Developing an interactive reproductive health equity session for pre-clerkship medical students.

In the United States, sexual, reproductive, and perinatal health inequities are well documented and known to be caused by a history of systemic oppression along many axes, including but not limited to race, ethnicity, gender, socioeconomic position, sexual orientation, and disability. Medical schools are responsible for educating students on systems of oppression and their impact on health. Reproductive justice advocates, including lay persons, medical students, and teaching faculty, have urged for integrating the reproductive justice framework into medical education and clinical practice. In response to medical student advocacy, we developed introductory didactic sessions on social and reproductive justice for preclinical medical students. These were created in a team-based learning format and include pre-course primer materials on reproductive justice. During the sessions, students engaged with hypothetical clinical vignettes in small groups to identify oppressive structures that may have contributed to the health outcomes described and potential avenues for contextually relevant and level-appropriate advocacy. The sessions took place in November 2019 (in-person) and 2020 (virtually) and were well attended by students. We highlight our experience, student feedback, and next steps, including further integration of reproductive health equity into medical school curricula in concert with department-wide education for faculty, residents, nursing, and allied health professionals. This introduction to social and reproductive justice can be adapted and scaled across different medical school curricula, enhancing the training of a new generation of physicians to become critically aware of how oppressive structures create health inequities and able to mitigate their impact through their roles as clinicians, researchers, and advocates.

Dressings and securement devices to prevent complications for peripheral arterial catheters.

