Résumé
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 #INRAEAuteurs, date et publication :
Auteurs Christopher Baraloto , Bruno Hérault , C. E. Timothy Paine , Hélène Massot , Lilian Blanc , Damien Bonal , Jean-François Molino , Eric A. Nicolini , Daniel Sabatier
Publication : Journal of Applied Ecology
Date : 2012
Volume : 49
Issue : 4
Pages : 861–870
Catégorie(s)
#CIRAD #FORET ParacouRésumé
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 #INRAEAuteurs, date et publication :
Auteurs Dan Binkley , Mark Adams , Todd Fredericksen , Jean Paul Laclau , Harri Mäkinen , Cindy Prescott
Publication : Forest Ecology and Management
Date : 2025
Volume : 410
Pages : 157-163
Catégorie(s)
#CIRAD #FORET Itatinga #INRAERésumé
The structure of forests is an important indicator of ecosystem dynamics and enables the modeling and monitoring of ecological change. Synthetic aperture radar tomography (TomoSAR) provides scene reflectivity estimation of vegetation along elevation coordinates. Due to the advantages of superresolution imaging and a small number of measurements, compressive sensing (CS) inversion techniques for SAR tomography were successfully developed and applied. This paper addresses the 3-D imaging of forested areas based on the framework of CS using fully polarimetric (FP) multibaseline SAR interferometric (MB-InSAR) tomography at P-band. A new CS-based FP MB-InSAR tomography method is proposed: a sum of Kronecker product (SKP) decomposition-based CS FP MB-InSAR tomography method (FP-SKPCS TomoSAR method). The method, based on an assumption that the reflectivity signal of a single scattering mechanism (SM) is more sparse than that of a composite of SMs, recovers the reflectivity profile of different SMs by using the CS technique. This method not only allows superresolution imaging with a low number of acquisitions but also can estimate the polarimetric SM of the vertical structure of forested areas. The effectiveness of these novel techniques for polarimetric SAR tomography is demonstrated using FP P-band airborne data sets acquired by the ONERA SETHI airborne system over a test site in Paracou, French Guiana, and the results of the vertical structure of forested areas derived by the method are verified by in situ test data.
Auteurs, date et publication :
Auteurs Xinwu Li , Lei Liang , Huadong Guo , Yue Huang
Publication : IEEE Transactions on Geoscience and Remote Sensing
Date : 2016
Volume : 54
Issue : 1
Pages : 153–166
Catégorie(s)
#CIRAD #FORET ParacouAuteurs, date et publication :
Auteurs Adriane Esquivel-Muelbert , Timothy R. Baker , Kyle G. Dexter , Simon L. Lewis , Roel J. W. Brienen , Ted R. Feldpausch , Jon Lloyd , Abel Monteagudo-Mendoza , Luzmila Arroyo , Esteban Álvarez-Dávila , Niro Higuchi , Beatriz S. Marimon , Ben Hur Marimon-Junior , Marcos Silveira , Emilio Vilanova , Emanuel Gloor , Yadvinder Malhi , Jerôme Chave , Jos Barlow , Damien Bonal
Publication : Global Change Biology
Date : 2018
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Global environmental change necessitates increased predictive capacity; for forests, recent advances in technology provide the response to this challenge. “Next‐generation” remote‐sensing instruments can measure forest biogeochemistry and structural change, and individual‐based models can predict the fates of vast numbers of simulated trees, all growing and competing according to their ecological attributes in altered environments across large areas. Application of these models at continental scales is now feasible using current computing power. The results obtained from individual‐based models are testable against remotely sensed data, and so can be used to predict changes in forests at plot, landscape, and regional scales. This model–data comparison allows the detailed prediction, observation, and testing of forest ecosystem changes at very large scales and under novel environmental conditions, a capability that is greatly needed in this time of potentially massive ecological change.
