Exotic herbaceous species interact with severe drought to alter soil N cycling in a semi-arid shrubland

Mediterranean-type ecosystems are increasingly threatened by climate change and exotic annual species, jeopardizing the native communities and their global biodiversity. In these systems, soil nitrogen (N) limits net primary production, and its availability can be influenced by both of these stressors. To understand the interactive effects of droughts and exotic herbaceous species on soil N, we monitored the temporal variability of soil inorganic N, net N mineralization, net nitrification, and NO3- leaching under native- and exotic-dominated stands exposed to rainfall manipulation plots in a Mediterranean-type shrub-dominated community. Increasing drought severity resulted in the accumulation of soil NH4+ and NO3-, with a more pronounced increase in exotic-dominated plots. Increased net N mineralization and net nitrification and reduced leaching losses were observed as mechanisms of inorganic N accumulation. In comparison to soils under native plants, soils under exotic plants had enhanced leaching losses upon soil rewetting. We propose that distinct traits of exotic annual herbaceous species associated with higher N inputs, faster turnover, and reduced temporal uptake determine the changes in N cycling in response to droughts. Severe droughts and exotic plants may produce a larger, more vulnerable pool of N that is prone to losses while providing a competitive advantage to promote exotic growth in these N-limited ecosystems

Metabolic trade-offs and the maintenance of the fittest and the flattest.

This is the post print version of the article, deposited in accordance with SHERPA RoMEO guidelines. The final definitive version is available from: http://www.nature.com/nature/journal/v472/n7343/full/nature09905.htmlHow is diversity maintained? Environmental heterogeneity is considered to be important, yet diversity in seemingly homogeneous environments is nonetheless observed. This, it is assumed, must either be owing to weak selection, mutational input or a fitness advantage to genotypes when rare. Here we demonstrate the possibility of a new general mechanism of stable diversity maintenance, one that stems from metabolic and physiological trade-offs. The model requires that such trade-offs translate into a fitness landscape in which the most fit has unfit near-mutational neighbours, and a lower fitness peak also exists that is more mutationally robust. The 'survival of the fittest' applies at low mutation rates, giving way to 'survival of the flattest' at high mutation rates. However, as a consequence of quasispecies-level negative frequency-dependent selection and differences in mutational robustness we observe a transition zone in which both fittest and flattest coexist. Although diversity maintenance is possible for simple organisms in simple environments, the more trade-offs there are, the wider the maintenance zone becomes. The principle may be applied to lineages within a species or species within a community, potentially explaining why competitive exclusion need not be observed in homogeneous environments. This principle predicts the enigmatic richness of metabolic strategies in clonal bacteria and questions the safety of lethal mutagenesis as an antimicrobial treatment

Once-Daily Triple Therapy in Patients with COPD: Patient-Reported Symptoms and Quality of Life.

INTRODUCTION: Directly recorded patient experience of symptoms and health-related quality of life (HRQoL) can complement lung function and exacerbation rate data in chronic obstructive pulmonary disease (COPD) clinical studies. The FULFIL study recorded daily symptoms and activity limitation together with additional patient-reported outcomes of dyspnea and HRQoL, as part of the prespecified analyses. FULFIL co-primary endpoint data have been previously reported. METHODS: FULFIL was a phase III, 24-week, randomized, double-blind, double-dummy, multicenter study comparing once-daily single inhaler triple therapy [fluticasone furoate/umeclidinium/vilanterol (FF/UMEC/VI)] 100 µg/62.5 µg/25 µg with twice-daily inhaled corticosteroid/long-acting β2-agonist therapy [budesonide/formoterol (BUD/FOR)] 400 µg/12 µg in patients with symptomatic COPD at risk of exacerbations. A subset participated for 52 weeks. Patient-reported assessments were: Evaluating Respiratory Symptoms in COPD™ (E-RS: COPD), St George's Respiratory Questionnaire (SGRQ) for COPD, COPD Assessment Test (CAT), baseline and transitional dyspnea indices (TDI) and daily and global anchor questions for activity limitation. RESULTS: FF/UMEC/VI showed greater reductions from baseline in 4-weekly mean E-RS: COPD total and all subscale scores compared with BUD/FOR; differences were statistically significant (P < 0.05) at each time period. FF/UMEC/VI also demonstrated greater improvements from baseline at weeks 4 and 24 in SGRQ domain scores and TDI focal score compared with BUD/FOR. At weeks 4 and 24, improvements greater than the minimal clinically important difference from baseline were observed in CAT score with FF/UMEC/VI, but not BUD/FOR; differences were statistically significant (P ≤ 0.003). CONCLUSION: These findings demonstrate sustained daily symptom and HRQoL benefits of FF/UMEC/VI versus BUD/FOR. The inclusion of the CAT may provide data that are readily generalizable to everyday clinical practice. TRIAL REGISTRATION: ClinicalTrials.gov number: NCT02345161. FUNDING: GSK

