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Marcon, E.; Puech, F. |
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Title |
Measures of the geographic concentration of industries: improving distance-based methods |
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Journal Article |
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2010 |
Publication |
Journal of Economic Geography |
Abbreviated Journal |
J. Econ. Geogr. |
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10 |
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5 |
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745-762 |
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Geographic concentration; distance-based methods; K-density function; Ripley's K function; M function; C40; C60; R12; L60 |
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We discuss a property of distance-based measures that has not been addressed with regard to evaluating the geographic concentration of economic activities. The article focuses on the choice between a probability density function of point-pair distances or a cumulative function. We begin by introducing a new cumulative function, M, for evaluating the relative geographic concentration and the co-location of industries in a non-homogeneous spatial framework. Secondly, some rigorous comparisons are made with the leading probability density function of Duranton and Overman (2005), Kd. The merits of the simultaneous use of Kd and M is proved, underlining the complementary nature of the results they provide. |
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[Marcon, Eric] AgroParisTech ENGREF, UMR EcoFoG, Kourou 97310, French Guiana, Email: Florence.Puech@univ-lyon2.fr |
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OXFORD UNIV PRESS |
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1468-2702 |
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ISI:000281183300009 |
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EcoFoG @ eric.marcon @ |
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43 |
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Author |
Marcon, E.; Puech, F. |
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Title |
Evaluating the geographic concentration of industries using distance-based methods |
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Journal Article |
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2003 |
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Journal of Economic Geography |
Abbreviated Journal |
J. Econ. Geogr. |
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3 |
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4 |
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409-428 |
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agglomeration; clustering; geographic concentration; location of firms |
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We propose new methods for evaluating the spatial distribution of firms. To assess whether firms are concentrated or dispersed, economists have traditionally used indices that analyse the heterogeneity of a spatial structure at a single geographic level. We introduce distance-based methods, Besag's L function (derived from Ripley's K function) and Diggle and Chetwynd's D function to describe simultaneously spatial distribution at different geographical scales. Our empirical applications consider the distribution of French manufacturing firms in the Paris area and in France generally. For some geographic levels, results show significant concentration or dispersion of firms according to their sector of activity. |
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ENGREF, Kourou 97310, French Guiana |
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OXFORD UNIV PRESS |
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1468-2702 |
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ISI:000185742500004 |
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EcoFoG @ eric.marcon @ |
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269 |
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Author |
Marcon, E.; Puech, F. |
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Title |
A typology of distance-based measures of spatial concentration |
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Year |
2017 |
Publication |
Regional Science and Urban Economics |
Abbreviated Journal |
Regional Science and Urban Economics |
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62 |
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56-67 |
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Agglomeration; Aggregation; Economic geography; Point patterns; Spatial concentration |
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Over the last decade, distance-based methods have been introduced and then improved in the field of spatial economics to gauge the geographic concentration of activities. There is a growing literature on this theme including new tools, discussions on their specific properties and various applications. However, there is currently no typology of distance-based methods. This paper fills that gap. The proposed classification helps understand all the properties of distance-based methods and proves that they are variations on the same framework. © 2016 Elsevier B.V. |
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RITM, Univ. Paris-Sud, CREST, Université Paris-Saclay, Sceaux, France |
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Export Date: 17 January 2017 |
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EcoFoG @ webmaster @ |
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704 |
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Marcon, E.; Herault, B.; Baraloto, C.; Lang, G. |
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Title |
The decomposition of Shannon's entropy and a confidence interval for beta diversity |
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Journal Article |
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2012 |
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Oikos |
Abbreviated Journal |
Oikos |
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121 |
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4 |
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516-522 |
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Beta diversity is among the most employed theoretical concepts in ecology and biodiversity conservation. Up to date, a self-contained definition of it, with no reference to alpha and gamma diversity, has never been proposed. Using Kullback-Leibler divergence, we present the explicit formula of Shannon's β entropy, a bias correction for its estimator and a confidence interval. We also provide the mathematical framework to decompose Shannon diversity into several hierarchical nested levels. From botanical inventories of tropical forest plots in French Guiana, we estimate Shannon diversity at the plot, forest and regional level. We believe this is a complete and usefulness toolbox for ecologists interested in partitioning biodiversity. © 2011 The Authors. Oikos © 2012 Nordic Society Oikos. |
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AgroParisTech, UMR 518 Math. Info. Appli., 16 rue Claude Bernard, FR-75005 Paris, France |
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00301299 (Issn) |
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Export Date: 28 March 2012; Source: Scopus; Coden: Oiksa; doi: 10.1111/j.1600-0706.2011.19267.x; Language of Original Document: English; Correspondence Address: Marcon, E.; AgroParisTech, UMR EcoFoG, BP 709, FR-97310 Kourou, France; email: eric.marcon@ecofog.gf |
