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Showing papers by "Colorado State University published in 2015"


Journal ArticleDOI
28 Aug 2015-Science
TL;DR: A large-scale assessment suggests that experimental reproducibility in psychology leaves a lot to be desired, and correlational tests suggest that replication success was better predicted by the strength of original evidence than by characteristics of the original and replication teams.
Abstract: Reproducibility is a defining feature of science, but the extent to which it characterizes current research is unknown. We conducted replications of 100 experimental and correlational studies published in three psychology journals using high-powered designs and original materials when available. Replication effects were half the magnitude of original effects, representing a substantial decline. Ninety-seven percent of original studies had statistically significant results. Thirty-six percent of replications had statistically significant results; 47% of original effect sizes were in the 95% confidence interval of the replication effect size; 39% of effects were subjectively rated to have replicated the original result; and if no bias in original results is assumed, combining original and replication results left 68% with statistically significant effects. Correlational tests suggest that replication success was better predicted by the strength of original evidence than by characteristics of the original and replication teams.

5,532 citations


Journal ArticleDOI
TL;DR: The lncRNA landscape characterized here may shed light on normal biology and cancer pathogenesis and may be valuable for future biomarker development.
Abstract: Long noncoding RNAs (lncRNAs) are emerging as important regulators of tissue physiology and disease processes including cancer. To delineate genome-wide lncRNA expression, we curated 7,256 RNA sequencing (RNA-seq) libraries from tumors, normal tissues and cell lines comprising over 43 Tb of sequence from 25 independent studies. We applied ab initio assembly methodology to this data set, yielding a consensus human transcriptome of 91,013 expressed genes. Over 68% (58,648) of genes were classified as lncRNAs, of which 79% were previously unannotated. About 1% (597) of the lncRNAs harbored ultraconserved elements, and 7% (3,900) overlapped disease-associated SNPs. To prioritize lineage-specific, disease-associated lncRNA expression, we employed non-parametric differential expression testing and nominated 7,942 lineage- or cancer-associated lncRNA genes. The lncRNA landscape characterized here may shed light on normal biology and cancer pathogenesis and may be valuable for future biomarker development.

2,209 citations


Journal ArticleDOI
30 Jun 2015-eLife
TL;DR: In this paper, the authors compile the largest contemporary database for both species and pair it with relevant environmental variables predicting their global distribution, showing Aedes distributions to be the widest ever recorded; now extensive in all continents, including North America and Europe.
Abstract: Dengue and chikungunya are increasing global public health concerns due to their rapid geographical spread and increasing disease burden. Knowledge of the contemporary distribution of their shared vectors, Aedes aegypti and Aedes albopictus remains incomplete and is complicated by an ongoing range expansion fuelled by increased global trade and travel. Mapping the global distribution of these vectors and the geographical determinants of their ranges is essential for public health planning. Here we compile the largest contemporary database for both species and pair it with relevant environmental variables predicting their global distribution. We show Aedes distributions to be the widest ever recorded; now extensive in all continents, including North America and Europe. These maps will help define the spatial limits of current autochthonous transmission of dengue and chikungunya viruses. It is only with this kind of rigorous entomological baseline that we can hope to project future health impacts of these viruses.

1,416 citations



Journal ArticleDOI
TL;DR: The advances made toward understanding the basis of cancer immune evasion are discussed, the efficacy of various therapeutic measures and targets that have been developed or are being investigated to enhance tumor rejection are summarized and some natural agents and phytochemicals merit further study.

1,064 citations


Journal ArticleDOI
TL;DR: A mechanism where host-microbe interactions augment barrier function in the distal gut is highlighted, where the influences of butyrate are lost in cells lacking HIF, thus linkingbutyrate metabolism to stabilized HIF and barrier function.