BACKGROUND: Peripheral arterial catheters (ACs) are used in anaesthesia and intensive care settings for blood sampling and monitoring. Despite their importance, ACs often fail, requiring reinsertion. Dressings and securement devices maintain AC function and prevent complications such as infection. OBJECTIVES: To evaluate the effectiveness of peripheral AC dressing and securement devices to prevent failure and complications in hospitalised people. SEARCH METHODS: We searched the Cochrane Wounds Specialised Register, CENTRAL, MEDLINE, Embase, and CINAHL Plus up to 16 May 2023. We also searched ClinicalTrials.gov and the World Health Organization International Clinical Trials Registry Platform up to 16 May 2023. SELECTION CRITERIA: We included randomised controlled trials (RCTs) comparing different dressing and securement devices for the stabilisation of ACs in hospitalised people. DATA COLLECTION AND ANALYSIS: Two review authors independently selected trials for inclusion, extracted data, and assessed risk of bias using Cochrane's RoB 1 tool. We resolved disagreements by discussion, or by consulting a third review author when necessary. We assessed the certainty of evidence using GRADE. MAIN RESULTS: We included five RCTs with 1228 participants and 1228 ACs. All included studies had high risk of bias in one or more domains. We present the following four comparisons, with the remaining comparisons reported in the main review. Standard polyurethane (SPU) plus tissue adhesive (TA) compared with SPU: we are very uncertain whether use of SPU plus TA impacts rates of AC failure (risk ratio (RR) 0.44, 95% confidence interval (CI) 0.20 to 0.98; I² = 0%; 2 studies, 165 participants; very low-certainty evidence). Neither study (165 participants) reported catheter-related bloodstream infections (CRBSI), thus we are very uncertain whether SPU plus TA impacts on the incidence of CRBSI (very low-certainty evidence). It is very uncertain whether use of SPU plus TA impacts AC dislodgement risk (RR 0.54, 95% CI 0.03 to 9.62; I² = 44%; 2 studies, 165 participants; very low-certainty evidence). We are very uncertain whether use of SPU plus TA impacts AC occlusion rates (RR 1.20, 95% CI 0.37 to 3.91; I² = 3%; 2 studies, 165 participants; very low-certainty evidence). We are very uncertain whether use of SPU plus TA impacts rates of adverse events with few reported events across groups (RR 0.89, 95% CI 0.09 to 8.33; I² = 0%; 2 studies, 165 participants; very low-certainty evidence). Bordered polyurethane (BPU) compared to SPU: we are very uncertain whether use of BPU impacts rates of AC failure (RR 0.67, 95% CI 0.21 to 2.13; 1 study, 60 participants; very low-certainty evidence). BPU may make little or no difference to CRBSI compared to SPU (RR 3.05, 95% CI 0.12 to 74.45; I² = not applicable as 1 study (60 participants) reported 0 events; 2 studies, 572 participants; low-certainty evidence). BPU may make little or no difference to the risk of AC dislodgement compared with SPU (RR 0.75, 95% CI 0.17 to 3.22; I² = 0%; 2 studies, 572 participants; low-certainty evidence). BPU may make little or no difference to occlusion risk compared with SPU (RR 0.80, 95% CI 0.60 to 1.07; I² = 0%; 2 studies, 572 participants; low-certainty evidence). It is very uncertain whether BPU impacts on the risk of adverse events compared with SPU (RR 0.33, 95% CI 0.01 to 7.87; 1 study, 60 participants; very low-certainty evidence). SPU plus sutureless securement devices (SSD) compared to SPU: we are very uncertain whether SPU plus SSD impacts risk of AC failure compared with SPU (RR 0.78, 95% CI 0.40 to 1.52; I² = 0%; 2 studies, 157 participants; very low-certainty evidence). We are very uncertain if SPU plus SSD impacts CRBSI incidence rate with no events in both groups (2 studies, 157 participants; very low-certainty evidence). It is very uncertain whether SPU plus SSD impacts risk of dislodgement (RR 0.14, 95% CI 0.01 to 2.57; I² = not applicable as 1 study (96 participants) reported 0 events; 2 studies, 157 participants; very low-certainty evidence). It is very uncertain whether SPU plus SSD impacts risk of AC occlusion (RR 1.94, 95% CI 0.50 to 7.48; I² = 38%; 2 studies, 157 participants; very low-certainty evidence). We are very uncertain whether SPU plus SSD impacts on the risk of adverse events (RR 1.94, 95% CI 0.19 to 20.24; I² = not applicable as 1 study (96 participants) reported 0 events; 2 studies, 157 participants; very low-certainty evidence). Integrated securement dressings compared to SPU: integrated securement dressings may result in little or no difference in risk of AC failure compared with SPU (RR 1.96, 95% CI 0.80 to 4.84; 1 study, 105 participants; low-certainty evidence); may result in little or no difference in CRBSI incidence with no events reported (1 study, 105 participants; low-certainty evidence); may result in little or no difference in the risk of dislodgement (RR 0.33, 95% CI 0.04 to 3.04; 1 study, 105 participants; low-certainty evidence), may result in little or no difference in occlusion rates with no events reported (1 study, 105 participants; low-certainty evidence), and may result in little or no difference in the risk of adverse events (RR 0.35, 95% CI 0.01 to 8.45; 1 study, 105 participants; low-certainty evidence). AUTHORS' CONCLUSIONS: There is currently limited rigorous RCT evidence available about the relative clinical effectiveness of AC dressing and securement products. Limitations of current evidence include small sample size, infrequent events, and heterogeneous outcome measurements. We found no clear difference in the incidence of AC failure, CRBSI, or adverse events across AC dressing or securement products including SPU, BPU, SSD, TA, and integrated securement products. The limitations of current evidence means further rigorous RCTs are needed to reduce uncertainty around the use of dressing and securement devices for ACs.

Care bundles and peripheral arterial catheters.

HIGHLIGHTS: What we know about the topic: Recommendations for the use of vascular access care bundles to reduce infection are followed for different devices. The risk of arterial catheter-related infection is comparable with short-term, non-cuffed central venous catheters. There are practice concerns for clinicians inserting and caring for peripheral arterial catheters. What this paper adds: The selected studies had a theme of decreased infection after using bundled strategies for all devices. Few studies addressed use of bundles for care of peripheral arterial catheters. High-quality research should be performed about using care bundles for insertion and care of arterial catheters. INTRODUCTION: A scoping review of the literature was performed. AIMS/OBJECTIVES: To find information on the use of care bundles for care of arterial, central, and peripherally inserted venous catheters. METHODS: Data was extracted by 2 independent researchers using standardized methodology. RESULTS: Results of 84 studies included 2 (2.4%) randomized controlled trials, 38 (45.2%) observational studies, 29 (34.5%) quality projects, and 15 (17.9%) reviews. Populations had more adults than pediatric patients. All studies had the most prominent theme of decreased infection in all devices after using bundle strategies. DISCUSSION AND CONCLUSIONS: The mapping of available evidence strongly supports the use of care bundles to reduce infection in the care of all intravascular devices. However, deficiencies regarding practice concerns about insertion and care of arterial catheters highlight areas for future research with the aim to eliminate the gap in the evidence of studies of care bundles for peripheral arterial catheters.

