Systemic advantage has a meaningful relationship with grade outcomes in students' early STEM courses at six research universities.

Background: Large introductory lecture courses are frequently post-secondary students' first formal interaction with science, technology, engineering, and mathematics (STEM) disciplines. Grade outcomes in these courses are often disparate across student populations, which, in turn, has implications for student retention. This study positions such disparities as a manifestation of systemic inequities along the dimensions of sex, race/ethnicity, income, and first-generation status and investigates the extent to which they are similar across peer institutions. Results: We examined grade outcomes in a selected set of early STEM courses across six large, public, research-intensive universities in the United States over ten years. In this sample of more than 200,000 STEM course enrollments, we find that course grade benefits increase significantly with the number of systemic advantages students possess at all six institutions. The observed trends in academic outcomes versus advantage are strikingly similar across universities despite the fact that we did not control for differences in grading practices, contexts, and instructor and student populations. The findings are concerning given that these courses are often students' first post-secondary STEM experiences. Conclusions: STEM course grades are typically lower than those in other disciplines; students taking them often pay grade penalties. The systemic advantages some student groups experience are correlated with significant reductions in these grade penalties at all six institutions. The consistency of these findings across institutions and courses supports the claim that inequities in STEM education are a systemic problem, driven by factors that go beyond specific courses or individual institutions. Our work provides a basis for the exploration of contexts where inequities are exacerbated or reduced and can be used to advocate for structural change within STEM education. To cultivate more equitable learning environments, we must reckon with how pervasive structural barriers in STEM courses negatively shape the experiences of marginalized students. Supplementary Information: The online version contains supplementary material available at 10.1186/s40594-024-00474-7.

Adaptations to comprehensive abortion care during the COVID-19 pandemic: case studies of provision in Bolivia, Mali, Nepal, and the occupied Palestinian territory.

The COVID-19 pandemic impacted comprehensive abortion care provision. To maintain access to services while keeping individuals safe from infection, many organisations adapted their programmes. We conducted a programme evaluation to examine service adaptations implemented in Bolivia, Mali, Nepal, and the occupied Palestinian territory. Our programme evaluation used a case study approach to explore four programme adaptations through 14 group and individual interviews among 16 service providers, facility managers and representatives from supporting organisations. Data collection took place between October 2021 and January 2022. We identified adaptations to comprehensive abortion care services in relation to provision, health information systems and counselling, and referrals. Four overarching strategies emerged: (1) the use of digital technologies, (2) home and community outreach, (3) health worker optimisation, and (4) further consideration of groups in vulnerable situations. In Bolivia, the use of a messaging application increased access to confidential gender-based violence support and comprehensive abortion care. In Mali, the adoption of digital approaches created timely and complete data reporting and trained members of the community served as "interlocutors" between the communities and providers. In Nepal, an interim law expanded medical abortion provision to pharmacies, and home visits complemented facility-based services. In the occupied Palestinian territory, the use of a hotline and social media expanded access to quick and reliable information, counselling, referrals, and post-abortion care. Adaptations to comprehensive abortion care service delivery to mitigate disruptions to services during the COVID-19 pandemic may continue to benefit service quality of care, access to care, routine monitoring, as well as inclusivity and communication in the longer term.

Abiotic and Biotic Drivers of Soil Fungal Communities in Response to Dairy Manure Amendment.

Modern agriculture often relies on large inputs of synthetic fertilizers to maximize crop yield potential, yet their intensive use has led to nutrient losses and impaired soil health. Alternatively, manure amendments provide plant available nutrients, build organic carbon, and enhance soil health. However, we lack a clear understanding of how consistently manure impacts fungal communities, the mechanisms via which manure impacts soil fungi, and the fate of manure-borne fungi in soils. We assembled soil microcosms using five soils to investigate how manure amendments impact fungal communities over a 60-day incubation. Further, we used autoclaving treatments of soils and manure to determine if observed changes in soil fungal communities were due to abiotic or biotic properties, and if indigenous soil communities constrained colonization of manure-borne fungi. We found that manure amended soil fungal communities diverged from nonamended communities over time, often in concert with a reduction in diversity. Fungal communities responded to live and autoclaved manure in a similar manner, suggesting that abiotic forces are primarily responsible for the observed dynamics. Finally, manure-borne fungi declined quickly in both live and autoclaved soil, indicating that the soil environment is unsuitable for their survival. IMPORTANCE Manure amendments in agricultural systems can impact soil microbial communities via supplying growth substrates for indigenous microbes or by introducing manure-borne taxa. This study explores the consistency of these impacts on soil fungal communities and the relative importance of abiotic and biotic drivers across distinct soils. Different fungal taxa responded to manure among distinct soils, and shifts in soil fungal communities were driven largely by abiotic factors, rather than introduced microbes. This work demonstrates that manure may have inconsistent impacts on indigenous soil fungi, and that abiotic properties of soils render them largely resistant to invasion by manure-borne fungi.

