Large-scale Experiment Research Articles

Functional traits of field-droughted contrasting rice genotypes reveal multiple independent genomic adaptations and metabolic responses

Drought is the most critical environmental stress limiting crop productivity and yield. Rice is one of the top leading food crops worldwide and modern rice varieties are notably drought-sensitive due to their high-water requirements. Generating drought-resilient varieties and fine-tuning their yield performance are time-consuming tasks that could be achieved by exploiting the genetic diversity expressed by the wild ancestors of current-day crop species. We conducted a large-scale field experiment, imposing pre-flowering and post-flowering water shortages on 20 Oryza genotypes. Using detailed agro-physiological, isotopomics, and metabolite characterization of different Asian and African rice accessions, we shed light on the evolutionary biases that have evolved into the spectrum of strategies used to adapt to drought and have added to the rice knowledge base. We find that relevant decreases in photosynthetic rates (linked with stomatal opening) that differed between genotypes. We also identified genotypic differences in core C and N metabolism, and central metabolic pathways, highlighting the possible mechanisms of drought tolerance. Additionally, data suggest strong genetic associations of several amino acids that are significantly enriched during drought. We provide strong evidence of the distinctiveness of agro-physiological and metabolic pathway behaviors to drought across the use of diverse germplasm resources. Also, the resulting data provide insight into the wide variety of germplasm responses triggered by drought.

A new Rothamsted long-term field experiment for the twenty-first century: principles and practice

Agriculture faces potentially competing societal demands to produce food, fiber and fuel while reducing negative environmental impacts and delivering regulating, supporting and cultural ecosystem services. This necessitates a new generation of long-term agricultural field experiments designed to study the behavior of contrasting cropping systems in terms of multiple outcomes. We document the principles and practices of a new long-term experiment of this type at Rothamsted, established at two contrasting sites in 2017 and 2018, and report initial yield data at the crop and system level. The objective of the Large-Scale Rotation Experiment was to establish gradients of system properties and outcomes to improve our fundamental understanding of UK cropping systems. It is composed of four management factors—phased rotations, cultivation (conventional vs reduced tillage), nutrition (additional organic amendment vs standard mineral fertilization) and crop protection (conventional vs smart crop protection). These factors were combined in a balanced design resulting in 24 emergent cropping systems at each site and can be analyzed at the level of the system or component management factors. We observed interactions between management factors and with the environment on crop yields, justifying the systems level, multi-site approach. Reduced tillage resulted in lower wheat yields but the effect varied with rotation, previous-crop and site. Organic amendments significantly increased spring barley yield by 8% on average though the effect again varied with site. The plowed cropping systems tended to produce higher caloric yield overall than systems under reduced tillage. Additional response variables are being monitored to study synergies and trade-offs with outcomes other than yield at the cropping system level. The experiment has been established as a long-term resource for inter-disciplinary research. By documenting the design process, we aim to facilitate the adoption of similar approaches to system-scale agricultural experimentation to inform the transition to more sustainable cropping systems.

Reef-building corals farm and feed on their photosynthetic symbionts

Coral reefs are highly diverse ecosystems that thrive in nutrient-poor waters, a phenomenon frequently referred to as the Darwin paradox1. The energy demand of coral animal hosts can often be fully met by the excess production of carbon-rich photosynthates by their algal symbionts2,3. However, the understanding of mechanisms that enable corals to acquire the vital nutrients nitrogen and phosphorus from their symbionts is incomplete4–9. Here we show, through a series of long-term experiments, that the uptake of dissolved inorganic nitrogen and phosphorus by the symbionts alone is sufficient to sustain rapid coral growth. Next, considering the nitrogen and phosphorus budgets of host and symbionts, we identify that these nutrients are gathered through symbiont ‘farming’ and are translocated to the host by digestion of excess symbiont cells. Finally, we use a large-scale natural experiment in which seabirds fertilize some reefs but not others, to show that the efficient utilization of dissolved inorganic nutrients by symbiotic corals established in our laboratory experiments has the potential to enhance coral growth in the wild at the ecosystem level. Feeding on symbionts enables coral animals to tap into an important nutrient pool and helps to explain the evolutionary and ecological success of symbiotic corals in nutrient-limited waters.

