Contrasting Responses Research Articles

Continuous motion tracking for accurate and efficient color vision assessment.

The assessment of color vision is crucial in both fundamental visual research and clinical diagnosis. However, existing tools for color vision assessment are limited by various factors. This study introduces a novel, efficient method for color vision assessment, which is based on a continuous motion tracking task and a Kalman filter model. The effectiveness of this new method was evaluated by assessing the color vision of both color-deficient observers and normal controls. The results from both a small sample (N = 29, Experiment 1) and a large sample (N = 171, Experiment 2) showed that color-deficient observers could be perfectly identified within 20s using the tracking performance. We also compared the new method with a traditional psychophysical detection task to examine the consistency of perceptual noise estimation between the two methods, and the results showed a moderate correlation (Pearson's r = .59 ~ .64). The results also demonstrated that the new method could measure individuals' contrast response functions of both red-green and blue-yellow colors (e.g., the L-M and S-(L + M) axes in DKL color space) in just a few minutes, showing much higher efficiency than traditional methods. All the findings from this study indicate that the continuous motion tracking method is a promising tool for both rapid screening of color vision deficiencies and fundamental research on color vision.

Contrasting pollution responses of native and non-native fish communities in anthropogenically disturbed estuaries unveiled by eDNA metabarcoding

Understanding the influence of environmental pollutants on the assembly mechanisms of estuarine fish communities is vital for addressing conservation challenges in these biodiverse ecosystems. Although significant research has explored the toxic impacts of pollutants such as petroleum, heavy metals, and eutrophication on individual species and populations, their effects on community assembly processes and the differential responses of native versus non-native fish at the meta-community level remain inadequately understood. This study utilized environmental DNA (eDNA) metabarcoding to analyze fish community diversity across 28 subtropical estuaries in China, assessing how these pollutants affect community composition and assembly mechanisms. Results indicated that eDNA was 2.54 times more effective than traditional methods in species identification, while also enabling the detection of a higher number of non-native fish species and more diverse functional guilds within estuarine ecosystems. A significant distance decay pattern (p < 0.05) was observed among native fish, whereas non-native species exhibited non-significant patterns. Neutral and null models showed that non-native species had significantly higher migration rates (0.005939 vs 0.001757) and a greater contribution of stochastic processes (82.38% vs 70.59%) compared to native species. Additionally, distance-based redundancy analysis (db-RDA), variance partitioning analysis (VPA), and correlation analyses revealed that native species were strongly constrained by environmental factors, particularly oil, Hg, Zn, Pb, Cr6+, and NH4+, while non-native species displayed notable resilience to these pollutants. These findings highlight the potential for non-native species to disproportionately influence community dynamics and assembly through unrestricted random dispersal amid environmental disturbances. This research clarifies the contrasting ecological responses of native and non-native fish communities to anthropogenic pressures in estuarine environments, offering essential insights into ecosystem resilience and informing biodiversity conservation strategies in rapidly changing coastal ecosystems.

Contrasting responses of soil organic carbon dynamics to long-term canopy and understory nitrogen addition in a subtropical forest

Elucidating the impacts of chronic atmospheric nitrogen (N) deposition on soil organic carbon (SOC) is crucial for predicting the dynamics of terrestrial C sinks, particularly in N-rich subtropical forests. Experiments using understory N addition (UN) have provided valuable insights into these impacts, but unavoidably neglect processes such as interception and absorption of N within forest canopy. We assessed the effects of long-term (11-yr) fertilization via both canopy N addition (CN) and UN on SOC in a subtropical forest. Our results showed significantly different responses of SOC between the approaches, with UN displaying greater effects on SOC than CN. Specifically, both low and high rates of UN substantially increased the concentrations of particulate organic C (POC), whereas the high rate of CN significantly increased those of mineral-associated organic C (MAOC) rather than POC. Long-term CN and UN treatments had distinct effects on plant- and microbial-derived C processes. UN treatments significantly increased soil available N and improved the litter quality, enhancing the formation of POC, and suppressing microbial decomposition of POC due to the significant decreases in soil pH. However, CN treatments significantly improved litter quality and mitigated soil acidification, thus stimulating microbial C utilization and accelerating the microbial transformation of POC to MAOC. Our findings imply that the underlying mechanisms of natural N deposition influencing forest SOC may differ from those obtained from UN, and conventional fertilization experiments may overestimate the benefits of elevated N deposition to forest SOC.

