Résumé

Aim: Edaphic heterogeneity may be an important driver of population differentiation in the Amazon but remains to be investigated in trees. We compared the phylogeographic structure across the geographic distribution of two Protium (Burseraceae) species with different degrees of edaphic specialization: Protium alvarezianum, an edaphic specialist of white-sand habitat islands; and Protium subserratum, an edaphic generalist found in white sand as well as in more widespread soil types. We predicted that in the edaphic specialist, geographic distance would structure populations more strongly than in the edaphic generalist, and that soil type would not structure populations in the edaphic generalist unless habitat acts as a barrier promoting population differentiation. Location: Tropical rain forests of the Peruvian and Brazilian Amazon, Guyana and French Guiana. Methods: We sequenced 1209—1211 bp of non-coding nuclear ribosomal DNA (internal transcribed spacer and external transcribed spacer) and a neutral low-copy nuclear gene (phytochrome C) from P. subserratum (n = 65, 10 populations) and P. alvarezianum (n = 19, three populations). We conducted a Bayesian phylogenetic analysis, constructed maximum parsimony haplotype networks and assessed population differentiation among groups (soil type or geographic locality) using analysis of molecular variance and spatial analysis of molecular variance. Results: The edaphic specialist exhibited considerable genetic differentiation among geographically distant populations. The edaphic generalist showed significant genetic differentiation between the Guianan and Amazon Basin populations. Within Peru, soil type and not geographic distance explained most of the variation among populations. Non-white-sand populations in Peru exhibited lower haplotype/nucleotide diversity than white-sand populations, were each other's close relatives, and formed an unresolved clade derived from within the white-sand populations. Main conclusions: Geographic distance is a stronger driver of population differentiation in the edaphic specialist than in the generalist. However, this difference did not appear to be related to edaphic generalism per se as adjacent populations from both soil types in the edaphic generalist did not share many haplotypes. Populations of the edaphic generalist in white-sand habitats exhibited high haplotype diversity and shared haplotypes with distant white-sand habitat islands, indicating that they have either efficient long-distance dispersal and/or larger ancestral effective population sizes and thus retain ancestral polymorphisms. These results highlight the importance of edaphic heterogeneity in promoting population differentiation in tropical trees. CR - Copyright © 2013 Wiley

Auteurs, date et publication :

Auteurs Paul V.A. A. Fine , Felipe Zapata , Douglas C. Daly , Italo Mesones , Tracy M. Misiewicz , Hillary F. Cooper , C. E.A. A. Barbosa

Publication : Journal of Biogeography

Date : 2013

Volume : 40

Issue : 4

Pages : 646–661

Catégorie(s)

#CIRAD #FORET Paracou

Résumé

Tree mortality in tropical forests is a complex ecological process for which modelling approaches need to be improved to better understand, and then predict, the evolution of tree mortality in response to global change. The mortality model introduced here computes an individual probability of dying for each tree in a community. The mortality model uses the ontogenetic stage of the tree because youngest and oldest trees are more likely to die. Functional traits are integrated as proxies of the ecological strategies of the trees to permit generalization among all species in the community. Data used to parametrize the model were collected at Paracou study site, a tropical rain forest in French Guiana, where 20,408 trees have been censused for 18 years. A Bayesian framework was used to select useful covariates and to estimate the model parameters. This framework was developed to deal with sources of uncertainty, including the complexity of the mortality process itself and the field data, especially historical data for which taxonomic determinations were uncertain. Uncertainty about the functional traits was also considered, to maximize the information they contain. Four functional traits were strong predictors of tree mortality: wood density, maximum height, laminar toughness and stem and branch orientation, which together distinguished the light-demanding, fast-growing trees from slow-growing trees with lower mortality rates. Our modelling approach formalizes a complex ecological problem and offers a relevant mathematical framework for tropical ecologists to process similar uncertain data at the community level.

Auteurs, date et publication :

Auteurs Mélaine Aubry-Kientz , Bruno Hérault , Charles Ayotte-Trépanier , Christopher Baraloto , Vivien Rossi , Francesco de Bello

Publication : Plos One

Date : 2013

Volume : 8

Issue : 5

Pages : e63678

Catégorie(s)

