Levels Of Resource Availability Research Articles

Allometric equations for biomass and carbon pool estimation in short rotation Pinus radiata stands of the Western Cape, South Africa

AbstractThe quantification of tree growth and carbon storage over time is an important task for sustainable forest management and carbon sequestration projects. For the South African short-rotation Pinus radiata (D. Don) forests, this knowledge is lacking. We developed allometric equations and compared the estimated weights to previously published biomass studies and we used Dirichlet Regression (DR) modelling to ensure additivity of the component proportions. The biomass components and their contribution to carbon storage depend strongly on forest structure and mean tree size but also on-site conditions and tree architecture. Our first two hypotheses were that the (1) best model for stemwood (SW), bark and total mass will include the combined variable DBH2H and (2) that the DR will yield statistically similar estimates for all components when compared to the best models. Our third hypothesis was that allometric equations developed for sites with high resource availability (e.g. wet, fertile sites) will yield biased estimates when extrapolated to sites with lower levels of resource availability (drier and/or infertile sites). The results indicated that DBH2H was the best variable to describe SW, bark and total mass and the DR yield similar estimates for all component proportions when compared to the best models. There were strong similarities in the SW and total mass of independent test sites in comparison to the SW and total mass of this study but greater variability in the bark, needle and branch mass. This can be associated to site and seasonal differences as well as variability in tree architecture brought about by different silvicultural operations on individual sites. Previously developed equations by other authors for sites with high resource availability overpredicted the SW and total mass of the models developed in this study. Our set of additive component equations performed well even when applied to sites of similar productivity over a climate gradient. The presented new equations bridge the gap in knowledge where allometric equations for short rotation Radiata pine stands are lacking.

Sustainable Farming: Insights from Data Clustering

This study delves into the perceptions and practices of the agricultural community regarding eco-friendly technologies and air pollution through a detailed clustering analysis of survey data. The primary objective is to identify distinct groups within the agricultural sector based on their responses to various factors, including demographic information, types of crops grown, perceptions of air pollution, and attitudes toward sustainable practices. The analysis employs K-Means clustering to categorize respondents into three distinct clusters, each representing a unique combination of views and practices. The findings are visualized using scatter plots and box plots, offering a clear depiction of the variations and commonalities within each cluster. The study reveals significant diversity in the adoption and perception of eco-friendly practices in agriculture. Some groups demonstrate high satisfaction and effectiveness, indicating successful integration of sustainable methods, while others show skepticism and challenges, possibly due to economic constraints or lack of access to resources and knowledge. The economic interpretation of these clusters suggests that varying levels of resource availability, technological access, and knowledge dissemination influence differences in the adoption of sustainable practices. The study concludes with recommendations for targeted policy-making, educational initiatives, and resource allocation to support and enhance the adoption of eco-friendly practices across different segments of the agricultural community. This tailored approach can significantly contribute to the broader objective of promoting sustainable agriculture and environmental stewardship.

DEFINING STRATEGIC INVESTMENT PRIORITIES IN BUSINESS ACTIVITIES

This paper underscores the role and position of investment activity within the framework of strategic enterprise management. It explores the economic essence and distinct characteristics of the investment process, which encompasses the issuance and accumulation of production resources as investment goods and services. It is argued that the investment process at an enterprise can be viewed from two perspectives: as a complex of potential alternative investment decisions based on available financial resources and the capability to attract additional funds (implemented through the development of the enterprise's investment policy strategy); and from the standpoint of each specific investment decision (the rationale and specific investment projects). The paper provides comprehensive recommendations that cover all aspects of the investment process to enhance the methodological support for selecting strategic investment priorities to ensure the enterprise's sustainable development. Distinctive features of financial and investment resources in the system of resource provision for enterprise development when forming an investment development strategy are highlighted. A matrix for defining the plan's priorities for investment provision of enterprise development is developed. It is substantiated that investment risk depends on numerous factors that directly influence the choice of investment strategy. To generalize the impact of these factors, a rating indicator is proposed, which considers the characteristics of investment attractiveness and the level of investment risk. The composition of attributes for assessing the investment attractiveness of the enterprise is justified, including the state of critical factors determining investment efficiency: technical-technological base of production; level of resource availability and efficiency of their use; economic parameters of business activity and financial condition of the enterprise; market demand dynamics and competitive intensity on the target market; level of management organization. Recommendations are provided for determining investment risk based on a summary of quantitative assessments of a complex of dangers and threats that are individual to each investment process participant.