Changes in Distribution Ranges of Abies Species Dominating in the Forests of Northeast Asia Since the Last Glacial Maximum

ABSTRACTAimClimate variations within the stadial–interstadial cycles drive shifts in the distribution of forest dominants. This study examines how climate dynamic alters the distribution ranges of two boreal and one cold‐temperate Abies species dominating in Northeast Asia.LocationNortheast Asia: China, Japan, Korea and Russia.TaxonAbies nephrolepis, A. sachalinensis (sect. Balsamea) and A. holophylla (sect. Pseudopicea).MethodsWe developed climate envelope species distribution models (SDMs) using warmth and coldness indices, the continentality index, and proxies of rain and snow precipitation indices. We interpolated SDMs on reconstructed climates for the Last Glacial Maximum (LGM) and the Holocene Climatic Optimum (HCO) and to predicted climates for 2070 under global warming scenarios RCP2.6 and RCP8.5.ResultsDuring the LGM, the climatic optimum for all species covered extensive areas on the shelves of the Japanese and Yellow Seas, facilitated by the global sea level drop. The interglacial climatic optimum supports the expansion of A. nephrolepis and A. sachalinensis compared to the LGM, whereas the range of A. holophylla climatic niche range experiences a reduction.Main ConclusionsOur findings highlight the significant impact of climatic oscillations on the spatial distribution and ecological dynamics of Abies species in Northeast Asia. The contrasting responses of boreal and temperate fir species to glacial and interglacial periods underscore the complex interplay between climate change and the distribution of forest dominants. Projections under future warming scenarios suggest that Abies species will face further range shifts, emphasising the need for adaptive forest management and conservation strategies, especially in the southern part of their distribution.

Hydraulic strategy defines contrasting responses to an abrupt precipitation during a successive lethal drought

BackgroundAs precipitation patterns are predicted to become more erratic, it’s vital to understand how abrupt climate events will affect woody seedlings that develop different hydraulic strategies. We cultivated anisohydric Robinia pseudoacacia L. and isohydric Quercus acutissima Carr. in a greenhouse, and subjected an abrupt precipitation event during a successive drought. Patterns of leaf and root gas exchange, leaf and stem hydraulics, seedlings growth, and non-structural carbohydrate (NSC) patterns were determined.ResultsWe found that as an anisohydric species, R. pseudoacacia seedlings adopted a strategy of sacrificing leaves in response to stress, resulting in the lowered photosynthesis and ultimately leading to a decrease in NSC accumulation. In contrast, isohydric Q. acutissima maintained the integrity of leaves by reducing respiratory consumption in response to drought stress, thereby ensured the stability of NSC pool.ConclusionR. pseudoacacia exhibited an extravagant strategy with efficient water transport, photosynthetic assimilation, and growth capabilities, but its resistance to embolism was relatively weak, while Q. acutissima adopted a resource-saving strategy with higher hydraulic safety. We also found that Q. acutissima seedlings were prone to allocate carbohydrates to maintain growth, while R. pseudoacacia preferred to sacrifice growth and aboveground NSC limitation only happened when precipitation was subjected after total stomatal closure. We thus believe that hydraulic strategy could define seedlings responses to drought and recovery, and further may adversely affect their re-sprouting capacity after drought stress relief.

Contrasting responses of soil organic and inorganic carbon pools under plant invasion in tropical coral islands

Contrasting responses of soil organic and inorganic carbon pools under plant invasion in tropical coral islands

Dynamics of PCV2 and PCV3 in the Serum and Oral Fluids of Pigs After PCV2 Vaccination in a Commercial Farm

