Links between soil microbial communities and plant traits in a species-rich grassland under long-term climate change.

Climate change can influence soil microorganisms directly by altering their growth and activity but also indirectly via effects on the vegetation, which modifies the availability of resources. Direct impacts of climate change on soil microorganisms can occur rapidly, whereas indirect effects mediated by shifts in plant community composition are not immediately apparent and likely to increase over time. We used molecular fingerprinting of bacterial and fungal communities in the soil to investigate the effects of 17 years of temperature and rainfall manipulations in a species-rich grassland near Buxton, UK. We compared shifts in microbial community structure to changes in plant species composition and key plant traits across 78 microsites within plots subjected to winter heating, rainfall supplementation, or summer drought. We observed marked shifts in soil fungal and bacterial community structure in response to chronic summer drought. Importantly, although dominant microbial taxa were largely unaffected by drought, there were substantial changes in the abundances of subordinate fungal and bacterial taxa. In contrast to short-term studies that report high resistance of soil fungi to drought, we observed substantial losses of fungal taxa in the summer drought treatments. There was moderate concordance between soil microbial communities and plant species composition within microsites. Vector fitting of community-weighted mean plant traits to ordinations of soil bacterial and fungal communities showed that shifts in soil microbial community structure were related to plant traits representing the quality of resources available to soil microorganisms: the construction cost of leaf material, foliar carbon-to-nitrogen ratios, and leaf dry matter content. Thus, our study provides evidence that climate change could affect soil microbial communities indirectly via changes in plant inputs and highlights the importance of considering long-term climate change effects, especially in nutrient-poor systems with slow-growing vegetation.

Comment on "Productivity is a poor predictor of plant species richness".

Adler et al. (Reports, 23 September 2011, p. 1750) reported "weak and variable" relationships between productivity and species richness and dispute the "humped-back" model (HBM) of plant diversity. We show that their analysis lacks sufficient high-productivity sites, ignores litter, and excludes anthropogenic sites. If corrected, the data set of Adler et al. would apparently yield strong HBM support.

Fine-scale community and genetic structure are tightly linked in species-rich grasslands.

Recent evidence indicates that grassland community structure and species diversity are influenced by genetic variation within species. We review what is known regarding the impact of intraspecific diversity on grassland community structure, using an ancient limestone pasture as a focal example. Two genotype-dependent effects appear to modify community structure in this system. First, the abundance of individual constituent species can depend upon the combined influence of direct genetic effects stemming from individuals within the population. Second, the outcome of localized interspecific interactions occurring within the community can depend on the genotypes of participating individuals (indicating indirect genetic effects). Only genotypic interactions are thought to be capable of allowing the long-term coexistence of both genotypes and species. We discuss the implications of these effects for the maintenance of diversity in grasslands. Next, we present new observations indicating that losses of genotypic diversity from each of two species can be predicted by the abundance of other coexisting species within experimental grassland communities. These results suggest genotype-specific responses to abundance in other coexisting species. We conclude that both direct and indirect genetic effects are likely to shape community structure and species coexistence in grasslands, implying tight linkage between fine-scale genetic and community structure.

Underdeveloped embryos and germination in Aristolochia galeata seeds.

Aristolochiaceae have been described as having seeds with underdeveloped embryos and morphological or morphophysiological dormancy. Aristolochia galeata is a native climber found in the Cerrado biome, associated with road and gallery forest edges. The aims of this study were to investigate: embryo growth rate, morphology and seed germination parameters under different treatments. Embryos were excised to obtain embryo length at four stages: initial, seeds after coat rupture, radicle tip protrusion and cotyledon emergence from the seed coat. Germination tests were conducted at 30 °C under three nitrate concentrations (1, 10 and 20 mM), fluctuating temperature (27/20 °C) and light and dark conditions. We found that seeds have underdeveloped embryos, which take about 301 ± 178 h (±SD) to achieve seed coat rupture, another 205 ± 126 h to reach radicle protrusion and 176 ± 76 h more to the final stage of cotyledon emergence. Germinability was above 52% in all treatments, except in the dark (15%). For all treatments, average germination time was above 290 ± 123 h. Potassium nitrate increased germinability to >87%. No particular treatment was required for embryo development, but seeds in the population that continued to germinate after 1 month were probably in various states of non-deep, simple morphophysiological dormancy. Increased germinability in nitrate treatments and light requirement for germination could prevent germination under unsuitable environmental conditions and be a strategy to increase seedling establishment in the cerrado.