Instructional materials availability and lecturers’ task performance in Nigerian universities

Purpose: This study examined the effects of educational resource accessibility on lecturers' task performance in public universities in Cross River State, Nigeria. It also explored the possibility of developing instructional resources with culturally relevant information to support creative teaching methods. 
 Design/Methodology/Approach: The study used a survey research method with a sample of 577 lecturers or tutors selected randomly from various departments of local public universities. Data was collected through a questionnaire and analyzed using a one-way analysis of variance and Fisher's least significant difference (LSD).
 Findings: The analysis of the data showed that lecturers' and instructors' performance in terms of teaching, research and community work is significantly impacted by the availability of educational resources. 
 Conclusion: The effectiveness of lecturers' tasks is proportional to the calibre of instructional materials provided by their institutions. Lecturers with high levels of instructional resource availability outperformed those with moderate or low levels of resource availability.
 Research Limitations/Future Research: The current study was limited to the general influence of instructional materials’ availability on lecturers’ task performance. Future researchers should focus on identifying local content areas for improvement and student-lecturers’ collaboration in instructional resource design and fabrication.
 Practical Implications: This study may serve as the impetus for university administrators to collaborate with sociologists, anthropologists and educational technologists in order to improve student-lecturer collaboration in the creation of culturally embedded instructional materials for better task performance from lecturers and increased student engagement in learning processes.
 Contribution to the Literature: The findings of this study may provide literature for scholastic reviews and also become a policy -making tool for educational resource planners.

Disaster response strategies of governments and social organizations: From the perspective of infrastructure damage and asymmetric resource dependence

Natural disaster response is commonly regarded as a dynamic process that reflects intricate relationships between physical and social factors. The resilience of physical infrastructure impacts the availability of emergency resources, while asymmetric resource dependence among emergency cooperation organizations influences the effectiveness of the coordinated emergency response. This study has formulated differential game encompassing three emergency response models: autonomous participation, government-led, and collaborative response. These models have been designed to account for scenarios involving infrastructure damage and asymmetric resource dependence scenarios to compute the optimal level of emergency response efforts by both government and social organizations, the government cost-sharing ratio, the optimal level of emergency resource availability, and disaster response performance. The results indicated that, under specific conditions, government cost-sharing can motivate social organizations to actively engage in disaster response, leading to improvement in disaster response performance. The collaborative emergency response model outperformed the other models regarding optimal emergency response strategy and disaster response performance. Notably, infrastructure damage and asymmetric resource dependence lead to a reduction in the optimal level of emergency response efforts and system disaster response performance for both parties. Furthermore, the impact of infrastructure damage on disaster response performance and the optimization of emergency resource availability levels are shown to be more substantial than the effects of asymmetric resource dependence. This research provided theoretical support for strategic decision-making in natural disaster response and is more aligned with disaster response.

Effects of resource availability on the growth, Cd accumulation, and photosynthetic efficiency of three hyperaccumulator plant species

Plants that hyperaccumulate heavy metals such as cadmium (Cd) are important agents of phytoremediation. Availability of resources such as light, nutrients, and water can affect heavy metal accumulation by plants, but the responses of hyperaccumulators to different levels of resource availability remain little studied. To test such responses, three Cd hyperaccumulators, Solanum nigrum, Bidens pilosa, and Taraxacum mongolicum, were grown in Cd-contaminated soil; subjected to three levels of light, nutrient, or water availability; and measured for growth, Cd accumulation, and photosynthetic efficiency. All three species accumulated more total biomass and grew taller if given high than low water or light (each P < 0.001). Species accumulated four to eight times more Cd (190−309 versus 24−68 μg Cd g−1 mass) under high than low light. High water availability increased Cd accumulation by 89% in B. pilosa but decreased it by 31% and 40% in S. nigrum and B. pilosa, respectively. Effects of nutrients on both growth and accumulation varied between species; Cd accumulation by S. nigrum and T. mongolicum was respectively 14% and 54% lower at high than low nutrients, while it was 130% higher in B. pilosa. Light but not water or nutrient availability affected effective and maximum quantum yields and electron transport rate. Findings from this study suggest that low levels of light may constrain phytoremediation of Cd in soil and that testing species of Cd hyperaccumulators individually for responses to levels of water and nutrients will inform selection of species for phytoremediation.