1,039 citations



Journal ArticleDOI
22 Oct 2015-Nature
TL;DR: Biodiversity mainly stabilizes ecosystem productivity, and productivity-dependent ecosystem services, by increasing resistance to climate events, and restoration of biodiversity to increase it, mainly by changing the resistance of ecosystem productivity toClimate events.
Abstract: It remains unclear whether biodiversity buffers ecosystems against climate extremes, which are becoming increasingly frequent worldwide1. Early results suggested that the ecosystem productivity of diverse grassland plant communities was more resistant, changing less during drought, and more resilient, recovering more quickly after drought, than that of depauperate communities2. However, subsequent experimental tests produced mixed results3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13. Here we use data from 46 experiments that manipulated grassland plant diversity to test whether biodiversity provides resistance during and resilience after climate events. We show that biodiversity increased ecosystem resistance for a broad range of climate events, including wet or dry, moderate or extreme, and brief or prolonged events. Across all studies and climate events, the productivity of low-diversity communities with one or two species changed by approximately 50% during climate events, whereas that of high-diversity communities with 16–32 species was more resistant, changing by only approximately 25%. By a year after each climate event, ecosystem productivity had often fully recovered, or overshot, normal levels of productivity in both high- and low-diversity communities, leading to no detectable dependence of ecosystem resilience on biodiversity. Our results suggest that biodiversity mainly stabilizes ecosystem productivity, and productivity-dependent ecosystem services, by increasing resistance to climate events. Anthropogenic environmental changes that drive biodiversity loss thus seem likely to decrease ecosystem stability14, and restoration of biodiversity to increase it, mainly by changing the resistance of ecosystem productivity to climate events.

917 citations


Journal ArticleDOI
TL;DR: In this article, the authors followed the decomposition of isotopically labelled above-ground litter and its incorporation into soil organic matter over three years in a grassland in Kansas, USA, and used laboratory incubations to determine the decay rates and pool structure of litter-derived organic matter.
Abstract: Soil organic matter is a large global carbon pool. Isotopic labelling of litter in the lab and the field reveals that soil organic matter forms from labile organic compounds and litter fragments early and late in decomposition, respectively. Soil organic matter is the largest terrestrial carbon pool1. The pool size depends on the balance between formation of soil organic matter from decomposition of plant litter and its mineralization to inorganic carbon. Knowledge of soil organic matter formation remains limited2 and current C numerical models assume that stable soil organic matter is formed primarily from recalcitrant plant litter3. However, labile components of plant litter could also form mineral-stabilized soil organic matter4. Here we followed the decomposition of isotopically labelled above-ground litter and its incorporation into soil organic matter over three years in a grassland in Kansas, USA, and used laboratory incubations to determine the decay rates and pool structure of litter-derived organic matter. Early in decomposition, soil organic matter formed when non-structural compounds were lost from litter. Soil organic matter also formed at the end of decomposition, when both non-structural and structural compounds were lost at similar rates. We conclude that two pathways yield soil organic matter efficiently. A dissolved organic matter–microbial path occurs early in decomposition when litter loses mostly non-structural compounds, which are incorporated into microbial biomass at high rates, resulting in efficient soil organic matter formation. An equally efficient physical-transfer path occurs when litter fragments move into soil.

910 citations


Book ChapterDOI
01 Jan 2015
TL;DR: In the field of soil biology, the potential for an exciting, dynamic future if we understand it and apply its unifying principles can be found in the recent advances in genomic studies as discussed by the authors.
Abstract: Our science, based on a successful past, has great potential for an exciting, dynamic future if we understand it and apply its unifying principles. Advances in genomic studies are identifying multitudes of new soil biota. Automated, analytical instrumentation and modeling are characterizing soil organic matter and its dynamics. Soil nutrient transformations, plant–microbial interactions, substrate availability, and interactions with the soil matrix at the nanometer and micrometer levels must be understood. They also need to be interpreted to kilometer–megameter scales required for both global C and N cycling as well as an increased understanding of human resources. The turnover of soil organic matter, now considered to be primarily microbial products, controls nutrients such as phosphorus, sulfur, and metals. Our complex field requires a greater knowledge of physiological, ecological, and modeling concepts. These concepts must be integrated with information on soil characteristics and breakthroughs in methodology to understand the diversity, occurrence, and interactions of organisms with their environment.

