Résumé
Evapotranspiration and energy partitioning are complex to estimate because they result from the interaction of many different processes, especially in multi-species and multi-strata ecosystems. We used MAESPA model, a mechanistic, 3D model of coupled radiative transfer, photosynthesis, and balances of energy and water, to simulate the partitioning of energy and evapotranspiration in homogeneous tree plantations, as well as in heterogeneous multi-species, multi-strata agroforests with diverse spatial scales and management schemes. The MAESPA model was modified to add (1) calculation of foliage surface water evaporation at the voxel scale; (2) computation of an average within-canopy air temperature and vapour pressure; and (3) use of (1) and (2) in iterative calculations of soil and leaf temperatures to close ecosystem-level energy balances. We tested MAESPA model simulations on a simple monospecific Eucalyptus stand in Brazil, and also in two complex, heterogeneous Coffea agroforests in Costa Rica. MAESPA satisfactorily simulated the daily and seasonal dynamics of net radiation (RMSE = 29.6 and 28.4 W m−2; R2 = 0.99 and 0.99 for Eucalyptus and Coffea sites respectively) and its partitioning between latent-(RMSE = 68.1 and 37.2 W m−2; R2 = 0.87 and 0.85) and sensible-energy (RMSE = 54.6 and 45.8 W m−2; R2 = 0.57 and 0.88) over a one-year simulation at half-hourly time-step. After validation, we use the modified MAESPA to calculate partitioning of evapotranspiration and energy between plants and soil in the above-mentioned agro-ecosystems. In the Eucalyptus plantation, 95% of the outgoing energy was emitted as latent-heat, while the Coffea agroforestry system's partitioning between sensible and latent-heat fluxes was roughly equal. We conclude that MAESPA process-based model has an appropriate balance of detail, accuracy, and computational speed to be applicable to simple or complex forest ecosystems and at different scales for energy and evapotranspiration partitioning. (Résumé d'auteur)
Auteurs, date et publication :
Auteurs Rémy Vezy , Mathias Christina , Olivier Roupsard , Yann Nouvellon , Remko A. Duursma , Belinda E. Medlyn , Maxime Soma , Fabien Charbonnier , Céline Blitz-Frayret , Jose Luiz Stape , Jean-Paul Laclau , Elias de Melo Virginio Filho , Jean-Marc Bonnefond , Bruno Rapidel , Frédéric C. Do , Alain Rocheteau , Delphine Picart , Carlos Borgonovo , Denis Loustau , Guerric Le Maire
Publication : Agricultural and Forest Meteorology
Date : 2025
Volume : 253-254
Pages : 203-2017
Catégorie(s)
#CIRAD #FORET CoffeeFlux #FORET Itatinga #FORET RubberfluxRésumé
The rubber tree (Hevea brasiliensis) is an important economic crop, particularly in Thailand. As the plantations extend to new and drier areas, information on physiological parameters such as water use efficiency (WUE) is required to help breeding for adapted genotypes. Carbon isotope composition of bulk leaf (δ¹³C) can be used as an indicator of intrinsic water use efficiency (WUEi) of plants. A prerequisite step is to analyse the genetic variability of δ¹³C. We compared the carbon isotope composition of bulk rubber tree leaf (δ¹³C) in rainy and dry seasons in a collection of 49 wild genotypes of rubber in Northern Thailand. There were large δ¹³C variations among the genotypes at all seasons. δ¹³C ranged between -33.3‰ to -30.0‰ in rainy season and -33.1‰ to -29.9‰ in dry season. δ¹³C was rather stable with a good correlation between rainy and dry season. In rainy season, there was a positive significant correlation between δ¹³C, leaf mass per area (LMA) and leaf nitrogen per area (NA). The average δ¹³C was significantly different between two genetic clusters previously identified in this population. The large genetic variability of δ¹³C in wild rubber population is promising for breeding genotypes using less water.
Auteurs, date et publication :
Auteurs N. Kampanon , P. Kamensap , P. Thaler , B. Kositsup , Ratchanee Rattanawong , Daniel Epron
Publication : Journal of Rubber Research
Date : 2025
Volume : 20
Issue : 1
Pages : 58-70
Catégorie(s)
#CIRAD #FORET RubberfluxRésumé
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 RubberfluxRésumé
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
Methods Fine root growth and mortality of Eucalyptus grandis trees were observed fortnightly using minirhizotrons down to a soil depth of 6 m, from 2 to 4 years after planting.
Results In the topsoil, the highest live root length production was during the rainy summer (20 cm m−2 d−1) whereas, below 2 m deep, it was at the end of the dry winter (51 cm m−2 d−1). The maximum root elongation rates increased with soil depth to 3.6 cm d−1 in the 5–6 m soil layer.
Conclusions Our study shows that the effect of the soil depth on the seasonal variations in fine root growth should be taken into account when modelling the carbon, water and nutrient cycles in forests growing on deep tropical soils.