Pharyngeal haematoma and partial airway obstruction caused by interaction between warfarin and topical miconazole gel.

A man in his 70s on warfarin attended the emergency department three times over a 24-hour period, complaining of a sore throat, neck swelling and difficulty swallowing. He was initially diagnosed with pharyngitis, given antibiotics and discharged home, which was reconfirmed on the second attendance after an episode of haemoptysis. On the third, he was diagnosed with a pharyngeal haematoma causing partial airway obstruction and admitted to critical care. His international normalised ratio (INR) was reported initially as unreadable by the laboratory, then eventually came back as >20. After a thorough medication history, he said that he had recently been prescribed topical miconazole oromucosal gel by his dentist for oral candidiasis, which had interacted with the warfarin to cause this life-threatening haematoma.

Foliar fungal endophyte communities are structured by environment but not host ecotype in Panicum virgatum (switchgrass).

Experimental tests of community assembly mechanisms for host-associated microbiomes in nature are lacking. Asymptomatic foliar fungal endophytes are a major component of the plant microbiome and are increasingly recognized for their impacts on plant performance, including pathogen defense, hormonal manipulation, and drought tolerance. However, it remains unclear whether fungal endophytes preferentially colonize certain host ecotypes or genotypes, reflecting some degree of biotic adaptation in the symbioses, or whether colonization is simply a function of spore type and abundance within the local environment. Whether host ecotype, local environment, or some combination of both controls the pattern of microbiome formation across hosts represents a new dimension to the age-old debate of nature versus nurture. Here, we used a reciprocal transplant design to explore the extent of host specificity and biotic adaptation in the plant microbiome, as evidenced by differential colonization of host genetic types by endophytes. Specifically, replicate plants from three locally-adapted ecotypes of the native grass Panicum virgatum (switchgrass) were transplanted at three geographically distinct field sites (one home and two away) in the Midwestern US. At the end of the growing season, plant leaves were harvested and the fungal microbiome characterized using culture-dependent sequencing techniques. Our results demonstrated that fungal endophyte community structure was determined by local environment (i.e., site), but not by host ecotype. Fungal richness and diversity also strongly differed by site, with lower fungal diversity at a riparian field site, whereas host ecotype had no effect. By contrast, there were significant differences in plant phenotypes across all ecotypes and sites, indicating ecotypic differentiation of host phenotype. Overall, our results indicate that environmental factors are the primary drivers of community structure in the switchgrass fungal microbiome.

Accumulation and potential health risks of cadmium, lead and arsenic in vegetables grown near mining sites in Northern Vietnam.

The effect of environmental pollution on the safety of vegetable crops is a serious global public health issue. This study was conducted to assess heavy metal concentrations in soil, irrigation water, and 21 local vegetable species collected from four sites near mining activities and one control site in Northern Vietnam. Soils from vegetable fields in the mining areas were contaminated with cadmium (Cd), lead (Pb), and arsenic (As), while irrigation water was contaminated with Pb. Average concentrations of Pb and As in fresh vegetable samples collected at the four mining sites exceeded maximum levels (MLs) set by international food standards for Pb (70.6 % of vegetable samples) and As (44.1 % of vegetable samples), while average Cd concentrations in vegetables at all sites were below the MLs of 0.2. The average total target hazard quotient (TTHQ) across all vegetable species sampled was higher than the safety threshold of 1.0, indicating a health risk. Based on the weight of evidence, we find that cultivation of vegetables in the studied mining sites is an important risk contributor for local residents' health.

Plant-soil feedbacks shift from negative to positive with decreasing light in forest understory species.

