Eric Marcon

Eric Marcon

Enseignant-chercheur en écologie

AgroParisTech

Biographie

Je suis chercheur en écologie tropicale à l’UMR Amap, enseignant à AgroParisTech et coordinateur du parcours BioGET du master Biodiversité, Ecologie et Evolution (AgroParisTech et Université de Montpellier).

Intérêts
  • Ecologie des communautés
  • Foresterie tropicale
  • Ecologie Statistique
  • Développement avec R
Éducation
  • Habilitation à Diriger des Recherches en écologie, 2016

    Université de Guyane

  • Doctorat en écologie, 2010

    AgroParisTech

  • Ingénieur du Génie Rural, des Eaux et des Forêts, 1999

    Ecole Nationale du Génie Rural, des Eaux et des Forêts

  • DEA en économie internationale, 1999

    Université Paris I, Panthéon Sorbonne

  • Ingénieur des Travaux des Eaux et Forêts, 1990

    Ecole Nationale des Ingénieurs des Travaux des Eaux et Forêts

Experience

 
 
 
 
 
AgroParisTech
Directeur de l’Unité Mixte de Recherche Ecologie des Forêts de Guyane (UMR EcoFoG)
janvier 2010 – août 2020 Kourou, Guyane française

Responsabilités:

  • Administration de la Recherche
  • Encadrement
  • Enseignement (niveaux bac+5 et plus)
  • Recherche

Publications récentes

Local Forest Structure and Host Specificity Influence Liana Community Composition in a Moist Central African Forest

Lianas are important components of tropical forest diversity and dynamics, yet little is known about the drivers of their community structure and composition. Combining extensive field and LiDAR data, we investigated the influence of local topography, forest structure, and tree composition on liana community structure, and their floristic and functional composition, in a moist forest in northern Republic of Congo. We inventoried all lianas ≥ 1 cm in diameter in 144 20 × 20‐m quadrats located in four 9‐ha permanent plots, where trees and giant herbs were inventoried. We characterized the functional strategies of selected representatives of the main liana taxa using a set of resource‐use leaf and wood traits. Finally, we used complementary statistical analyses, including multivariate and randomization approaches, to test whether forest structure, topography, and tree composition influence the structure, floristic composition, and functional composition of liana communities. The structure of liana communities was strongly shaped by local forest structure, with higher abundances and total basal areas in relatively open‐canopy forests, where lianas competed with giant herbs. Liana floristic composition exhibited a weak spatial structure over the study site but was marginally influenced by the local forest structure and topography. Only forest structure had a weak but significant effect on liana functional composition, with more conservative strategies—higher stem tissue density and lower PO4 leaf concentration and SLA values—in tall and dense forests. Finally, we found evidence of host specificity with significant attraction/repulsion for 19% of the tested liana and tree species associations, suggesting that the unexplained floristic variation may be partly attributed to these host‐species‐specific associations, although the underlying mechanisms behind remain elusive. Overall, our findings demonstrate that liana communities’ structure can be much better predicted than their composition, calling for a better understanding of the implications of the large functional diversity observed in liana communities.

Dissecting earthworm diversity in tropical rainforests

Tropical rainforests are among the most emblematic ecosystems in terms of biodiversity. However, our understanding of the structure of tropical biodiversity is still incomplete, particularly for certain groups of soil organisms such as earthworms, whose importance for ecosystem functioning is widely recognised. This study aims at determining the relative contribution of alpha and beta components to earthworm regional diversity at a hierarchy of nested spatial scales in natural ecosystems of French Guiana. For this, we performed a hierarchical diversity partitioning of a large dataset on earthworm communities, in which DNA barcode‐based operational taxonomic units (OTUs) were used as species surrogates. Observed regional diversity comprised 256 OTUs. We found that alpha diversity was lower than predicted by chance, regardless of the scale considered. Community‐scale alpha diversity was on average 7 OTUs. Beta diversity among remote landscapes was higher than expected by chance, explaining as much as 87% of regional diversity. This points to regional mechanisms as the main driver of species diversity distribution in this group of organisms with low dispersal capacity. At more local scales, multiplicative beta diversity was higher than expected by chance between habitats, while it was lower than expected by chance between communities in the same habitat. This highlights the local effect of environmental filters on the species composition of communities. The calculation of a Chao 2 index predicts that as many as 1700 species could be present in French Guiana, which represents a spectacular increase compared with available checklists, and calls into question the commonly accepted estimates of global number of earthworm species.

