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Search Results: 1 - 10 of 90438 matches for " PHILIP W RUNDEL "
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Land Use Compounds Habitat Losses under Projected Climate Change in a Threatened California Ecosystem
Erin Coulter Riordan, Philip W. Rundel
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0086487
Abstract: Given the rapidly growing human population in mediterranean-climate systems, land use may pose a more immediate threat to biodiversity than climate change this century, yet few studies address the relative future impacts of both drivers. We assess spatial and temporal patterns of projected 21st century land use and climate change on California sage scrub (CSS), a plant association of considerable diversity and threatened status in the mediterranean-climate California Floristic Province. Using a species distribution modeling approach combined with spatially-explicit land use projections, we model habitat loss for 20 dominant shrub species under unlimited and no dispersal scenarios at two time intervals (early and late century) in two ecoregions in California (Central Coast and South Coast). Overall, projected climate change impacts were highly variable across CSS species and heavily dependent on dispersal assumptions. Projected anthropogenic land use drove greater relative habitat losses compared to projected climate change in many species. This pattern was only significant under assumptions of unlimited dispersal, however, where considerable climate-driven habitat gains offset some concurrent climate-driven habitat losses. Additionally, some of the habitat gained with projected climate change overlapped with projected land use. Most species showed potential northern habitat expansion and southern habitat contraction due to projected climate change, resulting in sharply contrasting patterns of impact between Central and South Coast Ecoregions. In the Central Coast, dispersal could play an important role moderating losses from both climate change and land use. In contrast, high geographic overlap in habitat losses driven by projected climate change and projected land use in the South Coast underscores the potential for compounding negative impacts of both drivers. Limiting habitat conversion may be a broadly beneficial strategy under climate change. We emphasize the importance of addressing both drivers in conservation and resource management planning.
Plant community variation across a puna landscape in the Chilean Andes
LAMBRINOS,JOHN G; KLEIER,CATHERINE C; RUNDEL,PHILIP W;
Revista chilena de historia natural , 2006, DOI: 10.4067/S0716-078X2006000200009
Abstract: we describe patterns of plant species and growth form abundance in the puna vegetation of parque nacional lauca, chile. at more than 4,300 m, the extreme habitat of the study site supported relatively few species. these few species, however, represented a diverse array of growth forms that were organized with respect to distinct environmental gradients. both species richness and growth form diversity increased with the degree of habitat rockiness and on more xeric north and east facing slopes. these xeric, rocky sites supported the greatest overall abundance of cushion forms. less rocky sites with more soil development supported a greater abundance of tussock grass and shrub forms. congeneric species occupied distinct microhabitats and were often markedly divergent in growth form. these patterns suggest that water and thermal stress are critical forces shaping functional form as well as community organization in the high andean puna
Plant community variation across a puna landscape in the Chilean Andes Variación en la comunidad vegetal de un paisaje de puna en los Andes chilenos
JOHN G LAMBRINOS,CATHERINE C KLEIER,PHILIP W RUNDEL
Revista chilena de historia natural , 2006,
Abstract: We describe patterns of plant species and growth form abundance in the puna vegetation of Parque Nacional Lauca, Chile. At more than 4,300 m, the extreme habitat of the study site supported relatively few species. These few species, however, represented a diverse array of growth forms that were organized with respect to distinct environmental gradients. Both species richness and growth form diversity increased with the degree of habitat rockiness and on more xeric north and east facing slopes. These xeric, rocky sites supported the greatest overall abundance of cushion forms. Less rocky sites with more soil development supported a greater abundance of tussock grass and shrub forms. Congeneric species occupied distinct microhabitats and were often markedly divergent in growth form. These patterns suggest that water and thermal stress are critical forces shaping functional form as well as community organization in the high Andean puna Describimos los patrones de abundancia de las especies vegetales y las formas de vida en la vegetación de puna en el Parque Nacional Lauca, Chile. A una altitud que excede los 4.300 m de altitud, el hábitat extremo de nuestro sitio de estudio presenta relativamente pocas especies. Dichas especies, sin embargo, representan un arreglo diverso de formas de vida organizadas con respecto a distintos gradientes ambientales. Tanto la riqueza de especies como el hábito de crecimiento aumentaron en los suelos más rocosos y en las pendientes expuestas al norte y al este, cuya vegetación es más xerófila. Dichos sitios presentaron la mayor abundancia en formas de cojines. Los sitios menos rocosos con un suelo más desarrollado presentaron una mayor abundancia de pastos y arbustos. Distintos microhábitats fueron ocupados por especies congénericas que con frecuencia divergieron en su hábito de crecimiento. Los patrones observados sugieren que el agua y el estrés térmico son fuerzas críticas que moldean la forma funcional de las especies vegetales así como la organización de las comunidades de plantas en la puna altoandina
Population dynamics and orientation of the central Andean cushion Azorella compacta
Catherine Kleier,Tim Trenary,Eric A Graham,Philip W Rundel
PeerJ , 2015, DOI: 10.7287/peerj.preprints.607v1
Abstract: Azorella compacta (llareta; Apiaceae), a large woody cushion plant, is a remarkable species forming dense cushions and characterizing the high elevation rocky slopes of the central Andean Altiplano. Field studies of an elevational gradient of A. compacta within Lauca National Park in northern Chile found a reverse J-shape distribution of size classes of individuals with abundant small plants at all elevations. A new elevational limit for A. compacta was found at 5250 m. A series of cushions marked 14 years earlier showed either slight shrinkage or small degrees of growth up to 2.2 cm yr-1. Despite their irregularity in growth, cushions of A. compacta show a strong orientation, centered on a north-facing aspect and angle of about 20o from horizontal. This exposure to maximize solar irradiance closely matches previous observations of a population favoring north-facing slopes at a similar angle. Populations of A. compacta appear to be stable, or even expanding, with young plants abundant and recolonization of disturbed habitats.