Community and ecosystem effects of intraspecific genetic diversity in grassland microcosms of varying species diversity.

Studies of whether plant community structure and ecosystem properties depend on the genetic diversity of component populations have been largely restricted to species monocultures and have involved levels of genetic differentiation that do not necessarily correspond to that exhibited by neighboring mature individuals in the field. We established experimental communities of varying intraspecific genetic diversity, using genotypes of eight species propagated from clonal material of individuals derived from a small (100-m2) limestone grassland community, and tested whether genetic diversity (one, four, and eight genotypes per species) influenced community composition and annual aboveground productivity across communities of one, four, and eight species. Eight-species communities were represented by common grass, sedge, and forb species, and four- and one-species communities were represented by four graminoids and the dominant grass Festuca ovina, respectively. After three years of community development, there was a marginal increase of species diversity with increased genetic diversity in four- and eight-species communities, and genetic diversity altered the performance of genotypes in monospecific communities of F. ovina. However, shifts in composition from genetic diversity were not sufficient to alter patterns of community productivity. Neighborhood models describing pairwise interactions between species indicated that genetic diversity decreased the intensity of competition between species in four-species mixtures, thereby promoting competitive equivalency and enhancing species equitability. In F. ovina monocultures, neighborhood models revealed both synergistic and antagonistic interactions between genotypes that were reduced in intensity on more stressful shallow soils. Although the dependence of F. ovina genotype performance on neighborhood genetic composition did not influence total productivity, such dependence was sufficient to uncouple genotype performance in genetic mixtures and monocultures. Our results point to an important connection between local genetic diversity and species diversity in this species-rich ecosystem but suggest that such community-level dependence on genetic diversity may not feedback to ecosystem productivity.

Genetic variation in plant morphology contributes to the species-level structure of grassland communities.

It is becoming apparent that genetic diversity can influence the species diversity and structure of ecological communities. Here, we investigated the intraspecific trait variation responsible for this relationship. We grew 10 genotypes of the sedge Carex caryophyllea, as monocultures, under standardized conditions and measured traits related to morphology, growth, and life history. The same genotypes had been prominent in determining the structure of multispecies experimental communities, equivalent in species diversity, in which the genetic diversity of the constituent plant species had been varied in parallel. The trait measurements revealed substantial phenotypic variation among Carex genotypes, related predominantly to differences in physical size and to the spatial deployment of above- and belowground tissue. Genotypes successful in experimental communities were larger in size and tended to adopt a "guerrilla" clonal growth strategy. In general, multivariate trait summaries of genotype size (and to a lesser extent, variation along a linear discriminant axis) predicted genotype and species abundance in experimental communities. However, one genotype exhibited a large disparity in this respect. The performance of this genotype lay closer to prediction when it was growing with a highly competitive grass genotype. The strength of the relationship between genotype size and performance within communities decreased with decreasing community genetic diversity. These results indicate that intraspecific trait measurements are useful for predicting and understanding community structure. They also imply that competitive interactions between the genotypes of different species play an increased role in determining phenotype in genetically impoverished communities.

Long-term resistance to simulated climate change in an infertile grassland.

Climate shifts over this century are widely expected to alter the structure and functioning of temperate plant communities. However, long-term climate experiments in natural vegetation are rare and largely confined to systems with the capacity for rapid compositional change. In unproductive, grazed grassland at Buxton in northern England (U.K.), one of the longest running experimental manipulations of temperature and rainfall reveals vegetation highly resistant to climate shifts maintained over 13 yr. Here we document this resistance in the form of: (i) constancy in the relative abundance of growth forms and maintained dominance by long-lived, slow-growing grasses, sedges, and small forbs; (ii) immediate but minor shifts in the abundance of several species that have remained stable over the course of the experiment; (iii) no change in productivity in response to climate treatments with the exception of reduction from chronic summer drought; and (iv) only minor species losses in response to drought and winter heating. Overall, compositional changes induced by 13-yr exposure to climate regime change were less than short-term fluctuations in species abundances driven by interannual climate fluctuations. The lack of progressive compositional change, coupled with the long-term historical persistence of unproductive grasslands in northern England, suggests the community at Buxton possesses a stabilizing capacity that leads to long-term persistence of dominant species. Unproductive ecosystems provide a refuge for many threatened plants and animals and perform a diversity of ecosystem services. Our results support the view that changing land use and overexploitation rather than climate change per se constitute the primary threats to these fragile ecosystems.