Community perspectives on family planning service quality among users and non-users: a qualitative study from two cities in Burkina Faso.

BACKGROUND: Most studies that focus on quality of family planning (FP) services collect data from facilities. These studies miss the perspectives of quality from women who do not visit a facility and for whom perceived quality may be a barrier to service utilization. METHODS: This qualitative study from two cities in Burkina Faso examines perceived quality of FP services from women who were recruited at the community level to avoid potential biases based on recruiting women at facilities. Twenty focus group discussions were undertaken with varying groups of women of different ages (15-19; 20-24; 25+), marital statuses (unmarried; married), and current modern contraceptive use experiences (current non-users; current users). All focus group discussions were undertaken in the local language and transcribed and translated into French for coding and analysis. RESULTS: Women discuss FP service quality in a variety of locations, depending on their age group. Perspectives on service quality for younger women are often informed by others' experiences whereas for the older women, they are formed by their own and others' experiences. Two important aspects of service delivery emerge from the discussions including interactions with providers and selected system-level aspects of service provision. Important components of provider interactions relate to (a) the initial reception from the provider, (b) the quality of counseling received, (c) stigma and bias from providers, and d) privacy and confidentiality. At the health system level, discussions revolved around (a) wait time; (b) stockouts of methods; (c) costs of services/methods; (d) the expectation for tests as part of service provision; and (e) difficulties with method removal. CONCLUSIONS: To increase contraceptive use among women, it is crucial to address the components of service quality they identify as related to higher quality services. This means supporting providers to offer services in a more friendly and respectful manner. In addition, it is important to ensure that full information is provided to clients on what to expect during a visit to avoid false expectations that lead to poor perceived quality. These types of client-focused activities can improve perceptions of service quality and ideally support use of FP to meet women's needs.

"You could find a good or a bad provider, I would say you just have to go and see": A qualitative study of the influence of perceptions of service quality on family planning service use in Burkina Faso.

This qualitative study from Burkina Faso explores community-level perceptions of family planning (FP) service quality among FP users and non-users. It examines how perspectives on service quality may influence women's motivation to seek modern methods from health facilities. For this study, twenty focus group discussions were undertaken with non-users and current users of modern FP including unmarried, sexually active women ages 15-19 and 20-24 and ever married women ages 15-24 and 25+ in Bobo Dioulasso and Banfora, Burkina Faso. The findings demonstrate that respondents prioritized a welcoming environment, positive provider-client exchanges, the full provision of information (especially about side-effects), a pain-free experience, a short waiting time, and privacy and confidentiality. Poor service quality did not, in general, reduce women's demand or need to use a FP method. Some women who were reluctant to use formal health services used a non-facility-based method (calendar method, withdrawal, condoms or abstinence). Importantly, many unmarried, younger women and adolescents, who were more likely to be stigmatized by providers, exhibited agency by proactively seeking a method despite the potential for a negative experience. They prioritized their health and wellbeing over and above any interpersonal barriers they were likely to encounter. Incorporating strategies to improve the quality of FP services based on locally defined elements of quality should be a specific programmatic goal. These strategies can be identified through quality assessments employing a woman-centered lens. Women who visit facilities can be encouraged to share their positive experiences with their networks to improve community-level perspectives of facility quality. Improving service quality can attract new users, especially adolescents, and retain those who have already adopted a FP method. Through these multi-pronged actions, women's (and community) expectations and experience of quality can improve. This, in turn, may lead to greater client satisfaction and associated higher FP prevalence.

Integrating Critical Approaches into Quantitative STEM Equity Work.