Experimental study on equilibrium initiation and extension of multiple clusters of fractures based on true triaxial physical simulation

In the context of tight sandstone reservoirs in the Ordos Basin characterized by compact and heterogeneous rock formations, conventional fracturing techniques yield monolithic fracture shapes, rendering 3D reservoir reconstruction unattainable. This study investigates the principles governing balanced initiation and propagation of fractures in multi-cluster fracturing within unconventional fracturing technology. Employing a large-scale true triaxial simulation experiment system, we utilize the dimensional analysis method (π theorem) to design a physical simulation experiment similarity criterion. Through various experimental adjustments involving proportioning, curing, and mechanical testing, we generate an artificially cured rock mass with mechanical parameters akin to the target layer. The rock mass is maintained at a size of 30 cm × 30 cm × 30 cm. Systematic physical simulation experiments on unconventional volume fracturing are carried out using the 30 cm-sized dense sandstone outcrop rock mass. Taking the conventional fracturing technology as a reference and manipulating experimental conditions and design parameters, we simulate the non-equilibrium initiation and extension behaviors of fracturing fractures under five unconventional volume fracturing technologies, namely hydraulic pulse pretreatment, temporary plugging between clusters, flow-limiting method, cyclic loading and unloading, and pulse intermittent fracturing. Through this, we elucidate the non-equilibrium initiation and extension laws governing multi-cluster fractures. Comparative analysis with conventional fracturing, known for inducing stress interference on fractures and inhibiting their expansion, revels that the five unconventional volume fracturing techniques mitigate stress interference in multi-cluster fracturing. This promotes uniform fracture initiation and expansion, facilitating the creation of complex fractures and larger reconstructed volumes. Among these techniques, inter-cluster block fracturing stands out for its exceptional ability to generate complex fracture networks. The research culminates in the development and refinement of a balanced fracture and extension control technique tailored for multiple cluster fractures in bulk fracturing. This technique significantly contributes to enhancing the degree of 3D reconstruction achievable in unconventional tight oil and gas reservoirs.

Understory vegetation supports more abundant and diverse butterfly communities in oil palm plantations

IntroductionThe cultivation of oil palm, from which palm oil, the world’s most widely traded vegetable oil, is processed, has had marked effects on ecosystems and native species across the tropics. While declines in biodiversity due to conversion to oil palm have been well recorded across plant and animal taxa, less work has been done to identify approaches to plantation management which will enable producers to satisfy growing global demand while limiting environmental damage.MethodsThrough a large-scale understory management experiment, we investigated the long- and short-term effects of varying vegetation management regimes on the abundance, richness, and diversity of day-flying Lepidoptera.ResultsOver the long-term, the lowest levels of vegetation complexity resulted in significantly lower Lepidoptera abundance, species richness and evenness. Less intensive understory clearing resulted in healthier communities, with limited differences between removal by herbicide application or chemical-free removal. Over the short-term, biodiversity was not directly affected by vegetation complexity, suggesting that manual removal of vegetation may be equally damaging to butterfly or moth communities as removal by intermediate levels of herbicide spraying.DiscussionThese findings substantiate calls to limit vegetation clearing and maintain habitat heterogeneity on both a local and landscape scale, while also suggesting that a hard “no-spray” guideline may not be the only option to support butterfly friendly plantations.

Sedimentation issues of the Four Major Rivers Restoration Project in South Korea

In 2009, South Korea started a large multi-purpose water project on its four major rivers. The main purposes of the Four Major Rivers Restoration Project (FMRRP), which are directly related to water itself, were: (1) securing water resources to combat water scarcity; (2) reducing flood risks by riverbed dredging and reinforcing levees; and (3) restoring the river's environmental functions. Despite socio-environmental opposition, the project was completed in 2011. This article reviews the sedimentation issues raised during and after the FMRRP regarding technological developments and the lessons learned from the project. A total of five sedimentation issues raised directly from the project are reviewed in this article: (1) riverbed dredging and sediment redeposition; (2) tributary headcut; (3) riverbed scour downstream of the movable weir structures; (4) sedimentation management schemes; and (5) a near-prototype river experiment facility. Each issue is addressed by identifying and analyzing field data, developing new numerical models, and testing at a large-scale experiment facility. From this project, we have found that a comprehensive numerical technique is required to predict the sediment issues as mentioned above in a watershed-scale riverwork.

