (SOM), we showed that leaf litter amendment primed 264% more organic C from the young SOM than from the old soil with very stable C. Hierarchical partitioning analysis confirmed that SOM stability, reflected mainly by available C and aggregate protection of SOM, is the most important predictor of leaf litter-induced PE. The addition of complex FOM (i.e., leaf litter) caused a higher bacterial oligotroph/copiotroph (K-/r-strategists) ratio, leading to a PE that was 583% and 126% greater than when simple FOM (i.e., glucose) was added to the young and old soils, respectively. This implies that the PE intensity depends on the chemical similarity between the primer (here FOM) and SOM. Nitrogen (N) mining existed when N and simple FOM were added (i.e., Glucose+N), and N addition raised the leaf litter-induced PE in the old soil that had low N availability, which was well explained by the microbial stoichiometry. In conclusion, the PE induced by FOM inputs strongly decreases with increasing SOM stability. However, the contribution of stable SOM to CO₂ efflux cannot be disregarded due to its huge pool size.

Investigating the modulation of stimulus types on language switching costs: Do semantic and repetition priming effect matter?

Introduction

In the present study, I investigated the influence of stimulus types on bilingual control in the language switching process. The commonly employed stimuli in language switching studies - Arabic digits and objects - were compared to further investigate the way in which inhibitory control could be modulated by semantic and repetition priming effects. The digit stimuli have two unique characteristics in the language switching paradigm, for example, they are present repeatedly and are semantically related to each other, compared with pictural stimuli. Thus, these unique characteristics might influence the operation of inhibitory control in bilingual language production, modulating the size and asymmetry of switching costs.

Methods

Two picture control sets were set up to match those characteristics: (1) a semantic control set, in which picture stimuli belong to the same category group, such as, animals, occupations or transportation and specific semantic categories were presented in a blocked condition; and (2) a repeated control set, in which nine different picture stimuli were repeatedly presented like the Arabic digits from 1 to 9.

Results

When comparing the digit condition and the standard picture condition, analyses of naming latencies and accuracy rates revealed that switching costs were reliably smaller for digit naming than for picture naming and the L1 elicited more switching costs for picture naming than for digit naming. On the other hand, when comparing the digit condition and the two picture control sets, it was found that the magnitude of switching costs became identical and the asymmetry in switching costs became much smaller between the two languages.

Probing potential priming: Defining, quantifying, and testing the causal priming effect using the potential outcomes framework

Having previously seen an item helps uncover the item another time, given a perceptual or cognitive cue. Oftentimes, however, it may be difficult to quantify or test the existence and size of a perceptual or cognitive effect, in general, and a priming effect, in particular. This is because to examine the existence of and quantify the effect, one needs to compare two outcomes: the outcome had one previously seen the item vs. the outcome had one not seen the item. But only one of the two outcomes is observable. Here, we argue that the potential outcomes framework is useful to define, quantify, and test the causal priming effect. To demonstrate its efficacy, we apply the framework to study the priming effect using data from a between-subjects study involving English word identification. In addition, we show that what has been used intuitively by experimentalists to assess the priming effect in the past has a sound mathematical foundation. Finally, we examine the links between the proposed method in studying priming and the multinomial processing tree (MPT) model, and how to extend the method to study experimental paradigms involving exclusion and inclusion instructional conditions.

[Effects of different carbon addition modes on the soil priming effect of a subtropical Phyllostachys edulis forest under nitrogen deposition]

Priming effect (PE) plays an important role in regulating terrestrial soil carbon (C) cycling, but the impact of different C addition modes on the PE in subtropical forest ecosystems with increasing nitrogen (N) deposition is unclear. In this study, we investigated the effects of C addition patterns (single or repeated C addition) on soil PE by adding ¹³C-labeled glucose for 90 d in an incubation experiment with different levels of N application (0, 20, and 80 kg N·hm^-2·a^-1). The different patterns of glucose addition significantly increased soil organic C (SOC) mineralization and produced positive PE. Single glucose addition resulted in stronger PE than repeated addition. PE was significantly weakened with increasing N application levels, indicating that N deposition inhibited soil excitation in Phyllostachys edulis forests. The cumulative PE was significantly negatively correlated with β-N-acetylaminoglucosidase (NAG) and peroxidase (PEO) activities, and was significantly positively correlated with microbial biomass P (MBP) and potential of hydrogen (pH). Our findings indicated that, when acting together on soil, N application and C addition could strongly affect soil C stocks by stimulating the mineralization of native soil organic matter in subtropical forests. The findings further indicated that single C addition model might overestimate the effect of exogenous readily decomposable organic C on PE and ignore the effect of N deposition on PE, which in turn would overestimate the mineralization loss of forest SOC.

[Effect of Long-term Straw Returning on the Mineralization and Priming Effect of Rice Root-carbon]

Long-term straw returning to the field changes the environmental conditions of rice paddy soil, which affects the mineralization and priming effect of residual rice roots in the soil, but the direction and intensity of its influence is not clear. Therefore, based on a long-term fertilization field experiment, ¹³C-CO₂ isotopic labeling technology and laboratorial incubation were used to analyze the characteristics of mineralization of rice roots and native soil organic carbon, the intensity and direction of the priming effect, and the source partitioning of CO₂ emissions in three treatments, consisting of no fertilization (CK), chemical fertilizer (CF), and straw returning with chemical fertilizer (CFS). The results showed that after 120 days of flooding incubation, the root residue (R) increased the cumulative CO₂ emissions by 617.41-726.27 mg·kg^-1. The cumulative CO₂ emissions from roots and root mineralized proportions in the CFS+R and CF+R treatments were 470.82 and 444.04 mg·kg^-1, respectively, and 18.8% and 17.8%, respectively. These were significantly higher than those in the CK+R treatment (384.19 mg·kg^-1, 15.4%). There was no significant difference in the cumulative CO₂ emissions from native soil organic carbon among the three treatments. However, the mineralized proportion of native soil organic carbon in the CFS+R treatment (4.2%) was significantly lower than that in the CF+R and CK+R treatments (5.4% and 5.8%). The priming effect in the CFS+R treatment was 29.6%, which was significantly lower than that in the CK+R treatment (42.5%) and higher than that in the CF+R treatment (14.4%). A total of 23.47% to 27.59% of the cumulative CO₂ emission of the flooded paddy soil was from the roots, and the remainder was from the soil. In addition, the proportion of CO₂ emission caused by the priming effect was smaller in the CFS+R treatment than that in the CK+R treatment and larger than that in the CF+R treatment. In summary, the long-term straw returning in the flooded paddy soil will increase the mineralization potential of rice roots, but it is more conducive to the stability of the native soil organic carbon.