The recent anti-racist movements in the United States have inspired a national call for more research on the experiences of racially marginalized and minoritized students in science, technology, engineering, and mathematics (STEM) fields. As researchers focused on promoting diversity, equity, and inclusion, we contend that STEM education must, as a discipline, grapple with how analytic approaches may not fully support equity efforts. We discuss how researchers and educational practitioners should more critically approach STEM equity analyses and why modifying our approaches matters for STEM equity goals. Engaging with equity as a process rather than a static goal, we provide a primer of reflective questions to assist researchers with framing, analysis, and interpretation of student-level data frequently used to identify disparities and assess course-level and programmatic interventions. This guidance can inform analyses conducted by campus units such as departments and programs, but also across universities and the scientific community to enhance how we understand and address systemic inequity in STEM fields.

The impacts of agroforestry interventions on agricultural productivity, ecosystem services, and human well-being in low- and middle-income countries: A systematic review.

Background: Agroforestry, the intentional integration of trees or other woody perennials with crops or livestock in production systems, is being widely promoted as a conservation and development tool to help meet the 2030 UN Sustainable Development Goals. Donors, governments, and nongovernmental organizations have invested significant time and resources into developing and promoting agroforestry policies and programs in low- and middle-income countries (LMICs) worldwide. While a large body of literature on the impacts of agroforestry practices in LMICs is available, the social-ecological impacts of agroforestry interventions is less well-studied. This knowledge gap on the effectiveness of agroforestry interventions constrains possibilities for evidence-based policy and investment decisions to advance sustainable development objectives. Objectives: The primary objective of this Campbell systematic review was to synthesize the available evidence on the impacts of agroforestry interventions in LMICs on agricultural productivity, ecosystem services, and human well-being. The secondary objectives were to identify key pathways through which agroforestry interventions lead to various outcomes and how the interventions affect different sub-groups of the population. Search Methods: This review is based on a previously created evidence and gap map (EGM) of studies evaluating the impacts of agroforestry practices and interventions on agricultural productivity, ecosystem services, and human well-being. We included published and unpublished literature in the English language covering the period between 2000 and October 20, 2017. We searched six academic databases and 19 organization websites to identify potentially relevant studies. The search was conducted for our EGM in mid-2017, and we did not conduct an additional search for this systematic review. Selection Criteria: We included randomized control trials (RCTs) and quasi-experimental studies assessing the effect of an agroforestry intervention on at least one outcome measure of agricultural productivity, ecosystem services, or human well-being for farmers and their farmland in LMICs. Agroforestry interventions include any program or policy designed to promote and support the adoption or maintenance of agroforestry practices, which include trees on farms, silvopasture, shade-grown crops, and homegardens with trees, among others. Moreover, the studies needed to include a nonagroforestry comparator, such as conventional agriculture or forestry systems or a before-after comparison. Data Collection and Analysis: We used a standardized data extraction spreadsheet to extract details about each included study. We also used a standardized form to assess risk of bias for each of the included studies in this SR. Meta-analysis techniques were used to combine and synthesize effect size estimates for the outcomes measures that had sufficient data. We used a random effects models for the meta-analyses and use Hedge's g (difference in means divided by the pooled standard deviation) to report effect size estimates. The outcomes without enough evidence for meta-analysis were discussed narratively. Main Results: We identified 11 studies across nine countries, all of which used quasi-experimental methods. Overall, the quality of the evidence base was assessed as being low. Studies were rated as having high or critical risk of bias if they failed to convincingly address more than one of the main potential sources of bias, namely selection bias, group equivalence, and spillover effects. Given the low number of studies and the high risk of bias of the evidence base, the results of this SR are limited and should be considered a baseline for future work. The results of the meta-analysis for impacts on yields indicated that agroforestry interventions overall may lead to a large, positive impact on yield (Hedge's g = 1.16 [-0.35, 2.67] (p = .13)), though there was high heterogeneity in the results (I 2 = 98.99%, τ 2 = 2.94, Q(df = 4) = 370.7). There were positive yield impacts for soil fertility replenishment practices, including incorporating trees in agricultural fields and improved fallow practices in fields where there are severe soil fertility issues. In other cases, incorporating trees into the production system reduced productivity and took land out of production for conservation benefits. These systems generally used an incentive provision scheme to economically offset the reductions in yields. The result of the meta-analysis on income suggests that agroforestry interventions overall may lead to a small, positive impact on income (Hedge's g = 0.12 [-0.06, 0.30] (p = .20)), with moderately high heterogeneity in the results (I 2 = 75.29%, τ 2 = 0.04, Q(df = 6) = 19.16). In cases where improvement yields were reported, there were generally attendant improvements in income. In the cases where payments were provided to offset the potential loss in yields, incomes also generally improved, though there were mixed results for the certification programs and the tenure security permitting scheme. One program, which study authors suggested may have been poorly targeted, had negative yield impacts. There was not enough comparable evidence to quantitatively synthesize the impacts of agroforestry interventions on nutrition and food security outcomes, though the results indicted positive or neutral impacts on dietary diversity and food intake were likely. Surprisingly, there was little evidence on the impacts of agroforestry interventions on environmental outcomes, and there was no consistency of environmental indicator variables used. However, what has been studied indicates that the environmental benefits are being achieved to at least some extent, consistent with the broader literature on agroforestry practices. The evidence base was insufficient to evaluate the interaction between environmental and social impacts. Several studies explicitly considered variable impacts across different population sub-groups, including differential impacts on small-holders versus large-holders, on woman-headed households versus male-headed households, and on richer groups versus poorer groups. Small-holder farmers typically experienced the most positive effect sizes due to the agroforestry interventions. Women and poorer groups had mixed outcomes relative to men and richer households, highlighting the importance of considering these groups in intervention design. Authors' Conclusions: There is limited evidence of the impacts of agroforestry interventions, restricting our ability to draw conclusions on the effect sizes of different intervention types. The existing evidence forms a baseline for future research and highlights the importance of considering equity and socio-economic factors in determining suitable intervention design. Some key implications for practice and policy include investing in programs that include pilot programs, funding for project evaluation, and that address key equity issues, such as targeting to smallholders, women, poor, and marginalized groups. Funding should also be given to implementing RCTs and more rigorous quasi-experimental impact evaluations of agroforestry interventions over longer time-periods to collect robust evidence of the effectiveness of various schemes promoting agroforestry practices.