NHC-Catalyzed Regioselective Intramolecular Radical Cyclization Reaction for the Synthesis of Benzazepine Derivatives.

A novel and efficient strategy for the synthesis of a series of structurally interesting benzazepine derivatives via an N-heterocyclic carbene-catalyzed regioselective intramolecular radical cyclization has been developed. This protocol features good regioselectivity, good functional-group compatibility, and wide substrate scope, providing a transition-metal- and oxidant-free pathway to access the seven-membered rings under mild reaction conditions. Additionally, further transformation of benzazepines and a large-scale experiment were also conducted.

Measuring Perceptual Color Differences of Smartphone Photographs

Measuring perceptual color differences (CDs) is of great importance in modern smartphone photography. Despite the long history, most CD measures have been constrained by psychophysical data of homogeneous color patches or a limited number of simplistic natural photographic images. It is thus questionable whether existing CD measures generalize in the age of smartphone photography characterized by greater content complexities and learning-based image signal processors. In this paper, we put together so far the largest image dataset for perceptual CD assessment, in which the photographic images are 1) captured by six flagship smartphones, 2) altered by Photoshop®, 3) post-processed by built-in filters of the smartphones, and 4) reproduced with incorrect color profiles. We then conduct a large-scale psychophysical experiment to gather perceptual CDs of 30,000 image pairs in a carefully controlled laboratory environment. Based on the newly established dataset, we make one of the first attempts to construct an end-to-end learnable CD formula based on a lightweight neural network, as a generalization of several previous metrics. Extensive experiments demonstrate that the optimized formula outperforms 33 existing CD measures by a large margin, offers reasonable local CD maps without the use of dense supervision, generalizes well to homogeneous color patch data, and empirically behaves as a proper metric in the mathematical sense. Our dataset and code are publicly available at https://github.com/hellooks/CDNet.

Electoral system preferences of citizens compared: evidence from a conjoint experiment in Germany, the Netherlands, and the United Kingdom

AbstractElectoral systems fulfill different functions. Typically, they cannot meet all demands at the same time, so that the evaluation of specific electoral systems depends on subjective preferences about the single demands. We argue that it is the electorate which transfers its power to representatives and, therefore, its preferences should be considered in debates about electoral systems. Consequently, our contribution presents results of citizens’ demands regarding electoral system attributes. Specifically, we rely on a large-scale conjoint experiment conducted in Germany, the Netherlands, and the UK in which subjects were asked to choose between two electoral systems which randomly differed on a set of attributes referring to electoral systems’ core functions. Our results show that all core functions are generally of importance for the respondents but reveal a higher preference for proportional electoral systems. These preferences are largely stable for citizens in different countries but also for other subgroups of subjects.

Scallop ice shape characteristics of swept wing based on large-scale icing wind tunnel experiment

Scallop ice is a special phenomenon that occurs during swept wing aircraft passing through icing clouds. It poses a great challenge for the icing safety assessment that the complex scallop ice shape feature and its mechanism are still unclear. In this work, a large-scale icing wind tunnel experiment of swept wing designed by NACA0012 airfoil is conducted in the Icing Wind Tunnel of China Aerodynamics Research and Development Center. The detailed three-dimensional ice shapes under 0°, 15°, 30° and 45° swept angles are obtained by laser scanning technology. The experimental results show that with the swept angle increasing from 0° to 45°, the 2D double ice horn structures show certain spanwise variation, and finally transform into complete scallop ice with ice thickness greatly enhanced in the stagnation line region. The empirical mode decomposition of the spanwise ice curve captures the high-frequency fluctuation on the scallop ice caused by the small-scale roughness element, while the trend with low frequency is not obvious. Based on the experimental data, a new complete scallop ice geometric model, named 5Points-5Lines-2Arcs (5P-5L-2A) model, is proposed, which can provide important basis for the quantitative description of complex scallop ice shape.