Plant community composition, not diversity, regulates soil respiration in grasslands.

Soil respiration is responsible for recycling considerable quantities of carbon from terrestrial ecosystems to the atmosphere. There is a growing body of evidence that suggests that the richness of plants in a community can have significant impacts on ecosystem functioning, but the specific influences of plant species richness (SR), plant functional-type richness and plant community composition on soil respiration rates are unknown. Here we use 10-year-old model plant communities, comprising mature plants transplanted into natural non-sterile soil, to determine how the diversity and composition of plant communities influence soil respiration rates. Our analysis revealed that soil respiration was driven by plant community composition and that there was no significant effect of biodiversity at the three levels tested (SR, functional group and species per functional group). Above-ground plant biomass and root density were included in the analysis as covariates and found to have no effect on soil respiration. This finding is important, because it suggests that loss of particular species will have the greatest impact on soil respiration, rather than changes in biodiversity per se.

The scale-precision trade-off in spacial resource foraging by plants: restoring perspective.

BACKGROUND AND AIMS: From the results of a comparative study using quantitative standardized assays of the scale and precision of responses of root and shoot systems to resource patchiness, Campbell et al. (1991; Oecologia 87: 532-538) proposed a mechanism of species coexistence in herbaceous communities involving a dynamic equilibrium between, respectively, the coarse- and fine-scale foraging of dominant and subordinate species. The purpose of this paper is to reject a recent assertion that with respect to root systems the scale-precision hypothesis has been falsified. DISCUSSION AND CONCLUSION: Reference to the original papers confirms that the scope of the hypothesis was confined to circumstances (eg. mown meadows) where the vigour of potential dominants is restricted by intermittent removal of biomass. This qualification in the original hypothesis is a crucial omission from the meta-analysis conducted by Kembel and Cahill (2005; American Naturalist 166: 216-230). The original papers also contain examples that illustrate the operation of forms of selection that prevent the development of precise foraging below ground; these also appear to have escaped the attention of recent participants in this field of research.

A systematic review of quantitative and qualitative research on the role and effectiveness of written information available to patients about individual medicines.

OBJECTIVES: To establish the role and value of written information available to patients about individual medicines from the perspective of patients, carers and professionals. To determine how effective this information is in improving patients' knowledge and understanding of treatment and health outcomes. DATA SOURCES: Electronic databases searched to late 2004, experts in information design, and stakeholder workshops (including patients and patient organisations). REVIEW METHODS: Data from selected studies were tabulated and the results were qualitatively synthesised along with findings from the information design and stakeholder workshop strands. RESULTS: Most people do not value the written information they receive. They had concerns about the use of complex language and poor visual presentation and in most cases the research showed that the information did not increase knowledge. The research showed that patients valued written information that was tailored to their individual circumstances and illness, and that contained a balance of harm and benefit information. Most patients wanted to know about any adverse effects that could arise. Patients require information to help decision-making about whether to take a medicine or not and (once taking a medicine) with ongoing decisions about the management of the medicine and interpreting symptoms. Patients did not want written information to be a substitute for spoken information from their prescriber. While not everyone wanted written information, those who did wanted sufficient detail to meet their need. Some health professionals thought that written information for patients should be brief and simple, with concerns about providing side-effect information. They saw increasing compliance as a prime function, in contrast to patients who saw an informed decision not to take a medicine as an acceptable outcome. CONCLUSIONS: The combination of a quantitative and qualitative review, an exploration of best practice in information design, plus the input of patients at stakeholder workshops, allowed this review to look at all perspectives. There is a gap between currently provided leaflets and information which patients would value and find more useful. The challenge is to develop methods of provision flexible enough to allow uptake of varying amounts and types of information, depending on needs at different times in an illness. This review has identified a number of areas where future research could be improved in terms of the robustness of its design and conduct, and the use of patient-focused outcomes. The scope for this research includes determining the content, delivery and layout of statutory leaflets that best meet patients' needs, and providing individualised information, which includes both benefit and harm information. In particular, studies of the effectiveness and role and value of Internet-based medicines information are needed.