Successful programmatic approaches to facilitating IUD uptake: CARE's experience in DRC.

BACKGROUND: Achieving the unfinished agenda towards sexual and reproductive health and rights requires overcoming remaining barriers to contraceptive uptake, which can be method-specific. Women's uptake of the IUD is poor across sub-Saharan Africa. The objective of this paper is to identify the reasons for comparatively high IUD use observed in a CARE project in DRC, together with the programmatic characteristics which facilitated uptake. METHODS: Qualitative data were collected in 2015 as part of a reproductive health project in the DRC. Using purposive sampling, 15 focus group discussions took place with IUD users, users of other methods and non-users of modern contraception as well as their male partners. Eighteen in-depth interviews were conducted with health providers, project staff, community health workers and local stakeholders to capture a range of experiences. Data were analyzed using content theory approach and contextualized through a review of routine monitoring data. RESULTS: In an area with practically no previous IUD use, 38,662 new FP clients were served during the first 5 years of the project and 82% (31,569) chose long-acting or permanent methods. Over 10,000 clients chose an IUD, representing 30% of the total FP clients. Key informants expressed mainly positive views about the IUD and quality of service. Concerns related to method insertion, which some perceived as too intimate or shameful. Findings indicate that this uptake reflects effective supply chains, good provider training and supervision and multiple communication strategies including those which target men. Community engagement was enhanced by local stakeholders' participation in sensitization and quality assurance as well in analysis of data for decision-making. CONCLUSIONS: The findings of the paper showed that by involving local stakeholders in addressing structural and socio-cultural barriers to women's free access to FP, programs can positively influence quality of service and method mix as well as knowledge and attitudes surrounding FP use and thus improve the uptake of FP in general and IUDs in particular, even in conflict-affected settings. A Theory of Change for enhancing IUD provision within family planning programs is suggested.

Impacts of Sampling Design on Estimates of Microbial Community Diversity and Composition in Agricultural Soils.