Environmental and genetic variation in an asexual plant

Species may respond to variation in environmental conditions by modifying their phenotype to match local levels of resource availability. This phenotypic response can be driven by plastic physiological change, or by adaptive genetic change. Here we use Lemna minor (lesser duckweed), a small aquatic macrophyte that is increasingly used as a model in ecology and evolution, to investigate the source and maintenance of phenotypic variation in natural environments. We found substantial phenotypic variation in L. minor in the field, with its frond area and root length changing predictably over natural environmental gradients of resource availability. Separating environmental and genetic variation in these traits in a common garden, we attribute the majority of phenotypic variation we observed in the field to phenotypic plasticity. Despite this, there was substantial within-site genetic variation. We found evidence of strong purifying selection in the field, that is necessarily balanced by mutation and migration. Using measures of environmental and genetic variation in phenotype and fitness, we estimate the rates of dispersal and evolution of fitness necessary to sustain the observed levels of genetic variation.

Do urban habitats induce physiological changes in Mediterranean lizards?

AbstractUrban environments offer dramatically different habitats for wildlife compared with natural environments. They provide, for example, different levels of resource availability, anthropogenic night light, and microclimates (e.g., urban heat islands). For reptiles, increased temperatures in the city can lead to increased energetic demands and metabolic rates unless they change their morphology and physiology and adapt or acclimatize to the urban conditions. We explored differences in metabolic rate, evaporative water loss, and body size of two lizard species – rock agamas (Laudakia vulgaris) and Mediterranean house geckos (Hemidactylus turcicus), from urban habitats and nearby natural open areas. When tested in the lab, we expected to identify physiological adaptations resulting in decreased metabolism in urban individuals. Both species had similar body lengths and masses at both habitat types, suggesting any differences in costs and benefits between urban and natural environments do not affect their overall size or body condition. In the laboratory, metabolic rates were similar in individuals from both habitats for both species, indicating no long‐term adaptations in this trait. However, urban geckos (but not agamas) had higher evaporative water loss than conspecifics from more natural habitats. This may suggest different compositions of epidermal lipids affecting the gecko skin's resistance to evaporation between the habitats. Overall, our results highlight different elements of the urban environment that might affect reptiles. However, the differences between species urge caution in interpreting the results to other species and locations. With increasing urbanization worldwide, understanding when and to what degree local adaptations can occur can help us predict reptile species distribution and survival in light of future anthropogenic changes.

New insights into trait introgression with the look-ahead intercrossing strategy.

Trait introgression (TI) can be a time-consuming and costly task that typically requires multiple generations of backcrossing (BC). Usually, the aim is to introduce one or more alleles (e.g. QTLs) from a single donor into an elite recipient, both of which are fully inbred. This article studies the potential advantages of incorporating intercrossing (IC) into TI programs when compared with relying solely on the traditional BC framework. We simulate a TI breeding pipeline using 3 previously proposed selection strategies for the traditional BC scheme and 3 modified strategies that allow IC. Our proposed look-ahead intercrossing method (LAS-IC) combines look-ahead Monte Carlo simulations, intercrossing, and additional selection criteria to improve computational efficiency. We compared the efficiency of the 6 strategies across 5 levels of resource availability considering the generation when the major QTLs have been successfully introduced into the recipient and a desired background recovery rate reached. Simulations demonstrate that the inclusion of intercrossing in a TI program can substantially increase efficiency and the probability of success. The proposed LAS-IC provides the highest probability of success across the different scenarios using fewer resources compared with BC-only strategies.