Net pairwise plant-soil feedbacks (PSF) may be an important factor structuring plant communities, yet the influence of abiotic context on PSF is not yet understood. Abiotic factors such as light availability can alter plant-soil interactions, potentially resulting in strong context dependence of PSF. Here, we present an experiment in which we measured whole-soil net pairwise feedbacks amongst six common forest understory species across a gradient of light availability. Light treatments were imposed throughout both phases (the conditioning phase and the response phase) of the feedback experiment. Across the plant community, PSF shifted from negative at high light availability to weakly positive under low light (P = 0.0 13). Differences in the biomass of plants during the conditioning phase did not fully explain light-imposed differences in feedbacks, indicating that reduced light availability qualitatively changes the nature of PSF rather than simply weakening feedbacks by reducing plant growth. Results indicate that abiotic context can fundamentally alter the role of PSF in structuring plant communities.

Securing All intraVenous devices Effectively in hospitalised patients--the SAVE trial: study protocol for a multicentre randomised controlled trial.

INTRODUCTION: Over 70% of all hospital admissions have a peripheral intravenous device (PIV) inserted; however, the failure rate of PIVs is unacceptably high, with up to 69% of these devices failing before treatment is complete. Failure can be due to dislodgement, phlebitis, occlusion/infiltration and/or infection. This results in interrupted medical therapy; painful phlebitis and reinsertions; increased hospital length of stay, morbidity and mortality from infections; and wasted medical/nursing time. Appropriate PIV dressing and securement may prevent many cases of PIV failure, but little comparative data exist regarding the efficacy of various PIV dressing and securement methods. This trial will investigate the clinical and cost-effectiveness of 4 methods of PIV dressing and securement in preventing PIV failure. METHODS AND ANALYSIS: A multicentre, parallel group, superiority randomised controlled trial with 4 arms, 3 experimental groups (tissue adhesive, bordered polyurethane dressing, sutureless securement device) and 1 control (standard polyurethane dressing) is planned. There will be a 3-year recruitment of 1708 adult patients, with allocation concealment until randomisation by a centralised web-based service. The primary outcome is PIV failure which includes any of: dislodgement, occlusion/infiltration, phlebitis and infection. Secondary outcomes include: types of PIV failure, PIV dwell time, costs, device colonisation, skin colonisation, patient and staff satisfaction. Relative incidence rates of device failure per 100 devices and per 1000 device days with 95% CIs will summarise the impact of each dressing, and test differences between groups. Kaplan-Meier survival curves (with log-rank Mantel-Cox test) will compare device failure over time. p Values of <0.05 will be considered significant. Secondary end points will be compared between groups using parametric or non-parametric techniques appropriate to level of measurement. ETHICS AND DISSEMINATION: Ethical approval has been received from Queensland Health (HREC/11/QRCH/152) and Griffith University (NRS/46/11/HREC). Results will be published according to the CONSORT statement and presented at relevant conferences. TRIAL REGISTRATION NUMBER: Australian New Zealand Clinical Trial Registry (ACTRN); 12611000769987.

Novel technologies can provide effective dressing and securement for peripheral arterial catheters: A pilot randomised controlled trial in the operating theatre and the intensive care unit.

BACKGROUND: Peripheral arterial catheters are widely used in the care of intensive care patients for continuous blood pressure monitoring and blood sampling, yet failure - from dislodgement, accidental removal, and complications of phlebitis, pain, occlusion and infection - is common. While appropriate methods of dressing and securement are required to reduce these complications that cause failure, few studies have been conducted in this area. OBJECTIVES: To determine initial effectiveness of one dressing and two securement methods versus usual care, in minimising failure in peripheral arterial catheters. Feasibility objectives were considered successful if 90/120 patients (75%) received the study intervention and protocol correctly, and had ease and satisfaction scores for the study dressing and securement devices of ≥ 7 on Numerical Rating Scale scores 1-10. METHODS: In this single-site, four-arm, parallel, pilot randomised controlled trial, patients with arterial catheters, inserted in the operating theatre and admitted to the intensive care unit postoperatively, were randomly assigned to either one of the three treatment groups (bordered polyurethane dressing (n=30); a sutureless securement device (n=31); tissue adhesive (n=32)), or a control group (usual practice polyurethane dressing (not bordered) (n=30)). RESULTS: One hundred and twenty-three patients completed the trial. The primary outcome of catheter failure was 2/32 (6.3%) for tissue adhesive, 4/30 (13.3%) for bordered polyurethane, 5/31 (16.1%) for the sutureless securement device, and 6/30 (20%) for the control usual care polyurethane. Feasibility criteria were fulfilled. Cost analysis suggested that tissue adhesive was the most cost effective. CONCLUSIONS: The pilot trial showed that the novel technologies were at least as effective as the present method of a polyurethane dressing for dressing and securement of arterial catheters, and may be cost effective. The trial also provided evidence that a larger, multicentre trial would be feasible.