The global distribution and drivers of wood density and their impact on forest carbon stocks

The density of wood is a key indicator of the carbon investment strategies of trees, impacting productivity and carbon storage. Despite its importance, the global variation in wood density and its environmental controls remain poorly understood, preventing accurate predictions of global forest carbon stocks. Here we analyse information from 1.1 million forest inventory plots alongside wood density data from 10,703 tree species to create a spatially explicit understanding of the global wood density distribution and its drivers. Our findings reveal a pronounced latitudinal gradient, with wood in tropical forests being up to 30% denser than that in boreal forests. In both angiosperms and gymnosperms, hydrothermal conditions represented by annual mean temperature and soil moisture emerged as the primary factors influencing the variation in wood density globally. This indicates similar environmental filters and evolutionary adaptations among distinct plant groups, underscoring the essential role of abiotic factors in determining wood density in forest ecosystems. Additionally, our study highlights the prominent role of disturbance, such as human modification and fire risk, in influencing wood density at more local scales. Factoring in the spatial variation of wood density notably changes the estimates of forest carbon stocks, leading to differences of up to 21% within biomes. Therefore, our research contributes to a deeper understanding of terrestrial biomass distribution and how environmental changes and disturbances impact forest ecosystems.

Dominance and rarity in tree communities across the globe: Patterns, predictors and threats

  • Aim: Ecological and anthropogenic factors shift the abundances of dominant and rare tree species within local forest communities, thus affecting species composition and ecosystem functioning. To inform forest and conservation management it is important to understand the drivers of dominance and rarity in local tree communities. We answer the following research questions: (1) What are the patterns of dominance and rarity in tree communities? (2) Which ecological and anthropogenic factors predict these patterns? And (3) what is the extinction risk of locally dominant and rare tree species? Location Global.
  • Time period: 1990-2017.
  • Major taxa studied: Trees.
  • Methods: We used 1.2 million forest plots and quantified local tree dominance as the relative plot basal area of the single most dominant species and local rarity as the percentage of species that contribute together to the least 10% of plot basal area. We mapped global community dominance and rarity using machine learning models and evaluated the ecological and anthropogenic predictors with linear models. Extinction risk, for example threatened status, of geographically widespread dominant and rare species was evaluated.
  • Results: Community dominance and rarity show contrasting latitudinal trends, with boreal forests having high levels of dominance and tropical forests having high levels of rarity. Increasing annual precipitation reduces community dominance, probably because precipitation is related to an increase in tree density and richness. Additionally, stand age is positively related to community dominance, due to stem diameter increase of the most dominant species. Surprisingly, we find that locally dominant and rare species, which are geographically widespread in our data, have an equally high rate of elevated extinction due to declining populations through large-scale land degradation.
  • Main conclusions: By linking patterns and predictors of community dominance and rarity to extinction risk, our results suggest that also widespread species should be considered in large-scale management and conservation practices.