Mechanistic Modeling of Microtopographic Impacts on CO2 and CH4 Fluxes in an Alaskan Tundra Ecosystem Using the CLM-Microbe Model

Spatial heterogeneities in soil hydrology have been confirmed as a key control on CO2 and CH4 fluxes in the Arctic tundra ecosystem. In this study, we applied a mechanistic ecosystem model, CLM-Microbe, to examine the microtopographic impacts on CO2 and CH4 fluxes across seven landscape types in Utqiaġvik, Alaska: trough, low-centered polygon (LCP) center, LCP transition, LCP rim, high-centered polygon (HCP) center, HCP transition, and HCP rim. We first validated the CLM-Microbe model against static-chamber measured CO2 and CH4 fluxes in 2013 for three landscape types: trough, LCP center, and LCP rim. Model application showed that low-elevation and thus wetter landscape types (i.e., trough, transitions, and LCP center) had larger CH4 emissions rates with greater seasonal variations than high-elevation and drier landscape types (rims and HCP center). Sensitivity analysis indicated that substrate availability for methanogenesis (acetate, CO2&nbsp;+&nbsp;H2) is the most important factor determining CH4 emission, and vegetation physiological properties largely affect the net ecosystem carbon exchange and ecosystem respiration in Arctic tundra ecosystems. Modeled CH4 emissions for different microtopographic features were upscaled to the eddy covariance (EC) domain with an area-weighted approach before validation against EC-measured CH4 fluxes. The model underestimated the EC-measured CH4 flux by 20% and 25% at daily and hourly time steps, suggesting the importance of the time step in reporting CH4 flux. The strong microtopographic impacts on CO2 and CH4 fluxes call for a model-data integration framework for better understanding and predicting carbon flux in the highly heterogeneous Arctic landscape

Response of CO₂ and CH₄ emissions from Arctic tundra soils to a multifactorial manipulation of water table, temperature and thaw depth

Significant uncertainties persist concerning how Arctic soil tundra carbon emission responds to environmental changes. In this study, 24 cores were sampled from drier (high centre polygons and rims) and wetter (low centre polygons and troughs) permafrost tundra ecosystems. We examined how soil CO2 and CH4 fluxes responded to laboratory-based manipulations of soil temperature (and associated thaw depth) and water table depth, representing current and projected conditions in the Arctic. Similar soil CO2 respiration rates occurred in both the drier and the wetter sites, suggesting that a significant proportion of soil CO2 emission occurs via anaerobic respiration under water-saturated conditions in these Arctic tundra ecosystems. In the absence of vegetation, soil CO2 respiration rates decreased sharply within the first 7 weeks of the experiment, while CH4 emissions remained stable for the entire 26 weeks of the experiment. These patterns suggest that soil CO2 emission is more related to plant input than CH4 production and emission. The stable and substantial CH4 emission observed over the entire course of the experiment suggests that temperature limitations, rather than labile carbon limitations, play a predominant role in CH4 production in deeper soil layers. This is likely due to the presence of a substantial source of labile carbon in these carbon-rich soils. The small soil temperature difference (a median difference of 1 ◦C) and a more substantial thaw depth difference (a median difference of 6 cm) between the high and low temperature treatments resulted in a non-significant difference between soil CO2 and CH4 emissions. Although hydrology continued to be the primary factor influencing CH4 emissions, these emissions remained low in the drier ecosystem, even with a water table at the surface. This result suggests the potential absence of a methanogenic microbial community in high-centre polygon and rim ecosystems. Overall, our results suggest that the temperature increases reported for these Arctic regions are not responsible for increases in carbon losses. Instead, it is the changes in hydrology that exert significant control over soil CO2 and CH4 emissions