881 citations


Journal ArticleDOI
TL;DR: In the first worldwide synthesis of in situ and satellite-derived lake data, this paper found that lake summer surface water temperatures rose rapidly (global mean = 0.34°C decade−1) between 1985 and 2009.
Abstract: In this first worldwide synthesis of in situ and satellite-derived lake data, we find that lake summer surface water temperatures rose rapidly (global mean = 0.34°C decade−1) between 1985 and 2009. Our analyses show that surface water warming rates are dependent on combinations of climate and local characteristics, rather than just lake location, leading to the counterintuitive result that regional consistency in lake warming is the exception, rather than the rule. The most rapidly warming lakes are widely geographically distributed, and their warming is associated with interactions among different climatic factors—from seasonally ice-covered lakes in areas where temperature and solar radiation are increasing while cloud cover is diminishing (0.72°C decade−1) to ice-free lakes experiencing increases in air temperature and solar radiation (0.53°C decade−1). The pervasive and rapid warming observed here signals the urgent need to incorporate climate impacts into vulnerability assessments and adaptation efforts for lakes.

Journal ArticleDOI
18 Aug 2015-JAMA
TL;DR: Those who had ever used e-cigarettes at baseline compared with nonusers were more likely to report initiation of combustible tobacco use over the next year, and further research is needed to understand whether this association may be causal.
Abstract: Importance Exposure to nicotine in electronic cigarettes (e-cigarettes) is becoming increasingly common among adolescents who report never having smoked combustible tobacco. Objective To evaluate whether e-cigarette use among 14-year-old adolescents who have never tried combustible tobacco is associated with risk of initiating use of 3 combustible tobacco products (ie, cigarettes, cigars, and hookah). Design, Setting, and Participants Longitudinal repeated assessment of a school-based cohort at baseline (fall 2013, 9th grade, mean age = 14.1 years) and at a 6-month follow-up (spring 2014, 9th grade) and a 12-month follow-up (fall 2014, 10th grade). Ten public high schools in Los Angeles, California, were recruited through convenience sampling. Participants were students who reported never using combustible tobacco at baseline and completed follow-up assessments at 6 or 12 months (N = 2530). At each time point, students completed self-report surveys during in-classroom data collections. Exposure Student self-report of whether he or she ever used e-cigarettes (yes or no) at baseline. Main Outcomes and Measures Six- and 12-month follow-up reports on use of any of the following tobacco products within the prior 6 months: (1) any combustible tobacco product (yes or no); (2) combustible cigarettes (yes or no), (3) cigars (yes or no); (4) hookah (yes or no); and (5) number of combustible tobacco products (range: 0-3). Results Past 6-month use of any combustible tobacco product was more frequent in baseline e-cigarette ever users (n = 222) than never users (n = 2308) at the 6-month follow-up (30.7% vs 8.1%, respectively; difference between groups in prevalence rates, 22.7% [95% CI, 16.4%-28.9%]) and at the 12-month follow-up (25.2% vs 9.3%, respectively; difference between groups, 15.9% [95% CI, 10.0%-21.8%]). Baseline e-cigarette use was associated with greater likelihood of use of any combustible tobacco product averaged across the 2 follow-up periods in the unadjusted analyses (odds ratio [OR], 4.27 [95% CI, 3.19-5.71]) and in the analyses adjusted for sociodemographic, environmental, and intrapersonal risk factors for smoking (OR, 2.73 [95% CI, 2.00-3.73]). Product-specific analyses showed that baseline e-cigarette use was positively associated with combustible cigarette (OR, 2.65 [95% CI, 1.73-4.05]), cigar (OR, 4.85 [95% CI, 3.38-6.96]), and hookah (OR, 3.25 [95% CI, 2.29-4.62]) use and with the number of different combustible products used (OR, 4.26 [95% CI, 3.16-5.74]) averaged across the 2 follow-up periods. Conclusions and Relevance Among high school students in Los Angeles, those who had ever used e-cigarettes at baseline compared with nonusers were more likely to report initiation of combustible tobacco use over the next year. Further research is needed to understand whether this association may be causal.