Prognostic potential of hepatocyte volume and cytokine expression in cirrhotic portal hypertension.

BACKGROUND: Differentiating the prognosis of Child-Pugh A and B patients is difficult, particularly following an acute variceal hemorrhage. We have examined the prognostic significance of hepatocyte volume (HV) and the expression of selected cytokines controlling liver repair and regeneration. METHODS: Forty Child-Pugh A and B cirrhotic patients surviving a first acute variceal hemorrhage were recruited prospectively. Hematological, biochemical, neurological, hemodynamic, radio-nuclear and histological assessments were carried out following recovery (at 3 weeks). Fibrosis (%) and HV were calculated using histological morphometry and radio-nuclear liver volume assessment. Immunohistochemistry was used in liver biopsy specimens to assess markers of proliferation (PCNA) and the expression of mitogens (TGF-alpha, TGF-beta(1)) or their receptors (C-met and EGFR). RESULTS: In total, 27 patients died during the follow-up period. HV was predictive of survival in Child-Pugh grade A patients (chi(2) = 10.5, P = 0.0012), but percentage fibrosis and regeneration factor expression were not predictive in either Child-Pugh A or B patients. Cox regression modeling with Child-Pugh grade demonstrated HV to be an independent predictor of survival (chi(2) = 7.1, P = 0.02). CONCLUSIONS: HV predicts survival independently in cirrhotic portal hypertension, and may help to differentiate prognosis in those at the more favorable end of the disease spectrum. Liver cytokine expression 3 weeks following an acute variceal bleed did not appear useful in determining prognosis.

Plant communities affect arbuscular mycorrhizal fungal diversity and community composition in grassland microcosms.

• The diversity of arbuscular mycorrhizal (AM) fungi was investigated in an unfertilized limestone grassland soil supporting different synthesized vascular plant assemblages that had developed for 3 yr. • The experimental treatments comprised: bare soil; monocultures of the nonmycotrophic sedge Carex flacca; monocultures of the mycotrophic grass Festuca ovina; and a species-rich mixture of four forbs, four grasses and four sedges. The diversity of AM fungi was analysed in roots of Plantago lanceolata bioassay seedlings using terminal-restriction fragment length polymorphism (T-RFLP). The extent of AM colonization, shoot biomass and nitrogen and phosphorus concentrations were also measured. • The AM diversity was affected significantly by the floristic composition of the microcosms and shoot phosphorus concentration was positively correlated with AM diversity. The diversity of AM fungi in P. lanceolata decreased in the order: bare soil > C. flacca > 12 species > F. ovina. • The unexpectedly high diversity in the bare soil and sedge monoculture likely reflects differences in the modes of colonization and sources of inoculum in these treatments compared with the assemblages containing established AM-compatible plants.

How do younger patients view long-term treatment with proton pump inhibitors?

Dyspepsia (also called indigestion or heartburn) is a common reason for consulting a general practitioner (GP). One of the medicines available for treating dyspepsia is a type of acid suppressant called a proton pump inhibitor or PPI. There is a growing concern over the rapid increase in prescribing PPI drugs and the escalating costs associated with this trend. There has been an effort to reduce prescribing of PPIs. Most patients who are prescribed these drugs are aged over 45 years. Younger patients (those under 45) are a minority but, in absolute terms, a sizeable number who could potentially be taking PPIs for many years and therefore be expensive. This is a group for whom the appropriateness of prescribing PPIs is often questioned because of the everyday and non-life threatening nature of gastric disorders. A widespread association between dyspeptic symptoms and features of adverse lifestyle that are, at least in principle, easily avoidable has led to the suggestion that PPIs might be used to support unhealthy lifestyles. The perspective of younger patients taking PPIs in the long term has been neglected. In this paper the accounts of ten younger respondents, from a large qualitative investigation of patient and GP perspectives on long-term PPI prescribing, are examined to gain insight into how younger patients viewed their stomach problem, the effectiveness of PPIs and long-term PPI taking. The findings showed a gap between patient experience and medical perception. The perspectives of younger patients need to be recognised in order to deal adequately with their concerns about illness and treat their gastrointestinal conditions effectively.

Biodiversity and ecosystem functioning: current knowledge and future challenges.