Global pattern of soil priming effect intensity and its environmental drivers

The microbial priming effect - the decomposition of soil organic carbon (SOC) induced by plant inputs - has long been considered an important driver of SOC dynamics, yet we have limited understanding about the direction, intensitiy, and drivers of priming across ecosystem types and biomes. This gap hinders our ability to predict how shifts in litter inputs under global change can affect climate feedbacks. Here, we synthesized 18,919 observations of CO₂ effluxes in 802 soils across the globe to test the relative effects (i.e., log response ratio; RR) of litter additions on native SOC decomposition, and identified the dominant environmental drivers in natural ecosystems and agricultural lands. Globally, litter additions enhanced native SOC decomposition (RR = 0.35, 95% CI: 0.32 ~ 0.38), with greater priming effects occurring with decreasing latitude, and more in agricultural soils (RR = 0.43) than in uncultivated soils (RR = 0.28). In natural ecosystems, soil pH and microbial community composition (e.g., bacteria:fungi ratio) were the best predictors of priming, with greater effects occurring in acidic, bacterial-dominated, sandy soils. In contrast, substrate properties of plant litter and soils were the most important drivers of priming in agricultural systems, as soils with high C:N ratio and those receiving large inputs of low quality litter had the highest priming effects. Collectively, our results suggest that while different factors may control priming effects, the ubquitious nature of priming means that alterations of litter quality and quantity owing to global changes will likely have consequences for global C cycling and climate forcing.

Toward Improved Bioremediation Strategies: Response of BAM-Degradation Activity to Concentration and Flow Changes in an Inoculated Bench-Scale Sediment Tank

Compound-specific isotope analysis (CSIA) can reveal mass-transfer limitations during biodegradation of organic pollutants by enabling the detection of masked isotope fractionation. Here, we applied CSIA to monitor the adaptive response of bacterial degradation in inoculated sediment to low contaminant concentrations over time. We characterized Aminobacter sp. MSH1 activity in a flow-through sediment tank in response to a transient supply of elevated 2,6-dichlorobenzamide (BAM) concentrations as a priming strategy and took advantage of an inadvertent intermittence to investigate the effect of short-term flow fluctuations. Priming and flow fluctuations yielded improved biodegradation performance and increased biodegradation capacity, as evaluated from bacterial activity and residual concentration time series. However, changes in isotope ratios in space and over time evidenced that mass transfer became increasingly limiting for degradation of BAM at low concentrations under such stimulated conditions, and that activity decreased further due to bacterial adaptation at low BAM (μg/L) levels. Isotope ratios, in conjunction with residual substrate concentrations, therefore helped identifying underlying limitations of biodegradation in such a stimulated system, offering important insight for future optimization of remediation schemes.

The Right Inferior Frontal Gyrus Plays an Important Role in Unconscious Information Processing: Activation Likelihood Estimation Analysis Based on Functional Magnetic Resonance Imaging

Unconsciousness is a kind of brain activity that occurs below the level of consciousness, and the masked priming paradigm is a classic paradigm to study unconscious perceptual processing. With the deepening of unconscious perception research, different researchers mostly use different experimental materials and different masked priming paradigms in a single experiment but not for the comprehensive analysis of the unconscious information processing mechanism itself. Thus, the purpose of this study is to conduct a comprehensive analysis through a cross-experimental paradigm, cross-experimental materials, and cross-experimental purposes. We used activation likelihood estimation to test functional magnetic resonance imaging studies, involving 361 subjects, 124 foci in eight studies representing direct comparison of unconscious processing with baseline, and 115 foci in 10 studies representing direct comparison of unconscious priming effects. In the comparison of unconscious processing and baseline, clusters formed in the left superior parietal gyrus, the right insular gyrus, and the right inferior frontal gyrus (IFG) triangular part after correcting for familywise error (FWE). In the comparison of priming effects, clusters formed in only the right IFG triangular part after correcting for FWE. Here, we found that ventral and dorsal pathways jointly regulate unconscious perceptual processes, but only the ventral pathway is involved in the regulation of unconscious priming effects. The IFG triangular part is involved in the regulation of unconscious perceptual processing and unconscious priming effects and may be an important brain area in unconscious information processing. These preliminary data provide conditions for further study of the neural correlation of unconscious information processing.

Priming effects in soils across Europe

Land use is a key factor driving changes in soil carbon (C) cycle and contents worldwide. The priming effect (PE)-CO₂ emissions from changed soil organic matter decomposition in response to fresh C inputs-is one of the most unpredictable phenomena associated with C cycling and related nutrient mobilization. Yet, we know very little about the influence of land use on soil PE across contrasting environments. Here, we conducted a continental-scale study to (i) determine the PE induced by ¹³ C-glucose additions to 126 cropland and seminatural (forests and grasslands) soils from 22 European countries; (ii) compare PE magnitude in soils under various crop types (i.e., cereals, nonpermanent industrial crops, and orchards); and (iii) model the environmental factors influencing PE. On average, PEs were negative in seminatural (with values ranging between -60 and 26 µg C g^-1 soil after 35 days of incubation; median = -11) and cropland (from -55 to 27 µC g^-1 soil; median = -4.3) soils, meaning that microbial communities preferentially switched from soil organic C decomposition to glucose mineralization. PE was significantly less negative in croplands compared with seminatural ecosystems and not influenced by the crop type. PE was driven by soil basal respiration (reflecting microbial activity), microbial biomass C, and soil organic C, which were all higher in seminatural ecosystems compared with croplands. This cross European experimental and modeling study elucidated that PE intensity is dependent on land use and allowed to clarify the factors regulating this important C cycling process.

