Résumé

Intraspecific variation in leaf functional traits has gained widespread attention as a means to evaluate, predict, and manage plant responses to environmental conditions, however there are considerable uncertainties regarding the extent and drivers of intraspecific trait variation (ITV) in domesticated plants. In a coffee (Coffea arabica) agroforestry system, we quantified ITV in seven leaf traits [i.e. area (LA), mass per area (LMA), dry matter content (LDMC), thickness (Lth), nitrogen concentrations (LNC), maximum photosynthetic rate on area and mass bases (Asat, Amass, respectively)] across managed gradients of soil fertility and light availability. Leaf physiological traits (Asat, Amass), as well as LA, showed the greatest extent of variation within coffee, while morphological traits (LMA, LDMC, Lth) and leaf N were less variable. All traits differed significantly as a function of light and fertilization treatment, however light was more influential in driving ITV in coffee leaves. Low light availability resulted in greater ITV for physiological leaf traits (Asat and Amass), while high light constrained ITV in most morphological-(LA, LMA, LDMC), physiological-(Asat, Amass) and chemical-(LNC) traits. Fertilization treatments did not induce systematic shifts in the extent of ITV. In addition, shade management treatments explained 9.2% of the variation in multivariate trait syndromes, while nutrient management regimes explained only 2.9%. Our results indicate that highly heterogeneous aboveground resource environments such those created by agroforestry, results in greater ITV for key crop physiological parameters. Based on ecological theory, such patterns indicate that management systems promoting resource heterogeneity should promote higher rates of resource partitioning, and greater resource-use efficiency in agroecosystems.

Auteurs, date et publication :

Auteurs Serra Buchanan , Marney E. Isaac , Karel Van den Meersche , Adam R. Martin

Publication : Agroforestry Systems

Date : 2019

Volume : 93

Issue : 4

Pages : 1261-1273

Catégorie(s)

#ANR-Citation #CIRAD #FORET CoffeeFlux

Résumé

Wood performs several functions to ensure tree survival and carbon allocation to a finite stem volume leads to trade-offs among cell types. It is not known to what extent these trade-offs modify functional trade-offs and if they are consistent across climates and evolutionary lineages. Twelve wood traits were measured in stems and coarse roots across 60 adult angiosperm tree species from temperate, Mediterranean and tropical climates. Regardless of climate, clear trade-offs occurred among cellular fractions, but did not translate into specific functional trade-offs. Wood density was negatively related to hydraulic conductivity (Kth) in stems and roots, but was not linked to nonstructural carbohydrates (NSC), implying a functional trade-off between mechanical integrity and transport but not with storage. NSC storage capacity was positively associated with Kth in stems and negatively in roots, reflecting a potential role for NSC in the maintenance of hydraulic integrity in stems but not in roots. Results of phylogenetic analyses suggest that evolutionary histories cannot explain covariations among traits. Trade-offs occur among cellular fractions, without necessarily modifying trade-offs in function. However, functional trade-offs are driven by coordinated changes among xylem cell types depending on the dominant role of each cell type in stems and roots.

Auteurs, date et publication :

Auteurs Guangqi Zhang , Zhun Mao , Pascale Maillard , Loïc Brancheriau , Bastien Gérard , Julien Engel , Claire Fortunel , Patrick Heuret , Jean Luc Maeght , Jordi Martínez-Vilalta , Alexia Stokes

Publication : New Phytologist

Date : 2025

Volume : 240

Issue : 3

Pages : 1162–1176

Catégorie(s)

#CIRAD #FORET Paracou

Résumé

Forest height and underlying terrain reconstruction is one of the main aims in dealing with forested areas. Theoretically, synthetic aperture radar tomography (TomoSAR) offers the possibility to solve the layover problem, making it possible to estimate the elevation of scatters located in the same resolution cell. This article describes a deep learning approach, named tomographic SAR neural network (TSNN), which aims at reconstructing forest and ground height using multipolarimetric multibaseline (MPMB) SAR data and light detection and ranging (LiDAR)-based data. The reconstruction of the forest and ground height is formulated as a classification problem, in which TSNN, a feedforward network, is trained using covariance matrix elements as input vectors and quantized LiDAR-based data as the reference. In our work, TSNN is trained and tested with P-band MPMB data acquired by ONERA over Paracou region of French Guiana in the frame of the European Space Agency's campaign TROPISAR and LiDAR-based data provided by the French Agricultural Research Center. The novelty of the proposed TSNN is related to its ability to estimate the height with a high agreement with LiDAR-based measurement and actual height with no requirement for phase calibration. Experimental results of different covariance window sizes are included to demonstrate that TSNN conducts height measurement with high spatial resolution and vertical accuracy outperforming the other two TomoSAR methods. Moreover, the conducted experiments on the effects of phase errors in different ranges show that TSNN has a good tolerance for small errors and is still able to precisely reconstruct forest heights.