Objectives: This study investigated the dynamics of porcine circovirus type 2 (PCV2) and PCV3 on a commercial farm following PCV2 vaccination. Methods: Serum samples from 35 pigs, starting at 3 weeks of age, were collected weekly until 21 weeks of age. Oral fluids from six pens of pigs of the same age were also analyzed. Viral DNA was assessed in pooled sera and individual oral fluid samples, while antibodies (IgG and IgA) were measured in the serum and oral fluids. Productive parameters, including weekly mortality and cumulative mortality, were evaluated. Results: The results revealed that PCV2 and PCV3 co-infection was detected in pigs at 8 weeks of age, with PCV3 being detected in oral fluids two weeks earlier. PCV3 DNA was detected in oral fluids at 4 weeks of age. PCV2 IgG antibodies in the serum increased gradually after vaccination, peaking at 7 weeks of age, then declined and stabilized until 21 weeks of age. PCV3 IgG antibodies fluctuated early but were uniformly positive after 13 weeks of age. In oral fluids, PCV2 IgG and IgA antibodies showed a strong response only at 3 and 23 weeks of age. In contrast, a strong and consistent IgG response was observed in oral fluids in the absence of PCV2 and PCV3 co-infection of pigs at 3 to 11 weeks of age. The farm’s productive parameters remained stable throughout the study. Conclusions: These findings suggest that PCV2 and PCV3 co-infection, along with high PCV3 detection levels in serum and oral fluids, may have an impact on the efficacy of PCV2 vaccination.

A phantom study on the applicability of a detectability index in ultrasound imaging

The assessment of clinical image quality on ultrasound is currently often subjective. While image quality factors such as contrast response or depth of penetration can be evaluated semi-automatically, the evaluation of high contrast resolution requires test objects with specific inserts. The aim of this study was to evaluate the applicability of image quality metrics which were derived from Linear System Theory in the field of medical ultrasound imaging. Modular Transfer Function (MTF) and noise power spectrum (NPS) were determined on four phantoms. Image quality was assessed using a detectability index for different diameters. One phantom contained a cylinder filled with water, which appears as a circle in the US images. The other three phantoms were homogeneous and consisted of three different materials all based on PVA (polyvinyl alcohol). The basic phantom material was a 10% PVA hydrogel. The two other materials included microplastic spheres and starch to increase echogeneity. NPS and the MTF were determined using MATLAB routines. Two linear US transducers with bandwidths of 2.4–10 and 4–15 MHz were used to show the dependence of the index on the principal frequency of the US wave. The results show that for all phantom materials and object sizes (1–10 mm diameter), the detectability indices decreased with increasing penetration depth (from 6 to 10 cm). In addition, all indices of the higher frequency transducer were higher than those of the lower frequency transducer. When comparing the different phantom materials (PVA, PVA with starch and PVA with microspheres), different mean pixel value (MPV) were found, while the standard deviations for the materials were similar. This enabled us to evaluate the detectability index at different signal-to-noise ratios (SNR). Measures of image homogeneity (coefficient of the variance and variation) showed no significant difference to a commercial phantom (p-values ranging from 0.16 to 1, average p-value 0.5). These results suggest that the concept of a detectability index can also be applied to US imaging.

Contrasting behavioural responses to concurrent stressors in an aquatic snail: the importance of stress type and combination.

Behaviour is a fundamental parameter for understanding the animal fitness, serving as an indicator of exposure to stressors. In ecosystems, animals often face multiple stressors simultaneously. Their behavioural responses may vary when exposed to individual stressors, whilst synergistic, additive, or antagonistic effects can result from the interaction of multiple stressors. Therefore, it is imperative to conduct studies that take into account the common occurrence of multi-stress scenarios in aquatic ecosystems. We tested the effects of three sources of stress (acidity (A), toxicity with acetone (T) and conspecific chemical cues (S)) on the behaviour of the aquatic snail Potamopyrgus antipodarum (Tateidae, Mollusca). We evaluated the impact of each stressor, as well as in combinations of two or three stressors simultaneously. The highest time to initiate movement was shown by the animals of the low water pH (A) followed by those exposed to the combination of low water pH and acetone exposure (AT). The differences between the time to initiate movement of each treatment with control revealed a marked decrease in the differences for the snails from the conspecific chemical cues (S) and ST treatments, which mean a higher time to initiate movements. It is concluded that behaviour varied depending on the source and combination of stress. While an acid environment and conspecific signals had contrasting effects when applied separately, their simultaneous exposure resulted in no significant impact. This highlights the importance of considering the combined effects of multiple stressors when extrapolating laboratory results to real-world scenarios, where organisms are often exposed to more than one stressor at a time.

Labor, Management, Government, and Labor Markets: A Festschrift in Honor of Thomas A. Kochan

In September 2022, former students and colleagues of Thomas A. Kochan organized a Festschrift, a “festival of writing,” to honor his impact on Industrial Relations and related fields. The Festschrift generated more than two dozen articles and commentaries in a forthcoming book, as well as the four articles featured here in the ILR Review. These articles include “A Tale of Two Locals,” focused on contrasting responses to the 2019 GM-UAW strike; “The Need for Speed,” focused on the role of employers in immigrant work visa prioritization; “Incentives to Comply with the Minimum Wage,” comparing enforcement in the United States and the United Kingdom; and “Gendered Job Search” focused on gender differences in reservation wages and job applications. The articles highlight the roles of labor, management, and government as actors in an industrial relations system. Together these articles and the additional collection in the forthcoming book exemplify Tom Kochan’s leadership in advancing industrial relations theory, policy, and practice.

Transgressive segregation and the inheritance of paraquat resistance in Canada fleabane (Conyza canadensis)

Abstract Transgressive segregation refers to the phenomenon whereby the progeny of a diverse cross exhibit phenotypes that fall outside the range of the parents for a particular trait of interest. Segregants that exceed the parental values in life history traits contributing to survival and reproduction may represent beneficial new allelic combinations that are fitter than respective parental genotypes. In this research, we use geographically disparate paraquat resistant biotypes of horseweed (Canada fleabane) [Conyza canadensis (L.) Cronquist; syn. Erigeron canadensis L.] to explore transgressive segregation in biomass accumulation and the inheritance of the paraquat resistance trait in this highly self-fertilizing species. Results of this research indicated that the paraquat resistance traits in E. canadensis biotypes originating in California, USA and Ontario, Canada were not conferred by single major gene mechanisms. Segregating generations from crosses among resistant and susceptible biotypes all displayed transgressive segregation in biomass accumulation in the absence of the original selective agent, paraquat. However, when challenged with a discriminating dose of paraquat, progeny from the crosses of susceptible x resistant and resistant x resistant biotypes displayed contrasting responses with those arising from the cross of two resistant biotypes no longer displaying transgressive segregation. These results support the prediction that transgressive segregation is frequently expressed in self-fertilizing lineages and is positively correlated with the genetic diversity of the parental genotypes. When exposed to a new environment, transgressive segregation was observed regardless of parental identity or history. However, if hybrid progenies were returned to the parental environment with exposure to paraquat, the identity of fittest genotype (i.e., parent or segregant) depends on the history of directional selection in the parental lineages and the dose to which the hybrid progeny was exposed. It is only in the original selective environment that the impact of allelic fixation on transgressive segregation can be observed.

COVID-19 and Market Response: Evidence From Listed Firms in Tanzania and Kenya

This study investigates the effects of COVID-19 on the financial performance of listed firms in the financial and consumer goods industries in Tanzania and Kenya. The choice of Tanzania and Kenya as focal points is motivated by their contrasting responses to the pandemic and their roles as economic powerhouses in the region. Using data from the Dar es Salaam Stock Exchange and Nairobi Stock Exchange spanning the period from 2015 to 2022, the study employs the Dynamic panel-data model, the two-step system GMM, to quantify the impact of the pandemic. The research has two specific objectives: to analyze the effect of COVID-19 on the financial performance of listed firms in the financial industry and to assess its impact on the consumer goods industry in both countries. Key findings reveal that in the financial sector, firms showed resilience with a positive impact on profitability during the pandemic, driven by the adoption of digital financial services and effective risk management. In contrast, the consumer goods sector experienced a significant negative impact, highlighting severe disruptions in supply chains and consumer demand. Notably, firms in Tanzania outperformed those in Kenya, due to less restrictive COVID-19 measures. These findings suggest policymakers should support digital innovations, prudent leveraging, and economic growth to sustain and improve firm profitability during future disruptions.