Microbial traits determine soil C emission in response to fresh carbon inputs in forests across biomes

Soil priming is a microbial-driven process, which determines key soil-climate feedbacks in response to fresh carbon inputs. Despite its importance, the microbial traits behind this process are largely undetermined. Knowledge of the role of these traits is integral to advance our understanding of how soil microbes regulate carbon (C) emissions in forests, which support the largest soil carbon stocks globally. Using metagenomic sequencing and ¹³ C-glucose, we provide unprecedented evidence that microbial traits explain a unique portion of the variation in soil priming across forest biomes from tropical to cold temperature regions. We show that microbial functional profiles associated with the degradation of labile C, especially rapid simple sugar metabolism, drive soil priming in different forests. Genes involved in the degradation of lignin and aromatic compounds were negatively associated with priming effects in temperate forests, whereas the highest level of soil priming was associated with β-glucosidase genes in tropical/subtropical forests. Moreover, we reconstructed, for the first time, 42 whole bacterial genomes associated with the soil priming effect and found that these organisms support important gene machinery involved in priming effect. Collectively, our work demonstrates the importance of microbial traits to explain soil priming across forest biomes and suggests that rapid carbon metabolism is responsible for priming effects in forests. This knowledge is important because it advances our understanding on the microbial mechanisms mediating soil-climate feedbacks at a continental scale.

Living, dead, and absent trees-How do moth outbreaks shape small-scale patterns of soil organic matter stocks and dynamics at the Subarctic mountain birch treeline?

Mountain birch forests (Betula pubescens Ehrh. ssp. czerepanovii) at the subarctic treeline not only benefit from global warming, but are also increasingly affected by caterpillar outbreaks from foliage-feeding geometrid moths. Both of these factors have unknown consequences on soil organic carbon (SOC) stocks and biogeochemical cycles. We measured SOC stocks down to the bedrock under living trees and under two stages of dead trees (12 and 55 years since moth outbreak) and treeless tundra in northern Finland. We also measured in-situ soil respiration, potential SOC decomposability, biological (enzyme activities and microbial biomass), and chemical (N, mineral N, and pH) soil properties. SOC stocks were significantly higher under living trees (4.1 ± 2.1 kg m²) than in the treeless tundra (2.4 ± 0.6 kg m²), and remained at an elevated level even 12 (3.7 ± 1.7 kg m²) and 55 years (4.9 ± 3.0 kg m²) after tree death. Effects of tree status on SOC stocks decreased with increasing distance from the tree and with increasing depth, that is, a significant effect of tree status was found in the organic layer, but not in mineral soil. Soil under living trees was characterized by higher mineral N contents, microbial biomass, microbial activity, and soil respiration compared with the treeless tundra; soils under dead trees were intermediate between these two. The results suggest accelerated organic matter turnover under living trees but a positive net effect on SOC stocks. Slowed organic matter turnover and continuous supply of deadwood may explain why SOC stocks remained elevated under dead trees, despite the heavy decrease in aboveground C stocks. We conclude that the increased occurrence of moth damage with climate change would have minor effects on SOC stocks, but ultimately decrease ecosystem C stocks (49% within 55 years in this area), if the mountain birch forests will not be able to recover from the outbreaks.

Plant input does not exert stronger control on topsoil carbon persistence than climate in alpine grasslands

Chen et al. (Ecology Letters, 2021, 24, 1018) concluded that plant input governs topsoil carbon persistence in alpine grasslands. We demonstrated that the excluded direct effect of precipitation on topsoil Δ¹⁴ C in their analysis was significant and strong. Our results provide an alternative viewpoint on the drivers of soil carbon turnover.

Ulva intestinalis Extract Acts as Biostimulant and Modulates Metabolites and Hormone Balance in Basil (Ocimum basilicum L.) and Parsley (Petroselinum crispum L.)

Natural elicitors from macroalgae may affect plant secondary metabolites. Ulvan is a sulfated heteropolysaccharide extracted from green seaweed, acting as both a plant biotic protecting agent, and a plant elicitor, leading to the synthesis of signal molecules. In this work, the aqueous extract of Ulva intestinalis L., mainly composed of ulvan, was used as foliar-spraying treatment and its eliciting effect was investigated in basil (Ocimum basilicum L.) and parsley (Petroselinum crispum L.). Antioxidant metabolites (polyphenols and carotenoids), volatile compounds (both in headspace emissions and hydrodistilled essential oils), and hormones (jasmonic acid, salicylic acid, salicylic acid 2-O-β-D-glucoside, abscisic acid, and azelaic acid) were quantified. The foliar-spraying treatment with U. intestinalis extract increased salicylic acid and its β-glucoside in parsley; in basil, it induced the accumulation of jasmonic and abscisic acids, indicating the presence of a priming effect. In basil, the elicitation caused a change of the essential oil (EO) chemotype from methyl eugenol/eugenol to epi-α-cadinol and increased sesquiterpenes. In parsley EO it caused a significant accumulation of 1,3,8-p-menthatriene, responsible of the typical “parsley-like” smell. In both species, the phenylpropanoids decreased in headspace and EO compositions, while the salicylic acid concentration increased; this could indicate a primarily defensive response to U. intestinalis extract. Due to the evidenced significant biological activity, U. intestinalis extract used as an elicitor may represent a suitable tool to obtain higher amounts of metabolites for optimizing plant flavor metabolites.