Auteurs, date et publication :
Auteurs Herman H Shugart , Gregory P Asner , Rico Fischer , Andreas Huth , Nikolai Knapp , Thuy Le Toan , Jacquelyn K Shuman
Publication : Frontiers in Ecology and the Environment
Date : 2015
Volume : 13
Issue : 9
Pages : 503–511
Catégorie(s)
#CIRAD #FORET ParacouRésumé
textlessptextgreater Within tree communities, the differential use of soil N mineral resources, a key factor in ecosystem functioning, may reflect functional complementarity, a major mechanism that could explain species coexistence in tropical rainforests. textlessitalictextgreaterEperua falcatatextless/italictextgreater and textlessitalictextgreaterDicorynia guianensistextless/italictextgreater , two abundant species cooccurring in rainforests of French Guiana, were chosen as representative of two functional groups with complementary N uptake strategies (contrasting leaf textlessitalictextgreaterδtextless/italictextgreater textlesssuptextgreater15textless/suptextgreater N signatures related to the textlessitalictextgreaterδtextless/italictextgreater textlesssuptextgreater15textless/suptextgreater N of their soil N source, textlessmath id="M1"textgreater textlessmrowtextgreater textlessmsuptextgreater textlessmrowtextgreater textlessmrowtextgreater textlessmtexttextgreaterNOtextless/mtexttextgreater textless/mrowtextgreater textlessmrowtextgreater textlessmn mathvariant="normal"textgreater3textless/mntextgreater textless/mrowtextgreater textless/mrowtextgreater textlessmrowtextgreater textlessmotextgreater-textless/motextgreater textless/mrowtextgreater textless/msuptextgreater textless/mrowtextgreater textless/mathtextgreater or textlessmath id="M2"textgreater textlessmrowtextgreater textlessmsuptextgreater textlessmrowtextgreater textlessmrowtextgreater textlessmtexttextgreaterNHtextless/mtexttextgreater textless/mrowtextgreater textlessmrowtextgreater textlessmn mathvariant="normal"textgreater4textless/mntextgreater textless/mrowtextgreater textless/mrowtextgreater textlessmrowtextgreater textlessmotextgreater+textless/motextgreater textless/mrowtextgreater textless/msuptextgreater textless/mrowtextgreater textless/mathtextgreater ). The objectives were to investigate if these strategies occurred under contrasted soil N resources in sites with distinct geological substrates representative of the coastal rainforests. Results showed that species displayed contrasting leaf textlessitalictextgreaterδtextless/italictextgreater textlesssuptextgreater15textless/suptextgreater N signatures on both substrates, confirming their complementary N uptake strategy. Consequently, their leaf textlesssuptextgreater15textless/suptextgreater N can be used to trace the presence of inorganic N-forms in soils ( textlessmath id="M3"textgreater textlessmrowtextgreater textlessmsuptextgreater textlessmrowtextgreater textlessmrowtextgreater textlessmtexttextgreaterNHtextless/mtexttextgreater textless/mrowtextgreater textlessmrowtextgreater textlessmn mathvariant="normal"textgreater4textless/mntextgreater textless/mrowtextgreater textless/mrowtextgreater textlessmrowtextgreater textlessmotextgreater+textless/motextgreater textless/mrowtextgreater textless/msuptextgreater textless/mrowtextgreater textless/mathtextgreater and textlessmath id="M4"textgreater textlessmrowtextgreater textlessmsuptextgreater textlessmrowtextgreater textlessmrowtextgreater textlessmtexttextgreaterNOtextless/mtexttextgreater textless/mrowtextgreater textlessmrowtextgreater textlessmn mathvariant="normal"textgreater3textless/mntextgreater textless/mrowtextgreater textless/mrowtextgreater textlessmrowtextgreater textlessmotextgreater-textless/motextgreater textless/mrowtextgreater textless/msuptextgreater textless/mrowtextgreater textless/mathtextgreater ) and thus to indicate the capacity of soils to provide each of these two N sources to the plant community. textless/ptextgreater
Auteurs, date et publication :
Auteurs J. C. Roggy , H. Schimann , D. Sabatier , J. F. Molino , V. Freycon , Anne-Marie Domenach
Publication : International Scholarly Research Notices
Date : 2014
Volume : 2014
Pages : 1–6
Catégorie(s)
#CIRAD #FORET ParacouRésumé
In agroforestry systems (AFS), quantifying the competition for light is a prerequisite toward understanding the impact of shade trees on the productivity of the under-crop. Models for homogeneous canopies and shade/full-sun approaches do not address the intra-plot heterogeneity, typical of AFS. For the first time, MAESTRA, a 3D light absorption model, was fully parameterized in a heterogeneous 2-canopy layers AFS. We quantified competition for photosynthetic photon flux density (Q) between shade trees (Erythrine poepiggiana) and coffee (Coffea arabica), with a spatial resolution from the plant to the plot (2.7 ha) and a temporal resolution from half-hour to one full year. The predicted transmittance through the 2-canopy layers was verified against field measurements. The goodness of fit (R-2 > 0.75, RRMSE < 26%) was comparable to the predictions from 10 other studies using 3D light models and mostly verified in one-layered systems (mean R-2 = 0.89 and mean RRMSE = 17%). Maps of absorbed Q showed that despite their low density in the plot (5.2 trees ha(-1)), the tall Erythrina trees reduced Q available for the coffee layer by 14% annually. Annual pruning of the oldest unproductive coffee resprouts maintained a large horizontal heterogeneity in coffee LAI, with direct impact on the Q absorption map. This management practice had a strong impact on seasonal variations of absorbed Q by the coffee canopy. We proposed also a simple approach to estimate Q absorbed yearly by the coffee plants in AFS of variable tree density, requiring only few measurements in the field. An extrapolation indicated that the amount of Q absorbed by the coffee canopy would display a negative exponential relationship (k = -0.34) when increasing shade tree density (from nil to 29 trees ha(-1)). The estimated k was similar to the shade tree extinction coefficient of diffuse radiation measured with a plant canopy analyzer. We showed that the presence of shade trees tends to reverse the diurnal time course of the fraction of Q(a) when compared to a plantation in the open. Overall, MAESTRA proved to successfully unlock the question of intra-plot heterogeneity for light absorption and to provide defensible light budgets as a continuous and mapped covariable, a crucial step for many field experimentations. (C) 2013 Elsevier B.V. All rights reserved.
Auteurs, date et publication :
Auteurs Fabien Charbonnier , Guerric le Maire , Erwin Dreyer , Fernando Casanoves , Mathias Christina , Jean Dauzat , Jan U. H. Eitel , Philippe Vaast , Lee A. Vierling , Olivier Roupsard
Publication : Agricultural and Forest Meteorology
Date : 2013
Volume : 181
Pages : 152-169
Catégorie(s)
#CIRAD #FORET CoffeeFluxRésumé
Synthetic aperture radar Tomography (TomoSAR) provides scene reflectivity estimation of vegetation along elevation coordinates. However, the more multi-baselines acquisition, the longer the time span of acquisition, which will result in serious temporal decorrelation in forested area. In this way, we expect to use as smaller number of baselines as possible to obtain high estimation accuracy in elevation direction. We thus investigate the performance of Polarimetric SAR tomography (Pol-TomoSAR) with small number of baselines in forested areas. The results show that compressive sensingbased Pol-TomoSAR has higher estimation accuracy in elevation direction than conventional Pol-TomoSAR with small number of baselines.
Auteurs, date et publication :
Auteurs Lei Liang , Chenghu Zhou , Xinwu Li , Xizhang Gao , Wenjin Wu
Publication : Chinese Journal of Electronics
Date : 2019
Volume : 28
Issue : 5
Pages : 1073-1079