A dual‐scale system dynamics prediction method for post‐earthquake repair of urban building groups

AbstractThe interaction between individual buildings and a city during the post‐earthquake repair process (e.g., the urban repair resource allocation for a building) has a significant influence on urban resilience. To consider such an interaction, a dual‐scale system dynamics prediction method for post‐earthquake repair of urban building groups is proposed, by which the detailed repair process of each individual building and the entire city can be systematically simulated. First, an urban priority for building repair is determined, and an algorithm for calculating the repair workload of individual buildings considering such an urban priority is developed for the following repair simulation of buildings. Next, a system dynamics model is established for simulating the repair process for individual buildings based on four types of resources, that is, workers, equipment, materials, and funds. Finally, a repair prediction model with a dual building‐to‐city scale is developed considering the resource allocation process of buildings. Two historical case studies were used to validate the accuracy of the system dynamics model for individual‐building repair. A case study on a small‐sized city was performed to reveal the influence patterns of different resource availability levels, repair modes, and structural systems on the repair process. The proposed method can predict in detail the post‐earthquake repair process with a dual building‐to‐city scale, supporting the decision‐making of city resilience.

Evaluation of Integrated Community Case Management of Common Childhood Illness Program: Quality of Program Implementation in Hadiya Zone, Ethiopia

<i>Background:</i> Integrated community case management of common childhood illnesses (ICCM) is life saving curative health service delivery for common childhood illnesses (CHI) at health post and community level before developing a complication. ICCMCHI quality has little information in the study area. <i>Methods and Materials:</i> The focus of this evaluation was to evaluate the process of ICCMCHI program, and the approach of this evaluation was formative. Availability of program resources, compliance of health extension workers with ICCM guideline and acceptability of services were the dimensions of this study. The case study was conducted with both quantitative and qualitative data. Fifty-seven health posts were included from three woreda of the zone by deviant sampling techniques. For qualitative data health extension workers and health care managers were included. Data was analyzed by using SPSS soft ware version-20. Univariate, bivariate and multivariate logistic regression were used for quantitative data, and qualitative data was analyzed by using thematic analysis. <i>Result:</i> Compliance was 76% which is good even though most of health extension workers (HEW) were missing opportunities and identified reasons were an inadequate use of ICCM chart booklet and poor supportive supervision. 423 mothers or caregivers with sick under-five children were interviewed from 57 health posts. The mean score of client satisfaction on the quality of ICCM services received was 48.97. Satisfaction of caregivers with a mean score of client satisfaction on quality ICCM services was associated with primary level education, family annual income of and Muslim religion and received information about when to return for next revisit were found to be more likely to satisfy on the quality of ICCM services provided. <i>Conclusion and Recommendation:</i> Quality of ICCMCHI program was evaluated as good. There was an inadequate level of resource availability. Client’s satisfaction with integrated community case management of common childhood illness services was also good. All concerned bodies from local government and development partners are expected to strengthen regular supportive supervision, clinical mentoring, and continues performance review.

Social context mediates the expression of a personality trait in a gregarious lizard

The social environment is a key factor that influences behavioural traits across a wide array of species. Yet, when investigating individual differences in behaviour, studies tend to measure animals in isolation from other conspecifics—even in social species. Surprisingly, whether behavioural traits measured in isolation are predictive of individual-level behaviour when in social groups is still poorly understood. Here, we repeatedly measured risk-taking behaviour (i.e. boldness; 741 total trials) in both the presence and absence of conspecifics in a social lizard, the delicate skink (Lampropholis delicata). Further, we manipulated food availability during group trials to test whether the effect of the social environment on risk-taking behaviour was mediated by competition over resources. Using 105 lizards collected from three independent populations, we found that individual risk-taking behaviour was repeatable when measured in either social isolation or within groups both with and without food resources available. However, lizards that were bolder during individual trials were not also bolder when in groups, regardless of resource availability. This was largely driven by individual differences in social behavioural plasticity, whereby individual skinks responded differently to the presence of conspecifics. Together, this resulted in a rank order change of individual behavioural types across the social conditions. Our results highlight the importance of the social environment in mediating animal personality traits across varying levels of resource availability. Further, these findings suggest that behavioural traits when measured in isolation, may not reflect individual variation in behaviour when measured in more ecologically realistic social groups.