Think globally, research locally: paradigms and place in agroecological research.

Conducting science for practical ends implicates scientists, whether they wish it or not, as agents in social-ecological systems, raising ethical, economic, environmental, and political issues. Considering these issues helps scientists to increase the relevance and sustainability of research outcomes. As we rise to the worthy call to connect basic research with food production, scientists have the opportunity to evaluate alternative food production paradigms and consider how our research funds and efforts are best employed. In this contribution, we review some of the problems produced by science conducted in service of industrial agriculture and its associated economic growth paradigm. We discuss whether the new concept of "ecological intensification" can rescue the industrial agriculture/growth paradigm and present an emerging alternative paradigm of decentralized, localized, biodiversity-promoting agriculture for a steady-state economy. This "custom fit" agriculture engages constructively with complex and highly localized ecosystems, and we draw from examples of published work to demonstrate how ecologists can contribute by using approaches that acknowledge local agricultural practices and draw on community participation.

Value of information analysis optimizing future trial design from a pilot study on catheter securement devices.

BACKGROUND: Value of information analysis has been proposed as an alternative to the standard hypothesis testing approach, which is based on type I and type II errors, in determining sample sizes for randomized clinical trials. However, in addition to sample size calculation, value of information analysis can optimize other aspects of research design such as possible comparator arms and alternative follow-up times, by considering trial designs that maximize the expected net benefit of research, which is the difference between the expected cost of the trial and the expected value of additional information. PURPOSE: To apply value of information methods to the results of a pilot study on catheter securement devices to determine the optimal design of a future larger clinical trial. METHODS: An economic evaluation was performed using data from a multi-arm randomized controlled pilot study comparing the efficacy of four types of catheter securement devices: standard polyurethane, tissue adhesive, bordered polyurethane and sutureless securement device. Probabilistic Monte Carlo simulation was used to characterize uncertainty surrounding the study results and to calculate the expected value of additional information. To guide the optimal future trial design, the expected costs and benefits of the alternative trial designs were estimated and compared. RESULTS: Analysis of the value of further information indicated that a randomized controlled trial on catheter securement devices is potentially worthwhile. Among the possible designs for the future trial, a four-arm study with 220 patients/arm would provide the highest expected net benefit corresponding to 130% return-on-investment. The initially considered design of 388 patients/arm, based on hypothesis testing calculations, would provide lower net benefit with return-on-investment of 79%. LIMITATIONS: Cost-effectiveness and value of information analyses were based on the data from a single pilot trial which might affect the accuracy of our uncertainty estimation. Another limitation was that different follow-up durations for the larger trial were not evaluated. CONCLUSION: The value of information approach allows efficient trial design by maximizing the expected net benefit of additional research. This approach should be considered early in the design of randomized clinical trials.

Tailoring clinical services to address the unique needs of adolescents from the pregnancy test to parenthood.

Clinicians across disciplines and practice settings are likely to encounter adolescents who are at risk for a pregnancy. In 2010, 34.2/1000 15-19-year-old teens had a live birth in the United States, many more will seek care for a pregnancy scare or options counseling. Teen mothers are also at risk for a second or higher-order pregnancy during adolescence. This paper provides clinicians with adolescent-friendly clinical and counseling strategies for pregnancy prevention, pre- and post-pregnancy test counseling, pregnancy-related care, and a review of the developmental challenges encountered by teens in the transition to parenthood. Clinicians are in a better position to approach the developmental, health and mental health needs of adolescents related to pregnancy if they understand and appreciate the obstacles adolescents may face negotiating the healthcare system. In addition, when clinical services are specially tailored to the needs of the adolescent, fewer opportunities will be lost to prevent unintended pregnancies, assist teens into timely prenatal services, and improve outcomes for their pregnancies and the transition to parenthood.