Auteurs, date et publication :
Auteurs George Rodrigues Lambais , Christophe Jourdan , Marisa de Cássia Piccolo , Amandine Germon , Rafael Costa Pinheiro , Yann Nouvellon , José Luiz Stape , Otávio Camargo Campoe , Agnès Robin , Jean-Pierre Bouillet , Guerric le Maire , Jean-Paul Laclau
Publication : Plant and Soil
Date : 2025
Volume : 421
Issue : 1-2
Pages : 301-318
Catégorie(s)
#CIRAD #FORET Itatinga #FORET Rubberflux #INRAERésumé
Method Fine roots (diameter < 2 mm) were sampled in a randomized block design with three treatments: monospecific stands of Acacia mangium (100A), Eucalyptus grandis (100E), and mixed stands with 50% of each species (50A50E). Root ingrowth bags were installed at 4 depths (from 0.1 m to 6 m) in the three treatments within three different blocks, to study the fine-root production over 2 periods of 3 months. Results Down to 17 m depth, total fine-root biomass was 1127 g m−2 in 50A50E, 780 g m−2 in 100A and 714 g m−2 in 100E. Specific root length and specific root area were 110–150% higher in 50A50E than in 100A for Acacia mangium trees and 34% higher in 50A50E than in 100E for Eucalyptus grandis trees. Ingrowth bags showed that the capacity of fine roots to explore soil patches did not decrease down to a depth of 6 m for the two species. Conclusions Belowground interactions between Acacia mangium and Eucalyptus grandis trees greatly increased the exploration of very deep soil layers by fine roots, which is likely to enhance the uptake of soil resources. Mixing tree species might therefore increase the resilience of tropical planted forests through a better exploration of deep soils.
Auteurs, date et publication :
Auteurs Amandine Germon , Iraê Amaral Guerrini , Bruno Bordron , Jean-Pierre Bouillet , Yann Nouvellon , José Leonardo de Moraes Gonçalves , Christophe Jourdan , Ranieri Ribeiro Paula , Jean-Paul Laclau
Publication : Plant and Soil
Date : 2017
Catégorie(s)
#CIRAD #FORET Itatinga #FORET Rubberflux #INRAERésumé
The article “Conceptualization, modeling and environmental impact assessment of a natural rubber techno-ecological system with nutrient, water and energy integration” by Martinez-Hernandez E and Hernandez JE (2018, 185: 707–722) is based on a compilation of published information processed through a model linking natural rubber making to latex yield in rubber tree fields. Its main conclusion is that recycling processing wastewater could increase the yield by 62%. However, the statement that nitrogen input can significantly increase latex yield is based on a wrong quotation of the only cited reference. Moreover, the outputs of the model were not validated by actual data. The published literature actually shows that possible increase of latex yield by fertilization or irrigation would be much lower than 62%, and this invalidates the model. Its conclusions can then not be considered scientifically established.
Auteurs, date et publication :
Auteurs Philippe Thaler
Publication : Journal of Cleaner Production
Date : 2019
Volume : 210
Pages : 1063-1064
Catégorie(s)
#CIRAD #FORET RubberfluxRésumé
Selection for drought-tolerant clones has become a major challenge in rubber breeding programs undertaken to ensure the sustainability of natural rubber production, as rubber plantations are expanding in drought-prone areas. Xylem vulnerability to cavitation is a trait related to drought-induced mortality. It can be rapidly evaluated without subjecting plant materials to drought stress, making it useful in large-scale screening for drought tolerance in the near future. We first compared the most widely used techniques for measuring vulnerability to cavitation (air pressurization and Cavitron) on this species, and the effect of sample conditions (size, age and sunlight exposure), in order to ensure reliable analysis. Secondly, ten rubber clones were compared for their xylem vulnerability to cavitation in branches and petioles, and for other traits related to drought response, including stomatal response and leaf shedding occurring during a simulated drought. We also tested the plasticity of vulnerability to cavitation on two clones grown in three locations with contrasting precipitation regimes. We found no clonal variability and a small phenotypic plasticity for xylem vulnerability to cavitation in branches. However, clonal differences in xylem vulnerability to cavitation were found in petioles, and clones also showed differences in stomatal response and in leaf shedding behavior in response to a simulated drought. Our study suggests a genetic canalization for vulnerability to cavitation in organs critical for survival, such as branches, whereas there are clonal differences for traits related to drought avoidance: vulnerability to cavitation of petioles, leaf shedding behavior and stomatal response. The insights gained in this study for screening rubber tree clones for drought tolerance is also discussed.
Auteurs, date et publication :
Auteurs Wanploy Jinagool , Ratchanee Rattanawong , Krissada Sangsing , Têtè Sévérien Barigah , Frederic Gay , Hervé Cochard , Poonpipope Kasemsap , Stéphane Herbette
Publication : The Journal of Plant Hydraulics
Date : 2025
Volume : 2
Pages : 14
Catégorie(s)
#CIRAD #FORET RubberfluxRésumé
Climate change and fast extension in climatically suboptimal areas threaten the sustainability of rubber tree cultivation. A simple framework based on reduction factors of potential transpiration was tested to evaluate the water constraints on seasonal transpiration in tropical sub-humid climates, according pedoclimatic conditions. We selected a representative, mature stand in a drought-prone area. Tree transpiration, evaporative demand and soil water availability were measured every day over 15 months. The results showed that basic relationships with evaporative demand, leaf area index and soil water availability were globally supported. However, the implementation of a regulation of transpiration at high evaporative demand whatever soil water availability was necessary to avoid large overestimates of transpiration. The details of regulation were confirmed by the analysis of canopy conductance response to vapor pressure deficit. The final objective of providing hierarchy between the main regulation factors of seasonal and annual transpiration was achieved. In the tested environmental conditions, the impact of atmospheric drought appeared larger importance than soil drought contrary to expectations. Our results support the interest in simple models to provide a first diagnosis of water constraints on transpiration with limited data, and to help decision making toward more sustainable rubber plantations.
Auteurs, date et publication :
Auteurs Jessada Sopharat , Frederic Gay , Philippe Thaler , Sayan Sdoodee , Supat Isarangkool Na Ayutthaya , Charlchai Tanavud , Claude Hammecker , Frederic C. Do
Publication : Frontiers in Plant Science
Date : 2015
Volume : 5