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1. LiDAR-based reference aboveground biomass maps for tropical forests of South Asia and Central Africa

Author

Suraj Reddy Rodda, Rakesh Fararoda, Rajashekar Gopalakrishnan, Nidhi Jha, Maxime Réjou-Méchain, Pierre Couteron, Nicolas Barbier, Alonso Alfonso, Ousmane Bako, Patrick Bassama, Debabrata Behera, Pulcherie Bissiengou, Hervé Biyiha, Warren Y. Brockelman, Wirong Chanthorn, Prakash Chauhan, Vinay Kumar Dadhwal, Gilles Dauby, Vincent Deblauwe, Narcis Dongmo, Vincent Droissart, Selvaraj Jeyakumar, Chandra Shekar Jha, Narcisse G. Kandem, John Katembo, Ronald Kougue, Hugo Leblanc, Simon Lewis, Moses Libalah, Maya Manikandan, Olivier Martin-Ducup, Germain Mbock, Hervé Memiaghe, Gislain Mofack, Praveen Mutyala, Ayyappan Narayanan, Anuttara Nathalang, Gilbert Oum Ndjock, Fernandez Ngoula, Rama Rao Nidamanuri, Raphaël Pélissier, Sassan Saatchi, Le Bienfaiteur Sagang, Patrick Salla, Murielle Simo-Droissart, Thomas B. Smith, Bonaventure Sonké, Tariq Stevart, Danièle Tjomb, Donatien Zebaze, Lise Zemagho, and Pierre Ploton

Subjects
Science
Abstract

Abstract Accurate mapping and monitoring of tropical forests aboveground biomass (AGB) is crucial to design effective carbon emission reduction strategies and improving our understanding of Earth’s carbon cycle. However, existing large-scale maps of tropical forest AGB generated through combinations of Earth Observation (EO) and forest inventory data show markedly divergent estimates, even after accounting for reported uncertainties. To address this, a network of high-quality reference data is needed to calibrate and validate mapping algorithms. This study aims to generate reference AGB datasets using field inventory plots and airborne LiDAR data for eight sites in Central Africa and five sites in South Asia, two regions largely underrepresented in global reference AGB datasets. The study provides access to these reference AGB maps, including uncertainty maps, at 100 m and 40 m spatial resolutions covering a total LiDAR footprint of 1,11,650 ha [ranging from 150 to 40,000 ha at site level]. These maps serve as calibration/validation datasets to improve the accuracy and reliability of AGB mapping for current and upcoming EO missions (viz., GEDI, BIOMASS, and NISAR).

Published
2024
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2. A matter of warts: a taxonomic treatment for Drypetes verrucosa (Putranjivaceae, Malpighiales) and a new cauliflorous species from Cameroon and Nigeria, D. stevartii

Author

Alejandro Quintanar, Bonaventure Sonké, Murielle Simo-Droissart, Patricia Barberá, Moses Libalah, and David J. Harris

Subjects
Plant ecology, QK900-989
Abstract

Background and aims – Specimens of a new tree species in the genus Drypetes (Putranjivaceae) distributed in Cameroon and eastern Nigeria, D. stevartii, were associated with D. verrucosa, another tree species endemic to Gabon, due to its warty fruits and to the overall morphological resemblances of both species. Material and methods – The present study is based on the study of 20 gatherings of D. verrucosa and 26 gatherings of D. stevartii. Morphological observations on herbarium specimens belonging to the new species and D. verrucosa were carried out in order to describe them. Key results – This treatment includes the detailed descriptions of these two species, the typification of their names, a comparative table summarizing their main morphological differences, an identification key, photographs of both, as well as information about their distribution, habitat, and phenology. Preliminary IUCN Red List assessments show that both D. verrucosa and D. stevartii are ‘Near Threatened’ species.