#CIRAD #FORET Paracou

Résumé

textlessptextgreatertextlessptextgreatertextlessstrongtextgreaterAbstract.textless/strongtextgreater The fixation of carbon in tropical forests mainly occurs through the production of wood and leaves, both being the principal components of net primary production. Currently field and satellite observations are independently used to describe the forest carbon cycle, but the link between satellite-derived forest phenology and field-derived forest productivity remains opaque. We used a unique combination of a MODIS enhanced vegetation index (EVI) dataset, a wood production model based on climate data and direct litterfall observations at an intra-annual timescale in order to question the synchronism of leaf and wood production in tropical forests. Even though leaf and wood biomass fluxes had the same range (respectively 2.4 ± 1.4 and 2.2 ± 0.4 Mg C hatextlesssuptextgreater−1textless/suptextgreater yrtextlesssuptextgreater−1textless/suptextgreater), they occurred separately in time. EVI increased with leaf renewal at the beginning of the dry season, when solar irradiance was at its maximum. At this time, wood production stopped. At the onset of the rainy season, when new leaves were fully mature and water available again, wood production quickly increased to reach its maximum in less than a month, reflecting a change in carbon allocation from short-lived pools (leaves) to long-lived pools (wood). The time lag between peaks of EVI and wood production (109 days) revealed a substantial decoupling between the leaf renewal assumed to be driven by irradiance and the water-driven wood production. Our work is a first attempt to link EVI data, wood production and leaf phenology at a seasonal timescale in a tropical evergreen rainforest and pave the way to develop more sophisticated global carbon cycle models in tropical forests.textless/ptextgreatertextless/ptextgreater

Auteurs, date et publication :

Auteurs F. Wagner , V. Rossi , C. Stahl , D. Bonal , B. Hérault

Publication : Biogeosciences

Date : 2013

Volume : 10

Issue : 11

Pages : 7307–7321

Catégorie(s)

#CIRAD #FORET Paracou

Auteurs, date et publication :

Auteurs L. Rowland , C. Stahl , D. Bonal , L. Siebicke , M. Williams , P. Meir

Publication : Ecosystems

Date : 2013

Volume : 16

Issue : 7

Pages : 1294–1309

Catégorie(s)

#CIRAD #FORET Paracou

Résumé

textlessptextgreaterThe objective of this study was to examine the water relations and hydraulic architecture and vulnerability to cavitation in textlessemtextgreaterVirola surinamensis textless/emtextgreaterandtextlessemtextgreater V. micheliitextless/emtextgreater and to compare to similar measurements in textlessemtextgreaterEperua falcata. textless/emtextgreaterIn several previous reports textlessemtextgreaterVirolatextless/emtextgreater was seen to have a rather narrow range of xylem pressure potentials (textlessemtextgreaterΨtextless/emtextgreatertextlessemtextgreatertextlesssubtextgreaterxtextless/subtextgreatertextless/emtextgreater) near zero in the course of a wet-season day while having water fluxes quite close to textlessemtextgreaterEperuatextless/emtextgreater. We tested the hypothesis that the narrow range of textlessemtextgreaterΨtextless/emtextgreatertextlessemtextgreatertextlesssubtextgreaterxtextless/subtextgreatertextless/emtextgreater might be consistent with very high hydraulic conductivities of stems, roots and shoots and high vulnerability to cavitation in textlessemtextgreaterVirolatextless/emtextgreater compared to textlessemtextgreaterEperuatextless/emtextgreater. When this hypothesis proved false we concluded that the previous determinations of textlessemtextgreaterΨtextless/emtextgreatertextlessemtextgreatertextlesssubtextgreaterxtextless/subtextgreatertextless/emtextgreater might be wrong in textlessemtextgreaterVirolatextless/emtextgreater due to latex. We re-examined the determination of textlessemtextgreaterΨtextless/emtextgreatertextlessemtextgreatertextlesssubtextgreaterxtextless/subtextgreatertextless/emtextgreater in textlessemtextgreaterVirolatextless/emtextgreater by the pressure chamber technique and compared results to determination of textlessemtextgreaterΨtextless/emtextgreatertextlessemtextgreatertextlesssubtextgreaterleaftextless/subtextgreatertextless/emtextgreater by the thermocouple psychrometer technique and found that the likely range of textlessemtextgreaterΨtextless/emtextgreatertextlessemtextgreatertextlesssubtextgreaterxtextless/subtextgreatertextless/emtextgreater are more negative than previously reported. Problems concerning the determination of textlessemtextgreaterΨtextless/emtextgreatertextlessemtextgreatertextlesssubtextgreaterxtextless/subtextgreatertextless/emtextgreater in species with latex are discussed.textless/ptextgreater

Auteurs, date et publication :

Auteurs Têtè Sévérien Barigah , Gilbert Aussenac , Christopher Baraloto , Damien Bonal , Hervé Cochard , André Granier , Jean-Marc Guehl , Roland Huc , Mari A. Sobrado , Melvin T. Tyree

Publication : Journal of Plant Hydraulics

Date : 2014

Volume : 1

Pages : 002

Catégorie(s)