Divergent Drying Mechanisms in Humid and Non-Humid Regions Across China

Understanding the drying mechanism is critical for formulating targeted mitigation strategies to combat drought impacts. This study aimed to reveal divergent drying mechanisms in humid and non-humid regions across China from the multidimensional perspectives of climate, vegetation, and energy balance. During the period 1982–2012, the Standardized Precipitation Evapotranspiration Index (SPEI) revealed non-significant drying trends across China. Simultaneously, temperature and precipitation indicated a warming and drying pattern in the humid regions, contrasted with a warming and moistening pattern in the non-humid areas. The coupling effects of declined precipitation, increased vegetation coverage, and elevated temperature exacerbated dryness in the humid regions, while pronounced warming dominantly caused dryness in the non-humid regions. The inverse correlations between the actual evapotranspiration (ET) with precipitation and potential ET (PET) highlighted the principal role of moisture availability in divergent drying mechanisms over humid and non-humid regions. Random Forest models recognized precipitation and PET as the primary factors influencing SPEI in the humid and non-humid regions, respectively. Ongoing warming from 2013 to 2022 mitigated dryness in the humid regions due to the increased latent heat at the expense of sensible heat. Conversely, warming, amplified by the heightened sensible heat, exacerbated drought in the non-humid regions. By identifying the contrasting responses of humid and non-humid regions to warming and moisture availability, this study provides crucial insights for policymakers to mitigate drought impacts and enhance resilience in vulnerable non-humid areas.

Contrasting responses of commercially important Northwest Atlantic bivalve species to ocean acidification and temperature conditions

Modern calcifying marine organisms face numerous environmental stressors, including overfishing, deoxygenation, increasing ocean temperatures, and ocean acidification (OA). Coastal marine settings are predicted to become warmer and more acidic in coming decades, heightening the risks of extreme events such as marine heat waves. Given these threats, it is important to understand the vulnerabilities of marine organisms that construct their shells from calcium carbonate, which are particularly susceptible to warming and decreasing pH levels. To investigate the response of four commercially relevant bivalve species to OA and differing temperatures, juvenile Mercenaria mercenaria (hard shell clams), juvenile Mya arenaria (soft shell clams), adult and juvenile Arctica islandica (ocean quahog), and juvenile Placopecten magellanicus (Atlantic sea scallops) were grown in varying pH and temperature conditions. Species were exposed to four controlled pH conditions (7.4, 7.6, 7.8, and ambient/8.0) and three controlled temperature conditions (6, 9, and 12°C) for 20.5 weeks and then shell growth and coloration were analyzed. This research marks the first direct comparison of these species’ biological responses to both temperature and OA conditions within the same experiment. The four species exhibited varying responses to temperature and OA conditions. Mortality rates were not significantly associated with pH or temperature conditions for any of the species studied. Growth (measured as change in maximum shell height) was observed to be higher in warmer tanks for all species and was not significantly impacted by pH. Two groups (juvenile M. arenaria and juvenile M. mercenaria) exhibited lightening in the color of their shells at lower pH levels at all temperatures, attributed to a loss of shell periostracum. The variable responses of the studied bivalve species, despite belonging to the same phylogenetic class and geographic region, highlights the need for further study into implications for health and management of bivalves in the face of variable stressors.

Contrasting Response of Mesoscale Convective Systems Occurrence Over Tropical Land and Ocean to Increased Sea Surface Temperature

AbstractMesoscale convective systems (MCSs) are pivotal in global energy/water cycles and typically produce extreme weather events. Despite their importance, our understanding of their future change remains limited, largely due to inadequate representation in current climate models. Here, using a global storm‐resolving model that accurately simulates MCSs, we conclude contrasting responses to increased SST in their occurrence, that is, notable decreases over land but increases over ocean. This land‐ocean contrast is attributed to the changes in convective available potential energy (CAPE) and convective inhibition (CIN). Over land, notable rises in CIN alongside moderate increases in CAPE effectively suppress (favor) weak to moderate (intense) MCSs, resulting in an overall reduction in MCS occurrences. In contrast, substantial increases in CAPE with minimal changes in CIN over ocean contribute to a significant rise in MCS occurrences. The divergent response in MCS occurrence has profound impacts on both mean and extreme precipitation.