Published
2023
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3. A map of African humid tropical forest aboveground biomass derived from management inventories

Author

Ploton, Pierre, Mortier, Frédéric, Barbier, Nicolas, Cornu, Guillaume, Réjou-Méchain, Maxime, Rossi, Vivien, Alonso, Alfonso, Bastin, Jean-François, Bayol, Nicolas, Bénédet, Fabrice, Bissiengou, Pulchérie, Chuyong, Georges, Demarquez, Benoît, Doucet, Jean-Louis, Droissart, Vincent, Kamdem, Narcisse Guy, Kenfack, David, Memiaghe, Hervé, Moses, Libalah, Sonké, Bonaventure, Texier, Nicolas, Thomas, Duncan, Zebaze, Donatien, Pélissier, Raphaël, and Gourlet-Fleury, Sylvie

Published
2020
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5. Additive influences of soil and climate gradients drive tree community composition of Central African rain forests

Author

Nicolas Texier, Raphaël Pélissier, Donatien Zebaze, Moses Libalah, Stéphane Takoudjou Momo, Bonaventure Sonké, Narcisse Guy Kamdem, Nicolas Barbier, Gislain Ii Mofack, Claire Fortunel, Pierre Couteron, Simon L. Lewis, Gilles Dauby, Vincent Droissart, Pierre Ploton, Gyslene Kamdem, Botanique et Modélisation de l'Architecture des Plantes et des Végétations (UMR AMAP), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de la Recherche Agronomique (INRA)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD [France-Sud]), University of Yaoundé [Cameroun], Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Laboratoire de Botanique et Ecologie, Université de Yaoundé I, Université libre de Bruxelles (ULB), Laboratoire de Botanique systématique et d'Ecologie [ENS Yaoudé], and Université de Yaoundé I-École normale supérieure [ENS] - Yaoundé 1

Subjects
0106 biological sciences, 010504 meteorology & atmospheric sciences, Soil gradient, Plant Science, Rainforest, [SDV.BID.SPT]Life Sciences [q-bio]/Biodiversity/Systematics, Phylogenetics and taxonomy, 010603 evolutionary biology, 01 natural sciences, Climate gradient, [SDV.EE.ECO]Life Sciences [q-bio]/Ecology, environment/Ecosystems, Cameroon, Relative species abundance, 0105 earth and related environmental sciences, 2. Zero hunger, Ecology, Species abundance, [SDV.BV.BOT]Life Sciences [q-bio]/Vegetal Biology/Botanics, 15. Life on land, Tropical rain forest, Tree (data structure), Community composition, 13. Climate action, Species occurrence, Environmental science, Tropical rainforests, [SDE.BE]Environmental Sciences/Biodiversity and Ecology
Abstract

International audience; Aim: Examining tree species-environment association can offer insight into the drivers of vegetation patterns and key information of practical relevance to forest management. Here, we aim to quantify the contribution of climate and soil gradients to variation in Central African tree species composition (abundance and occurrence). Location: Tropical rainforests of southern and eastern Cameroon. Methods: We established 82 1-ha permanent plots across seven localities and censused all trees ≥ 10 cm in diameter, representing a total of 37,733 trees and 455 species. In 60 of those plots, we measured ten soil variables describing texture and nutrients levels and extracted ten bioclimatic variables from global-gridded climate databases. We synthesized the main environmental gradients by conducting principal component analyses on climate and soil data respectively. We performed unconstrained and constrained non-symmetric correspondence analyses to account for the individual and joint contributions of climate and soil on species abundance and occurrence. Results: Climate and soil contributed similarly to variances of species abundance and occurrence (12–15 % variance for climate vs. 11–12 % variance for soil). Climate influence mostly concerns some abundant species, while some of the less abundant species were mainly driven by soil. Fractions of species variances accounted for by climate and soil show strong correlation when assessed from species occurrence and abundance data. Conclusion: Variation in occurrence and abundance of tropical forest trees can be partly shaped by both climate and soil gradients in Cameroon, which emphasizes the importance to jointly consider soil and climate in species distribution modeling. Less abundant species may express environmental influence differently than abundant species and convey complementary information about community assemblage. Though showing congruent patterns here, species abundance and occurrence reflect different interacting community processes and both should be examined to better understand vegetation patterns.