The ecological consequences of biodiversity loss have aroused considerable interest and controversy during the past decade. Major advances have been made in describing the relationship between species diversity and ecosystem processes, in identifying functionally important species, and in revealing underlying mechanisms. There is, however, uncertainty as to how results obtained in recent experiments scale up to landscape and regional levels and generalize across ecosystem types and processes. Larger numbers of species are probably needed to reduce temporal variability in ecosystem processes in changing environments. A major future challenge is to determine how biodiversity dynamics, ecosystem processes, and abiotic factors interact.

Proton pump inhibitors: perspectives of patients and their GPs.

BACKGROUND: There is growing concern with the rapid increase in prescribing proton pump inhibitor drugs (PPIs) for a variety of gastrointestinal disorders, and the escalating costs associated with this trend. Explanations have included that general practitioners (GPs) prescribe PPIs inappropriately and that patients demand PPIs and use them as a way of avoiding having to make lifestyle changes. AIM: To compare the perspectives of GPs and their patients on the need for PPIs, to examine the pressure to prescribe, and to examine the effect of PPIs on lifestyle. DESIGN OF STUDY: Qualitative comparative study based on semi-structured interviews. SETTING: Twenty-six GPs in seven practices in the West Midlands and 82 of their patients on repeat prescriptions for PPIs. METHOD: Interviews were conducted covering a wide range of topics, including: experience, cause, course, and outcome of stomach problems; effectiveness of PPIs; and role of lifestyle in controlling symptoms. The transcripts were studied repeatedly to look for the occurrence and distribution of material relating to these issues, as well as other responder-driven issues. Codebooks were devised to enable a simple categorisation and systematic comparison of cases. RESULTS: GPs and patients agreed about the severity and unpleasantness of stomach symptoms for which PPIs were prescribed. While GPs and patients regarded PPIs as a very effective treatment, GPs rated their efficacy more highly than patients. Half of the GP interviews reproduced the stereotype of the demanding patient and of patients using PPIs to support unhealthy lifestyles. There was little evidence from patient interviews to support either stereotype. Doctors underestimated patient concerns about side-effects, safety, and long-term use of PPIs, and the willingness of patients to achieve the minimum effective dose by experimenting with their treatment. GPs felt that the pressure to prescribe PPIs was outweighed by the pressure not to prescribe, and most GPs had responded to the call to cut the prescribing of PPIs. Different strategies were employed to cut prescribing, including the wholesale switching of patients on a treatment dose of one brand of PPI to a maintenance dose of a cheaper brand of PPI, known as 'double switching'. CONCLUSION: The stereotypes of 'profligate prescriber', 'demanding patient', and 'adverse lifestyle', as explanations for the increase in the prescribing of PPIs, were not upheld. The stereotype of patients demanding PPIs may arise from GPs' internal pressure to prescribe being externalised onto patients. The extent to which health behaviour contributes to gastric disorders needs to be established empirically. Labelling PPI patients as having a poor lifestyle may be used as a means of reducing legitimate need for PPIs. Current policy relating to switching of dose and brand of PPI should be reviewed.

Renal tubular peptide catabolism in chronic vascular rejection.