Soil priming effect and its responses to nutrient addition along a tropical forest elevation gradient

Priming plays important roles in terrestrial carbon cycling, but the patterns and drivers of priming and its responses to nutrient addition in tropical forests remain unclear. By collecting soils along a tropical forest elevation gradient, we conducted an incubation experiment with ¹³ C-labeled glucose and nutrient (N and/or P) additions. Results showed that priming effects increased soil organic matter decomposition by 44 ± 12% across elevations, and priming intensity decreased significantly with elevation. Among soil and microbial properties, soil organic carbon (SOC) content and pH were two key factors negatively and positively regulating priming, respectively. Across elevations, the additions of N, P, or both of them (NP) did not significantly change priming. However, the variations in the effects of nutrient (N and/or P) addition on priming significantly correlated with initial soil nutrient (N or P) availability. The intensity for the effects of N addition on priming decreased significantly with initial soil N availability, and that for the effects of P and NP addition on priming decreased with initial soil P availability. Based on these relationships, we proposed a conceptual framework linking stoichiometric decomposition and nutrient mining hypotheses, in which the former dominates in low-nutrient availability soils and the latter dominates in high-nutrient availability soils. This conceptual framework can help to explain the contrasting effects of nutrient addition on priming. Collectively, our findings highlight the roles of SOC content and soil pH in regulating priming intensity, and the role of initial soil nutrient availability in regulating the effects of nutrient addition on priming.

[Effects of soil moisture on priming effect of soil organic carbon in meadow in Wuyi Mountain, China.]

Moisture is an important factor affecting the priming effect of soil organic carbon (SOC). However, empirical evidence for its effect in mountain meadows soil is lacking. We conducted a 126-day laboratory incubation experiment with the high altitude (2130 m) mountain meadow soil in Wuyi Mountain, by adding ¹³C-labelled glucose combined with controlling soil moisture (30% and 60% of field water capacity, FWC). The CO₂ concentration and ¹³C-CO₂ abundance were measured regularly to examine the differences of SOC mineralization and priming effects under different water conditions and the driving factors. Our results showed that SOC mineralization rate increased with increasing soil water content. The priming effect of meadow soil with different soil moisture showed a decreasing trend with the increases of incubation time. The priming effect in soils with low FWC soil was significantly greater than that with high FWC. At the end of incubation, the cumulative priming effect of low FWC soil was 61.4% higher than that of high FWC soil. Compared with low FWC soil, high FWC soil released more CO₂ from glucose, and the ratio of cumulative primed carbon to glucose mineralization under low FWC was significantly higher than that under high FWC soil, indicating that soil microorganisms under the high FWC condition might preferentially mineralize more glucose than SOC and consequently lower priming effect. Therefore, the priming effect under high FWC was smaller than that under low FWC. There was a significant positive relationship between priming effect and microbial biomass carbon, microbial biomass carbon/microbial biomass nitrogen, and NH₄⁺-N, indicating that soil microbial biomass and composition could be changed under low FWC condition. The improved microbial "nitrogen-mining" would increase priming effect. Consequently, the decline of soil moisture of mountain meadow induced by global climate change may increase the priming effect of carbon, with consequences on carbon loss.

Warming-induced global soil carbon loss attenuated by downward carbon movement

The fate of soil organic carbon (SOC) under warming is poorly understood, particularly across large extents and in the whole-soil profile. Using a data-model integration approach applied across the globe, we find that downward movement of SOC along the soil profile reduces SOC loss under warming. We predict that global SOC stocks (down to 2 m) will decline by 4% (~80 Pg) on average when SOC reaches the steady state under 2°C warming, assuming no changes in net primary productivity (NPP). To compensate such decline (i.e. maintain current SOC stocks), a 3% increase of NPP is required. Without the downward SOC movement, global SOC declines by 15%, while a 20% increase in NPP is needed to compensate that loss. This vital role of downward SOC movement in controlling whole-soil profile SOC dynamics in response to warming is due to the protection afforded to downward-moving SOC by depth, indicated by much longer residence times of SOC in deeper layers. Additionally, we find that this protection could not be counteracted by promoted decomposition due to the priming of downward-moving new SOC from upper layers on native old SOC in deeper layers. This study provides the first estimation of whole-soil SOC changes under warming and additional NPP required to compensate such changes across the globe, and reveals the vital role of downward movement of SOC in reducing SOC loss under global warming.

Learned valuation during forage decision-making in cuttlefish

Decision-making, when humans and other animals choose between two options, is not always based on the absolute values of the options but can also depend on their relative values. The present study examines whether decision-making by cuttlefish is dependent on relative values learned from previous experience. Cuttlefish preferred a larger quantity when making a choice between one or two shrimps (1 versus 2) during a two-alternative forced choice. However, after cuttlefish were primed under conditions where they were given a small reward for choosing one shrimp in a no shrimp versus one shrimp test (0 versus 1) six times in a row, they chose one shrimp significantly more frequently in the 1 versus 2 test. This reversed preference for a smaller quantity was not due to satiation at the time of decision-making, as cuttlefish fed a small shrimp six times without any choice test prior to the experiment still preferred two shrimps significantly more often in a subsequent 1 versus 2 test. This suggests that the preference of one shrimp in the quantity comparison test occurs via a process of learned valuation. Foraging preference in cuttlefish thus depends on the relative value of previous prey choices.

[Impacts of Nitrogen Application on Ammonia Volatilization During Maize Season in Northern China]

Ammonia volatilization is one of the major paths of nitrogen (N) loss and may exert a substantial impact on air quality. This study aims to explore the effects of nitrogen (N) fertilizer types, fertilization rate, and application timing and gas collection method on NH₃ volatilization during the maize season in Northern China. This study collected the publications on the NH₃ volatilization from maize farming which were conducted in Northern China from 1980 to 2018, and undertook a systematic analysis. The study found that with the increase of N rate, the total and net NH₃ volatilization at the basal and topdressing fertilization stages increased at exponential and power function, respectively. When the ratio of basal/topdressing N rate was 1/1, the total and net NH₃ volatilization during the topdressing stage (58.4% of the whole season emission) was significantly higher than that in the basal fertilization stage (41.6%) (P<0.05). The priming effect first showed a negative effect and then gradually turned into a positive effect with the increase of N rate. Due to the positive priming effect, the net NH₃ volatilization, without considering the priming effect, was overestimated under the conventional N application (>297 kg·hm^-2). There is a significant difference between the NH₃ volatilization measured by the venting method and the sponge absorption method, and the data from the venting method are more stable (P<0.01). Compared with conventional urea, slow-release urea may reduce NH₃ volatilization by 20% to 50%. Control fertilizer N rate at the topdressing stage is more efficient in reducing the NH₃ volatilization from maize production in Northern China, and the venting method is more suitable for the quantification of NH₃ volatilization than the sponge absorption method under a high rate of fertilizer N.