Sasi (Gam): Local wisdom of Koiwai People in managing and utilizing the coastal and marine resources

This article aims to describe and analyze in depth the practice of sasi (gam) in the culture of the Koiwai people in Kaimana Regency. They perceive sasi (gam) as an embodiment of local wisdom in the context of managing and utilizing coastal &amp; marine resources, by highlighting the mechanism for enforcing sasi, sanctions and penalties, as well as analyzing the function and value of sasi for the Koiwai community and what changes have occurred. The method used is descriptive qualitative using an ethnographic approach. The location of the research is in Namatota Island, Kaimana Regency, West Papua Province. I used observation and interviews as data collection techniques. Also, data analysis includes the stages of data reduction, data presentation and data interpretation. The results of the research show that sasi (gam) in the Koiwai people is carried out at sea and on land which aims to maintain the level of resource availability which has implications for the balance of the ecosystem. In addition to conservation purposes, sasi (gam) also has functions and values ​​in social and economic aspects and maintains the order of the Koiwai community. However, on the other hand, there has been a shift caused by internal and external factors that threaten the sustainability of the practice of the sasi.

Weed suppression in cover crop mixtures under contrasted levels of resource availability

Cover crop (CC) mixtures appear as a promising agroecological tool for weed management. Although CC supress weed growth by competing for resources, their suppressive effect under contrasting levels of soil resource availability remains poorly documented. A two field:year experiment was conducted to investigate the weed suppressive effect of four CC mixtures. They were composed of 2 or 8 species including or not legume species and compared to a bare soil control. The experiment included two levels of irrigation and nitrogen fertilisation at CC sowing. The objectives were to assess (i) weed and CC aboveground biomass response to CC mixtures and resource availability, (ii) the weed suppressive effect of CC mixtures across a gradient of CC biomass and (iii) weed community response to CC mixtures and resource availability. CC and weed biomass were mainly influenced by interactions between CC mixtures and fertilisation and between CC mixtures and irrigation, with contrasted effects between field:years. Nitrogen fertilisation increased biomass of non-legume based CC mixtures but this only resulted into a further reduction of weed biomass of little biological relevance. Legume-based CC mixtures suppressed weeds to a greater extent without nitrogen fertilisation in year 2 but not in year 1, possibly due to contrasted initial soil nitrogen availability (lower in year 2). Weed biomass generally benefited more from irrigation than CC mixtures. Among the 33 weed species recorded, weed communities in each plot were dominated by wheat volunteers, Geranium dissectum, Veronica persica and Echinochloa crus-galli, whose biomass varied depending on the interaction between year, CC mixture and resource availability. Our results revealed that competitive outcomes between CC mixtures and weed species were driven by a complex interaction between resource availability and species traits. Further experiments focusing on plant traits should improve our understanding of weed:CC competitive outcomes under various levels of resource availability.

Understanding the Sustainability of the Energy–Water–Land Flow Nexus in Transnational Trade of the Belt and Road Countries

Increasing economic and population growth has put immense pressure on energy, water and land resources to satisfy national and supra-national demand. Through trade, a large proportion of such a demand is fulfilled. With trade as one of its key priorities, the China Belt and Road Initiative is a long-term transcontinental investment program. The initiative gained significant attention due to greater opportunities for economic development, large population and different levels of resource availability. The nexus approach has appeared as a new viewpoint in discussions on balancing the competing sectoral demands. However, following years of work, constraints exist in the scope and focus of studies. The newly developed multi-regional input–output (MRIO) models covering the world’s economy and its use of resources permit a comprehensive analysis of resource usage by production and consumption at different levels, and bring more knowledge about resource nexus problems. Using the MRIO model, this work simultaneously tracks energy, water and land use flows and investigates the transnational resource nexus. A nexus strength indicator is proposed which depends on ternary diagrams to grade countries based on their combined resources’ use and sectoral weighting. Equal sectoral weighting is assigned. The analysis presented a sectorally balanced nexus approach. Findings support existing work by recognizing energy, water and land as the robust transnational connections, from both production and consumption points of view. Resource nexus issues differ from country to country owing to inequalities in industrial set-up, preferences in economic policy and resource endowments. The paper outlines how key resource nexus problems can be identified and prioritized in view of alternative and often opposing interests.