Positive feedbacks and alternative stable states in forest leaf types

The emergence of alternative stable states in forest systems has significant implications for the functioning and structure of the terrestrial biosphere, yet empirical evidence remains scarce. Here, we combine global forest biodiversity observations and simulations to test for alternative stable states in the presence of evergreen and deciduous forest types. We reveal a bimodal distribution of forest leaf types across temperate regions of the Northern Hemisphere that cannot be explained by the environment alone, suggesting signatures of alternative forest states. Moreover, we empirically demonstrate the existence of positive feedbacks in tree growth, recruitment and mortality, with trees having 4–43% higher growth rates, 14–17% higher survival rates and 4–7 times higher recruitment rates when they are surrounded by trees of their own leaf type. Simulations show that the observed positive feedbacks are necessary and sufficient to generate alternative forest states, which also lead to dependency on history (hysteresis) during ecosystem transition from evergreen to deciduous forests and vice versa. We identify hotspots of bistable forest types in evergreen-deciduous ecotones, which are likely driven by soil-related positive feedbacks. These findings are integral to predicting the distribution of forest biomes, and aid to our understanding of biodiversity, carbon turnover, and terrestrial climate feedbacks.

Logiciels

memoiR
memoiR est un paquet R qui fournit des modèles pour publier des documents bien formatés aux formats HTML et PDF. Les documents peuvent être produits localement ou hébergés sur GitHub, où les Actions GitHub peuvent mettre à jour les documents publiés en continu.
dbmss
dbmss est un package R destiné au calcul des statistiques spatiales non paramétriques pour caractériser la structure spatiale d’objets cartographiés. Les principales sont la fonction K de Ripley et ses dérivées et celles utilisées par les économistes comme la fonction Kd de Duranton et Overman et la fonction M de Marcon et Puech.
Entropart
entropart est un package R pour mesurer la diversité. Il fournit les fonctions nécessaires au calcul de la diversité $\alpha$, $\beta$ et $\gamma$, incluant la diversité phylogénétique et fonctionnelle, et l’ensemble des techniques d’estimation disponibles dans la littérature.

Cours

*
Dynamique des Forêts Tropicales
Ce cours est destiné aux étudiants d’AgroParisTech en dernière année, en dominante d’approfondissement GEEFT. C’est une introduction à la dynamique des forêts tropicales. Les objectifs sont de : Savoir décrire l’état et la dynamique d’une forêt, Comprendre la dynamique de succession et le rôle des perturbations, Connaître quelques théories fondamentales, Introduire les perturbations anthropiques, avant de voir l’aménagement et l’exploitation de la forêt.
Introduction à l’écologie forestière
Ce cours est destiné aux étudiants du master d’anthropologie, parcours Humanités environnementales. C’est une introduction à l’écologie forestière. Les objectifs sont de : Compléter l’introduction générale à l’écologie en présentant les spécificités de l’écologie forestière, Présenter un exemple théorique majeur (niche contre neutralité), Évoquer les fronts de science, en termes d’enjeux et de méthodes.
Statistiques sous R
Ce cours de remise à niveau en statistiques avec R est destiné aux étudiants d’AgroParisTech en dernière année, en dominante d’approfondissement GEEFT
Mesure de la Biodiversité
La définition originelle de la biodiversité est le nombre d’espèces d’une communauté. Elle a été élargie de nombreuses façons par des indices souvent ad-hoc. Ce cours introduit une approche unifiée de la mesure de la biodiversité qui s’appuie sur la théorie de l’information et permet de décrire la biodiversité comme un nombre effectif de catégories (en général, d’espèces) correspondant à la question traitée : la diversité taxonomique quand toutes les espèces sont considérées comme équivalentes, la diversité phylogénétique quand leur proximité évolutive est prise en compte et la diversité fonctionnelle quand la distance entre paires d’espèces ne s’inscrit pas dans un arbre.
Distributions d’abondances
No other general attribute of ecological communities besides species richness has commanded more theoretical and empirical attention than relative species abundance (Hubbell, 2001) L’objectif du cours est de comprendre les principales distributions d’abondance, maîtriser les différentes représentations et comprendre les relations aires-espèces, à différentes échelles.
Travailler avec R
Ce cours propose une organisation du travail autour de R et RStudio pour, au-delà des statistiques, rédiger des documents efficacement avec R Markdown, aux formats variés (mémos, articles scientifiques, mémoires d’étudiants, livres, diaporamas), créer son site web et des applications R en ligne (Shiny), produire des packages et utiliser R pour l’enseignement.

Contact