Comparative Patterns of Plant Invasions in the Mediterranean Biome
Margarita Arianoutsou, Pinelopi Delipetrou, Montserrat Vilà, Panayiotis G. Dimitrakopoulos, Laura Celesti-Grapow, Grant Wardell-Johnson, Lesley Henderson, Nicol Fuentes, Eduardo Ugarte-Mendes, Philip W. Rundel
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0079174
Abstract: The objective of this work was to compare and contrast the patterns of alien plant invasions in the world’s five mediterranean-climate regions (MCRs). We expected landscape age and disturbance history to have bearing on levels of invasion. We assembled a database on naturalized alien plant taxa occurring in natural and semi-natural terrestrial habitats of all five regions (specifically Spain, Italy, Greece and Cyprus from the Mediterranean Basin, California, central Chile, the Cape Region of South Africa and Southwestern - SW Australia). We used multivariate (hierarchical clustering and NMDS ordination) trait and habitat analysis to compare characteristics of regions, taxa and habitats across the mediterranean biome. Our database included 1627 naturalized species with an overall low taxonomic similarity among the five MCRs. Herbaceous perennials were the most frequent taxa, with SW Australia exhibiting both the highest numbers of naturalized species and the highest taxonomic similarity (homogenization) among habitats, and the Mediterranean Basin the lowest. Low stress and highly disturbed habitats had the highest frequency of invasion and homogenization in all regions, and high natural stress habitats the lowest, while taxonomic similarity was higher among different habitats in each region than among regions. Our analysis is the first to describe patterns of species characteristics and habitat vulnerability for a single biome. We have shown that a broad niche (i.e. more than one habitat) is typical of naturalized plant species, regardless of their geographical area of origin, leading to potential for high homogenization within each region. Habitats of the Mediterranean Basin are apparently the most resistant to plant invasion, possibly because their landscapes are generally of relatively recent origin, but with a more gradual exposure to human intervention over a longer period.
Search for the eta-mesic Helium bound state with the WASA-at-COSY facility
M. Skurzok,W. Krzemien,O. Rundel,P. Moskal
Physics , 2015,
Abstract: We performed a search for 4He-eta bound state with high statistics and high acceptance with the WASA-at-COSY facility using a ramped beam technique. The signature of eta-mesic nuclei is searched for in dd -> 3Henpi0 and dd -> 3Heppi- reactions by the measurement of the excitation functions in the vicinity of the {\eta} production threshold. This paper presents the experimental method and the preliminary results of the data analysis for dd -> 3Henpi0 process.
Predicting Polylepis distribution: vulnerable and increasingly important Andean woodlands Prediciendo la distribución de Polylepis: bosques Andinos vulnerables y cada vez más importantes
Brian R. Zutta,Phillip W. Rundel,Sassan Saatchi,Jorge D. Casana
Revista Peruana de Biología , 2012,
Abstract: Polylepis woodlands are a vital resource for preserving biodiversity and hydrological functions, which will be altered by climate change and challenge the sustainability of local human communities. However, these highaltitude Andean ecosystems are becoming increasingly vulnerable due to anthropogenic pressure including fragmentation, deforestation and the increase in livestock. Predicting the distribution of native woodlands has become increasingly important to counteract the negative effects of climate change through reforestation and conservation. The objective of this study was to develop and analyze the distribution models of two species that form extensive woodlands along the Andes, namely Polylepis sericea and P. weberbaueri. This study utilized the program Maxent, climate and remotely sensed environmental layers at 1 km resolution. The predicted distribution model for P. sericea indicated that the species could be located in a variety of habitats along the Andean Cordillera, while P. weberbaueri was restricted to the high elevations of southern Peru and Bolivia. For both species, elevation and temperature metrics were the most significant factors for predicted distribution. Further model refinement of Polylepis and other Andean species using increasingly available satellite data demonstrate the potential to help define areas of diversity and improve conservation strategies for the Andes. Los bosques de Polylepis son recursos vitales para la conservación de la biodiversidad y funciones hidrológicas, la cual se verá alterada por el cambio climático a nivel mundial desafiando la sostenibilidad de las comunidades locales. Sin embargo, estos ecosistemas andinos de gran altitud son cada vez más vulnerables debido a la presión antropogénica como la fragmentación, deforestación y el incremento en el ganado. La importancia para predecir la distribución de bosques nativos ha aumentado para contrarrestar los efectos negativos del cambio climático a través de la conservación y la reforestación. El objetivo de este estudio fue desarrollar y analizar los modelos de distribución de dos especies, Polylepis sericea y P. besseri, que forman bosques extensos a lo largo de los Andes. Este estudio utilizó el programa Maxent, el clima y capas ambientales de una resolución de 1 km. El modelo de distribución previsto para P. sericea indica que la especie podría estar situada en una variedad de hábitats a lo largo de la Cordillera de los Andes, mientras que P. besseri se limitaba a las grandes alturas del sur de Perú y Bolivia. Para ambas especies, los metros de elevació