Complementarity of road salt and heavy metal pollutant removal through invasive Typha and Phragmites harvest in urban wetland detention basins

Plant-based bioremediation has been proposed as a strategy to mitigate the growing risks associated with freshwater salinization, but large-scale experimental field tests of how harvesting plants can reduce deicing salts and heavy metals common in roadside environments are lacking. We implemented a three-year, large-scale field experiment (across 180 ha) in ten urban wetland detention basins in the Chicago region (Illinois, USA) to investigate the potential of plant biomass harvest to remove salts and heavy metals from roadside environments. Harvesting both Typha and Phragmites, ubiquitous plants that co-occur in wetlands around the globe, has the potential to remove both salts (Na, Cl, Ca, Mg) and heavy metals (Zn, Cu, Fe, Mn), as we observed complementarity in the pollutants concentrated in the aboveground tissues of these two species. We observed greater salt stocks in Typha biomass while heavy metals (especially Zn) were more abundant in Phragmites. Salts associated with deicing salts (Na, Cl) were particularly concentrated in live green Typha tissue, while metals tended to be more abundant (>50% of total stocks) in senescent litter, suggesting that plant phenology is important to consider when mitigating target pollutants via harvesting. Although repeated harvests reduced aboveground biomass and associated salt and metal stocks relative to unmanipulated controls, rotational harvest of common macrophytes growing in road-adjacent wetlands could maximize the reduction of roadside pollutants through harvesting. However, our data suggest that harvesting invasive macrophytes from urban roadside detention basins is not a silver bullet to remedy freshwater salinization, as it mitigates only a small fraction of added road salt loads.

Experimental Study and Theoretical Analysis of the Effect of Surcharge/Unloading at Both Sides of the Ground Surface on an Existing Shield Tunnel at Different Burial Depths

This paper investigates the impact of surcharge/unloading at both sides of the ground surface on an existing underground shield tunnel at varying burial depths. A large-scale indoor model experiment was conducted to study the vertical convergence deformation, tunnel settlement, and additional surrounding pressure of the tunnel at different burial depths when surcharge/unloading occurred at both sides of the ground surface. The effect of tunnel burial depth, surcharge mass, and uneven surcharge at both sides of the ground surface on the additional surrounding pressure of the existing underground shield tunnel was further investigated by theoretical calculation. The results indicate that under the same conditions, greater tunnel burial depth leads to reduced vertical convergence deformation, tunnel settlement, and additional surrounding pressure. Unloading can partially reduce the vertical convergence deformation and tunnel settlement, but it does not completely counteract the effect of the preceding surcharge. In cases of a symmetrical surcharge at both sides of the ground surface above the tunnel, the additional surrounding pressure of the tunnel is symmetrically distributed, with higher pressures at the arch top and arch bottom of the tunnel and lower pressures at the arch waist. This suggests that the arch top and arch bottom of the tunnel are vulnerable points under surcharge and require special attention. The surcharge above the tunnel has the most pronounced effect on the tunnel, followed by the surcharge at both sides of the ground surface, and, finally, the smallest effect from the bias load.

Microbial communities associated with landfarming amendments during bioremediation of crude oil in Niger Delta soils

Landfarming is a widely utilized process that involves using bacterial biodegradation to remediate contaminated soil resulting from oil spillages. Its effectiveness can be improved using amendments that include fertilizers, biosurfactants, enzymes, and natural sorbents. The effects of these amendments on biodegradation efficiency and the microbial community composition were investigated using 16S rRNA gene amplicon sequencing analyses performed on soil samples collected from a large-scale mesocosm experiment. The results showed that the use of amendments had a profound influence on the microbial community, which decreased with time following application of the amendment. Interestingly, the relationship between observed microbial diversity and biodegradation efficiency changed over time. During the initial phase, a higher biodegradation rate correlated with lower biodiversity indices, while during the later phase this relation reversed, and a higher biodegradation rate correlated with higher biodiversity indices. Two mesocosms types, one with biochar plus rhamnolipids and the other with agricultural lime, both in combination with fertilizer, degraded the oil significantly better than the ‘oil-only control’ with biodegradation improvements of 32.5 % and 25.8 %, respectively. Both combinations of amendments also promoted different adaptive responses of the microbial community with higher abundances of members of the genus Sphingomonas in both cases.

Influence of silvicultural practices in northern hardwood forests on a long-lived perennial herb, Trillium cernuum L.