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EcoFoG @ webmaster @ |
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386 |
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Author |
Marcon, E.; Herault, B. |
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Title |
Decomposing phylodiversity |
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Journal Article |
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Year |
2015 |
Publication |
Methods in Ecology and Evolution |
Abbreviated Journal |
Methods in Ecology and Evolution |
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Volume |
6 |
Issue |
3 |
Pages |
333-339 |
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Keywords |
Biodiversity; Entropy; Functional diversity; Phylogenetic diversity |
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Measuring functional or phylogenetic diversity is the object of an active literature. The main issues to address are relating measures to a clear conceptual framework, allowing unavoidable estimation-bias correction and decomposing diversity along spatial scales. We provide a general mathematical framework to decompose measures of species-neutral, phylogenetic or functional diversity into α and β components. We first unify the definitions of phylogenetic and functional entropy and diversity as a generalization of HCDT entropy and Hill numbers when an ultrametric tree is considered. We then derive the decomposition of diversity. We propose a bias correction of the estimates allowing meaningful computation from real, often undersampled communities. Entropy can be transformed into true diversity, that is an effective number of species or communities. Estimators of α- and β-entropy, phylogenetic and functional entropy are provided. Proper definition and estimation of diversity is the first step towards better understanding its underlying ecological and evolutionary mechanisms. © 2015 British Ecological Society. |
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Cirad, UMR EcoFoG, BP 709Kourou, French Guiana |
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Export Date: 31 March 2015 |
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EcoFoG @ webmaster @ |
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590 |
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Author |
Marcon, E.; Herault, B. |
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Title |
entropart: An R package to measure and partition diversity |
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Journal Article |
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Year |
2015 |
Publication |
Journal of Statistical Software |
Abbreviated Journal |
Journal of Statistical Software |
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67 |
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8 |
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1-26 |
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Biodiversity; Entropy; Partitioning |
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entropart is a package for R designed to estimate diversity based on HCDT entropy or similarity-based entropy. It allows calculating species-neutral, phylogenetic and functional entropy and diversity, partitioning them and correcting them for estimation bias. © 2015, American Statistical Association. All rights reserved. |
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Cirad, Campus agronomique, BP 316, Kourou, French Guiana |
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Export Date: 22 October 2015 |
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EcoFoG @ webmaster @ |
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633 |
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Author |
Marcon, E. |
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Title |
Entropy as a common measure of biodiversity and the spatial structure of economic activity |
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Journal Article |
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Year |
2019 |
Publication |
Revue Economique |
Abbreviated Journal |
Rev. Econ. |
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70 |
Issue |
3 |
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305-326 |
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Keywords |
Diversity; Economic geography; Spatial concentration; Specialization |
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Measures of spatial concentration and specialization in economics are similar to those of biodiversity and ubiquity of species in ecology. Entropy is the fundamental tool that originated in statistical physics and information theory. The definition of number equivalents or effective numbers, that is the number of types in an ideal, simplified distribution, is introduced along with the partitioning of the joint diversity of a bi-dimensional distribution into absolute and relative concentration or specialization and replication. The whole framework is theoretically robust and allows measuring the spatial structure of a discrete space. |
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AgroParisTech, UMR Écologie des forêts de Guyane, CNRS, Cirad, INRA, Université des Antilles, Université de Guyane, Campus Agronomique, BP 701, Kourou, 97310, French Guiana |
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Presses de Sciences Po |
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00352764 (Issn) |
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EcoFoG @ webmaster @ |
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912 |
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Marchal, R.; Mothe, F.; Denaud, L.E.; Thibaut, B.; Bleron, L. |
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Cutting forces in wood machining – Basics and applications in industrial processes. A review COST Action E35 2004-2008: Wood machining – micromechanics and fracture |
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2009 |
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Holzforschung |
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Holzforschung |
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63 |
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2 |
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157-167 |
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cutting forces; online control; peeling process; physico-mechanical model; sound; vibrations; wood industry; wood machining |
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The data available in the literature concerning wood cutting forces permits to build models or to simulate the main wood machining processes ( milling, sawing, peeling, etc.). This approach contributes to a better understanding of formation of wood surfaces and chips and the data may be helpful to optimise cutting geometry, reduce tool wear, improve tool material, and to size tool-machines. The models may also be useful for industrial application in two ways: ( 1) providing data to optimise the settings for a given operation ( batch approach), and ( 2) building predictive models that could be the basis of an online control system for the machining processes ( interactive approach). A prerequisite for this is that numerous machining tests on different wood materials are performed based on experiences with different kind of tools and experimental devices. With a focus on potential industrial applications, the emphasis of this review was on the wood peeling process, which is a very demanding special case of wood cutting. Although not so many industrial machines are equipped with expensive force sensors, there is a lot of high quality information available about cutting forces which may be useful to improve the scientific or technological knowledge in wood machining. Alternative parameters, such as vibration or sound measurements, appear to be promising substitutes in the praxis, particularly to feed online control systems of any wood cutting process. |