Salinity drives niche differentiation of soil bacteria and archaea in Hetao Plain, China

Soil salinization is a critical environmental issue that limits plant productivity and disrupts ecosystem functions. As important indicators of soil environment, soil microbes play essential roles in driving nutrient cycling and sustaining ecosystem services. Therefore, understanding how microbial communities and their functional potentials respond to varying levels of soil salinization across different land use types is crucial for the restoration and management of salt-affected ecosystems. In this study, we randomly selected 63 sites across the Hetao Plain, covering an area of ∼2500 km2. Our results showed that both salinity- and fertility-related soil parameters were significantly correlated with bacterial and archaeal diversities, with soil salinity emerging as the stronger predictor of prokaryotic diversity. Intriguingly, bacterial and archaeal communities were tightly interlinked but displayed opposite trends in response to environmental factors, indicating a clear microbial niche differentiation driven by soil salinity. Moreover, the generalist functions of bacteria and archaea (e.g., chemoheterotrophy) exhibited contrasting responses to environmental parameters, while their specialist functions (e.g., nitrification) responded consistently. These findings highlight the pivotal role of soil salinity in shaping the niche differentiation of bacterial and archaeal communities in saline soils, providing insights to guide salinity-centered restoration strategies for effective marginal land management.

Do Different Wheat Ploidy Levels Respond Differently Against Stripe Rust Infection: Interplay between Reactive Oxygen Species (ROS) and the Antioxidant Defense System?

Wheat stripe rust (Puccinia striiformis f. sp. tritici, Pst) is the most damaging wheat disease, causing substantial losses in global wheat production and productivity. Our study aimed to unravel the complex reciprocity between reactive oxygen species and the antioxidant defense system as a source of resistance against stripe rust in diploid, tetraploid and hexaploid wheat genotypes. The significant genetic variability for stripe rust in the materials under study was evident as the genotypes showed contrasting responses during both the adult and seedling stages. Our thorough perspective on the biochemical responses of wheat genotypes to stripe rust infection revealed distinct patterns in oxidative damage, antioxidant enzymes and photosynthetic pigments. Principal component analysis revealed inverse correlations between antioxidants and ROS, underscoring their key function in maintaining the cellular redox balance and protecting plants against oxidative damage. Diploid (Ae. tauschii) wild wheat exhibited a better biochemical defense system and greater resistance to stripe rust than the tetraploid (T. durum) and hexaploid (Triticum aestivum) wheat genotypes. The antioxidant enzyme activity of durum wheat was moderate compared to diploid and hexaploid wheat genotypes. The hexaploid wheat genotypes exhibited increased ROS production, reduced antioxidant enzyme activity and decreased photosynthetic pigment levels. This study enhances understanding of the antioxidant defense system across different wheat ploidies facing stripe rust, serving as a valuable strategy for improving crop disease resistance. This study validated the biochemical response of stripe rust-resistant and susceptible candidate genotypes, which will be used to develop genetic resources for discovering stripe rust resistance genes in wheat.

Spatial multi-criteria analysis based on food web model results: application to a marine conservation area

Effective marine management requires balancing conservation and sustainable use of resources. Food web models are useful for simulating direct and indirect effects of management scenarios on ecosystem functioning by using multiple indicators. However, a key challenge is consolidating these indicators into a single, comprehensive, measure, which is often required to guide management decisions, such as in Strategic Environmental Assessment. This study applies spatial multi-criteria analysis to food web model outputs to develop a single index for different marine management applications. We applied this framework to the case of the “Tegnùe di Chioggia”, a Special Area of Conservation (SAC; IT3250047) under the Natura 2000 European network, located in the northern Adriatic Sea (Italy). This area, characterised by the presence of biogenic rocky outcrops, currently lacks a formal management plan. Using the Ecospace module of the Ecopath with Ecosim software, we simulated three management scenarios: 1) SAC expansion; 2) winter artisanal fishing in the SAC; 3) a combination of both. In line with ecosystem-based management, we focused on economically important trophic groups in the region, such as the Mediterranean mussel, Mytilus galloprovincialis, and striped venus clam, Chamelea gallina, which are present near the SAC. We also considered the efforts of the local fishing fleets. Ecosystem structure and functioning indicators, generated by the spatial food-web model, were linked to three criteria aligned with the management priorities of the area: nature conservation, aquaculture productivity, and fishing productivity. These criteria were aggregated into a final score to compare the management scenarios. The results showed that none of the scenarios would significantly alter community composition or ecosystem functioning compared to the current situation. However, they did show contrasting responses in the food web model. The SAC expansion scenario notably increased total biomass and commercial fish biomass, especially pectinids and cephalopods. The fishing scenario had a minimal impact on trophic groups. Ecosystem resilience and structure indicators were less sensitive to management scenarios than biomass indicators. However, the multi-criteria analysis revealed that the fishing scenario limited the benefits of expanding the SAC, due to reduced catches. The final score effectively ranked proposed scenarios, highlighting key indicators that influenced these variations. The proposed approach shows potential for supporting participatory modelling and engaging stakeholders in developing management scenarios.