Published
2020
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6. Allometric Models to Estimate Leaf Area for Tropical African Broadleaved Forests

Author

Vincent Medjibe, Moses Libalah, Bonaventure Sonké, Nicolas Barbier, N. F. Sirri, Pierre Ploton, S. Momo Takoudjou, Gislain Ii Mofack, Narcisse Guy Kamdem, Higher Teachers' Training College, University of Yaoundé [Cameroun], Laboratoire de Botanique systématique et d'Ecologie [ENS Yaoudé], Université de Yaoundé I-École normale supérieure [ENS] - Yaoundé 1, Botanique et Modélisation de l'Architecture des Plantes et des Végétations (UMR AMAP), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de la Recherche Agronomique (INRA)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD [France-Sud]), University of Yaounde I, Université de Yaoundé I [Yaoundé]-École normale supérieure [ENS] - Yaoundé 1, and Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut National de la Recherche Agronomique (INRA)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])

Subjects
0106 biological sciences, Allometric models, Ecology, Allometric model, 04 agricultural and veterinary sciences, 15. Life on land, Tropical African broadleaved forests, [SDV.BV.BOT]Life Sciences [q-bio]/Vegetal Biology/Botanics, [SDV.BID.SPT]Life Sciences [q-bio]/Biodiversity/Systematics, Phylogenetics and taxonomy, 010603 evolutionary biology, 01 natural sciences, Leaf area, Geophysics, [SDV.EE.ECO]Life Sciences [q-bio]/Ecology, environment/Ecosystems, 040103 agronomy & agriculture, 0401 agriculture, forestry, and fisheries, General Earth and Planetary Sciences, Environmental science, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, ComputingMilieux_MISCELLANEOUS
Abstract

Direct and semidirect estimations of leaf area (LA) and leaf area index (LAI) are scarce in dense tropical forests despite their importance in calibrating remote sensing products, forest dynamics, and biogeochemical models. We destructively sampled 61 trees belonging to 13 most abundant species in a semideciduous forest in southeastern Cameroon. For each tree, all leaves were weighed, and for a subsample of branches, leaves were counted and the LA measured. Allometric models were calibrated to allow semidirect estimation of LAI at tree and stand levels based on forest inventory data (R-2 = 0.7, bias = 21.2%, error = 39.5%) and on predictors that could be extracted from very high resolution remote sensing data (R-2 = 0.63, bias = 35.1%, error = 58.73). Using twenty-one 1-ha forest plots, stand level estimations of LAI ranged from 4.42-13.99. These values are higher than previous estimates generally obtained using indirect methods. These results may have important consequences on ecosystem exchanges and the role of tropical forest in global cycles. Plain Language Summary Leaf area (LA) and leaf area index (LAI) are useful parameters characterizing the plant-atmosphere interface where matter and energy are exchanged. However, direct or semidirect estimations are not common in dense tropical forests. In this study, we used a destructive data set of trees of varied species and sizes from the semideciduous forest of southeastern Cameroon to predict total tree LA. Based on this data, we developed operational allometric models to allow for semidirect estimation of LA and LAI at tree and stand levels. These models would be of considerable use for climate-vegetation modeling and remote sensing communities.

Published
2019
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7. Pan-tropical prediction of forest structure from the largest trees