Chronic vascular rejection (CR) is the commonest cause of renal transplant loss, with few clues to etiology, but proteinuria is a common feature. In diseased native kidneys, proteinuria and progression to failure are linked. We proposed a pathogenic role for this excess protein at a tubular level in kidney diseases of dissimilar origin. We demonstrated in both nephrotic patients with normal function and in those with failing kidneys increased renal tubular catabolism and turnover rates of a peptide marker, Aprotinin (Apr), linked to increased ammonia excretion and tubular injury. These potentially injurious processes were suppressed by reducing proteinuria with Lisinopril. Do similar mechanisms of renal injury and such a linkage also occur in proteinuric transplanted patients with CR, and if so, is Lisinopril then of beneficial value? We now examine these aspects in 11 patients with moderate/severe renal impairment (51CrEDTA clearance 26.2+/-3.3 mL/min/1.73 m2), proteinuria (6.1+/-1.5 g/24 h) and biopsy proven CR. Lisinopril (10-40 mg) was given daily for 2 months in 7 patients. Four others were given oral sodium bicarbonate (Na HCO3) for 2 months before adding Lisinopril. Renal tubular catabolism of intravenous 99mTc-Apr (Apr* 0.5 mg, 80MBq), was measured before and after Lisinopril by gamma-ray renal imaging and urinary radioactivity of the free radiolabel over 26 h. Fractional degradation was calculated from these data. Total 24 h urinary N-acetyl-beta-glucoaminidase (NAG) and ammonia excretion in fresh timed urine collections were also measured every two weeks from two months before treatment. After Lisinopril proteinuria fell significantly (from 7.8+/-2.2 to 3.4+/-1.9 g/24 h, p<0.05). This was associated with a reduction in metabolism of Apr* over 26 h (from 0.5+/-0.05 to 0.3+/-0.005% dose/h, p < 0.02), and in fractional degradation (from 0.04+/-0.009 to 0.02+/-0.005/h, p<0.01). Urinary ammonia fell, but surprisingly not significantly and this was explained by the increased clinical acidosis after Lisinopril, (plasma bicarbonate fell from 19.1+/-0.7 to 17.4+/-0.8 mmol/L, p < 0.01), an original observation. Total urinary NAG did fall significantly from a median of 2108 (range 1044-3816) to 1008 (76-2147) micromol/L, p < 0.05. There was no significant change in blood pressure or in measurements of glomerular hemodynamics. In the 4 patients who were given Na HCO3 before adding Lisinopril, both acidosis (and hyperkalemia) were reversed and neither recurred after adding Lisinopril. These observations in proteinuric transplanted patients after Lisinopril treatment have not been previously described.

Strategies for reducing the prescribing of proton pump inhibitors (PPIs): patient self-regulation of treatment may be an under-exploited resource.

Escalating costs of proton pump inhibitor (PPI) prescribing are a source of increasing concern. To reduce costs, GPs in the UK have been coming under pressure to restrict PPI prescribing in primary care, e.g. by raising the prescribing threshold for new patients, and encouraging established patients to accept a reduced dose, if not stop taking PPIs altogether. The need to reduce prescribing costs impacts on patients by redefining, i.e. reducing, the boundaries of clinical need for which PPI prescribing is deemed appropriate. This may be rationalised by the assumptions that much existing prescribing is inappropriate, is applied to relatively minor and trivial afflictions, and that patients put pressure on their doctors to initiate prescribing of PPIs, after which they are very reluctant to give them up. The research involved extended interviews to elicit GP and patient views and experience of PPI prescribing. A particular focus was a comparison of the views of patients and GPs, and the understanding and articulation of the patient perspective on PPIs, which has been largely absent from the discussion to date. The research identified six distinct strategies used by GPs in their efforts to reduce PPI prescribing. Contrary to what GPs often assumed to be the case, patients were generally quite receptive to changes to their medication, provided they had the security of knowing that their original prescription would be restored if necessary. Most doctors assessed their rationing strategies as having some impact, but acknowledged the difficulties in achieving a significant and sustained reduction in PPIs. In the study sample nearly half of the patients who had experienced a prescribing switch or step down had drifted back to their former brand, and, especially, higher dose. However, far from being overly and unreflectively dependent on PPIs, patients were often keen to reduce their medicine taking to a minimum. A number of respondents had taken the initiative in experimenting to find the lowest effective dose of PPIs required to control their symptoms. GPs varied in their attitudes to this form of treatment self-management, but less than half actively encouraged patients to regulate their treatment in this way. Our findings suggest that there is considerable scope for encouraging patients to self-regulate with PPIs, and that many patients would be willing to do this if the practice was sanctioned by their doctors. The anticipated benefits of increased self-regulation include an overall reduction in PPI prescribing and associated costs, and an increase in patient autonomy and control which is in line with the concordance model of the ideal relationship between patients and doctors.

The response of two contrasting limestone grasslands to simulated climate change.

Two different UK limestone grasslands were exposed to simulated climate change with the use of nonintrusive techniques to manipulate local climate over 5 years. Resistance to climate change, defined as the ability of a community to maintain its composition and biomass in response to environmental stress, could be explained by reference to the functional composition and successional status of the grasslands. The more fertile, early-successional grassland was much more responsive to climate change. Resistance could not be explained by the particular climates experienced by the two grasslands. Productive, disturbed landscapes created by modern human activity may prove more vulnerable to climate change than older, traditional landscapes.