#CIRAD #FORET Paracou

Résumé

The Geoscience Laser Altimeter System (GLAS) has provided a useful dataset for estimating forest heights in many areas of the globe. Most of the studies on GLAS waveforms have focused on natural forests and only a few were conducted over forest plantations. This work set out to estimate the stand-scale dominant height and aboveground biomass of intensively managed Eucalyptus plantations in Brazil using the most commonly used models developed for natural forests. These forest plantations are valuable case studies, with large and numerous stands that are very uniform, in which field measurements are precise compared to natural forests. The height of planted Eucalyptus forest stands estimated from waveforms acquired by GLAS were compared with in situ measurements in order to determine the model that produced the best forest height estimates. For our slightly sloping study site (slope < 7 degrees), the direct method defined as the difference between the signal begin and the ground peak provided forest height estimates with an accuracy of 2.2 m. The use of statistical models based on waveform metrics and digital elevation models provided slightly better results (1.89 m accuracy) in comparison with the direct method and the most relevant metrics proved to be the trailing edge extent and the waveform extent. Moreover, a power law model was used to fit in situ aboveground biomass to in situ forest height. The results using this model with GLAS-derived heights showed an accuracy for biomass of 16.1 Mg/ha.

Auteurs, date et publication :

Auteurs N. Baghdadi , G. le Maire , I. Fayad , J.-S. Bailly , Y. Nouvellon , C. Lemos , R. Hakamada

Publication : IEEE Geoscience and Remote Sensing Letters

Date : 2014

Volume : 7

Issue : 1

Pages : 290-299

Catégorie(s)

#CIRAD #FORET Itatinga #INRAE

Auteurs, date et publication :

Auteurs Dinh Ho Tong Minh , Stefano Tebaldini , Fabio Rocca , Thuy Le Toan , Pierre Borderies , Thierry Koleck , Clement Albinet , Alia Hamadi , Ludovic Villard

Publication : IEEE Geoscience and Remote Sensing Letters

Date : 2014

Volume : 11

Issue : 8

Pages : 1438–1442

Catégorie(s)

#CIRAD #FORET Paracou

Auteurs, date et publication :

Auteurs A. Hamadi , C. Albinet , P. Borderies , T. Koleck , L. Villard , D. Ho Tong Minh , T. Le Toan

Publication : IEEE Transactions on Geoscience and Remote Sensing

Date : 2014

Volume : 52

Issue : 8

Pages : 4539–4547

Catégorie(s)

#CIRAD #FORET Paracou

Auteurs, date et publication :

Auteurs Grégoire Vincent , Daniel Sabatier , Ervan Rutishauser

Publication : Oecologia

Date : 2014

Volume : 175

Issue : 2

Pages : 439–443

Catégorie(s)

#CIRAD #FORET Paracou

Résumé

Differential growth response to light level is widely accepted as a potential mechanism for maintaining tree species richness in tropical forests. The position of tree species in the hierarchy of the canopy is considered an important indicator of species light capture and growth strategy. Paradoxically, the relative importance of species identity and competition for light in determining individual tree growth is poorly documented at the adult stage. In this study, we used a hierarchical Bayesian model to quantify the overall importance of species identity, light and belowground competition as determinants of tree growth in French Guiana tropical forest. Light competitive status is assessed by a crown exposure score and below ground competition is estimated from local crowding. We examined species sensitivity to both types of competition in relation to adult stature. Our results are based on annual diameter increments of more than 13,510 stems from 282 species monitored over 10years. Mean annual growth rate was 0.11cmy−1 with species identity explaining 35% of the individual variation in growth rate. Crown exposure and local crowding explained 3.5% and 2.4% of the variation in growth rate, respectively. Predicted changes in growth rate as crown exposure (resp. local crowding) index changed from lower to upper interquartile level was 0.03cmy−1 (resp. 0.02cmy−1). Species sensitivity to crown exposure and to local crowding were positively correlated (i) with predicted growth rate at high-light standardized conditions and (ii) with adult stature. This vertical niche partitioning is invoked to explain the limited contribution made by level of light competition for predicting individual tropical tree growth as the community-level response is dominated by the abundance of small-statured species with low sensitivity to light level. Light appears to drive the stem growth rate of tropical trees through species differentiation more than through individual tree growth limitation. This vertical stratification complements the previously reported regeneration niche and together these provide evidence for light niche partitioning in the three-dimensional space of tropical forests.

Auteurs, date et publication :

Auteurs Marilyne Laurans , Bruno Hérault , Ghislain Vieilledent , Grégoire Vincent

Publication : Forest Ecology and Management

Date : 2014

Volume : 329

Pages : 79–88

Catégorie(s)

#CIRAD #FORET Paracou