Impact of sea level change on coastal soil organic matter, priming effects and prokaryotic community assembly

Salt marshes are coastal areas storing high amounts of soil organic matter (SOM) while simultaneously being prone to tidal changes. Here, SOM-decomposition and accompanied priming effects (PE), which describe interactions between labile and old SOM, were studied under controlled flooding conditions. Soil samples from two Wadden Sea salt marsh zones, pioneer (Pio), flooded two times/day, and lower salt marsh (Low), flooded ∼eight times/month, were measured for 56 days concerning CO2-efflux and prokaryotic community shifts during three different inundation-treatments: total-drained (Drained), all-time-flooded (Waterlogged) or temporal-flooding (Tidal). Priming was induced by 14C-glucose addition. CO2-efflux from soil followed Low>Pio and Tidal>Drained>Waterlogged, likely due to O2-depletion and moisture maintenance, two key factors governed by tidal inundation with regard to SOM mineralisation. PEs in both zones were positive (Drained) or absent (Waterlogged, Tidal), presumably as a result of prokaryotes switching from production of extracellular enzymes to direct incorporation of labile C. A doubled amount of prokaryotic biomass in Low compared to Pio probably induced higher chances of cometabolic effects and higher PE. 16S-rRNA-gene-amplicon-based analysis revealed differences in bacterial and archaeal community composition between both zones, revealing temporal niche adaptation with flooding treatment. Strongest alterations were found in Drained, likely due to inundation-mediated changes in C-binding capacities.

Is It Speech or Song? Effect of Melody Priming on Pitch Perception of Modified Mandarin Speech

Tonal languages make use of pitch variation for distinguishing lexical semantics, and their melodic richness seems comparable to that of music. The present study investigated a novel priming effect of melody on the pitch processing of Mandarin speech. When a spoken Mandarin utterance is preceded by a musical melody, which mimics the melody of the utterance, the listener is likely to perceive this utterance as song. We used functional magnetic resonance imaging to examine the neural substrates of this speech-to-song transformation. Pitch contours of spoken utterances were modified so that these utterances can be perceived as either speech or song. When modified speech (target) was preceded by a musical melody (prime) that mimics the speech melody, a task of judging the melodic similarity between the target and prime was associated with increased activity in the inferior frontal gyrus (IFG) and superior/middle temporal gyrus (STG/MTG) during target perception. We suggest that the pars triangularis of the right IFG may allocate attentional resources to the multi-modal processing of speech melody, and the STG/MTG may integrate the phonological and musical (melodic) information of this stimulus. These results are discussed in relation to subvocal rehearsal, a speech-to-song illusion, and song perception.

Preferential Alternatives to Returning All Crop Residues as Biochar to the Crop Field? A Three-Source 13C and 14C Partitioning Study

The simultaneous effects of biochar on soil organic matter (SOM, C4) and sweet potato (SP) residue (Ipomoea batatas, C3) mineralization were studied over 180 days via ¹³C and ¹⁴C isotopic label partitioning. Upon concomitant SP residue addition, biochar mineralization decreased by 11% of the total added biochar-C. Compared to positive priming effects induced by biochar amendment alone on SOM (0.46 mg C g^-1 soil) at 180 days, amendment solely with SP residues induced significantly larger effects (1.5 mg C g^-1 soil). Combination biochar and SP residue addition reduced SOM mineralization by 20.5% and increased SP residue mineralization by 10.1%. Biochar addition caused preferential uptake of SP residues over SOM by microbes. Thus, the lower priming effects on SOM and CO₂ emission induced by biochar amendment with or without SP residues compared to that from SP residue addition alone may result in crop residues being partly pyrolyzed to biochar in the cropland.

Priming Emotional Salience Reveals the Role of Episodic Memory and Task Conflict in the Non-color Word Stroop Task

Previous research attempted to account for the emotional Stroop effect based on connectionist models of the Stroop task that implicate conflict in the output layer as the underlying mechanism (e.g., Williams et al., 1996). Based on Kalanthroff et al.’s (2015) proactive-control/task-conflict (PC-TC) model, our study argues that the interference from non-color words (neutral and negative words) is due to task conflict. Using a study-test procedure 120 participants (59 high and 61 low trait anxiety) studied negative and neutral control words prior to being tested on a color responding task that included studied and unstudied words. The results for the low anxiety group show no emotional Stroop effect, but do demonstrate the slowdown in response latencies to a block of studied and unstudied words compared to a block of unstudied words. In contrast, the high anxiety group shows (a) an emotional Stroop effect but only for studied negative words and (b) a reversed sequential modulation in which studied negative words slowed down the color-responding of studied negative words on the next trial. We consider how these findings can be incorporated into the PC-TC model and suggest the interacting role of trait anxiety, episodic memory, and emotional salience driving attention that is based on task conflict.

[Soil organic carbon mineralization and priming effects in the topsoil and subsoil under no-tillage black soil.]