FULFIL Trial: Once-Daily Triple Therapy in Patients with Chronic Obstructive Pulmonary Disease

RATIONALE: Randomized data comparing triple therapy with dual inhaled corticosteroid (ICS)/long-acting β2-agonist (LABA) therapy in patients with chronic obstructive pulmonary disease (COPD) are limited. OBJECTIVES: We compared the effects of once-daily triple therapy on lung function and health-related quality of life with twice-daily ICS/LABA therapy. METHODS: FULFIL was a randomized, double-blind, double-dummy study comparing 24 weeks of once-daily triple therapy (fluticasone furoate/umeclidinium/vilanterol 100 μg/62.5 μg/25 μg; ELLIPTA(®) inhaler) with twice-daily ICS/LABA therapy (budesonide/formoterol 400 μg/12 μg; Turbuhaler(®)). A patient subgroup remained on blinded treatment for up to 52 weeks. Co-primary endpoints were change from baseline in trough forced expiratory volume in 1 second (FEV1) and in St George's Respiratory Questionnaire (SGRQ) Total score, at Week 24. MEASUREMENTS AND MAIN RESULTS: In the intent-to-treat population (N = 1,810) at Week 24 for triple therapy (n = 911) and ICS/LABA therapy (n = 899): mean change from baseline in FEV1 was 142 mL (95% confidence interval [CI], 126,158) and -29 mL (95% CI, -46,-13), respectively; mean change from baseline SGRQ was -6.6 units (95% CI, -7.4,-5.7) and -4.3 units (95% CI, -5.2,-3.4), respectively. For both endpoints, the between-group differences were statistically significant (P < 0.001). There was a statistically significant reduction in moderate/severe exacerbation rate with triple versus ICS/LABA therapy (35% reduction, 95% CI, 14,51; P = 0.002). The safety profile of triple therapy reflected the known profiles of the components. CONCLUSIONS: These results support the benefits of single inhaler triple therapy compared with ICS/LABA therapy, in patients with advanced COPD. Clinical trial registration available at www.clinicaltrials.gov, ID NCT02345161

The Effect of ICS Withdrawal and Baseline Inhaled Treatment on Exacerbations in the IMPACT Study: A Randomized, Double-blind Multicenter Trial

RATIONALE: In the IMPACT trial fluticasone furoate/umeclidinium/ vilanterol (FF/UMEC/VI) significantly reduced exacerbations compared with FF/VI or UMEC/VI in patients with symptomatic chronic obstructive pulmonary disease and a history of exacerbations. OBJECTIVES: Understand whether inhaled corticosteroid (ICS) withdrawal affected IMPACT results given direct transition from prior maintenance medication to study medication at randomization. METHODS: Exacerbations and change from baseline in trough forced expiratory volume in 1 second (FEV1) and St George's Respiratory Questionnaire (SGRQ) were analyzed by prior ICS use. Exacerbations were also analyzed excluding data from the first 30 days. MEASUREMENTS AND MAIN RESULTS: FF/UMEC/VI significantly reduced annual moderate/severe exacerbation rate versus UMEC/VI in prior ICS users (29% reduction; p<0.001), but only a numerical reduction was seen among prior ICS non-users (12% reduction; p=0.115). To minimize impact from ICS withdrawal, in an analysis excluding the first 30 days, FF/UMEC/VI continued to significantly reduce annual on-treatment moderate/severe exacerbation rate (19%; p<0.001) versus UMEC/VI. Benefit of FF/UMEC/VI versus UMEC/VI was seen for severe exacerbation rates, regardless of prior ICS use (prior ICS users: 35% reduction, p<0.001; non-ICS users: 35% reduction, p=0.018) and overall when excluding the first 30 days (29%, p<0.001). Improvements from baseline with FF/UMEC/VI versus UMEC/VI were also maintained throughout the study for both trough FEV1 and SGRQ regardless of prior ICS use. CONCLUSIONS: These data support important treatment effects from FF/UMEC/VI combination therapy on exacerbation reduction, lung function and quality of life that do not appear to be related to abrupt ICS withdrawal. FUNDING: GSK (CTT116855/NCT02164513). Clinical trial registration available at www.clinicaltrials.gov, ID: NCT02164513. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Effect of Age on the Efficacy and Safety of Once-Daily Single-Inhaler Triple Therapy Fluticasone Furoate/Umeclidinium/Vilanterol in Patients With Chronic Obstructive Pulmonary Disease: A Post Hoc Analysis of the IMPACT Trial

