The Experts below are selected from a list of 501603 Experts worldwide ranked by ideXlab platform
S N Longmore - One of the best experts on this subject based on the ideXlab platform.
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an uncertainty principle for star formation i why galactic star formation relations break down below a certain Spatial Scale
Monthly Notices of the Royal Astronomical Society, 2014Co-Authors: J Diederik M Kruijssen, S N LongmoreAbstract:Galactic scaling relations between the (surface densities of) the gas mass and the star formation (SF) rate are known to develop substantial scatter or even change form when considered below a certain Spatial Scale. We quantify how this behaviour should be expected due to the incomplete statistical sampling of independent star-forming regions. Other included limiting factors are the incomplete sampling of SF tracers from the stellar initial mass function and the Spatial drift between gas and stars. We present a simple uncertainty principle for SF, which can be used to predict and interpret the failure of galactic SF relations on small Spatial Scales. This uncertainty principle explains how the scatter of SF relations depends on the Spatial Scale and predicts a Scale-dependent bias of the gas depletion time-Scale when centring an aperture on gas or SF tracer peaks. We show how the scatter and bias are sensitive to the physical size and time-Scales involved in the SF process (such as its duration or the molecular cloud lifetime), and illustrate how our formalism provides a powerful tool to constrain these largely unknown quantities. Thanks to its general form, the uncertainty principle can also be applied to other astrophysical systems, e.g. addressing the time evolution of star-forming cores, protoplanetary discs or galaxies and their nuclei.
Gerard Balent - One of the best experts on this subject based on the ideXlab platform.
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Is there a solution to the Spatial Scale mismatch between ecological processes and agricultural management?
2010Co-Authors: Céline Pelosi, Jacques Baudry, Michel Goulard, Gerard BalentAbstract:Is there a solution to the Spatial Scale mismatch between ecological processes and agricultural management?. Is What Humans Do Natural? 2010 US-IALE Twenty-fifth Anniversary Symposium
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The Spatial Scale mismatch between ecological processes and agricultural management: Do difficulties come from underlying theoretical frameworks?
Agriculture Ecosystems and Environment, 2010Co-Authors: Céline Pelosi, Michel Goulard, Gerard BalentAbstract:The difficulty to Spatially link the process levels of organizing agricultural management with those of investigating biodiversity preservation creates a Spatial Scale mismatch which affects the effectiveness of agri-environmental policies. Starting from a literature review this study offers a panorama of the ways authors approach Spatial Scale mismatch and the solutions they propose to resolve it. We made the hypothesis that the authors rely, sometimes implicitly, on theoretical frameworks to propose their solutions. Only 15% of the references in which the authors examine the question of Spatial Scale mismatch show a systemic approach to the question, taking into account simultaneously ecological and managerial processes. We identify two major types of theory linked to the solutions proposed by the authors: those that refer to “multi-Scale/multi-level” management for which hierarchy theory and landscape ecology are referred to explicitly; those that imply collective management and coordination, which refer to the theory of organization of biological systems and to social–ecological systems. These theories and their properties imply a change of paradigm which could allow for a better articulation between biodiversity and agricultural management. Based on this literature search we suggest that the problems in resolving Spatial Scale mismatch could be due to the fact that: (1) authors generally do not have a systemic approach since they consider ecological and managerial processes separately, and (2) terminology and theoretical frameworks are used inaccurately. While there are socio-economic difficulties in the implementation of biodiversity conservation programs in agricultural zones, there are also shortcomings linked to the theoretical representation framework. These shortcomings may hinder the articulation between ecological and managerial processes, this is why approaches are suggested here allowing for a better match between the representations of ecological and managerial processes
J Diederik M Kruijssen - One of the best experts on this subject based on the ideXlab platform.
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an uncertainty principle for star formation i why galactic star formation relations break down below a certain Spatial Scale
Monthly Notices of the Royal Astronomical Society, 2014Co-Authors: J Diederik M Kruijssen, S N LongmoreAbstract:Galactic scaling relations between the (surface densities of) the gas mass and the star formation (SF) rate are known to develop substantial scatter or even change form when considered below a certain Spatial Scale. We quantify how this behaviour should be expected due to the incomplete statistical sampling of independent star-forming regions. Other included limiting factors are the incomplete sampling of SF tracers from the stellar initial mass function and the Spatial drift between gas and stars. We present a simple uncertainty principle for SF, which can be used to predict and interpret the failure of galactic SF relations on small Spatial Scales. This uncertainty principle explains how the scatter of SF relations depends on the Spatial Scale and predicts a Scale-dependent bias of the gas depletion time-Scale when centring an aperture on gas or SF tracer peaks. We show how the scatter and bias are sensitive to the physical size and time-Scales involved in the SF process (such as its duration or the molecular cloud lifetime), and illustrate how our formalism provides a powerful tool to constrain these largely unknown quantities. Thanks to its general form, the uncertainty principle can also be applied to other astrophysical systems, e.g. addressing the time evolution of star-forming cores, protoplanetary discs or galaxies and their nuclei.
Haiyan Chu - One of the best experts on this subject based on the ideXlab platform.
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Spatial Scale affects the relative role of stochasticity versus determinism in soil bacterial communities in wheat fields across the north china plain
Microbiome, 2018Co-Authors: Yu Shi, Xingjia Xiang, Ruibo Sun, Teng Yang, Kaoping Zhang, Yongguan Zhu, Jonathan M Adams, Haiyan ChuAbstract:The relative importance of stochasticity versus determinism in soil bacterial communities is unclear, as are the possible influences that alter the balance between these. Here, we investigated the influence of Spatial Scale on the relative role of stochasticity and determinism in agricultural monocultures consisting only of wheat, thereby minimizing the influence of differences in plant species cover and in cultivation/disturbance regime, extending across a wide range of soils and climates of the North China Plain (NCP). We sampled 243 sites across 1092 km and sequenced the 16S rRNA bacterial gene using MiSeq. We hypothesized that determinism would play a relatively stronger role at the broadest Scales, due to the strong influence of climate and soil differences in selecting many distinct OTUs of bacteria adapted to the different environments. In order to test the more general applicability of the hypothesis, we also compared with a natural ecosystem on the Tibetan Plateau. Our results revealed that the relative importance of stochasticity vs. determinism did vary with Spatial Scale, in the direction predicted. On the North China Plain, stochasticity played a dominant role from 150 to 900 km (separation between pairs of sites) and determinism dominated at more than 900 km (broad Scale). On the Tibetan Plateau, determinism played a dominant role from 130 to 1200 km and stochasticity dominated at less than 130 km. Among the identifiable deterministic factors, soil pH showed the strongest influence on soil bacterial community structure and diversity across the North China Plain. Together, 23.9% of variation in soil microbial community composition could be explained, with environmental factors accounting for 19.7% and Spatial parameters 4.1%. Our findings revealed that (1) stochastic processes are relatively more important on the North China Plain, while deterministic processes are more important on the Tibetan Plateau; (2) soil pH was the major factor in shaping soil bacterial community structure of the North China Plain; and (3) most variation in soil microbial community composition could not be explained with existing environmental and Spatial factors. Further studies are needed to dissect the influence of stochastic factors (e.g., mutations or extinctions) on soil microbial community distribution, which might make it easier to predictably manipulate the microbial community to produce better yield and soil sustainability outcomes.
Dionysios A Antonopoulos - One of the best experts on this subject based on the ideXlab platform.
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Spatial Scale drives patterns in soil bacterial diversity
Environmental Microbiology, 2016Co-Authors: Sarah L Obrien, Sean M Gibbons, Sarah M Owens, Jarrad T Hamptonmarcell, Eric R Johnston, J D Jastrow, Jack A Gilbert, Folker Meyer, Dionysios A AntonopoulosAbstract:Soil microbial communities are essential for ecosystem function, but linking community composition to biogeochemical processes is challenging because of high microbial diversity and large Spatial variability of most soil characteristics. We investigated soil bacterial community structure in a switchgrass stand planted on soil with a history of grassland vegetation at high Spatial resolution to determine whether biogeographic trends occurred at the centimeter Scale. Moreover, we tested whether such heterogeneity, if present, influenced community structure within or among ecosystems. Pronounced heterogeneity was observed at centimeter Scales, with abrupt changes in relative abundance of phyla from sample to sample. At the ecosystem Scale (> 10 m), however, bacterial community composition and structure were subtly, but significantly, altered by fertilization, with higher alpha diversity in fertilized plots. Moreover, by comparing these data with data from 1772 soils from the Earth Microbiome Project, it was found that 20% of bacterial taxa were shared between their site and diverse globally sourced soil samples, while grassland soils shared approximately 40% of their operational taxonomic units with the current study. By spanning several orders of magnitude, the analysis suggested that extreme patchiness characterized community structure at smaller Scales but that coherent patterns emerged at larger length Scales.