A snapshot of guideline compliance reveals room for improvement: a survey of peripheral arterial catheter practices in Australian operating theatres.

AIM: To report a study in Australian operating theatres of compliance by the anaesthetic team with best peripheral arterial catheter practice for blood gas sampling and infection prevention. Comparisons are made with research recommendations and Centres for Disease Control Guidelines. BACKGROUND: There is wide global usage of peripheral arterial catheters in the operating theatre for haemodynamic monitoring and blood gas analysis. Frequent blood sampling from arterial catheters can lead to statistically significant blood loss and provide an infective potential. Evidence-based research and clinical guidelines prescribe best practice. DESIGN: Cross-sectional descriptive survey METHODS: Data were collected in 2009 from 64 major Australian hospitals using a self-designed internet survey. RESULTS/FINDINGS: Hand hygiene prior to catheter insertion was the only infection prevention practice entirely adherent with guidelines. The recommended ratio of discard to dead space volume of 2:1 to decrease unnecessary blood loss during blood gas sampling was reported by only 11 (17%) respondents. Less than 32 (50%) respondents used the preferred solution, chlorhexidine to disinfect the insertion site. Access ports were reported as 'never disinfected' before use by 30 (47%) respondents. CONCLUSION: The complex operating theatre environment presents barriers, which contribute to non-adherence with guidelines. These barriers need to be identified to plan strategies for improvement. A quality audit tool is proposed for development by nurses in collaboration with the anaesthetic team, providing a needed method to assess ongoing compliance with best peripheral arterial catheter care. Further international research would test the generalizability of our Australian findings.

Replacement of administration sets (including transducers) for peripheral arterial catheters: a systematic review.

AIMS AND OBJECTIVES: This article presents a systematic review of the evidence for the optimal interval for replacement of administration sets for peripheral arterial catheters. BACKGROUND: Peripheral arterial catheters are attached to administration sets, including transducers, which are changed routinely in some hospitals on the understanding that prolonged duration of administration sets use may cause a higher incidence of infection. DESIGN: Systematic review. METHODS: Medline, CINAHL, Scopus and the Cochrane Library were searched to access relevant studies published between 1966 and 2011. Inclusion criteria were quantitative studies of critically ill patients with peripheral arterial catheters that required administration sets for intra-arterial pressure monitoring and had a focus on administration sets duration of use. Studies were assessed for quality using either methodological quality assessments from Cochrane guidelines for systematic reviews for randomised controlled trials or with the Newcastle-Ottawa quality assessment scale for cohort studies. RESULTS: Six studies were selected for review. These included three randomised controlled trials (226 patients) and three cohort studies (219 patients). Cohort studies reported 1-4% catheter-related bloodstream infection and 0-8% infusate-related bloodstream infection when administration sets were changed every 48 hours. Two randomised controlled trials found no difference in infusate-related bloodstream infection (two days: 0%; four to eight days: 1·7%) and found no cases of catheter-related bloodstream infection in any group when administration sets were replaced every 24 or 48 hours. CONCLUSION: There is limited evidence on the optimum duration of administration sets used for peripheral arterial catheters. Large randomised trials of high quality are needed. RELEVANCE TO CLINICAL PRACTICE: This review provides clinicians with comprehensive information about the state of the evidence in relation to the duration of administration sets for peripheral arterial catheters to inform decision-making and further research.

Nitrogen-fixing bacteria, arbuscular mycorrhizal fungi, and the productivity and structure of prairie grassland communities.

Due to their complementary roles in meeting plant nutritional needs, arbuscular mycorrhizal fungi (AMF) and nitrogen-fixing bacteria (N(2)-fixers) may have synergistic effects on plant communities. Using greenhouse microcosms, we tested the effects of AMF, N(2)-fixers (symbiotic: rhizobia, and associative: Azospirillum brasilense), and their potential interactions on the productivity, diversity, and species composition of diverse tallgrass prairie communities and on the productivity of Panicum virgatum in monoculture. Our results demonstrate the importance of AMF and N(2)-fixers as drivers of plant community structure and function. In the communities, we found a positive effect of AMF on diversity and productivity, but a negative effect of N(2)-fixers on productivity. Both AMF and N(2)-fixers affected relative abundances of species. AMF shifted the communities from dominance by Elymus canadensis to Sorghastrum nutans, and seven other species increased in abundance with AMF, accounting for the increased diversity. N(2)-fixers led to increases in Astragalus canadensis and Desmanthus illinoense, two legumes that likely benefited from the presence of the appropriate rhizobia symbionts. Sorghastrum nutans declined 44 % in the presence of N(2)-fixers, with the most likely explanation being increased competition from legumes. Panicum monocultures were more productive with AMF, but showed no response to N(2)-fixers, although inference was constrained by low Azospirillum treatment effectivity. We did not find interactions between AMF and N(2)-fixers in communities or Panicum monocultures, indicating that short-term effects of these microbial functional groups are additive.