Priming effect is one of the important mechanisms regulating soil organic matter decomposition. However, the variation of priming effects in different soil layers remains unclear. In this study, we conducted a 30-day incubation experiment using no-tillage black soil from northeastern China. ¹³C-glucose and dynamic CO₂ trapping methods were employed to investigate soil organic carbon (SOC) mineralization rates and the priming effect of the added ¹³C-glucose in the upper soil layer (0-10 cm) and the lower soil layer (30-40 cm). Our results showed that the cumulative SOC-specific mineralization rate in the upper layer was similar to that in the lower layer soil without glucose addition. Glucose addition significantly altered the mineralization rates in both layers, resulting in a positive priming effect (36.7%) in the upper layer but a negative priming effect (-12.4%) in the lower layer. The cumulative priming effect during the 30-day incubation was 3.24 mg C·g^-1 SOC for the upper layer soil and -1.24 mg C·g^-1 SOC for the lower layer soil. There was still a net SOC increase, even with positive priming effects in the upper layer soil. This was due to considerable amount of added glucose-C remained un-mineralized in the soil which would compensate the carbon loss from priming effects. Overall, our results demonstrated that the magnitude and direction of priming effects might differ between soil layers. Our findings contribute to a better understanding of the effects of conservation tillage practices (no-tillage and straw incorporation) on soil organic matter dynamics in agroecosystems.

[Straw Returning Plus Nitrogen Fertilizer Affects the Soil Microbial Community and Organic Carbon Mineralization in Karst Farmland]

The use of straw returning plus nitrogen fertilizer on farmland is one of the important agronomic practices for adjusting soil organic carbon (SOC) transformations. To explore the mechanisms of straw and nitrogen fertilizer application on straw and SOC mineralization in long-term fertilized soils, an incubation experiment with the ¹³C isotope tracing technique was conducted, which involved three long-term fertilized models in typical karst soils (no fertilization, inorganic fertilization, and a combination of inorganic fertilization and straw). To study the mechanisms of ¹³C-labeled straw and SOC mineralization, four treatments were designed as follows:no straw and nitrogen (control), and straw combined with three levels of nitrogen fertilizer (0, 214.0, and 571.0 mg·kg^-1 soil). The results showed that cumulative mineralization amounts of straw-derived organic carbon in long-term fertilized soils were markedly higher than those in non-fertilized soil. Straw-derived organic carbon mineralization was significantly affected by nitrogen fertilizer levels. The positive priming effects (PE) in long-term fertilized soils were much lower than those in non-fertilized soil. The PE was decreased at the low nitrogen fertilizer level but increased at the high nitrogen fertilizer level. The principal component analysis (PCA) of phospholipid fatty acids (PLFAs) indicated that the soil microbial community structure was greatly affected by the long-term fertilization models and combined straw and nitrogen fertilizer application. Moreover, the content of PLFAs in soil microorganisms, namely, bacteria and fungi, were remarkably increased by the straw plus nitrogen fertilizer (values increased by 40.3%-53.0%, 41.1%-62.6%, and 60.5%-148.6% compared with control), but levels were not significantly affected by nitrogen fertilizer levels alone. The ratios between PLFAs of soil gram-positive and gram-negative bacteria (G⁺/G^-) decreased and were stable at around 0.8. The structure equation models (SEM) demonstrated that the combination of straw and nitrogen affected the soil gram-positive and gram-negative bacteria structure and increased the soil DOC content, which promoted the decomposition of straw and affected the mineralization of SOC. These results indicate that straw returning plus low nitrogen fertilizer can improve the SOC sequestration capacity in karst farmland.

[Characterization of Soil Organic Carbon Mineralization Under Different Gradient Carbon Loading in Paddy Soil]

Available carbon is the most active part of the soil carbon pool. It is also the main carbon source of soil microbes and plays an important role in the processes of soil organic carbon mineralization and accumulation. However, the mechanisms are still not clear how soil organic carbon mineralization and its priming effect (PE) are affected by different input levels of readily available carbon, based on the growth requirements of microbes in paddy soil. In this study, an incubation experiment was conducted by adding different levels (0.5, 1, 3, and 5 times of MBC) of exogenous source organic carbon (¹³C-glucose) to the soil. The mineralization dynamics of labile organic carbon and its priming effect was investigated. The mineralization rate of glucose-C increased significantly with the increasing carbon loading level. The distribution of glucose-C into rapid and slow C pools was also exponentially correlated with the carbon loading (R²=0.99, P<0.05 and R²=0.99, P<0.05, respectively). Negative PE was observed at high carbon loading (3×MBC and 5×MBC); while positive PE was induced by low carbon loading (0.5×MBC and 1×MBC). The cumulative PE was 160.0 mg·kg^-1 and 325.1 mg·kg^-1, respectively, at the end of the incubation. Redundancy analysis showed that the main factors affecting the cumulative PE were MBC, MBN, and DOC at the initial glucose mineralization stage, while β-glucosidase, chitinase, and ammonium nitrogen were the main factors at later stages. Therefore, the readily available carbon loading has an important effect on the organic carbon mineralization and PE in paddy soil. Higher carbon loading was good for the accumulation of organic carbon sequestration in paddy soil. This study is of great scientific significance for revealing the activity of organic carbon in paddy fields and for its contribution to the development of sustainable agriculture.

Do People Explicitly Make a Frame Choice Based on the Reference Point?

Previous studies have shown that when choosing one of two logically equivalent frames (e.g., “half full” or “half empty”), people tend to choose based on a reference point. For example, when the amount of water in a glass with 500 ml capacity was originally 0 ml (or 500 ml), and then increased (or decreased) to 250 ml, people tend to express the amount of water in the glass as “half full” (or “half empty”). In the present study, we examined whether participants explicitly made a frame choice based on the reference point. We conducted four behavioral experiments relating to frame choice tasks. Specifically, participants were presented with a story-based or prime-based reference point and then made a frame choice. Furthermore, participants provided their reasons for the choice. Our findings on frame choices and their reasons can be summarized as follows. First, when participants were presented with a story-based reference point, some of them reported that they made frame choices based on the reference point. Second, when a reference point was presented as a prime, participants’ frame choices were affected by this reference point. However, almost no participants reported that they made frame choices based on the reference point. These results indicate that the effect of reference points on frame choices is robust and that people do not always explicitly make frame choices based on the reference point.