Soil microbiota play important and diverse roles in agricultural crop nutrition and productivity. Yet, despite increasing efforts to characterize soil bacterial and fungal assemblages, it is challenging to disentangle the influences of sampling design on assessments of communities. Here, we sought to determine whether composite samples-often analyzed as a low cost and effort alternative to replicated individual samples-provide representative summary estimates of microbial communities. At three Minnesota agricultural research sites planted with an oat cover crop, we conducted amplicon sequencing for soil bacterial and fungal communities (16SV4 and ITS2) of replicated individual or homogenized composite soil samples. We compared soil microbiota from within and among plots and then among agricultural sites using both sampling strategies. Results indicated that single or multiple replicated individual samples, or a composite sample from each plot, were sufficient for distinguishing broad site-level macroecological differences among bacterial and fungal communities. Analysis of a single sample per plot captured only a small fraction of the distinct OTUs, diversity, and compositional variability detected in the analysis of multiple individual samples or a single composite sample. Likewise, composite samples captured only a fraction of the diversity represented by the six individual samples from which they were formed, and, on average, analysis of two or three individual samples offered greater compositional coverage (i.e., greater number of OTUs) than a single composite sample. We conclude that sampling design significantly impacts estimates of bacterial and fungal communities even in homogeneously managed agricultural soils, and our findings indicate that while either strategy may be sufficient for broad macroecological investigations, composites may be a poor substitute for replicated samples at finer spatial scales.

Carbon Amendments Influence Composition and Functional Capacities of Indigenous Soil Microbiomes.

Soil nutrient amendments are recognized for their potential to improve microbial activity and biomass in the soil. However, the specific selective impacts of carbon amendments on indigenous microbiomes and their metabolic functions in agricultural soils remain poorly understood. We investigated the changes in soil chemical characteristics and phenotypes of Streptomyces communities following carbon amendments to soil. Mesocosms were established with soil from two field sites varying in soil organic matter content (low organic matter, LOM; high organic matter, HOM), that were amended at intervals over nine months with low or high dose solutions of glucose, fructose, malic acid, a mixture of these compounds, or water only (non-amended control). Significant shifts in soil chemical characteristics and antibiotic inhibitory capacities of indigenous Streptomyces were observed in response to carbon additions. All high dose carbon amendments consistently increased soil total carbon, while amendments with malic acid decreased soil pH. In LOM soils, higher frequencies of Streptomyces inhibitory phenotypes of the two plant pathogens, Streptomyces scabies and Fusarium oxysporum, were observed in response to soil carbon additions. Additionally, to determine if shifts in Streptomyces functional characteristics correlated with microbiome composition, we investigated whether shifts in functional characteristics of soil Streptomyces correlated with composition of soil bacterial communities, analyzed using 16S rRNA gene sequencing. Regardless of dose, community composition differed significantly among carbon-amended and non-amended soils from both sites. Carbon type and dose had significant effects on bacterial community composition in both LOM and HOM soils. Relationships among microbial community richness (observed species number), diversity, and soil characteristics varied among soils from different sites. These results suggest that manipulation of soil resource availability has the potential to selectively modify the functional capacities of soil microbiomes, and specifically to enhance pathogen inhibitory populations of high value to agricultural systems.

Phosphorus, not nitrogen, limits plants and microbial primary producers following glacial retreat.

Current models of ecosystem development hold that low nitrogen availability limits the earliest stages of primary succession, but these models were developed from studies conducted in areas with temperate or wet climates. Global warming is now causing rapid glacial retreat even in inland areas with cold, dry climates, areas where ecological succession has not been adequately studied. We combine field and microcosm studies of both plant and microbial primary producers and show that phosphorus, not nitrogen, is the nutrient most limiting to the earliest stages of primary succession along glacial chronosequences in the Central Andes and central Alaska. We also show that phosphorus addition greatly accelerates the rate of succession for plants and for microbial phototrophs, even at the most extreme deglaciating site at over 5000 meters above sea level in the Andes of arid southern Peru. These results challenge the idea that nitrogen availability and a severe climate limit the rate of plant and microbial succession in cold-arid regions and will inform conservation efforts to mitigate the effects of global change on these fragile and threatened ecosystems.

Nutrient limitation of soil microbial activity during the earliest stages of ecosystem development.