Journal ArticleDOI
TL;DR: This guide serves as a reference for ecologists using Bayesian methods, so that they can better understand their options and can make an informed choice that is best aligned with their goals for inference.
Abstract: The steady upward trend in the use of model selection and Bayesian methods in ecological research has made it clear that both approaches to inference are important for modern analysis of models and data. However, in teaching Bayesian methods and in working with our research colleagues, we have noticed a general dissatisfaction with the available literature on Bayesian model selection and multimodel inference. Students and researchers new to Bayesian methods quickly find that the published advice on model selection is often preferential in its treatment of options for analysis, frequently advocating one particular method above others. The recent appearance of many articles and textbooks on Bayesian modeling has provided welcome background on relevant approaches to model selection in the Bayesian framework, but most of these are either very narrowly focused in scope or inaccessible to ecologists. Moreover, the methodological details of Bayesian model selection approaches are spread thinly throughout the literature, appearing in journals from many different fields. Our aim with this guide is to condense the large body of literature on Bayesian approaches to model selection and multimodel inference and present it specifically for quantitative ecologists as neutrally as possible. We also bring to light a few important and fundamental concepts relating directly to model selection that seem to have gone unnoticed in the ecological literature. Throughout, we provide only a minimal discussion of philosophy, preferring instead to examine the breadth of approaches as well as their practical advantages and disadvantages. This guide serves as a reference for ecologists using Bayesian methods, so that they can better understand their options and can make an informed choice that is best aligned with their goals for inference.

Journal ArticleDOI
A. Aab1, P. Abreu2, Marco Aglietta3, Marco Aglietta4  +640 moreInstitutions (64)
TL;DR: The Pierre Auger Observatory as mentioned in this paper, the world's largest cosmic ray observatory, has been in successful operation since completion in 2008 and has recorded data from an exposure exceeding 40,000 km$^2$ sr yr.
Abstract: The Pierre Auger Observatory, located on a vast, high plain in western Argentina, is the world's largest cosmic ray observatory. The objectives of the Observatory are to probe the origin and characteristics of cosmic rays above $10^{17}$ eV and to study the interactions of these, the most energetic particles observed in nature. The Auger design features an array of 1660 water-Cherenkov particle detector stations spread over 3000 km$^2$ overlooked by 24 air fluorescence telescopes. In addition, three high elevation fluorescence telescopes overlook a 23.5 km$^2$, 61 detector infill array. The Observatory has been in successful operation since completion in 2008 and has recorded data from an exposure exceeding 40,000 km$^2$ sr yr. This paper describes the design and performance of the detectors, related subsystems and infrastructure that make up the Auger Observatory.

Journal ArticleDOI
TL;DR: Genetic rescue is a tool that can stem biodiversity loss more than has been appreciated, provides population resilience, and will become increasingly useful if integrated with molecular advances in population genomics.
Abstract: Genetic rescue can increase the fitness of small, imperiled populations via immigration. A suite of studies from the past decade highlights the value of genetic rescue in increasing population fitness. Nonetheless, genetic rescue has not been widely applied to conserve many of the threatened populations that it could benefit. In this review, we highlight recent studies of genetic rescue and place it in the larger context of theoretical and empirical developments in evolutionary and conservation biology. We also propose directions to help shape future research on genetic rescue. Genetic rescue is a tool that can stem biodiversity loss more than has been appreciated, provides population resilience, and will become increasingly useful if integrated with molecular advances in population genomics.

Journal ArticleDOI
TL;DR: In this paper, the authors organize the last 10 years of empirical work around 10 main themes: research design, team inputs, team virtuality, technology, globalization, leadership, mediators and moderators, trust, outcomes, and ways to enhance virtual team success.


Journal ArticleDOI
03 Dec 2015-Nature
TL;DR: Current research indicates that soil biodiversity can be maintained and partially restored if managed sustainably, and promotes the ecological complexity and robustness of soil biodiversity through improved management practices.
Abstract: Soil biodiversity is increasingly recognized as providing benefits to human health because it can suppress disease-causing soil organisms and provide clean air, water and food. Poor land-management practices and environmental change are, however, affecting belowground communities globally, and the resulting declines in soil biodiversity reduce and impair these benefits. Importantly, current research indicates that soil biodiversity can be maintained and partially restored if managed sustainably. Promoting the ecological complexity and robustness of soil biodiversity through improved management practices represents an underutilized resource with the ability to improve human health.