Root Exudation of Primary Metabolites: Mechanisms and Their Roles in Plant Responses to Environmental Stimuli

Root exudation is an important process determining plant interactions with the soil environment. Many studies have linked this process to soil nutrient mobilization. Yet, it remains unresolved how exudation is controlled and how exactly and under what circumstances plants benefit from exudation. The majority of root exudates including primary metabolites (sugars, amino acids, and organic acids) are believed to be passively lost from the root and used by rhizosphere-dwelling microbes. In this review, we synthetize recent advances in ecology and plant biology to explain and propose mechanisms by which root exudation of primary metabolites is controlled, and what role their exudation plays in plant nutrient acquisition strategies. Specifically, we propose a novel conceptual framework for root exudates. This framework is built upon two main concepts: (1) root exudation of primary metabolites is driven by diffusion, with plants and microbes both modulating concentration gradients and therefore diffusion rates to soil depending on their nutritional status; (2) exuded metabolite concentrations can be sensed at the root tip and signals are translated to modify root architecture. The flux of primary metabolites through root exudation is mostly located at the root tip, where the lack of cell differentiation favors diffusion of metabolites to the soil. We show examples of how the root tip senses concentration changes of exuded metabolites and translates that into signals to modify root growth. Plants can modify the concentration of metabolites either by controlling source/sink processes or by expressing and regulating efflux carriers, therefore challenging the idea of root exudation as a purely unregulated passive process. Through root exudate flux, plants can locally enhance concentrations of many common metabolites, which can serve as sensors and integrators of the plant nutritional status and of the nutrient availability in the surrounding environment. Plant-associated micro-organisms also constitute a strong sink for plant carbon, thereby increasing concentration gradients of metabolites and affecting root exudation. Understanding the mechanisms of and the effects that environmental stimuli have on the magnitude and type of root exudation will ultimately improve our knowledge of processes determining soil CO₂ emissions, ecosystem functioning, and how to improve the sustainability of agricultural production.

Corrigendum: Root Exudation of Primary Metabolites: Mechanisms and Their Roles in Plant Responses to Environmental Stimuli

[This corrects the article DOI: 10.3389/fpls.2019.00157.].

[Effects of Varying Long-term Fertilization on Organic Carbon Mineralization and Priming Effect of Paddy Soil]

A laboratory incubation experiment was conducted using the ¹⁴C isotope labeling technique to study the characteristics of organic carbon mineralization and their response to glucose addition when treated with a combination of straw and chemical fertilizer (ST), inorganic fertilizer (NPK), and non-fertilization (CK). The cumulative mineralization rate (ratio of accumulated mineralization amount to total organic carbon content) in CK reaches 1.64% at the end of incubation (56 days). The cumulative mineralization rate during NPK and ST treatments is significantly lower than that in CK (by 0.34% and 0.39%, respectively). This indicates that long-term fertilization affects the soil carbon sequestration. Varying long-term fertilization influences the response of paddy soil to glucose addition and leads to different levels of the priming effect. The priming effect on soil organic carbon mineralization of the three treatments gradually changes from negative to positive with increasing incubation time. The significantly negative cumulative priming effect in ST and NPK after 56 d is 22.07 and 9.05 times higher than that in CK, respectively. The results of the structural equation model indicate that the NH₄⁺-N and DOC contents indirectly influence the cumulative priming effect on soil organic carbon by affecting the MBC and MBN contents. The NH₄⁺-N concentration has a direct and significant negative effect on the cumulative priming effect. In conclusion, long-term fertilization treatments reduce the cumulative organic carbon mineralization rate of paddy soil. Fertilizer, especially the combination of straw and chemical fertilizer, enhances the soil carbon sequestration and accumulation.

Virus-Like Particles Are a Superior Platform for Presenting M2e Epitopes to Prime Humoral and Cellular Immunity against Influenza Virus

Influenza virus M2 protein has a highly conserved ectodomain (M2e) as a cross-protective antigenic target. We investigated the antigenic and immunogenic properties of tandem repeat M2e (5xM2e) proteins and virus-like particles (5xM2e VLP) to better understand how VLP and protein platform vaccines induce innate and protective adaptive immune responses. Despite the high antigenic properties of 5xM2e proteins, the 5xM2e VLP was superior to 5xM2e proteins in inducing IgG2a isotype antibodies, T cell responses, plasma cells and germinal center B cells as well as in conferring cross protection. Mice primed with 5xM2e VLP were found to be highly responsive to 5xM2e protein boost, overcoming the low immunogenicity and protective efficacy of 5xM2e proteins. Immunogenic differences between VLPs and proteins in priming immune responses might be due to an intrinsic ability of 5xM2e VLP to stimulate dendritic cells secreting T helper type 1 (Th1) cytokines. We also found that 5xM2e VLP was effective in inducing inflammatory cytokines and chemokines, and in recruiting macrophages, monocytes, neutrophils, and CD11b⁺ dendritic cells at the injection site. Therefore, this study provides evidence that 5xM2e VLP is an effective vaccine platform, inducing cross-protection by stimulating innate and adaptive immune responses.

Shifts in priming partly explain impacts of long-term nitrogen input in different chemical forms on soil organic carbon storage

Input of labile organic carbon can enhance decomposition of extant soil organic carbon (SOC) through priming. We hypothesized that long-term nitrogen (N) input in different chemical forms alters SOC pools by altering priming effects associated with N-mediated changes in plants and soil microbes. The hypothesis was tested by integrating field experimental data of plants, soil microbes and two incubation experiments with soils that had experienced 10 years of N enrichment with three chemical forms (ammonium, nitrate and both ammonium and nitrate) in an alpine meadow on the Tibetan Plateau. Incubations with glucose-¹³ C addition at three rates were used to quantify effects of exogenous organic carbon input on the priming of SOC. Incubations with microbial inocula extracted from soils that had experienced different long-term N treatments were conducted to detect effects of N-mediated changes in soil microbes on priming effects. We found strong evidence and a mechanistic explanation for alteration of SOC pools following 10 years of N enrichment with different chemical forms. We detected significant negative priming effects both in soils collected from ammonium-addition plots and in sterilized soils inoculated with soil microbes extracted from ammonium-addition plots. In contrast, significant positive priming effects were found both in soils collected from nitrate-addition plots and in sterilized soils inoculated with soil microbes extracted from nitrate-addition plots. Meanwhile, the abundance and richness of graminoids were higher and the abundance of soil microbes was lower in ammonium-addition than in nitrate-addition plots. Our findings provide evidence that shifts toward higher graminoid abundance and changes in soil microbial abundance mediated by N chemical forms are key drivers for priming effects and SOC pool changes, thereby linking human interference with the N cycle to climate change.