Author

Narayanaswamy Parthasarathy, Stephen P. Hubbell, Cintia Rodrigues de Souza, Takeshi Toma, Ben Swanepoel, Raphaël Pélissier, Donatien Zebaze, Luzmila Arroyo, Juliana Stropp, James R. Kellner, Alejandro Araujo-Murakami, Thomas E. Lovejoy, Benoît Cassart, Ben Hur Marimon Junior, James Grogan, Sebastian K. Herzog, Yadvinder Malhi, Krisna Gajapersad, José Luís Camargo, Christelle Gonmadje, Renato Valencia, Connie J. Clark, Denise Sasaki, Fabien Wagner, Francesco Rovero, Katrin Boehning-Gaese, David Kenfack, Olaf Bánki, John Terborgh, Ferry Slik, Arafat S. Mtui, Javier Silva Espejo, Hans Beeckman, Germaine Alexander Parada Gutierrez, Tinde van Andel, Luis Valenzuela, Thalès de Haulleville, Hans ter Steege, Elizabeth Kearsley, Martin J. P. Sullivan, Wilson Roberto Spironello, Rodolfo Vasque, Emmanuel H. Martin, Thomas Duncan, William F. Laurance, Jason Vleminckx, Paulus Matius, Charles De Cannière, Yves Laumonier, Ted R. Feldpausch, Andrew R. Marshall, John R. Poulsen, J. Daniel Soto, Priya Davidar, Jean François Gillet, Iêda Leão do Amaral, Papi Puspa Warsudi, Eurídice N. Honorio Coronado, Vincent A. Vos, Laurent Descroix, Nicolas Texier, Philippe Saner, Roderick Zagt, Marc P. E. Parren, Luiz Marcelo Brum Rossi, Robert Bitariho, Fernando Cornejo Valverde, Jon Lloyd, Nina Farwig, James Singh, Jean-Louis Doucet, Francis Q. Brearley, Leandro Valle Ferreira, Celso Paulo de Azevedo, Ervan Rutishauser, Johanna Hurtado, Bruno Hérault, Albert Angbonga-Basia, Jérôme Chave, David A. Neill, Jean Claude Razafimahaimodison, Pierre Ploton, Hilandia Brandão, Susan G. Laurance, Richard Condit, Roel J. W. Brienen, Jean-François Bastin, Ana Andrade, Marcos Silveira, Oliver L. Phillips, Gauthier Ligot, David B. Clark, Casimero Mendoza Bautista, Narayanan Ayyappan, Robin L. Chazdon, Hans Verbeeck, Santiago Espinosa, Jürgen Homeier, Mireille Breuer-Ndoundou Hockemba, Simon L. Lewis, Patricia Alvarez-Loyayza, Vincent Droissart, Sassan Saatchi, Nigel C. A. Pitman, Victoria Meyer, Nicolas Barbier, Wannes Hubau, Jorcely Barroso, Nicolas Labrière, Plinio Sist, Georges Chuyong, Pascal Boeckx, Hugo Romero Saltos, Antonio Ferraz, David Harris, Verginia Wortel, Pandi Vivek, Mark Schulze, Bonaventure Sonké, Jan Bogaert, Abel Monteagudo-Mendoza, Guido Pardo, Quentin Ponette, Ahimsa Campos-Arceiz, Michael Kessler, Beatriz Schwantes Marimon, Samir Gonçalves Rolim, Maxime Réjou-Méchain, Koen Hufkens, Narcisse Guy Kamdem, Adeline Fayolle, Aurélie Dourdain, Christine Fletcher, Moses Libalah, B.R. Ramesh, Research Unit of Landscape Ecology and Plant Production Systems, Université libre de Bruxelles (ULB), Carbon For Expert, California Institute of Technology (CALTECH), Botanique et Modélisation de l'Architecture des Plantes et des Végétations (UMR AMAP), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut National de la Recherche Agronomique (INRA)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), Ecologie des forêts de Guyane (UMR ECOFOG), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut National de la Recherche Agronomique (INRA)-AgroParisTech-Université de Guyane (UG)-Centre National de la Recherche Scientifique (CNRS)-Université des Antilles (UA), Département Environnements et Sociétés (Cirad-ES), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad), Université de Liège, University of Mary Washington, Instituto Nacional de Pesquisas da Amazônia (INPA), Universidad Autonoma Gabriel René Moreno (UAGRM), Institut Français de Pondichéry (IFP), Ministère de l'Europe et des Affaires étrangères (MEAE)-Centre National de la Recherche Scientifique (CNRS), Institute for Biodiversity and Ecosystem Dynamics (IBED), University of Amsterdam [Amsterdam] (UvA), Universidade Federal do Acre (UFAC), School of Engineering and Science, Jacobs University [Bremen], Laboratory of Applied Physical Chemistry, Universiteit Gent = Ghent University (UGENT), School of Geography [Leeds], University of Leeds, Universidad Nacional de San Antonio Abad del Cusco (UNSAAC), Evolution et Diversité Biologique (EDB), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS), University of Buea, Department of Computer Science, King‘s College London, Patrimoines Locaux et Gouvernance (PALOC), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD), Gembloux Agro-Bio Tech [Gembloux], Department of Ecology-Conservation Ecology, Faculty of Biology, Philipps Universität Marburg = Philipps University of Marburg, AgroBioTech, Forest Research Institute Malaysia (FRIM), Mount Holyoke College, Royal Botanic Gardens, Georg-August-University = Georg-August-Universität Göttingen, Royal Museum for Central Africa [Tervuren] (RMCA), Smithsonian Conservation Biology Institute, Center for Conservation Education and Sustainability, MRC 705, Box 37012, Washington, DC, VA 20013-7012, USA, Universität Zürich [Zürich] = University of Zurich (UZH), AgroParisTech, Center for International Forestry Research (CIFOR), Consultative Group on International Agricultural Research [CGIAR] (CGIAR), Université de Yaoundé I, Imperial College London, Environmental Science and Policy Department and the Department of Public and International Affairs, George Mason University [Fairfax], Environmental Change Inst., School of Geography and the Environment, University of Oxford, Universidade do Estado de Mato Grosso (UNEMAT), Centre Maurice Halbwachs (CMH), École des hautes études en sciences sociales (EHESS)-Centre National de la Recherche Scientifique (CNRS)-Département de Sciences sociales ENS-PSL, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Missouri Botanical Garden, Universidad Estatal Amazonica, Universidad Autonoma del Beni, Analytical and Biophysical Environmental Chemistry (CABE), University of Geneva, Sciences II, Division of Marine Science and Conservation, Nicholas School of the Environment, Duke University [Durham], Université Catholique de Louvain = Catholic University of Louvain (UCL), Département Systèmes Biologiques (Cirad-BIOS), MUSE – Science Museum of Trento, Forêts et Sociétés (UPR Forêts et Sociétés), Amazonia Central, Brazilian Agricultural Research Corporation (Embrapa), JRC Institute for Environment and Sustainability (IES), European Commission - Joint Research Centre [Ispra] (JRC), Department of Forest Vegetation, Forestry and Forest Products Research Institute (FFPRI), Laboratorio de Ecología de Plantas y Herbario QCA, Escuela de Ciencias Biológicas, Pontificia Universidad Católica del Ecuador, Chercheur indépendant, Computational & Applied Vegetation Ecology (CAVElab), Instituto Nacional de Pesquisas Espaciais (INPE), Ministério da Ciência, Tecnologia e Inovação, Biodiversity Department, Center for Agricultural Research in Suriname (CELOS), Laboratoire de Botanique systématique et d'Ecologie [ENS Yaoudé], Université de Yaoundé I-École normale supérieure [ENS] - Yaoundé 1, Université Libre de Bruxelles [Bruxelles] (ULB), Université des Antilles (UA)-Université de Guyane (UG)-Centre National de la Recherche Scientifique (CNRS)-AgroParisTech-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut National de la Recherche Agronomique (INRA), Centre National de la Recherche Scientifique (CNRS)-Ministère de l'Europe et des Affaires étrangères (MEAE), Ghent University [Belgium] (UGENT), Universidad Nacional San Antonio Abad del Cusco, Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Phillips Universität (Marburg), Georg-August-Universität Göttingen, University of Zurich, Université de Yaoundé, École normale supérieure - Paris (ENS Paris)-École des hautes études en sciences sociales (EHESS)-Centre National de la Recherche Scientifique (CNRS), Missouri Botanical Garden (USA), Université Catholique de Louvain (UCL), Pontificia Universidad Catolica del Ecuador, Université de Yaoundé I [Yaoundé]-École normale supérieure [ENS] - Yaoundé 1, Systems Ecology, Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de la Recherche Agronomique (INRA)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD [France-Sud]), Universiteit Gent = Ghent University [Belgium] (UGENT), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées, