Résumé
This study aimed to correlate logging intensity with canopy opening using medium-resolution satellite images (SPOT-type) on a sample of 15 blocks totaling more than 3300ha in two French Guianan forests with different reliefs. The maps obtained show the cumulative impacts on the canopy over the entire logging period (2008–2010). The percentages of canopy openness and the unit areas per logged tree were examined with logging statistics and GPS mappings of felled stems for 4 sub-samples. At the block scale, a 20% canopy opening after logging was observed for a logging intensity of 3.5treesha−1. The average canopy opening size per harvested tree was 601m2, which included felling gaps and openings resulting from the construction of roads and trails needed to remove the timber. The coefficients of variation of these variables were low. General linear models (glm) were created to test the relationship between canopy damage, logging intensity and relief at local scales (1 and 4ha) and at the management unit scale (i.e. 200–300ha). The model created at management-unit level (block level) did not detect any significant effect of the variables on the percentage of canopy openness. However, a significant and concordant relationship was demonstrated at local levels between relief, logging intensity, their interaction on the one hand and the percentage of canopy openness on the other. A maximum local harvesting intensity of 8 trees per hectare on plateaus makes it possible to obtain an opening of less than 33% at an 85% probability threshold. In contrast, the same canopy openness threshold is obtained at only 5 trees per hectare on hillier terrain, which suggests that it would be advantageous to adjust silviculture recommendations according to forest landscape. The average openness of 20% observed in this sample, considered in relation to the cutting cycle in effect in French Guiana (65years), implies a complete renewal of forest stands after 325years, assuming multifunctional management objectives.
Auteurs, date et publication :
Auteurs Stéphane Guitet , Sophie Pithon , Olivier Brunaux , Guillaume Jubelin , Valéry Gond
Publication : Forest Ecology and Management
Date : 2012
Volume : 277
Pages : 124–131
Catégorie(s)
#CIRAD #FORET ParacouRésumé
1. Climate models predict that the frequency, intensity and duration of drought events will increase in tropical regions. Although water withdrawal from deep soil layers is generally considered to be an efficient adaptation to drought, there is little information on the role played by deep roots in tropical forests. Tropical Eucalyptus plantations managed in short rotation cycles are simple forest ecosystems that may provide an insight into the water use by trees in tropical forests. 2. The contribution made by water withdrawn from deep soil layers to the water required for evapotranspiration was quantified daily from planting to harvesting age for a Eucalyptus grandis stand using a soil water transfer model coupled with an ecophysiological forest model (MAESPA). The model was parameterized using an extensive data set and validated using time series of the soil water content down to a depth of 10 m and water-table level, as well as evapotranspiration measured using eddy covariance. 3. Fast root growth after planting provided access to large quantities of water stored in deep soil layers over the first 2 years. Eucalyptus roots reached the water-table at a depth of 12 m after 2 years. Although the mean water withdrawal from depths of over 10 m amounted to only 5% of canopy transpiration from planting to a harvesting age of 5 years, the proportion of water taken up near the water-table was much higher during dry periods. The water-table rose from 18 to 12 m below-ground over 2 years after the harvest of the previous stand and then fell until harvesting age as evapotranspiration rates exceeded the annual rainfall. 4. Deep rooting is an efficient strategy to increase the amount of water available for the trees, allowing the uptake of transient gravitational water and possibly giving access to a deep watertable. Deep soil layers have an important buffer role for large amounts of water stored during the wet season that is taken up by trees during dry periods. Our study confirms that deep rooting could be a major mechanism explaining high transpiration rates throughout the year in many tropical forests.