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[Marchal, Remy; Bleron, Laurent] Arts & Metiers ParisTech, LABOMAP, F-71250 Cluny, France, Email: remy.marchal@cluny.ensam.fr |
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WALTER DE GRUYTER & CO |
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0018-3830 |
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ISI:000263932200006 |
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EcoFoG @ eric.marcon @ |
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205 |
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Maréchaux, I.; Bonal, D.; Bartlett, M.K.; Burban, B.; Coste, S.; Courtois, E.A.; Dulormne, M.; Goret, J.-Y.; Mira, E.; Mirabel, A.; Sack, L.; Stahl, C.; Chave, J. |
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Title |
Dry-season decline in tree sapflux is correlated with leaf turgor loss point in a tropical rainforest |
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Journal Article |
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2018 |
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Functional Ecology |
Abbreviated Journal |
Funct Ecol |
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32 |
Issue |
10 |
Pages |
2285-2297 |
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drought tolerance; hydraulic conductance; sap flow; sapflux density; tropical trees; turgor loss point; water potential; wilting point |
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Water availability is a key determinant of forest ecosystem function and tree species distributions. While droughts are increasing in frequency in many ecosystems, including in the tropics, plant responses to water supply vary with species and drought intensity and are therefore difficult to model. Based on physiological first principles, we hypothesized that trees with a lower turgor loss point (pi-tlp), that is, a more negative leaf water potential at wilting, would maintain water transport for longer into a dry season. We measured sapflux density of 22 mature trees of 10 species during a dry season in an Amazonian rainforest, quantified sapflux decline as soil water content decreased and tested its relationship to tree pi-tlp, size and leaf predawn and midday water potentials measured after the onset of the dry season. The measured trees varied strongly in the response of water use to the seasonal drought, with sapflux at the end of the dry season ranging from 37 to 117% (on average 83 +/- 5 %) of that at the beginning of the dry season. The decline of water transport as soil dried was correlated with tree pi-tlp (Spearman's rho > 0.63), but not with tree size or predawn and midday water potentials. Thus, trees with more drought-tolerant leaves better maintained water transport during the seasonal drought. Our study provides an explicit correlation between a trait, measurable at the leaf level, and whole-plant performance under drying conditions. Physiological traits such as pi-tlp can be used to assess and model higher scale processes in response to drying conditions. |
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Wiley/Blackwell (10.1111) |
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0269-8463 |
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doi: 10.1111/1365-2435.13188 |
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EcoFoG @ webmaster @ |
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830 |
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Maréchaux, I.; Bartlett, M.K.; Sack, L.; Baraloto, C.; Engel, J.; Joetzjer, E.; Chave, J. |
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Drought tolerance as predicted by leaf water potential at turgor loss point varies strongly across species within an Amazonian forest |
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Journal Article |
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2015 |
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Functional Ecology |
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Functional Ecology |
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29 |
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10 |
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1268-1277 |
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Climate change; French Guiana; Functional traits; Plant-water relations; Tropical trees; Wilting |
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Amazonian droughts are predicted to become increasingly frequent and intense, and the vulnerability of Amazonian trees has become increasingly documented. However, little is known about the physiological mechanisms and the diversity of drought tolerance of tropical trees due to the lack of quantitative measurements. Leaf water potential at wilting or turgor loss point (π<inf>tlp</inf>) is a determinant of the tolerance of leaves to drought stress and contributes to plant-level physiological drought tolerance. Recently, it has been demonstrated that leaf osmotic water potential at full hydration (π<inf>o</inf>) is tightly correlated with π<inf>tlp</inf>. Estimating π<inf>tlp</inf> from osmometer measurements of π<inf>o</inf> is much faster than the standard pressure-volume curve approach of π<inf>tlp</inf> determination. We used this technique to estimate π<inf>tlp</inf> for 165 trees of 71 species, at three sites within forests in French Guiana. Our data set represents a significant increase in available data for this trait for tropical tree species. Tropical trees showed a wider range of drought tolerance than previously found in the literature, π<inf>tlp</inf> ranging from -1·4 to -3·2 MPa. This range likely corresponds in part to adaptation and acclimation to occasionally extreme droughts during the dry season. Leaf-level drought tolerance varied across species, in agreement with the available published observations of species variation in drought-induced mortality. On average, species with a more negative π<inf>tlp</inf> (i.e. with greater leaf-level drought tolerance) occurred less frequently across the region than drought-sensitive species. Across individuals, π<inf>tlp</inf> correlated positively but weakly with leaf toughness (R2 = 0·22, P = 0·04) and leaf thickness (R2 = 0·03, P = 0·03). No correlation was detected with other functional traits (leaf mass per area, leaf area, nitrogen or carbon concentrations, carbon isotope ratio, sapwood density or bark thickness). The variability in π<inf>tlp</inf> among species indicates a potential for highly diverse species responses to drought within given forest communities. Given the weak correlations between π<inf>tlp</inf> and traditionally measured plant functional traits, vegetation models seeking to predict forest response to drought should integrate improved quantification of comparative drought tolerance among tree species. © 2015 British Ecological Society. |
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CNRM-GAME – URA1357, 42 avenue G. Coriolis, Toulouse, France |
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Cited By :1; Export Date: 12 October 2015 |
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EcoFoG @ webmaster @ |
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