Auteurs, date et publication :

Auteurs Hossein Aghababaee , Gianfranco Fornaro , Gilda Schirinzi

Publication : IEEE Transactions on Geoscience and Remote Sensing

Date : 2025

Volume : PP

Pages : 1–13

Catégorie(s)

#CIRAD #FORET Paracou

Auteurs, date et publication :

Auteurs J.-P. Laclau , J.-L. de Moraes Goncalves , J.-L. Stape

Publication : Forest Ecology and Management

Date : 2013

Volume : 301

Pages : 1-5

Catégorie(s)

#CIRAD #FORET Itatinga #INRAE

Résumé

Although vast areas in tropical regions have weathered soils with low potassium (K) levels, little is known about the effects of K supply on the photosynthetic physiology of trees. This study assessed the effects of K and sodium (Na) supply on the diffusional and biochemical limitations to photosynthesis in Eucalyptus grandis leaves.A field experiment comparing treatments receiving K (+K) or Na (+Na) with a control treatment (C) was set up in a K-deficient soil. The net CO2 assimilation rates were twice as high in +K and 1.6 times
higher in +Na than in the C as a result of lower stomatal and mesophyll resistance to CO2 diffusion and higher photosynthetic capacity. The starch content was higher and soluble sugar was lower in +K than in C and +Na, suggesting that K starvation disturbed carbon storage and transport. The specific leaf area, leaf thickness, parenchyma thickness, stomatal size and intercellular air spaces increased in +K and +Na compared to C. Nitrogen and chlorophyll concentrations were also higher in +K and +Na than in C. These results suggest a strong relationship between the K and Na supply to E. grandis trees and the functional and structural limitations to CO2 assimilation rates.

Auteurs, date et publication :

Auteurs P. Battie-Laclau , J.-P. Laclau , C. Beri , L. Mietton , M.-R. Almeida Muniz , B. Cersózimo Arenque , M. de Cassia Piccolo , L. Jordan-Meille , J.-P. Bouillet , Y. Nouvellon

Publication : Plant, Cell and Environment

Date : 2025

Volume : 37

Pages : 70-81

Catégorie(s)

#CIRAD #FORET Itatinga #INRAE

Résumé

Hydraulic segmentation at the stem–leaf transition predicts higher hydraulic resistance in leaves than in stems. Vulnerability segmentation, however, predicts lower embolism resistance in leaves. Both mechanisms should theoretically favour runaway embolism in leaves to preserve expensive organs such as stems, and should be tested for any potential coordination. We investigated the theoretical leaf-specific conductivity based on an anatomical approach to quantify the degree of hydraulic segmentation across 21 tropical rainforest tree species. Xylem resistance to embolism in stems (flow-centrifugation technique) and leaves (optical visualization method) was quantified to assess vulnerability segmentation. We found a pervasive hydraulic segmentation across species, but with a strong variability in the degree of segmentation. Despite a clear continuum in the degree of vulnerability segmentation, eight species showed a positive vulnerability segmentation (leaves less resistant to embolism than stems), whereas the remaining species studied exhibited a negative or no vulnerability segmentation. The degree of vulnerability segmentation was positively related to the degree of hydraulic segmentation, such that segmented species promote both mechanisms to hydraulically decouple leaf xylem from stem xylem. To what extent hydraulic and vulnerability segmentation determine drought resistance requires further integration of the leaf–stem transition at the whole-plant level, including both xylem and outer xylem tissue.

Auteurs, date et publication :

Auteurs Sébastien Levionnois , Camille Ziegler , Steven Jansen , Emma Calvet , Sabrina Coste , Clément Stahl , Camille Salmon , Sylvain Delzon , Charlotte Guichard , Patrick Heuret

Publication : New Phytologist

Date : 2025

Volume : 228

Issue : 2

Pages : 512-524

Catégorie(s)

#CIRAD #FORET Paracou

Résumé

• Climate models for the coming century predict rainfall reduction in the Amazonian region, including change in water availability for tropical rainforests. Here, we test the extent to which climate variables related to water regime, temperature and irradiance shape the growth trajectories of neotropical trees. • We developed a diameter growth model explicitly designed to work with asynchronous climate and growth data. Growth trajectories of 205 individual trees from 54 neotropical species censused every 2 months over a 4-year period were used to rank 9 climate variables and find the best predictive model. • About 9% of the individual variation in tree growth was imputable to the seasonal variation of climate. Relative extractable water was the main predictor and alone explained more than 60% of the climate effect on tree growth, i.e. 5.4% of the individual variation in tree growth. Furthermore, the global annual tree growth was more dependent on the diameter increment at the onset of the rain season than on the duration of dry season. • The best predictive model included 3 climate variables: relative extractable water, minimum temperature and irradiance. The root mean squared error of prediction (0.035 mm.d–1) was slightly above the mean value of the growth (0.026 mm.d–1). • Amongst climate variables, we highlight the predominant role of water availability in determining seasonal variation in tree growth of neotropical forest trees and the need to include these relationships in forest simulators to test, in silico, the impact of different climate scenarios on the future dynamics of the rainforest.