Surviving or thriving? Trade-offs between growth, defense, and reproduction in a native versus an invasive Rubus

Little is known about limits to reproduction in plants, especially as to how their other life history functions (growth and defense) may constrain reproductive investment. Understanding these constraints can help researchers refine best practices for cultivating species like Rubus (Rosaceae) that produce nutritious fruits as well as for controlling invasive species. Here, we sought to elucidate potential trade-offs between growth, defense, and reproduction in native Rubus allegheniensis Porter (common blackberry) and invasive Rubus phoenicolasius Maxim. (wineberry) while accounting for the effects of varying insect herbivory and resource availability levels. We observed traits related to physical defense (e.g., prickle intensity), growth (e.g., cane length), and floral reproduction (e.g., ripe fruits), as well as carbon availability (e.g., canopy cover). We then used multiple regressions to characterize relationships between these variables for both species. We found potential evidence for 2 induced defenses in the invasive wineberry. Also, 5 models returned significant results indicative of trade-offs between reproduction and growth, reproduction and defense, and defense and growth in a single or both species. Our results highlight the importance of understanding the defensive strategies utilized by these species because inducible defenses may result in trade-offs that could reduce yields and (or) increase the invasive potential of Rubus species.

Evolutionary mechanisms underpinning fitness response to multiple stressors in Daphnia.

Multiple stressors linked to anthropogenic activities can influence how organisms adapt and evolve. So far, a consensus on how multiple stressors drive adaptive trajectories in natural populations has not been reached. Some meta‐analysis reports show predominance of additive effects of stressors on ecological endpoints (e.g., fecundity, mortality), whereas others show synergistic effects more frequently. Moreover, it is unclear what mechanisms of adaptation underpin responses to complex environments. Here, we use populations of Daphnia magna resurrected from different times in the past to investigate mechanisms of adaptation to multiple stressors and to understand how historical exposure to environmental stress shapes adaptive responses of modern populations. Using common garden experiments on resurrected modern and historical populations, we investigate (1) whether exposure to one stress results in higher tolerance to a second stressor; (2) the mechanisms of adaptation underpinning long‐term evolution to multistress (genetic evolution, plasticity, evolution of plasticity); and (3) the interaction effects of multiple stressors on fitness (synergism, antagonism, additivity). We measure the combined impact of different levels of resource availability (algae) and biocides on fitness‐linked life‐history traits and interpret these results in light of historical environmental exposures. We show that exposure to one stressor can alter tolerance to second stressors and that the interaction effect depends on the severity of either stressor. We also show that mechanisms of adaptation underpinning phenotypic evolution significantly differ in single‐stress and multistress scenarios. These adaptive responses are driven largely by synergistic effects on fecundity and size at maturity, and additive effects on age at maturity. Exposure to multiple stressors shifts the trade‐offs among fitness‐linked life‐history traits, with a stronger effect on Daphnia populations when low‐resource availability and high biocide levels are experienced. Our study indicates that mitigation interventions based on single‐stress analysis may not capture realistic threats.

Livestock grazing abandonment reduces soil microbial activity and carbon storage in a Mediterranean Dehesa

Extensive livestock grazing is a major determinant of local biodiversity and ecosystem functioning in many regio1ns of the world. In sub-humid Mediterranean areas with long history of extensive grazing, abandonment of grazing has been linked to changes in the composition and structure of vegetation communities and decreases in soil multifunctionality, with potential cascading consequences for ecosystem services such as soil fertility and potential for soil carbon storage. Herein, we assessed the effects of livestock grazing abandonment on soil fertility and the ability of soil microbial communities to process organic matter (enzymatic activity and decomposition rate using the Tea Bag Index) in twenty-four study sites in a Quercus ilex dehesa from Central Spain. Sites were distributed across four levels of grazing (none, very low, low and moderate) and two levels of resource availability in terms of water and nutrients (upper slope and lower slope zones). Grazing abandonment and upper slope zones were associated with a lower accumulation of organic matter and availability of nutrients such as phosphorus and potassium in the soil. Grazing abandonment also had a negative effect on microbial enzyme activity, which was directly related to litter decomposition and the ability of microbial communities to stabilize soil carbon. Microbial effects were particularly marked in the lower zones, indicating the modulating role of topography on the consequences of land use changes. Environmental management policies should consider the positive ecological effects of traditional grazing in regions with long evolutionary history of grazing by domestic livestock, and how the abandonment of these practices could negatively affect soil ecosystem functions and the provision of soil-related ecosystem services.

Variable temperature effects between heterotrophic stream processes and organisms

Abstract Temperature is known to stimulate metabolism with cascading effects on multiple biological processes. These effects may, however, vary across processes, types of organisms or levels of biological organisation. They can also vary with nutrient availability, with potentially stronger temperature effects when nutrients are not limiting. This context dependence of temperature effects on processes challenges our ability to anticipate their consequences on ecosystems in a changing world. In headwater streams, the decomposition of allochthonous leaf litter, driven by both microbial decomposers and invertebrates, is known to respond to both temperature and nutrient availability. These food webs are highly tractable and a useful model system to investigate the variations of temperature effects on processes across types of organisms (microbes versus invertebrates), resource availability levels (nutrient concentration), and levels of biological organisation (from individual to ecosystem). In a microcosm experiment, we measured the effects of temperature and nitrogen availability (four levels each) on respiration rates of litter-consuming microbes and invertebrates and their decomposition activity in different contexts of food web complexity. The latter included one treatment without invertebrate detritivore (microbial decomposers only), three single invertebrate taxa (Gammarus, Potamophylax, and Sericostoma) treatments, and one mixed invertebrate taxa treatment (three‐species altogether). Microbial processes increased nearly exponentially with temperature (Arrhenius model, activation energy (± 95% confidence interval) = 0.56 ± 0.53 and 1.00 ± 0.23 eV for litter decomposition and respiration), while invertebrate‐driven processes increased (activation energy from 0.47–1.15 eV) up to a maximal value at an intermediate temperature (c. 11–15°C depending on species and process), above which process rates decreased. By contrast, litter consumption in mixed invertebrate species treatments was not significantly influenced by temperature, because of a negative effect of species mixing occurring above 12°C. Nitrogen had a weaker influence, only slightly stimulating litter consumption by mixed‐species invertebrates, which limited the scope for synergies with temperature effects. Our results raise issues about how aquatic litter consumers meet their energy requirements at high temperature and suggest that a general consequence of warming could be loss of carbon through mineralisation in headwater stream food webs. In several aspects, our results deviate from expectations based on universal relationships between temperature and individual metabolism (e.g. metabolic theory of ecology), suggesting that we may need to develop less simplistic assumptions to predict the consequence of warming on ecosystem processes.

Agent-based modelling reveals strategies to reduce the fitness and metastatic potential of circulating tumour cell clusters.

Metastasis—the ability of cancer cells to disperse throughout the body and establish new tumours at distant locations—is responsible for most cancer‐related deaths. Although both single and clusters of circulating tumour cells (CTCs) have been isolated from cancer patients, CTC clusters are generally associated with higher metastatic potential and worse prognosis. From an evolutionary perspective, being part of a cluster can provide cells with several benefits both in terms of survival (e.g. protection) and reproduction (group dispersal). Thus, strategies aimed at inducing cluster dissociation could decrease the metastatic potential of CTCs. However, finding agents or conditions that induce the dissociation of CTC clusters is hampered by the fact that their detection, isolation and propagation remain challenging. Here, we used a mechanistic agent‐based model to (a) investigate the response of CTC clusters of various sizes and densities to different challenges—in terms of cell survival and cluster stability, and (b) make predictions as to the combination of factors and parameter values that could decrease the fitness and metastatic potential of CTC clusters. Our model shows that the resilience and stability of CTC clusters are dependent on both their size and density. Also, CTC clusters of distinct sizes and densities respond differently to changes in resource availability, with high‐density clusters being least affected. In terms of responses to microenvironmental threats (such as drugs), increasing their intensity is, generally, least effective on high‐density clusters. Lastly, we found that combining various levels of resource availability and threat intensity can be more effective at decreasing the survival of CTC clusters than each factor alone. We suggest that the complex effects that cluster density and size showed on both the resilience and stability of the CTC clusters are likely to have significant consequences for their metastatic potential and responses to therapies.