BACKGROUND: In the IMPACT trial, single-inhaler triple therapy fluticasone furoate/umeclidinium/vilanterol (FF/UMEC/VI) reduced moderate/severe exacerbation rates versus FF/VI and UMEC/VI in patients with symptomatic chronic obstructive pulmonary disease (COPD) and a history of exacerbations, with a similar safety profile. Research Question Does age have an effect on trial outcomes? STUDY DESIGN AND METHODS: IMPACT was a Phase III, double-blind, 52-week trial. Patients ≥40 years of age with symptomatic COPD and ≥1 moderate/severe exacerbation in the prior year were randomized 2:2:1 to FF/UMEC/VI 100/62.5/25 mcg, FF/VI 100/25 mcg, or UMEC/VI 62.5/25 mcg. Endpoints assessed by age included annual rate of moderate/severe exacerbations, change from baseline (CFB) in trough forced expiratory volume in 1 second (FEV1), proportion of St George's Respiratory Questionnaire (SGRQ) responders (≥4 units decrease from baseline in SGRQ total score) and safety. RESULTS: The intent-to-treat population comprised 10,355 patients; 4724 (46%), 4225 (41%), and 1406 (14%) were ≤64, 65-74, and ≥75 years of age, respectively. FF/UMEC/VI reduced on-treatment moderate/severe exacerbation rates versus FF/VI (% reduction [95% confidence interval (CI)], ≤64 years: 8% [-1, 16], p=0.070; 65-74 years: 22% [14, 29], p<0.001; ≥75 years 18% [3, 31], p=0.021) and versus UMEC/VI (≤64 years: 16% [7, 25], p=0.002; 65-74 years: 33% [25, 41], p<0.001; ≥75 years 24% [6, 38], p=0.012), with greatest rate reduction seen in the 65-74 and ≥75 years subgroups. Post hoc analyses of CFB in trough FEV1, and proportion of SGRQ responders at Week 52 were significantly greater with FF/UMEC/VI than FF/VI or UMEC/VI in all subgroups. No new safety signals were identified. INTERPRETATION: FF/UMEC/VI reduced the rate of moderate/severe exacerbations and improved lung function and health status versus FF/VI and UMEC/VI irrespective of age for most endpoints, with a similar safety profile. CLINICAL TRIAL REGISTRATION: GSK (CTT116855/NCT02164513)

Prognostic value of clinically important deterioration in COPD: IMPACT trial analysis

Introduction: Clinically important deterioration (CID) is a multicomponent measure for assessing disease worsening in chronic obstructive pulmonary disease (COPD). This analysis investigated the prognostic value of a CID event on future clinical outcomes and the effect of single-inhaler triple versus dual therapy on reducing CID risk in patients in the IMPACT trial. Methods: IMPACT was a phase III, double-blind, 52-week, multicentre trial. Patients with symptomatic COPD and at least one moderate/severe exacerbation in the prior year were randomised 2:2:1 to fluticasone furoate/umeclidinium/vilanterol (FF/UMEC/VI) 100/62.5/25 µg, FF/VI 100/25 µg or UMEC/VI 62.5/25 µg. CID at the time-point of interest was defined as a moderate/severe exacerbation, ≥100 mL decrease in trough forced expiratory volume in 1 s or deterioration in health status (increase of ≥4.0 units in St George's Respiratory Questionnaire total score or increase of ≥2.0 units in COPD Assessment Test score) from baseline. A treatment-independent post hoc prognostic analysis compared clinical outcomes up to week 52 in patients with/without a CID by week 28. A prospective analysis evaluated time to first CID with each treatment. Results: Patients with a CID by week 28 had significantly increased exacerbation rates after week 28, smaller improvements in lung function and health status at week 52 (all p<0.001), and increased risk of all-cause mortality after week 28 versus patients who were CID-free. FF/UMEC/VI significantly reduced CID risk versus dual therapies (all p<0.001). Conclusions: Prevention of short-term disease worsening was associated with better long-term clinical outcomes. FF/UMEC/VI reduced CID risk versus dual therapies; this effect may improve long-term prognosis in this population