Meta-analysis Of Field Experiments Research Articles

Most treatments to control freshwater algal blooms are not effective: Meta-analysis of field experiments.

Harmful algal blooms negatively impact freshwater, estuarine, and marine systems worldwide, including those used for drinking water, recreation, and aquaculture, through the production of toxic and nontoxic secondary metabolites as well as hypoxic events that occur when algal blooms degrade. Consequently, water resource managers often utilize chemical, bacterial, physical, and/or plant-based treatments to control algal blooms and improve water quality. However, awareness of available treatments may be limited, and there is ambiguity among the effects of algal bloom treatments across studies. Such variation within the literature and lack of knowledge of other tested treatments leave uncertainty for water resource managers when deciding what treatments are best to control algal blooms and improve water quality. Our primary objective was to synthesize data from 39 published and unpublished studies that used one of 28 chemical, bacterial, physical, and/or plant-based treatments in field experiments on various water quality measurements, including phytoplankton pigments and cell density, cyanobacterial toxins (microcystin), and common off-flavors (i.e., taste and odor compounds; geosmin and 2-methylisoborneol). We hypothesized that treatments would improve water quality. Across all studies and treatment types (227 effect sizes), water quality improvements were observed when measured at the time of greatest decline following treatment or at the end of the experiment. However, these findings were primarily mediated by only four chemicals, namely copper sulfate, hydrogen peroxide, peracetic acid, and simazine. None of the bacterial, physical, or plant-based treatments were shown to significantly improve water quality by themselves. Results from this synthesis quantitatively showed that most treatments fail to improve water quality in the field and highlight the need for more research on existing and alternative treatments.

Optimizing water management practice to increase potato yield and water use efficiency in North China

Potato is one of the staple food crops in North China. However, potato production in this region is threatened by the low amount and high spatial-temporal variation of precipitation. Increasing yield and water use efficiency (WUE) of potato by various water management practices under water resource limitation is of great importance for ensuring food security in China. However, the contributions of different water management practices to yield and WUE of potato have been rarely investigated across North China's potato planting region. Based on meta-analysis of field experiments from the literature and model simulation, this study quantified the potential yields of potatoes without water and fertilizer limitation, and yield under irrigated and rainfed conditions, and the corresponding WUEs across four potato planting regions including the Da Hinggan Mountains (DH), the Foothills of Yanshan hilly (YH), the North foot of the Yinshan Mountains (YM), and the Loess Plateau (LP) in North China. Simulated average potential potato tuber dry weight yield by the APSIM-Potato Model was 12.4 t ha−1 for the YH region, 11.4 t ha−1 for the YM region, 11.2 t ha−1 for the DH region, and 10.7 t ha−1 for the LP region, respectively. Observed rainfed potato tuber dry weight yield accounted for 61, 30, 28 and 24% of the potential yield in the DH, YH, YM, and LP regions. The maximum WUE of 2.2 kg m−3 in the YH region, 2.1 kg m−3 in the DH region, 1.9 kg m−3 in the YM region and 1.9 kg m−3 in the LP region was achieved under the potential yield level. Ridge-furrow planting could boost yield by 8–49% and WUE by 2–36% while ridge-furrow planting with film mulching could boost yield by 35–89% and WUE by 7–57% across North China. Our study demonstrates that there is a large potential to increase yield and WUE simultaneously by combining ridge-furrow planting with film mulching and supplemental irrigation in different potato planting regions with limited water resources.

Divergent response and adaptation of specific leaf area to environmental change at different spatio-temporal scales jointly improve plant survival.

Specific leaf area (SLA) is one of the most important plant functional traits. It integrates multiple functions and reflects strategies of plants to obtain resources. How plants employ different strategies (e.g., through SLA) to respond to dynamic environmental conditions remains poorly understood. This study aimed to explore the spatial variation in SLA and its divergent adaptation through the lens of biogeographic patterns, evolutionary history, and short-term responses. SLA data for 5424 plant species from 76 natural communities in China were systematically measured and integrated with meta-analysis of field experiments (i.e., global warming, drought, and nitrogen addition). The mean value of SLA across all species was 21.8m2 kg-1 , ranging from 0.9 to 110.2m2 kg-1 . SLA differed among different ecosystems, temperature zones, vegetation types, and functional groups. Phylogeny had a weak effect on SLA, but plant species evolved toward higher SLA. Furthermore, SLA responded nonlinearly to environmental change. Unexpectedly, radiation was one of the main factors determining the spatial variation in SLA on a large scale. Conversely, short-term manipulative experiments showed that SLA increased with increased resource availability and tended to stabilize with treatment duration. However, different species exhibited varying response patterns. Overall, variation in long-term adaptation of SLA to environmental gradients and its short-term response to resource pulses jointly improve plant adaptability to a changing environment. Overall SLA-environment relationships should be emphasized as a multidimensional strategy for elucidating environmental change in future research.

Emerging Marketing Research on Healthcare and Medical Decision Making: Toward a Consumer-Centric and Pluralistic Methodological Perspective

Emerging Marketing Research on Healthcare and Medical Decision Making: Toward a Consumer-Centric and Pluralistic Methodological Perspective

Discrimination of Black and Muslim Minority Groups in Western Societies: Evidence From a Meta-Analysis of Field Experiments

This article examines discrimination against black and Muslim minority groups in 20 Western labor markets. We analyze the outcomes of 94 field experiments, conducted between 1973 and 2016 and representing ∼240,000 fictitious job applications. Using meta-analysis, we find that black minority groups are more strongly discriminated against than non-black minority groups. The degree of discrimination of black minority groups varies cross-nationally, whereas Muslim minority groups are equally discriminated across national contexts. Unexpectedly, discrimination against black minority groups in the United States is mostly lower than in European countries. These findings suggest that racial–ethnic discrimination in hiring can be better understood by taking a multigroup and cross-country perspective.