Auteurs, date et publication :
Auteurs M. Christina , Y. Nouvellon , J. P. Laclau , J. L. Stape , J. P. Bouillet , G. R. Lambais , G. le Maire
Publication : Functional Ecology
Date : 2017
Volume : 31
Issue : 2
Pages : 509-519
Catégorie(s)
#CIRAD #FORET Itatinga #INRAERésumé
Selective logging, fragmentation, and understory fires directly degrade forest structure and composition. However, studies addressing the effects of forest degradation on carbon, water, and energy cycles are scarce. Here, we integrate field observations and high-resolution remote sensing from airborne lidar to provide realistic initial conditions to the Ecosystem Demography Model (ED-2.2) and investigate how disturbances from forest degradation affect gross primary production (GPP), evapotranspiration (ET), and sensible heat flux (H). We used forest structural information retrieved from airborne lidar samples (13,500 ha) and calibrated with 817 inventory plots (0.25 ha) across precipitation and degradation gradients in the eastern Amazon as initial conditions to ED-2.2 model. Our results show that the magnitude and seasonality of fluxes were modulated by changes in forest structure caused by degradation. During the dry season and under typical conditions, severely degraded forests (biomass loss ≥66%) experienced water stress with declines in ET (up to 34%) and GPP (up to 35%) and increases of H (up to 43%) and daily mean ground temperatures (up to 6.5°C) relative to intact forests. In contrast, the relative impact of forest degradation on energy, water, and carbon cycles markedly diminishes under extreme, multiyear droughts, as a consequence of severe stress experienced by intact forests. Our results highlight that the water and energy cycles in the Amazon are driven by not only climate and deforestation but also the past disturbance and changes of forest structure from degradation, suggesting a much broader influence of human land use activities on the tropical ecosystems.
Auteurs, date et publication :
Auteurs Marcos Longo , Sassan Saatchi , Michael Keller , Kevin Bowman , António Ferraz , Paul R. Moorcroft , Douglas C. Morton , Damien Bonal , Paulo Brando , Benoît Burban , Géraldine Derroire , Maiza N. dos‐Santos , Victoria Meyer , Scott Saleska , Susan Trumbore , Grégoire Vincent
Publication : Journal of Geophysical Research: Biogeosciences
Date : 2025
Volume : 125
Issue : 8
Pages : e2020JG005677
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Fine roots (FR) play a major role in the water and nutrient uptake of plants and contribute significantly to the carbon and nutrient cycles of ecosystems through their annual production and turnover. FR growth dynamics were studied to understand the endogenous and exogenous factors driving these processes in a 14 year-old plantation of rubber trees located in eastern Thailand. FR dynamics were observed using field rhizotrons from Oct. 2007 to Oct. 2009. This period covered two complete dry seasons (Nov.-Mar.) and two complete rainy seasons (Apr.-Oct.), allowing us to study the effect of rainfall seasonality on FR dynamics. Rainfall and its distribution during the two successive years showed strong differences with 1500 mm and 950 mm in 2008 and 2009, respectively. Fine root production (FRP) completely stopped during the dry seasons and resumed quickly after the first rains. During the rainy seasons, FRP and the daily root elongation rate (RER) were highly variable and exhibited strong annual variations with a total FRP of 139.8 and 40.4 m m-² and an average RER of 0.16 and 0.12 cm d-1 in 2008 and 2009, respectively. The significant positive correlations found between FRP, RER, the appearance of new roots and rainfall at monthly intervals revealed the impact of rainfall seasonality on FR dynamics. However, the rainfall patterns failed to explain the weekly variations of FR dynamics observed particularly during the rainy seasons. At this time step, FRP, RER and the appearance of new FR were negatively correlated to the average soil matric potential measured at a depth of between 30 and 60 cm. In addition, our study revealed a significant negative correlation between FR dynamics and the monthly production of dry rubber. Consequently, latex harvesting might disturb carbon dynamics in the whole tree, far beyond the trunk where the tapping was performed. These results exhibit the impact of climatic conditions and tapping system in the carbon budget of rubber plantations.
Auteurs, date et publication :
Auteurs Naruenat Chairungsee , Frédéric Gay , Philippe Thaler , Poonpipope Kasemsap , Sornprach Thanisawanyangura , Arak Chantuma , Christophe Jourdan
Publication : Frontiers in Plant Science
Date : 2025
Volume : 4
Catégorie(s)
#CIRAD #FORET RubberfluxRésumé
ULG & Ecofog
Auteurs, date et publication :
Auteurs à fin. Boriau, Elodie; Université de Liège textgreater Master bioingé. gest. forêts & esp. nat. , à fin. Université de Liège textgreater Master bioingé. gest. forêts & esp. nat.
Date : 2025
Catégorie(s)
#CIRAD #FORET ParacouAuteurs, date et publication :
Auteurs Sylvain Schmitt , Marion Boisseaux
Publication : Annals of Botany
Date : 2023
Catégorie(s)
#CIRAD #FORET ParacouAuteurs, date et publication :
Auteurs Sylvain Schmitt , Bruno Hérault , Géraldine Derroire
Publication : Ecology Letters
Date : 2025
Catégorie(s)
#CIRAD #FORET ParacouRésumé
The aim of Copernicus Climate Change Service (C3S) is to supply reliable climate data in support of strategies to adaptation and mitigation to climate change. The C3S provides access to high-quality climate data through its Climate Data Records (CDRs) of atmospheric, marine and land Essential Climate Variables (ECVs). Global Earth Surface Albedo (SA) satellite-based products are included in the land (biosphere) portfolio. SA is a magnitude which quantifies the fraction of solar energy reflected by the surface of the Earth. This paper details the retrieval methodology and preliminary validation results for global estimates of surface albedo based on Sentinel-3 observations for the C3S ECVs data (C3S SA v3.0). The retrieval algorithm exploits the synergistic use of the Ocean and Land Colour Instrument (OLCI) and the Sea and Land Surface Temperature Radiometer (SLSTR) on-board Sentinel-3 A and B satellites. Firstly, the atmospherically corrected reflectances are generated in the Copernicus Global Land Service framework. After that, the Bidirectional Reflectance Distribution Function (BRDF) inversion module concludes the BRDF model parameters, which are transferred to the angular integration module in order to generate spectral albedo quantities for the selected OLCI (Oa03, Oa04, Oa07, Oa17 and Oa21) and SLSTR (S1, S2, S5 and S6) bands. At the end, the spectral integration module generates broadband albedo quantities in three different standard broadband spectral regions (visible [0.4μm − 0.7μm ], near infrared [0.7μm − 4μm] and total shortwave [0.3μm − 4μm]). Preliminary validation results over 10-months demonstration period (July 2018–April 2019) show, in terms of spatial and temporal consistency, that C3S Sentinel-3 SA global estimates reached in general good agreement as compared to other satellite operational references derived from MODIS (MCD43A3 C6) and PROBA-V (C3S PROBA-V SA v1.0) acquisitions. The comparison with ground data shows similar results to the MCD43A3 C6 comparisons but opposite sign in differences (marginally positive in case of Sentinel-3), with accuracy of 0.005 (3.7%), precision of 0.016 (11.3%) and uncertainty of 0.032 (22.7%). Our results have demonstrated the feasibility to estimate global fields of SA from Sentinel-3 observations, with similar quality of existing operational products. These Sentinel-3 based SA datasets will give the continuity to the existing C3S SA CDR, introducing improvements in terms of spatial resolution (300 m) and spectral information (9 spectral albedos) in contrast to previous datasets based on Advanced Very High Resolution Radiometer (AVHRR; 4 km, 4 channels) and Vegetation instruments (VGT; 1 km, 4 channels).
Auteurs, date et publication :
Auteurs Jorge Sánchez-Zapero , Fernando Camacho , Enrique Martínez-Sánchez , Javier Gorroño , Jonathan León-Tavares , Iskander Benhadj , Carolien Toté , Else Swinnen , Joaquín Muñoz-Sabater
Publication : Remote Sensing of Environment
Date : 2025
Volume : 287
Issue : December 2022
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Aim To determine the relationships between the functional trait composition of forest communities and environmental gradients across scales and biomes and the role of species relative abundances in these relationships. Location Global. Time period Recent. Major taxa studied Trees. Methods We integrated species abundance records from worldwide forest inventories and associated functional traits (wood density, specific leaf area and seed mass) to obtain a data set of 99,953 to 149,285 plots (depending on the trait) spanning all forested continents. We computed community-weighted and unweighted means of trait values for each plot and related them to three broad environmental gradients and their interactions (energy availability, precipitation and soil properties) at two scales (global and biomes). Results Our models explained up to 60% of the variance in trait distribution. At global scale, the energy gradient had the strongest influence on traits. However, within-biome models revealed different relationships among biomes. Notably, the functional composition of tropical forests was more influenced by precipitation and soil properties than energy availability, whereas temperate forests showed the opposite pattern. Depending on the trait studied, response to gradients was more variable and proportionally weaker in boreal forests. Community unweighted means were better predicted than weighted means for almost all models. Main conclusions Worldwide, trees require a large amount of energy (following latitude) to produce dense wood and seeds, while leaves with large surface to weight ratios are concentrated in temperate forests. However, patterns of functional composition within-biome differ from global patterns due to biome specificities such as the presence of conifers or unique combinations of climatic and soil properties. We recommend assessing the sensitivity of tree functional traits to environmental changes in their geographic context. Furthermore, at a given site, the distribution of tree functional traits appears to be driven more by species presence than species abundance.