Contemporary and predicted declines in tree species diversity and forest resilience have prompted renewed interest in even-aged systems and/or site preparation to overcome bottlenecks to tree recruitment or facilitate range expansion of future-adapted species. The impact of this intensification on the herbaceous layer in forests traditionally managed with uneven-aged systems, however, is unclear, especially for uncommon dispersal limited species with heterogenous distributions. We leveraged a large-scale experiment (the Northern Hardwood Silvicultural Experiment to Enhance Diversity) to investigate the response of Trillium cernuum L., a somewhat uncommon and heterogeneously distributed non-clonal herb in our study system, to a gradient of canopy removal and soil disturbance. We monitored 16 small populations from 2015 (the year prior to treatment) to 2019 (3-years post treatment). Our results suggest that initial population size and stage structure were inextricably coupled with T. cernuum response. Independent of treatment, T. cernuum abundance and flowering generally increased over time commensurate with initial population size. Moreover, our study highlights the confounding effect of deer herbivory, which increased significantly following treatment. Collectively, our findings suggest that T. cernuum populations were resilient to canopy disturbance associated with single-tree selection and shelterwood harvests and the levels of scarification applied as part of our study. Higher levels of site impact or other site preparation methods such as herbicides will likely have greater impacts and warrant further investigation. Our results also suggest that directly monitoring populations of interest may be necessary to quantify treatment effects for uncommon and/or heterogenous species that are missed with common plot-based sampling designs or of conservation concern.

Barriers to charitable giving

Donating to charity requires time, effort and attention. If the costs to give are perceived to be large, charities may lose out on donations. We develop a nonparametric test for the presence of these general nuisance costs and conduct a large-scale field experiment to show that costs to give are sizable and impactful. Potential donors were offered a 5:1 fixed match if their donation met or exceeded a minimum amount (e.g. $1, $5 or $10). Absent nuisance costs, the probability of donating should decrease as the minimum amount increases. We find the opposite. We estimate that about half of donors in our sample have nuisance costs of $7 or more. Eliminating these costs would double donations. Charities seeking to expand donations from small donors thus face challenges. Offering a fixed match for donations above a certain threshold may be more effective, by essentially covering nuisance costs, than the standard practice of subsidizing all donations with dollar-for-dollar matches.

Influencing recommendation algorithms to reduce the spread of unreliable news by encouraging humans to fact-check articles, in a field experiment

Society often relies on social algorithms that adapt to human behavior. Yet scientists struggle to generalize the combined behavior of mutually-adapting humans and algorithms. This scientific challenge is a governance problem when algorithms amplify human responses to falsehoods. Could attempts to influence humans have second-order effects on algorithms? Using a large-scale field experiment, I test if influencing readers to fact-check unreliable sources causes news aggregation algorithms to promote or lessen the visibility of those sources. Interventions encouraged readers to fact-check articles or fact-check and provide votes to the algorithm. Across 1104 discussions, these encouragements increased human fact-checking and reduced vote scores on average. The fact-checking condition also caused the algorithm to reduce the promotion of articles over time by as much as −25 rank positions on average, enough to remove an article from the front page. Overall, this study offers a path for the science of human-algorithm behavior by experimentally demonstrating how influencing collective human behavior can also influence algorithm behavior.

Experimental upscaling analyses for a surfactant-enhanced in-situ chemical oxidation (S-ISCO) remediation design

Surfactant-enhanced in-situ chemical oxidation (S-ISCO) is an emerging innovative remediation technology for the treatment of dense non-aqueous phase liquids (DNAPLs). S-ISCO combines the solubilization of contaminants by means of surfactants with the chemical oxidation by an oxidizing agent, thus, potentially increasing the efficiency of the state-of-the-art ISCO technique. Scientific investigations are needed to enable the technology transfer for potential field applications based on the development of a remediation design under well-defined boundary conditions.For this purpose, experimental upscaling analyses were performed using the special infrastructure of the research facility for subsurface remediation (VEGAS). Batch tests showed that oxidation of the selected surfactant E-Mulse 3® (EM3) by activated persulfate (Na-PS) reduced the solubilization of the model contaminants 1,4-DCB, naphthalene, and PCE. As a consequence, the processes of contaminant solubilization and degradation were temporally and spatially separated in the developed remediation design.A proof of concept was provided by performing an S-ISCO medium-scale experiment (100 cm length, 70 cm height, 12.5 cm width), with 1,2-DCB as model DNAPL contaminant to be treated. A groundwater circulation well (GCW) was used to inject a 60 g/L Na-PS solution and to effectively mix the reagents. Sampling of the experiment's outflow and the soil material after treatment showed that neither rebound effects nor residual mass loadings on the soil material could be detected after termination of the S-ISCO treatment.To further evaluate the S-ISCO remediation design under field-like conditions, a large-scale S-ISCO experiment was conducted (6 m length, 3 m height, 1 m width), allowing for an extensive sampling campaign to monitor relevant processes. An efficient contaminant removal from the former source zone could be reached by surfactant solubilization, decreasing contaminant levels from initially over 2000 mg/L 1,2-DCB to final concentrations below 5 mg/L 1,2-DCB. The heterogeneously distributed contaminant degradation, implemented by a three-filter GCW, was attributed to density-induced migration processes that impeded an optimal reaction zone. A density-dependent numerical transport could qualitatively match the observations. By comparing different simulation scenarios, an adapted operation of the GCW was established that provides for a more efficient distribution of the density-influenced oxidant injection.