Journal ArticleDOI
17 Sep 2015-Nature
TL;DR: The results support models predicting that adaptive plasticity constrains evolution, whereas non-adaptive plasticity potentiates evolution by increasing the strength of directional selection, and suggest that it may be an important mechanism that predicts evolutionary responses to new environments.
Abstract: Phenotypic plasticity is the capacity for an individual genotype to produce different phenotypes in response to environmental variation. Most traits are plastic, but the degree to which plasticity is adaptive or non-adaptive depends on whether environmentally induced phenotypes are closer or further away from the local optimum. Existing theories make conflicting predictions about whether plasticity constrains or facilitates adaptive evolution. Debate persists because few empirical studies have tested the relationship between initial plasticity and subsequent adaptive evolution in natural populations. Here we show that the direction of plasticity in gene expression is generally opposite to the direction of adaptive evolution. We experimentally transplanted Trinidadian guppies (Poecilia reticulata) adapted to living with cichlid predators to cichlid-free streams, and tested for evolutionary divergence in brain gene expression patterns after three to four generations. We find 135 transcripts that evolved parallel changes in expression within the replicated introduction populations. These changes are in the same direction exhibited in a native cichlid-free population, suggesting rapid adaptive evolution. We find 89% of these transcripts exhibited non-adaptive plastic changes in expression when the source population was reared in the absence of predators, as they are in the opposite direction to the evolved changes. By contrast, the remaining transcripts exhibiting adaptive plasticity show reduced population divergence. Furthermore, the most plastic transcripts in the source population evolved reduced plasticity in the introduction populations, suggesting strong selection against non-adaptive plasticity. These results support models predicting that adaptive plasticity constrains evolution, whereas non-adaptive plasticity potentiates evolution by increasing the strength of directional selection. The role of non-adaptive plasticity in evolution has received relatively little attention; however, our results suggest that it may be an important mechanism that predicts evolutionary responses to new environments.

Journal ArticleDOI
TL;DR: Before the real-world conservation potential of genomic research can be realized, current infrastructures need to be modified, methods must mature, analytical pipelines need to been developed, and successful case studies must be disseminated to practitioners.
Abstract: The global loss of biodiversity continues at an alarming rate. Genomic approaches have been suggested as a promising tool for conservation practice as scaling up to genome-wide data can improve traditional conservation genetic inferences and provide qualitatively novel insights. However, the generation of genomic data and subsequent analyses and interpretations remain challenging and largely confined to academic research in ecology and evolution. This generates a gap between basic research and applicable solutions for conservation managers faced with multifaceted problems. Before the real-world conservation potential of genomic research can be realized, we suggest that current infrastructures need to be modified, methods must mature, analytical pipelines need to be developed, and successful case studies must be disseminated to practitioners.

Journal ArticleDOI
18 Feb 2015-Heredity
TL;DR: It is advocated for the view that relaxed selection and variable selection intensities are likely more important constraints to the evolution of plasticity than the costs of Plasticity, and opportunities to offset costs of phenotypes through ontogeny, amelioration of phenotypic costs across environments, and the condition-dependent hypothesis are examined.
Abstract: Phenotypic plasticity is ubiquitous and generally regarded as a key mechanism for enabling organisms to survive in the face of environmental change Because no organism is infinitely or ideally plastic, theory suggests that there must be limits (for example, the lack of ability to produce an optimal trait) to the evolution of phenotypic plasticity, or that plasticity may have inherent significant costs Yet numerous experimental studies have not detected widespread costs Explicitly differentiating plasticity costs from phenotype costs, we re-evaluate fundamental questions of the limits to the evolution of plasticity and of generalists vs specialists We advocate for the view that relaxed selection and variable selection intensities are likely more important constraints to the evolution of plasticity than the costs of plasticity Some forms of plasticity, such as learning, may be inherently costly In addition, we examine opportunities to offset costs of phenotypes through ontogeny, amelioration of phenotypic costs across environments, and the condition-dependent hypothesis We propose avenues of further inquiry in the limits of plasticity using new and classic methods of ecological parameterization, phylogenetics and omics in the context of answering questions on the constraints of plasticity Given plasticity's key role in coping with environmental change, approaches spanning the spectrum from applied to basic will greatly enrich our understanding of the evolution of plasticity and resolve our understanding of limits