Auteurs, date et publication :

Auteurs Wenyu Yang , Sergio Vitale , Hossein Aghababaei , Giampaolo Ferraioli , Vito Pascazio , Gilda Schirinzi

Publication : IEEE Transactions on Geoscience and Remote Sensing

Date : 2025

Volume : 61

Pages : 1–1

Catégorie(s)

#CIRAD #FORET Paracou

Résumé

1. Despite their exceptional biodiversity and carbon stocks, more than 80% of tropical forests are disturbed. However, a lot of interrogations remain around the ability of vegetation attributes in tropical forests to recover from the various anthropogenic disturbances coexisting in many tropical landscapes. While these different disturbances are usually studied separately, this work provides, for the first time, a common modelling framework of vegetation attribute recovery in differently disturbed forests. 2. We develop an original Bayesian hierarchical model of recovery trajectories, considering disturbed forests in a common framework, through a disturbance intensity gradient. As a case study, we test our modelling approach on data from two long-term experiments, Tirimbina (Costa Rica) and Paracou (French Guiana), where forest permanent sample plots have been set up following selective logging (63.25 ha), agriculture (4 ha), and clearcutting+fire (6.25 ha). 3. We build a modelling framework that stands out by: (i) its interpretability, with model parameters having a clear ecological meaning; (ii) its robustness, allowing to compare parameter values amongst ecological systems to ensure that predictions are ecologically sound; (iii) its versatility to consider disturbance intensity through post-disturbance changes in a structural variable, either as input data, or as a transformed parameter without requiring pre-disturbance monitoring; (iv) its flexibility to explicitly consider, and test, the effects on forest recovery of various disturbance types, along an intensity gradient, in a single integrative model. 4. First conclusions drawn from our common framework underline the strongest above-ground biomass and diversity recovery rate offered by selective logging, compared to agriculture and clearcutting+fire, as well as the strong effect of disturbance intensity on taxonomic composition recovery. 5. Considering disturbed forests in a common framework might help managers to know which disturbance types need to be firmly avoided, which intensity range makes human activities sustainable in forested environments, and where inexpensive natural regeneration should be favoured over active restoration, such as tree planting. Testing this framework with various monitoring tools to estimate disturbance intensity and model vegetation attribute recovery, i.e., with forest monitoring or remote sensing data, will be the next step to make it widely applicable.

Auteurs, date et publication :

Auteurs Eliott Maurent , Bruno Hérault , Camille Piponiot , Géraldine Derroire , Diego Delgado , Bryan Finegan , Mélaine Aubry Kientz , Bienvenu H.K. Amani , Marie Ange Ngo Bieng

Publication : Ecological Modelling

Date : 2025

Volume : 483

Issue : May

Catégorie(s)

#CIRAD #FORET Paracou

Résumé

Even where Reduced-Impact Logging (RIL) practices are applied, selective logging causes substantial damage to tropical forests. To further reduce selective logging damage, the practices that cause the most damage need to be identified and alternatives tested. To this end, we developed the R package LoggingLab, a spatially-explicit and individual tree-based selective logging simulator and demonstrated its functions using data from French Guiana. LoggingLab explicitly simulates damage during each stage of the selective logging process taking into account topography and hydrography, which are main constraints on logging. Most LoggingLab parameters can be easily adjusted to a wide range of local contexts. LoggingLab can also be coupled with forest dynamics models to simulate the long- term effects of different selective logging scenarios.

Auteurs, date et publication :

Auteurs Vincyane Badouard , Sylvain Schmitt , Guillaume Salzet , Thomas Gaquiere , Margaux Rojat , Caroline Bedeau , Olivier Brunaux , Géraldine Derroire

Publication : Ecological Modelling

Date : 2024

Volume : 487

Pages : 110539

Catégorie(s)

#CIRAD #FORET Paracou

Résumé

Aim: To investigate the geographic patterns and ecological correlates in the geographic distribution of the most common tree dispersal modes in Amazonia (endozoochory, synzoochory, anemochory and hydrochory). We examined if the proportional abundance of these dispersal modes could be explained by the availability of dispersal agents (disperser-availability hypothesis) and/or the availability of resources for constructing zoochorous fruits (resource-availability hypothesis). Time period: Tree-inventory plots established between 1934 and 2019. Major taxa studied: Trees with a diameter at breast height (DBH) ≥ 9.55 cm. Location: Amazonia, here defined as the lowland rain forests of the Amazon River basin and the Guiana Shield. Methods: We assigned dispersal modes to a total of 5433 species and morphospecies within 1877 tree-inventory plots across terra-firme, seasonally flooded, and permanently flooded forests. We investigated geographic patterns in the proportional abundance of dispersal modes. We performed an abundance-weighted mean pairwise distance (MPD) test and fit generalized linear models (GLMs) to explain the geographic distribution of dispersal modes. Results: Anemochory was significantly, positively associated with mean annual wind speed, and hydrochory was significantly higher in flooded forests. Dispersal modes did not consistently show significant associations with the availability of resources for constructing zoochorous fruits. A lower dissimilarity in dispersal modes, resulting from a higher dominance of endozoochory, occurred in terra-firme forests (excluding podzols) compared to flooded forests. Main conclusions: The disperser-availability hypothesis was well supported for abiotic dispersal modes (anemochory and hydrochory). The availability of resources for constructing zoochorous fruits seems an unlikely explanation for the distribution of dispersal modes in Amazonia. The association between frugivores and the proportional abundance of zoochory requires further research, as tree recruitment not only depends on dispersal vectors but also on conditions that favour or limit seedling recruitment across forest types.