Competitive context alters plant-soil feedback in an experimental woodland community.

Recent findings on feedback between plants and soil microbial communities have improved our understanding of mechanisms underlying the success and consequences of invasions. However, additional studies to test for feedback in the presence and absence of interspecific competition, which may alter the strength or direction of feedbacks, are needed. We tested for soil microbial feedback in communities of the invasive grass Microstegium vimineum and commonly co-occurring native plant species. To incorporate competitive context, we used a factorial design with three plant treatments (M. vimineum alone, M. vimineum with the native plant community, and the native community without M. vimineum) and two soil inoculum treatments (experimentally invaded and uninvaded soil). When competing with M. vimineum, native communities were 27% more productive in invaded than uninvaded soil. In contrast, soil type did not significantly affect M. vimineum biomass or fecundity. At the community level, these results indicate a net negative soil microbial feedback when native plants and M. vimineum are grown in competitive mixture, but not when they are grown separately. Since positive, not negative, feedback is associated with dominance and invasion, our findings do not support plant-soil feedback as a driver of invasion in this species. Our results do show that the importance of soil feedback can change with competitive context. Such context-dependency implies that soil feedback may change when competitive interactions between natives and invading species shift as invasions progress.

Resource heterogeneity, soil fertility, and species diversity: effects of clonal species on plant communities.

Spatial heterogeneity in soil resources is widely thought to promote plant species coexistence, and this mechanism figures prominently in resource-ratio models of competition. However, most experimental studies have found that nutrient enhancements depress diversity regardless of whether nutrients are uniformly or heterogeneously applied. This mismatch between theory and empirical pattern is potentially due to an interaction between plant size and the scale of resource heterogeneity. Clonal plants that spread vegetatively via rhizomes or stolons can grow large and may integrate across resource patches, thus reducing the positive effect of small-scale resource heterogeneity on plant species richness. Many rhizomatous clonal species respond strongly to increased soil fertility, and they have been hypothesized to drive the descending arm of the hump-shaped productivity-diversity relationship in grasslands. We tested whether clonals reduce species richness in a grassland community by manipulating nutrient heterogeneity, soil fertility, and the presence of rhizomatous clonal species in a 6-year field experiment. We found strong and consistent negative effects of clonals on species richness. These effects were greatest at high fertility and when soil resources were applied at a scale at which rhizomatous clonals could integrate across resource patches. Thus, we find support for the hypothesis that plant size and resource heterogeneity interact to determine species diversity.

Perturbations alter community convergence, divergence, and formation of multiple community states.

Environmental perturbations (e.g., disturbance, fertilization) commonly shift communities to a new mean state, but much less is known about their effects on the variability (dispersion) of communities around the mean, particularly when perturbations are combined. Community dispersion may increase or decrease (representing a divergence or convergence among communities) if changing environmental conditions alter species interactions or magnify small initial differences that develop during community assembly. We used data from an experimental study of disturbance and fertilization in a low-productivity grassland to test how these two perturbations affect patterns of species composition and abundance. We found that a one-time biomass reduction decreased community dispersion, which persisted over four growing seasons. Conversely, continuous fertilization increased community dispersion and, when combined with disturbance, led to the formation of three distinct community states. These results illustrate that perturbations can have differing effects on community dispersion. Attention to the variance in community responses to perturbations lends insight into how ecological interactions determine community structure, which may be missed when focusing only on mean responses. Furthermore, multiple perturbations may have complex effects on community dispersion, yielding convergence or divergence patterns that are difficult to predict based on analysis of single factors.