Journal ArticleDOI
07 May 2015-Nature
TL;DR: This work shows that the waves begin as sinusoidal disturbances rather than arising from sharp hydraulic phenomena, and reveals the existence of >200-metre-high breaking internal waves in the region of generation that give rise to turbulence levels >10,000 times that in the open ocean.
Abstract: Internal oceanic waves are subsurface gravity waves that can be enormous and travel thousands of kilometres before breaking but they are difficult to study; here observations of such waves in the South China Sea reveal their formation mechanism, extreme turbulence, relationship to the Kuroshio Current and energy budget. Internal waves are the underwater version of more familiar surface waves. They can be enormous and travel thousands of kilometres before breaking. The South China Sea is known to be home to the largest internal waves in the world's oceans, but their size, generation mechanisms and role in the regional energy budget are unknown. Matthew Alford and colleagues now present the results from the IWISE observational campaign and reveal that internal waves more than 200 metres high break in the South China Sea and create turbulence that is orders of magnitude larger than in the open ocean, and that wave formation is influenced by the Kuroshio current. These results now allow for a complete energy budget of the South China Sea, and for a more accurate incorporation of internal waves into climate models. Internal gravity waves, the subsurface analogue of the familiar surface gravity waves that break on beaches, are ubiquitous in the ocean. Because of their strong vertical and horizontal currents, and the turbulent mixing caused by their breaking, they affect a panoply of ocean processes, such as the supply of nutrients for photosynthesis1, sediment and pollutant transport2 and acoustic transmission3; they also pose hazards for man-made structures in the ocean4. Generated primarily by the wind and the tides, internal waves can travel thousands of kilometres from their sources before breaking5, making it challenging to observe them and to include them in numerical climate models, which are sensitive to their effects6,7. For over a decade, studies8,9,10,11 have targeted the South China Sea, where the oceans’ most powerful known internal waves are generated in the Luzon Strait and steepen dramatically as they propagate west. Confusion has persisted regarding their mechanism of generation, variability and energy budget, however, owing to the lack of in situ data from the Luzon Strait, where extreme flow conditions make measurements difficult. Here we use new observations and numerical models to (1) show that the waves begin as sinusoidal disturbances rather than arising from sharp hydraulic phenomena, (2) reveal the existence of >200-metre-high breaking internal waves in the region of generation that give rise to turbulence levels >10,000 times that in the open ocean, (3) determine that the Kuroshio western boundary current noticeably refracts the internal wave field emanating from the Luzon Strait, and (4) demonstrate a factor-of-two agreement between modelled and observed energy fluxes, which allows us to produce an observationally supported energy budget of the region. Together, these findings give a cradle-to-grave picture of internal waves on a basin scale, which will support further improvements of their representation in numerical climate predictions.

Journal ArticleDOI
TL;DR: Novel ways by which researchers can apply and interpret the Bradford Hill criteria when considering data gathered using modern molecular techniques, such as epigenetics, biomarkers, mechanistic toxicology, and genotoxicology are discussed.
Abstract: In 1965, Sir Austin Bradford Hill published nine “viewpoints” to help determine if observed epidemiologic associations are causal. Since then, the “Bradford Hill Criteria” have become the most frequently cited framework for causal inference in epidemiologic studies. However, when Hill published his causal guidelines—just 12 years after the double-helix model for DNA was first suggested and 25 years before the Human Genome Project began—disease causation was understood on a more elementary level than it is today. Advancements in genetics, molecular biology, toxicology, exposure science, and statistics have increased our analytical capabilities for exploring potential cause-and-effect relationships, and have resulted in a greater understanding of the complexity behind human disease onset and progression. These additional tools for causal inference necessitate a re-evaluation of how each Bradford Hill criterion should be interpreted when considering a variety of data types beyond classic epidemiology studies. Herein, we explore the implications of data integration on the interpretation and application of the criteria. Using examples of recently discovered exposure–response associations in human disease, we discuss novel ways by which researchers can apply and interpret the Bradford Hill criteria when considering data gathered using modern molecular techniques, such as epigenetics, biomarkers, mechanistic toxicology, and genotoxicology.