Tracking a Maneuvering Object by Indirect Observations with Random Delays

A mathematical model for the target tracking problem is proposed. The model makes it possible to describe conditions when the time for an observer to receive the results of indirect observations of a moving object depends not only on the state of the observation environment but also on the state of the object itself. The source of such a model is the observation process, by stationary means, of an autonomous underwater vehicle, in which the time for obtaining up-to-date data depends on the unknown distance between the object and the observer. As part of the study of the problem, the equations of the optimal Bayesian filter are obtained. But this filter is not possible to implement. For practical purposes, it is proposed to use the conditionally minimax nonlinear filter, which has shown promising results in other complex tracking models. The conditions for the filter’s evaluation and its accuracy characteristics are given. A large-scale numerical experiment illustrating the filter’s operation and the observation system’s features with random delays are described.

A case study – The occurrence of pests in stands of newly introduced energy crops in large-scale pilot experiments in conditions of Central Europe

Abstract The objective of this paper is to document the occurrence of pests recorded in a large-scale pilot field experiment, where a unique set of newly-introduced herbaceous energy crops was tested under conditions of eastern Slovakia. The set consisted of Elymus elongatus, Secale cereanum, Silphium perfoliatum, Galega orientalis, Sida hermaphrodita, Panicum virgatum, Amaranthus spp., Panicum miliaceum, Sorghum sudanense, and Sorghum bicolor. A total of 14 cultivars were tested on 4 sites during 4 crop years (2016 – 2020). At least 17 species of pests were recorded in total, as some of the species may represent the identity of the couple or several relative ones, which was rare only as usually a fower common species. The occurred pests list consists of Anisoplia lata Erichson, Agriotes lineatus L., Capreolus capreolus L., Deroceras agreste L., Oulema gallaeciana Heyden, Lepisma saccharinum L., Lepus europaeus Pallas, Meloe proscarabaeus L., Metcalfa pruinosa Say, Microtus arvalis Pallas, Philaenus spumarius L., Psylliodes chrysocephala L., Rhopalosiphum padi L., stemborers as any insect larva or arthropod boring into plant stem, Sus scrofa L., Aleyrodes proletella L., Tettigonia viridissima L., and Trialeurodes vaporariorum Westwood. Overall, the occurrence of pests was regular and scattered, and damages caused by them were negligible usually, but a total destruction of the crop stand even cultivar-specific was recorded too. Most of the meaningful pests are primarily field hunting animals and only secondarily commonly occurring insect species, which for further observations are desirable in order to capture the tendency of important pests’ overpopulation, confirming respectively. Although even rare finding of the single caterpillar of Xylena exsoleta exsoleta L. was recorded in a buffer zone, within the experiment no newly introduced pest species was recorded.

Uncovering Peer Effects in Social and Academic Skills

This paper studies the impact of adolescent peers who are central in their social network on the formation of social skills and academic performance of fellow students. I conduct a novel large-scale field experiment at selective public boarding schools in Peru with two treatments: (i) more socially central versus less socially central peers, and (ii) higher-achieving versus lower-achieving peers. Peer effects are more pronounced for social skills than academic performance, and both vary by gender. While socially central peers lead boys to better social skills, higher-achieving peers decrease girls' test scores. Gender differences in self-confidence can explain both findings. (JEL C93, I21, I26, J13, J16, O15, Z13)