A meta-analysis of field-experiments using social norms to promote pro-environmental behaviors

Highlights • We conducted a meta-analysis on field-experiments using social norms to encourage pro-environmental behaviors. • Results of 91 field-experiments (N = 227′730) revealed a positive main effect of social norms on pro-environmental behaviors compared to no-treatment control conditions. • Moderation analysis found that social norms induced implicitly were more influential than social norms induced explicitly and that social norms tended to be more influential in individualistic countries than in collectivistic countries.

Racial discrimination in Britain, 1969-2017: a meta-analysis of field experiments on racial discrimination in the British labour market.

Field experiments represent the gold standard for determining whether discrimination occurs. Britain has a long and distinguished history of field experiments of racial discrimination in the labour market, with pioneering studies dating back to 1967 and 1969. This article reviews all the published reports of these and subsequent British field experiments of racial discrimination in the labour market, including new results from a 2016/17 field experiment. The article finds enduring contours of racial discrimination in Britain. Firstly, there is an enduring pattern of modest discrimination against white minorities of European heritage in contrast to much greater risks of discrimination faced by the main non-white groups, suggesting a strong racial component to discrimination. Secondly, while there is some uncertainty about the magnitude of the risks facing applicants with Chinese and Indian names, the black Caribbean, black African and Pakistani groups all face substantial and very similar risks of discrimination. Thirdly, there is no significant diminution in risks of discrimination over time either for Caribbeans or for South Asians as a whole. These results are broadly in line with those from the ethnic penalties literature, suggesting that discrimination is likely to be a major factor explaining the disproportionately and enduringly high unemployment rates of ethnic minorities.

Which Healthy Eating Nudges Work Best? A Meta-Analysis of Field Experiments

The effectiveness of healthy eating nudges in field settings increases as they shift from focusing on influencing cognition to affect to behavior.

Which Healthy Eating Nudges Work Best? A Meta-Analysis of Field Experiments

We examine the effectiveness in field settings of seven healthy eating nudges, classified according to whether they are 1) cognitively-oriented, such as “descriptive nutritional labeling,” “evaluative nutritional labeling,” or “visibility enhancements”; 2) affectively-oriented, such as “hedonic enhancements or “healthy eating calls”; or 3) behaviorally-oriented, such as “convenience enhancements” or “size enhancements.” Our multivariate three-level meta-analysis of 299 effect sizes, controlling for eating behavior, population, and study characteristics, yields a standardized mean difference (Cohen’s d) of .23 (equivalent to -124 kcal/day). Effect sizes increase as the focus of the nudges shifts from cognition (d=.12, -64 kcal) to affect (d=.24, -129 kcal) to behavior (d=.39, -209 kcal). Interventions are more effective at reducing unhealthy eating than increasing healthy eating or reducing total eating. Effect sizes are larger in the US than in other countries; in restaurants or cafeterias than in grocery stores; and in studies including a control group. Effect sizes are similar for food selection vs. consumption, for children vs. adults, and are independent of study duration. Compared to the typical nudge study (d=.12), one implementing the best nudge scenario can expect a six-fold increase in effectiveness (to d=.74), with half due to switching from cognitively-oriented to behaviorally-oriented nudges.

Which healthy eating nudges work best? A meta-analysis of field experiments

The effectiveness of healthy eating nudges in field settings increases as they shift from focusing on influencing cognition to affect to behavior.

Ecotechnology as a tool for restoring degraded drylands: A meta-analysis of field experiments

Land degradation and desertification are widespread in drylands, highlighting the need to restore them to reverse their negative effects. The restoration of degraded drylands is commonly initiated by restoring the vegetation using plantations of tree/shrub seedlings. We conducted a meta-analysis of published field experiments in drylands to analyze and compare the effects of different ecotechnological techniques (nursery mycorrhization, treeshelters, organic amendments, hydrogels and the combined use of mycorrhization and organic amendments) on the survival and growth of seedlings of woody species used during restoration activities. We also evaluated how these effects were influenced by the planting method used, and by the duration of the experiments. We gathered results from 1207 case studies from 88 studies conducted in 14 countries. Our analyses indicate that the inoculation with mycorrhizal fungi (mycorrhization) in the nursery (alone, or in combination with organic amendments) and the use of treeshelters were the most effective treatments for enhancing both the survival and growth of the planted seedlings. The use of organic amendments by themselves did not increase seedling survival. The combined use of mycorrhization and organic amendments in the field improved the results when compared to the use of organic amendments alone. The analysis of hydrophilic gels and organic amendments revealed evidence of publication bias, so more studies are needed before any generalization on their effects on seedling establishment can be made. The planting method influenced the effects of some of the treatments evaluated, though this response varied depending on the seedling performance variable considered. The length of the study was negatively related to growth variables in treatments including organic amendments. Our results provide general trends and guidelines for researchers and practitioners involved in dryland restoration, which can be used to maximize the benefits provided by the ecotechnological techniques evaluated.

The Interaction between Competition and Predation: A Meta-Analysis of Field Experiments

The Interaction between Competition and Predation: A Meta-Analysis of Field Experiments