Auteurs, date et publication :

Auteurs Fabien Wagner , Vivien Rossi , Clément Stahl , Damien Bonal , Bruno Hérault , Gil Bohrer

Publication : Plos One

Date : 2012

Volume : 7

Issue : 4

Pages : e34074

Catégorie(s)

#CIRAD #FORET Paracou

Résumé

The future of tropical managed forests is threatened by climate change. In anticipation of the increase in the frequency of drought episodes predicted by climatic models for intertropical regions, it is essential to study commercial trees' resilience and vulnerability to water stress by identifying potential interaction effects between selective logging and stress due to a lack of water. Focusing on 14 species representing a potential or acknowledged commercial interest for wood production in the Guiana Shield, a joint model coupling growth and mortality for each species was parametrized, including a climatic variable related to water stress and the quantity of aboveground biomass lost after logging. For the vast majority of the species, water stress had a negative impact on growth rate, while the impact of logging was positive. The opposite results were observed for the mortality. Combining results from growth and mortality models, we generate vulnerability profiles and ranking from species apparently quite resistant to water stress (Chrysophyllum spp., Goupia glabra Aubl., Qualea rosea Aubl.), even under logging pressure, to highly vulnerable species (Sterculia spp.). In light of our results, forest managers in the Guiana Shield may want to conduct (i) a conservation strategy of the most vulnerable species and (ii) a diversification of the logged species. Conservation of the already-adapted species may also be considered as the most certain way to protect the tropical forests under future climates.

Auteurs, date et publication :

Auteurs Hélène Fargeon , Mélaine Aubry-Kientz , Olivier Brunaux , Laurent Descroix , Romain Gaspard , Stéphane Guitet , Vivien Rossi , Bruno Hérault

Publication : Forests

Date : 2016

Volume : 7

Issue : 12

Pages : 105

Catégorie(s)

#CIRAD #FORET Paracou

Résumé

Aim: Water availability is the major driver of tropical forest structure and dynamics. Most research has focused on the impacts of climatic water availability, whereas remarkably little is known about the influence of water table depth and excess soil water on forest processes. Nevertheless, given that plants take up water from the soil, the impacts of climatic water supply on plants are likely to be modulated by soil water conditions. Location: Lowland Amazonian forests. Time period: 1971–2019. Methods: We used 344 long-term inventory plots distributed across Amazonia to analyse the effects of long-term climatic and edaphic water supply on forest functioning. We modelled forest structure and dynamics as a function of climatic, soil-water and edaphic properties. Results: Water supplied by both precipitation and groundwater affects forest structure and dynamics, but in different ways. Forests with a shallow water table (depth <5 m) had 18% less above-ground woody productivity and 23% less biomass stock than forests with a deep water table. Forests in drier climates (maximum cumulative water deficit < −160 mm) had 21% less productivity and 24% less biomass than those in wetter climates. Productivity was affected by the interaction between climatic water deficit and water table depth. On average, in drier climates the forests with a shallow water table had lower productivity than those with a deep water table, with this difference decreasing within wet climates, where lower productivity was confined to a very shallow water table. Main conclusions: We show that the two extremes of water availability (excess and deficit) both reduce productivity in Amazon upland (terra-firme) forests. Biomass and productivity across Amazonia respond not simply to regional climate, but rather to its interaction with water table conditions, exhibiting high local differentiation. Our study disentangles the relative contribution of those factors, helping to improve understanding of the functioning of tropical ecosystems and how they are likely to respond to climate change.

Auteurs, date et publication :

Auteurs Thaiane R. Sousa , Juliana Schietti , Igor O. Ribeiro , Thaise Emílio , Rafael Herrera Fernández , Hans Steege , Carolina V. Castilho , Adriane Esquivel‐Muelbert , Timothy Baker , Aline Pontes‐Lopes , Camila V. J. Silva , Juliana M. Silveira , Géraldine Derroire , Wendeson Castro , Abel Monteagudo Mendoza , Ademir Ruschel , Adriana Prieto , Adriano José Nogueira Lima , Agustín Rudas , Alejandro Araujo‐Murakami

Publication : Global Ecology and Biogeography

Date : 2025

Issue : October 2021

Pages : 1–18

Catégorie(s)

#CIRAD #FORET Paracou

Auteurs, date et publication :

Auteurs Maricar Aguilos , Bruno Hérault , Benoit Burban , Fabien Wagner , Damien Bonal

Publication : Agricultural and Forest Meteorology

Date : 2025

Volume : 253-254

Issue : March 2017

Pages : 114–123

Catégorie(s)

#CIRAD #FORET Paracou

Résumé

Fertilization of rubber plantations has been poorly documented despite the huge economic and ecological impact of this tropical perennial crop, especially in Southeast Asia. The main objective of this paper is to provide information on the fertilization practices of rubber smallholders in Thailand and to investigate the drivers of these practices. Data were sourced from individual interviews conducted with 414 rubber smallholders. The results showed that 99.4% of the mature rubber plantations were fertilized with either chemical or organic fertilizers, or both. The average dose of chemical fertilizers was 105/53/92 kg ha−1 of N/P/K that is consistent with the national recommendations. We estimated that almost two-thirds of the plantations had intensive or very intensive fertilization practices. Geographical location, especially the distinction between historical and new rubber-producing areas, appeared as a major factor explaining differences in fertilization practices. Several drivers commonly found in the literature did not affect the fertilization practices of the rubber farmers, highlighting some specificity of perennial crops and a context where access to fertilizer was not an issue. The high economic and environmental costs of intensive fertilization practices, while their benefit to the yield of rubber plantations continues to be debated, show the need to conduct research on sustainable fertilization practices in rubber smallholdings.

Auteurs, date et publication :

Auteurs Bénédicte Chambon , Xuan Lai Dao , Uraiwan Tongkaemkaew , Frédéric Gay

Publication : Experimental Agriculture

Date : 2018

Volume : 54

Issue : 6

Pages : 824-841

Catégorie(s)

#CIRAD #FORET Rubberflux

Auteurs, date et publication :

Auteurs Dan Binkley , Jean-Paul Laclau , Hubert Sterba

Publication : Forest Ecology and Management

Date : 2025

Volume : 288

Pages : 1-4

Catégorie(s)

#CIRAD #FORET Itatinga #INRAE