A dominant paradigm in ecology is that plants are limited by nitrogen (N) during primary succession. Whether generalizable patterns of nutrient limitation are also applicable to metabolically and phylogenetically diverse soil microbial communities, however, is not well understood. We investigated if measures of N and phosphorus (P) pools inform our understanding of the nutrient(s) most limiting to soil microbial community activities during primary succession. We evaluated soil biogeochemical properties and microbial processes using two complementary methodological approaches-a nutrient addition microcosm experiment and extracellular enzyme assays-to assess microbial nutrient limitation across three actively retreating glacial chronosequences. Microbial respiratory responses in the microcosm experiment provided evidence for N, P and N/P co-limitation at Easton Glacier, Washington, USA, Puca Glacier, Peru, and Mendenhall Glacier, Alaska, USA, respectively, and patterns of nutrient limitation generally reflected site-level differences in soil nutrient availability. The activities of three key extracellular enzymes known to vary with soil N and P availability developed in broadly similar ways among sites, increasing with succession and consistently correlating with changes in soil total N pools. Together, our findings demonstrate that during the earliest stages of soil development, microbial nutrient limitation and activity generally reflect soil nutrient supply, a result that is broadly consistent with biogeochemical theory.

Microbes as Engines of Ecosystem Function: When Does Community Structure Enhance Predictions of Ecosystem Processes?

Microorganisms are vital in mediating the earth's biogeochemical cycles; yet, despite our rapidly increasing ability to explore complex environmental microbial communities, the relationship between microbial community structure and ecosystem processes remains poorly understood. Here, we address a fundamental and unanswered question in microbial ecology: 'When do we need to understand microbial community structure to accurately predict function?' We present a statistical analysis investigating the value of environmental data and microbial community structure independently and in combination for explaining rates of carbon and nitrogen cycling processes within 82 global datasets. Environmental variables were the strongest predictors of process rates but left 44% of variation unexplained on average, suggesting the potential for microbial data to increase model accuracy. Although only 29% of our datasets were significantly improved by adding information on microbial community structure, we observed improvement in models of processes mediated by narrow phylogenetic guilds via functional gene data, and conversely, improvement in models of facultative microbial processes via community diversity metrics. Our results also suggest that microbial diversity can strengthen predictions of respiration rates beyond microbial biomass parameters, as 53% of models were improved by incorporating both sets of predictors compared to 35% by microbial biomass alone. Our analysis represents the first comprehensive analysis of research examining links between microbial community structure and ecosystem function. Taken together, our results indicate that a greater understanding of microbial communities informed by ecological principles may enhance our ability to predict ecosystem process rates relative to assessments based on environmental variables and microbial physiology.

Nutrient addition dramatically accelerates microbial community succession.

The ecological mechanisms driving community succession are widely debated, particularly for microorganisms. While successional soil microbial communities are known to undergo predictable changes in structure concomitant with shifts in a variety of edaphic properties, the causal mechanisms underlying these patterns are poorly understood. Thus, to specifically isolate how nutrients--important drivers of plant succession--affect soil microbial succession, we established a full factorial nitrogen (N) and phosphorus (P) fertilization plot experiment in recently deglaciated (∼3 years since exposure), unvegetated soils of the Puca Glacier forefield in Southeastern Peru. We evaluated soil properties and examined bacterial community composition in plots before and one year after fertilization. Fertilized soils were then compared to samples from three reference successional transects representing advancing stages of soil development ranging from 5 years to 85 years since exposure. We found that a single application of +NP fertilizer caused the soil bacterial community structure of the three-year old soils to most resemble the 85-year old soils after one year. Despite differences in a variety of soil edaphic properties between fertilizer plots and late successional soils, bacterial community composition of +NP plots converged with late successional communities. Thus, our work suggests a mechanism for microbial succession whereby changes in resource availability drive shifts in community composition, supporting a role for nutrient colimitation in primary succession. These results suggest that nutrients alone, independent of other edaphic factors that change with succession, act as an important control over soil microbial community development, greatly accelerating the rate of succession.

Assessing nutrient limitation in complex forested ecosystems: alternatives to large-scale fertilization experiments.