Journal ArticleDOI
TL;DR: It is suggested that multiple-nutrient constraints must be considered when assessing the ecosystem-scale consequences of nutrient enrichment, and significant variations in the type and degree of nutrient limitation are pointed to.
Abstract: Terrestrial ecosystem productivity is widely accepted to be nutrient limited(1). Although nitrogen (N) is deemed a key determinant of aboveground net primary production (ANPP) 2,3, the prevalence of co-limitation by N and phosphorus (P) is increasingly recognized(4-8). However, the extent to which terrestrial productivity is co-limited by nutrients other than N and P has remained unclear. Here, we report results from a standardized factorial nutrient addition experiment, in which we added N, P and potassium (K) combined with a selection of micronutrients (K+mu), alone or in concert, to 42 grassland sites spanning five continents, and monitored ANPP. Nutrient availability limited productivity at 31 of the 42 grassland sites. And pairwise combinations of N, P, and K+mu co-limited ANPP at 29 of the sites. Nitrogen limitation peaked in cool, high latitude sites. Our findings highlight the importance of less studied nutrients, such as K and micronutrients, for grassland productivity, and point to significant variations in the type and degree of nutrient limitation. We suggest that multiple-nutrient constraints must be considered when assessing the ecosystem-scale consequences of nutrient enrichment.

Journal ArticleDOI
TL;DR: The authors argue that one point of confusion has arisen due to ambiguities in the exact question being posed and argue that framing the discussion around the three questions: Can it?, Has it?, and Will it? provides insight into the common themes emerging in the literature as well as highlights the challenges ahead.
Abstract: The Arctic lower atmosphere has warmed more rapidly than that of the globe as a whole, and this has been accompanied by unprecedented sea ice melt. Such large environmental changes are already having profound impacts on the flora, fauna, and inhabitants of the Arctic region. An open question, however, is whether these Arctic changes have an effect on the jet-stream and thereby influence weather patterns farther south. This broad question has recently received a lot of scientific and media attention, but conclusions appear contradictory rather than consensual. We argue that one point of confusion has arisen due to ambiguities in the exact question being posed. In this study, we frame our inquiries around three distinct questions: Can Arctic warming influence the midlatitude jet-stream? Has Arctic warming significantly influenced the midlatitude jet-stream? Will Arctic warming significantly influence the midlatitude jet-stream? We argue that framing the discussion around the three questions: Can it?, Has it?, and Will it? provides insight into the common themes emerging in the literature as well as highlights the challenges ahead. WIREs Clim Change 2015, 6:277–286. doi: 10.1002/wcc.337 For further resources related to this article, please visit the WIREs website. Conflict of interest: The authors have declared no conflicts of interest for this article.

Journal ArticleDOI
TL;DR: In this paper, the authors present a database of globally distributed stomatal conductance (g(s) obtained in the field for a wide range of plant functional types (PFTs) and biomes.
Abstract: Stomatal conductance (g(s)) is a key land-surface attribute as it links transpiration, the dominant component of global land evapotranspiration, and photosynthesis, the driving force of the global carbon cycle. Despite the pivotal role of g(s) in predictions of global water and carbon cycle changes, a global-scale database and an associated globally applicable model of g(s) that allow predictions of stomatal behaviour are lacking. Here, we present a database of globally distributed g(s) obtained in the field for a wide range of plant functional types (PFTs) and biomes. We find that stomatal behaviour differs among PFTs according to their marginal carbon cost of water use, as predicted by the theory underpinning the optimal stomatal model(1) and the leaf and wood economics spectrum(2,3). We also demonstrate a global relationship with climate. These findin g(s) provide a robust theoretical framework for understanding and predicting the behaviour of g(s) across biomes and across PFTs that can be applied to regional, continental and global-scale modelling of ecosystem productivity, energy balance and ecohydrological processes in a future changing climate.