Global effects of plant litter alterations on soil CO2 to the atmosphere

Soil respiration (Rs) is the largest terrestrial carbon (C) efflux to the atmosphere and is predicted to increase drastically through global warming. However, the responses of Rs to global warming are complicated by the fact that terrestrial plant growth and the subsequent input of plant litter to soil are also altered by ongoing climate change and human activities. Despite a number of experiments established in various ecosystems around the world, it remains a challenge to predict the magnitude and direction of changes in Rs and its temperature sensitivity (Q₁₀ ) due to litter alteration. We present a meta-analysis of 100 published studies to examine the responses of Rs and Q₁₀ to manipulated aboveground and belowground litter alterations. We found that 100% aboveground litter addition (double litter) increased Rs by 26.1% (95% confident intervals, 18.4%-33.7%), whereas 100% aboveground litter removal, root removal and litter + root removal reduced Rs by 22.8% (18.5%-27.1%), 34.1% (27.2%-40.9%) and 43.4% (36.6%-50.2%) respectively. Moreover, the effects of aboveground double litter and litter removal on Rs increased with experimental duration, but not those of root removal. Aboveground litter removal marginally increased Q₁₀ by 6.2% (0.2%-12.3%) because of the higher temperature sensitivity of stable C substrate than fresh litter. Estimated from the studies that simultaneously tested the responses of Rs to aboveground litter addition and removal and assuming negligible changes in root-derived Rs, "priming effect" on average accounted for 7.3% (0.6%-14.0%) of Rs and increased over time. Across the global variation in terrestrial ecosystems, the effects of aboveground litter removal, root removal, litter + root removal on Rs as well as the positive effect of litter removal on Q₁₀ increased with water availability. Our meta-analysis indicates that priming effects should be considered in predicting Rs to climate change-induced increases in litterfall. Our analysis also highlights the need to incorporate spatial climate gradient in projecting long-term Rs responses to litter alterations.

I Thought I Saw "Zorro": An Inattentional Blindness Study

Objective

Inattentional blindness (IB) refers to an observer's failure to notice unexpected stimulus. The aim of this study was to investigate the effects of the priming type (perceptual, conceptual, and no priming) and emotional context (positive, negative, neutral) on IB with behavioral (IB, non-IB) and eye tracking measurements (latency of first fixation, total fixation time, and total fixation count in response to unexpected stimuli).

Methods

A total of 193 volunteered male university students were invited in the study. Three thematic videos (positive, negative, and neutral) were created to capture the IB. In the first stage, five pictures (a model dressed in different costumes Zorro as an unexpected stimulus, Vendetta, a judge, a doctor, and a worker) were shown to the participants for priming. In the second stage, a distractor task which involved 30 simple arithmetic operations were given. In the third stage, one of the thematic IB videos were shown to the participants, and then they answered the questions about those videos. Participants were assigned randomly to 9 different experimental conditions according to a 3 (Priming Type: Perceptual, Conceptual, No Priming) x 3 (Emotional Context: Positive, Negative, Neutral) factorial design. Finally, behavioral and eye tracking measurements were collected.

Results

Main and interaction effects of priming type and emotional contexts were not significant in terms of the behavioral measures. In addition, there were no significant differences between types of priming for eye tracking measures. However, there were significant differences between types of emotional contexts in all eye tracking measurements. In the negative context, participants made less total fixation, and looked shorter to unexpected stimulus than positive and neutral contexts. In addition, non-notifiers made less total fixation, and looked at unexpected stimulus for a shorter time compared to notifiers.

Conclusion

The fact of "looking without seeing" was again demonstrated experimentally. Priming and emotional context did not affect behavioral data, but eye movements were affected from the emotional context. Current findings showed a relation between emotion and attention.

Temporal and spatial impact of Spartina alterniflora invasion on methanogens community in Chongming Island, China

Methane production by methanogens in wetland is recognized as a significant contributor to global warming. Spartina alterniflora (S. alterniflora), which is an invasion plant in China's wetland, was reported to have enormous effects on methane production. But studies on shifts in the methanogen community in response to S. alterniflora invasion at temporal and spatial scales in the initial invasion years are rare. Sediments derived from the invasive species S. alterniflora and the native species Phragmites australis (P. australis) in pairwise sites and an invasion chronosequence patch (4 years) were analyzed to investigate the abundance and community structure of methanogens using quantitative real-time PCR (qPCR) and Denaturing gradient gel electrophoresis (DGGE) cloning of the methyl-coenzyme M reductase A (mcrA) gene. For the pairwise sites, the abundance of methanogens in S. alterniflora soils was lower than that of P. australis soils. For the chronosequence patch, the abundance and diversity of methanogens was highest in the soil subjected to two years invasion, in which we detected some rare groups including Methanocellales and Methanococcales. These results indicated a priming effect at the initial invasion stages of S. alterniflora for microorganisms in the soil, which was also supported by the diverse root exudates. The shifts of methanogen communities after S. alterniflora invasion were due to changes in pH, salinity and sulfate. The results indicate that root exudates from S. alterniflora have a priming effect on methanogens in the initial years after invasion, and the predominate methylotrophic groups (Methanosarcinales) may adapt to the availability of diverse substrates and reflects the potential for high methane production after invasion by S. alterniflora.