Quantifying nutrient limitation of primary productivity is a fundamental task of terrestrial ecosystem ecology, but in a high carbon dioxide environment it is even more critical that we understand potential nutrient constraints on plant growth. Ecologists often manipulate nutrients with fertilizer to assess nutrient limitation, yet for a variety of reasons, nutrient fertilization experiments are either impractical or incapable of resolving ecosystem responses to some global changes. The challenges of conducting large, in situ fertilization experiments are magnified in forests, especially the high-diversity forests common throughout the lowland tropics. A number of methods, including fertilization experiments, could be seen as tools in a toolbox that ecologists may use to attempt to assess nutrient limitation, but there has been no compilation or synthetic discussion of those methods in the literature. Here, we group these methods into one of three categories (indicators of soil nutrient supply, organismal indicators of nutrient limitation, and lab-based experiments and nutrient depletions), and discuss some of the strengths and limitations of each. Next, using a case study, we compare nutrient limitation assessed using these methods to results obtained using large-scale fertilizations across the Hawaiian Archipelago. We then explore the application of these methods in high-diversity tropical forests. In the end, we suggest that, although no single method is likely to predict nutrient limitation in all ecosystems and at all scales, by simultaneously utilizing a number of the methods we describe, investigators may begin to understand nutrient limitation in complex and diverse ecosystems such as tropical forests. In combination, these methods represent our best hope for understanding nutrient constraints on the global carbon cycle, especially in tropical forest ecosystems.

Rural children's attitudes to people with HIV/AIDS in Mali: the causes of stigma.

Qualitative research among young people and other community members in rural Mali elicited knowledge and attitudes with regard to HIV/AIDS. Findings indicated that rumours concerning methods of infection are likely to increase the stigmatization of those with the disease. The most frequently stated mode of transmission involved urinating in a place where someone with AIDS had already urinated. Shared clothes, food and water were seen as sources of infection. Both children and teachers recommended that people with AIDS be isolated. Even talking to them would lead to a risk of infection. Discriminatory views were likely to have been reinforced by parents and community elders who possessed the same misinformation. The notion that AIDS results from sexual encounters between young women and dogs belonging to white people in Côte d'Ivoire was also widespread. These discourses may reflect perceived xenophobia and risk to migrants associated with current tensions between the two countries, together with misgivings about Western sexual liberalism. A holistic educational programme is proposed to address not simply HIV/AIDS, but the social context in which infection occurs, with view to combating stigma and discrimination associated with not just HIV but also with migration in this setting.

Factors influencing young Malians' reluctance to use hormonal contraceptives.

During a qualitative evaluation of three peer-education programs in urban Mali, young people stated that they were wary of using either the pill or injectable contraceptives because they believed that these methods would make them sterile. Unmarried women's contraceptive decisionmaking was not primarily driven by a current need to limit fertility, but rather by a future need to maximize it in order to gain status through childbearing in their marital households. Further interviews explored notions of conception, menstruation, and the perceived action of hormonal methods on the reproductive system. Findings revealed that menstrual disruption (in the form of amenorrhea or prolonged bleeding) appeared to have dire repercussions, including accusations of witchcraft and immoral behavior that could result in a woman's being divorced or in her husband's acquiring an additional wife. The social consequences of side effects were perceived to be more important than their biological manifestations, and together with the fear of sterility, resulted in a preference for the condom.

Doubting the existence of AIDS: a barrier to voluntary HIV testing and counselling in urban Mali.

Qualitative research was carried out in the Malian cities of Sikasso and Bamako with a view to setting up HIV voluntary testing and counselling (VCT) services and a separate programme to enable young people to improve their sexual health. The most striking finding was that a large number of respondents said they did not believe in the existence of AIDS. Reasons for disbelief were related to the perceived lack of AIDS cases in China, the inability of the virus to be transmitted by mosquitoes and confusion about mother-to-child transmission. Highly educated individuals were very sceptical of the existence of the illness, thinking it to be a Western plot to encourage condom use in order to halt the growth of the African population. Those who were more likely to believe in the existence of the illness were less educated or uneducated people who had personally seen someone sick with AIDS, often when they had been on labour migration to Côte d'Ivoire where HIV prevalence is higher. Respondents thought it likely that this scepticism will limit the use of VCT services. Other reasons for the potential non-use of services included the fact that some people lacked confidence in the competence of the laboratory technicians and were afraid that those testing positive would be highly stigmatized by the community. Thus, widespread awareness-raising campaigns are needed before any centres can be set up. Participatory education programmes are required to address HIV in the context of other health risks. This would allow people to inter-actively shape the debate about HIV/AIDS to fit their own needs. Currently, they are presented with information about the illness in a unidirectional manner via the media or health educators which seems to fuel their scepticism.