Proceedings Article
27 Dec 2015
TL;DR: This work uses the infinite population models of simple genetic algorithms to study how Island Models can track multiple search trajectories and introduces a simple model for better understanding when Island Model genetic algorithms may have an advantage when processing some test problems.
Abstract: Parallel Genetic Algorithms have often been reported to yield better performance than Genetic Algorithms which use a single large panmictic population. In the case of the Island Model genetic algorithm, it has been informally argued that having multiple subpopulations helps to preserve genetic diversity, since each island can potentially follow a different search trajectory through the search space. It is also possible that since linearly separable problems are often used to test Genetic Algorithms, that Island Models may simply be particularly well suited to exploiting the separable nature of the test problems. We explore this possibility by using the infinite population models of simple genetic algorithms to study how Island Models can track multiple search trajectories. We also introduce a simple model for better understanding when Island Model genetic algorithms may have an advantage when processing some test problems. We provide empirical results for both linearly separable and nonseparable parameter optimization functions.

Journal ArticleDOI
TL;DR: Although selection at the level of the symbiotic community, or hologenome, occurs in some cases, it should not be accepted as the null hypothesis for explaining features of host–symbiont associations.
Abstract: With the increasing appreciation for the crucial roles that microbial symbionts play in the development and fitness of plant and animal hosts, there has been a recent push to interpret evolution through the lens of the “hologenome”—the collective genomic content of a host and its microbiome. But how symbionts evolve and, particularly, whether they undergo natural selection to benefit hosts are complex issues that are associated with several misconceptions about evolutionary processes in host-associated microbial communities. Microorganisms can have intimate, ancient, and/or mutualistic associations with hosts without having undergone natural selection to benefit hosts. Likewise, observing host-specific microbial community composition or greater community similarity among more closely related hosts does not imply that symbionts have coevolved with hosts, let alone that they have evolved for the benefit of the host. Although selection at the level of the symbiotic community, or hologenome, occurs in some cases, it should not be accepted as the null hypothesis for explaining features of host–symbiont associations.

Journal ArticleDOI
TL;DR: For the first time, a feasibility study of D2D for ITS is carried out based on both the features of D1D and the nature of vehicular networks to demonstrate the promising potential of this technology and propose novel remedies necessary to make D 2D technology practical as well as beneficial for ITS.
Abstract: Intelligent transportation systems (ITS) are becoming a crucial component of our society, whereas reliable and efficient vehicular communications consist of a key enabler of a well-functioning ITS. To meet a wide variety of ITS application needs, vehicular-to-vehicular and vehicular-to-infrastructure communications have to be jointly considered, configured, and optimized. The effective and efficient coexistence and cooperation of the two give rise to a dynamic spectrum management problem. One recently emerged and rapidly adopted solution of a similar problem in cellular networks is the so-termed device-to-device (D2D) communications. Its potential in the vehicular scenarios with unique challenges, however, has not been thoroughly investigated to date. In this paper, we for the first time carry out a feasibility study of D2D for ITS based on both the features of D2D and the nature of vehicular networks. In addition to demonstrating the promising potential of this technology, we will also propose novel remedies necessary to make D2D technology practical as well as beneficial for ITS.

Journal ArticleDOI
TL;DR: In this article, a global model evaluation project on vertical structure and physical processes of the Madden-Julian oscillation (MJO) was coordinated to reduce deficiencies in representing the MJO in general circulation models.
Abstract: Aimed at reducing deficiencies in representing the Madden-Julian oscillation (MJO) in general circulation models (GCMs), a global model evaluation project on vertical structure and physical processes of the MJO was coordinated. In this paper, results from the climate simulation component of this project are reported. It is shown that the MJO remains a great challenge in these latest generation GCMs. The systematic eastward propagation of the MJO is only well simulated in about one fourth of the total participating models. The observed vertical westward tilt with altitude of the MJO is well simulated in good MJO models but not in the poor ones. Damped Kelvin wave responses to the east of convection in the lower troposphere could be responsible for the missing MJO preconditioning process in these poor MJO models. Several process-oriented diagnostics were conducted to discriminate key processes for realistic MJO simulations. While large-scale rainfall partition and low-level mean zonal winds over the Indo-Pacific in a model are not found to be closely associated with its MJO skill, two metrics, including the low-level relative humidity difference between high- and low-rain events and seasonal mean gross moist stability, exhibit statistically significant correlations with the MJO performance. It is further indicated that increased cloud-radiative feedback tends to be associated with reduced amplitude of intraseasonal variability, which is incompatible with the radiative instability theory previously proposed for the MJO. Results in this study confirm that inclusion of air-sea interaction can lead to significant improvement in simulating the MJO.