Seasonal Variation in Flow and Metabolic Activity Drive Nitrate and Carbon Supply and Demand in a Temperate Agricultural Stream

AbstractIn‐stream biogeochemical processing, typically associated with base flow conditions, has recently been assessed at higher discharges, aided by high frequency monitoring. However, the potential for nutrient and carbon processing is still largely unknown in streams impacted by agriculture, representing major pathways for eutrophication and diffuse pollution. In this study, we measured solute concentrations and gross primary productivity (GPP) and ecosystem respiration (ER) to infer nitrate (NO3−) and dissolved organic carbon (DOC) supply and demand across contrasting hydrological conditions. As expected, solute supply greatly surpassed in‐stream biological demand for both NO3− and DOC for intermediate to large discharges. However, during four consecutive weeks in summer, lowered NO3− supply and high metabolic activity led to a 60% and 31% reduction in stream NO3− and DOC export. We also compared metabolism‐discharge versus solute concentration‐discharge patterns during storm events to better understand biogeochemical responses to high flows. Metabolic rates showed a contrasting response to storm events: ER increased while GPP decreased following declines in NO3− concentrations. The positive correlation between GPP and NO3− concentrations suggests that GPP suppression can be partially attributed to decreased NO3− availability during storm events. This study supports the idea that agricultural streams have a limited capacity to biologically process DOC and NO3−. However, it also emphasizes that the balance between supply and demand can vary from severe saturation to limitation, depending on seasonal fluctuations in discharge and metabolic activity, highlighting the crucial role of mitigating pollution at its source during hydrologically active periods to improve water quality.

Comparative transcriptome analysis reveals the key factors regulating nitrogen use efficiency in Chrysanthemum

Nitrogen (N) is a limiting factor that determines the yield and quality of Chrysanthemum. Genetic variation in N use efficiency (NUE) has been reported among Chrysanthemum genotypes. We performed a transcriptome analysis of two Chrysanthemum genotypes, ‘Nannonglihuang’ (‘LH’, N-efficient genotype) and ‘Nannongxuefeng’ (‘XF’, N-inefficient genotype), under low N (0.4 mmol·L-1 N) and normal N (8 mmol·L-1 N) treatments for 15 d and an N recovery treatment for 12 h (low N treatment for 15 d and then normal N treatment for 12 h) to understand the genetic factors impacting NUE in Chrysanthemum. The two genotypes exhibited contrasting responses to the different N treatments. The N-efficient genotype ‘LH’ had significant superiority in agronomic traits, N accumulation and glutamine synthase activity under both normal N and low N treatments. Low N treatment promoted root growth in ‘LH’, but inhibited root growth in ‘XF’. Transcriptome analysis revealed that the low N treatment increased the expression of some N metabolism genes, genes related to auxin and abscisic acid signal transduction in the roots of both genotypes, as well as genes related to gibberellin signal transduction in roots of ‘LH’. The N recovery treatment just increased the expression of genes related to cytokinin signal transduction in roots of ‘LH’. The expression levels of the NRT2.1, AMT1.1, and Gln1 genes related to gibberellin and cytokinin signal transduction were higher in roots of ‘LH’ than in ‘XF’ under different N treatments, suggesting that the genes related to N metabolism and hormone (auxin, abscisic acid, gibberellin, and cytokinin) signal transduction in roots of ‘LH’ are more sensitive to different N treatments than those of ‘XF’. Co-expression network analysis (WGCNA) also identified hub genes like bZIP43, bHLH93, NPF6.3, IBR10, MYB62, PP2C, PP2C06 and NLP7, which may be the key regulators of N-mediated responses in Chrysanthemum and play crucial roles in enhancing NUE and resistance to low N stress in the N-efficient Chrysanthemum genotype. These results revealed the key factors involved in regulating NUE in Chrysanthemum at the genetic level, which provides new insights into the complex mechanism of efficient nitrogen utilization in Chrysanthemum, and can be useful for the improvement and breeding of high NUE Chrysanthemum genotypes.