High order explicit Runge-Kutta pairs for ephemerides of the Solar System and the Moon
Philip W. Sharp
Advances in Decision Sciences , 2000, DOI: 10.1155/s1173912600000146
Abstract: Numerically integrated ephemerides of the Solar System and the Moon require very accurate integrations of systems of second order ordinary differential equations. We present a new family of 8-9 explicit Runge-Kutta pairs and assess the performance of two new 8-9 pairs on the equations used to create the ephemeris DE102. Part of this work is the introduction of these equations as a test problem for integrators of initial value ordinary differential equations.
Models of the human metabolic network: aiming to reconcile metabolomics and genomics
Philip W Kuchel
Genome Medicine , 2010, DOI: 10.1186/gm167
Abstract: There are approximately ten times as many expressed genes (proteins) as there are different metabolites in most cells. Biochemical analysis of cells has been the art of the possible; you know about what you can detect. In the past, assays have largely focused on small organic (bio)molecules analyzed by colorimetry or spectrophotometry. The genome projects have revealed a completely different data set from that of classical metabolic biochemistry, and a totally different perspective on metabolism. Two different perspectives, as neatly presented by Gerrard et al. [1], are presented in Figure 1; note how the genome draws attention to the proteins, many of which are enzymes, but many of which are not. So, measuring the concentrations of metabolites as we do in clinical biochemistry only indirectly reports on which of the enzymes, control proteins, or structural proteins are at fault in a case of chemical poisoning, drug side-effects, or in an inborn error of metabolism.Figure 2 reminds us that there are at least 5,000 different enzymes, with as many metabolites in pathways that interconvert molecules in well-ordered sequences of reactions in an 'average' human cell. Figure 3 emphasizes that any one metabolite (denoted γ in this case) can modulate reactions from within its own pathway, across pathways, and even alters expression of genes and translation of messenger RNA into protein. An enzyme can also serve to modulate the activity of another enzyme, and affect its level of expression. Cations, including H+, and extraneous compounds such as xenobiotics (H in Figure 3), also exert effects on enzymes and metabolites that potentially affect fluxes through multiple pathways.A modern and emerging form of advanced diagnostic strategy in chemical pathology is metabolomics, also called metabonomics [2]. There is a semantic and operational difference between these 'omics'. The former is the study of an extensive collection of metabolites present in a cell or tissue under a parti
Verbal autopsy and global mortality statistics: if not now, then when?
Philip W Setel
Population Health Metrics , 2011, DOI: 10.1186/1478-7954-9-20
Abstract: In 2000, the state of knowledge on verbal autopsy (VA, a term that covers the design and application of postmortem caregiver interviews, procedures for assigning one or more probable causes of death, and the aggregation and tabulation of population-level mortality statistics based on this data source) centered on a small group of demographers and epidemiologists, many of whom ran intervention trials in various demographic surveillance sites. Almost the entire community of scholarship was on a first-name basis; we could easily gather in a medium-sized conference room, and any of our students or colleagues could become an expert on the VA literature with a week or two of focused reading. Throughout this period, those who remained dedicated to maximizing the potential of VA made steady progress. Yet throughout, a deep and sometimes reflexive scepticism remained that VA could ever really deliver the goods as a reliable measurement tool. The persistent shortcomings in cause of death data, and reluctance to widely embrace VA outside of demographic surveillance sites, have forced the global health community to make do with sources of limited coverage and dubious quality and consistency, applying increasingly complex statistical analyses to "correct" for all manner of bias and nonsampling error.The papers in this issue of Population Health Metrics go far in addressing central questions about how much VA can contribute to our measurement of health and health impact. How close to truth can VA ever get? How good is "good enough" for decision-making? Is our putative "gold standard" of medically certified deaths all that robust to begin with - in industrialized or lower-income countries? Can we make the production of VA data better, faster, and cheaper? What alternatives to demographic surveillance systems exist to permit the collection of mortality data from large, representative population samples? Can VA detect disease outbreaks, the population effects of antiretroviral thera
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