Auteurs, date et publication :

Auteurs Diego F. Correa , Pablo R. Stevenson , Maria Natalia , Luiz De Souza , Coelho Diógenes , De Andrade Lima , Filho Rafael , Maria Natalia Umaña , Luiz de Souza Coelho , Diógenes de Andrade Lima Filho , Rafael P. Salomão , Iêda Leão do Amaral , Florian Wittmann , Francisca Dionízia de Almeida Matos , Carolina V. Castilho , Oliver L. Phillips , Juan Ernesto Guevara , Marcelo de Jesus Veiga Carim , William E. Magnusson , Daniel Sabatier

Publication : Global Ecology and Biogeography

Date : 2025

Issue : June 2021

Pages : 49–69

Catégorie(s)

#CIRAD #FORET Paracou

Résumé

A generalized notion of species richness is introduced. The generalization embeds the popular index of species richness on the boundary of a family of diversity indices each of which is the number of species in the community after a small proportion of individuals belonging to the least minorities is trimmed. It is established that the generalized species richness indices satisfy a weak version of the usual axioms for diversity indices, are qualitatively robust against small perturbations in the underlying distribution, and are collectively complete with respect to all information of diversity. In addition to a natural plug-in estimator of the generalized species richness, a bias-adjusted estimator is proposed, and its statistical reliability is gauged via bootstrapping. Finally an ecological example and supportive simulation results are given.

Auteurs, date et publication :

Auteurs Zhiyi Zhang

Publication : Entropy

Date : 2025

Volume : 24

Issue : 10

Catégorie(s)

#CIRAD #FORET Paracou

Résumé

In the context of climate change, identifying and then predicting the impacts of climatic drivers on tropical forest dynamics is becoming a matter of urgency. To look at these climate impacts, we used a coupled model of tropical tree growth and mortality, calibrated with forest dynamic data from the 20-year study site of Paracou, French Guiana, in order to introduce and test a set of climatic variables. Three major climatic drivers were identified through the variable selection procedure: drought, water saturation and temperature. Drought decreased annual growth and mortality rates, high precipitation increased mortality rates and high temperature decreased growth. Interactions between key functional traits, stature and climatic variables were investigated, showing best resistance to drought for trees with high wood density and for trees with small current diameters. Our results highlighted strong long-term impacts of climate variables on tropical forest dynamics, suggesting potential deep impacts of climate changes during the next century.

Auteurs, date et publication :

Auteurs M. Aubry-Kientz , V. Rossi , F. Wagner , B. Hérault

Publication : Biogeosciences

Date : 2015

Volume : 12

Issue : 19

Pages : 5583–5596

Catégorie(s)

#CIRAD #FORET Paracou

Auteurs, date et publication :

Auteurs Francois Catzeflis

Publication : Mammalia

Date : 2025

Catégorie(s)

#CIRAD #FORET Paracou

Résumé

Because territoriality is energetically costly, territorial animals frequently respond less aggressively to neighbours than to strangers, a reaction known as the “dear enemy phenomenon” (DEP). The contrary, the “nasty neighbour effect” (NNE), occurs mainly for group-living species defending resource-based territories. We studied the relationships between supercolonies of the pest fire ant Solenopsis saevissima and eight ant species able to live in the vicinity of its nests plus Eciton burchellii, an army ant predator of other ants. The workers from all of the eight ant species behaved submissively when confronted with S. saevissima (dominant) individuals, whereas the contrary was never true. Yet, S. saevissima were submissive towards E. burchellii workers. Both DEP and NNE were observed for the eight ant species, with submissive behaviours less frequent in the case of DEP. To distinguish what is due to chemical cues from what can be attributed to behaviour, we extracted cuticular compounds from all of the nine ant species compared and transferred them onto a number of S. saevissima workers that were then confronted with untreated conspecifics. The cuticular compounds from three species, particularly E. burchellii, triggered greater aggressiveness by S. saevissima workers, while those from the other species did not.

Auteurs, date et publication :

Auteurs Olivier Roux , Vivien Rossi , Régis Céréghino , Arthur Compin , Jean-Michel Martin , Alain Dejean , Roux , Olivier , Rossi , Vivien , Céréghino , Régis , Compin , Arthur , Martin , Jean-Michel , Dejean , Alain

Publication : Behavioural Processes

Date : 2013

Volume : 98

Pages : 51–57

Catégorie(s)

#CIRAD #FORET Paracou