Auteurs, date et publication :
Auteurs Elise Bouchard , Eric B. Searle , Pierre Drapeau , Jingjing Liang , Javier G. P. Gamarra , Meinrad Abegg , Giorgio Alberti , Angelica Almeyda Zambrano , Esteban Alvarez‐Davila , Luciana F. Alves , Valerio Avitabile , Gerardo Aymard , Jean‐François Bastin , Philippe Birnbaum , Frans Bongers , Olivier Bouriaud , Pedro Brancalion , Eben Broadbent , Filippo Bussotti , Roberto Cazzolla Gatti
Publication : Global Ecology and Biogeography
Date : 2025
Issue : October 2023
Pages : 303–324
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Aim Amazonia hosts more tree species from numerous evolutionary lineages, both young and ancient, than any other biogeographic region. Previous studies have shown that tree lineages colonized multiple edaphic environments and dispersed widely across Amazonia, leading to a hypothesis, which we test, that lineages should not be strongly associated with either geographic regions or edaphic forest types. Location Amazonia. Taxon Angiosperms (Magnoliids; Monocots; Eudicots). Methods Data for the abundance of 5082 tree species in 1989 plots were combined with a mega-phylogeny. We applied evolutionary ordination to assess how phylogenetic composition varies across Amazonia. We used variation partitioning and Moran's eigenvector maps (MEM) to test and quantify the separate and joint contributions of spatial and environmental variables to explain the phylogenetic composition of plots. We tested the indicator value of lineages for geographic regions and edaphic forest types and mapped associations onto the phylogeny. Results In the terra firme and várzea forest types, the phylogenetic composition varies by geographic region, but the igapó and white-sand forest types retain a unique evolutionary signature regardless of region. Overall, we find that soil chemistry, climate and topography explain 24% of the variation in phylogenetic composition, with 79% of that variation being spatially structured (R2 = 19% overall for combined spatial/environmental effects). The phylogenetic composition also shows substantial spatial patterns not related to the environmental variables we quantified (R2 = 28%). A greater number of lineages were significant indicators of geographic regions than forest types. Main Conclusion Numerous tree lineages, including some ancient ones (>66 Ma), show strong associations with geographic regions and edaphic forest types of Amazonia. This shows that specialization in specific edaphic environments has played a long-standing role in the evolutionary assembly of Amazonian forests. Furthermore, many lineages, even those that have dispersed across Amazonia, dominate within a specific region, likely because of phylogenetically conserved niches for environmental conditions that are prevalent within regions.
Auteurs, date et publication :
Auteurs Bruno Garcia Luize , David Bauman , Hans ter Steege , Clarisse Palma-Silva , Iêda Leão do Amaral , Luiz de Souza Coelho , Francisca Dionízia de Almeida Matos , Diógenes de Andrade Lima Filho , Rafael P. Salomão , Florian Wittmann , Carolina V. Castilho , Marcelo de Jesus Veiga Carim , Juan Ernesto Guevara , Oliver L. Phillips , William E. Magnusson , Daniel Sabatier , Juan David Cardenas Revilla , Jean-François Molino , Mariana Victória Irume , Maria Pires Martins
Publication : Journal of Biogeography
Date : 2025
Volume : 51
Issue : 7
Pages : 1163-1184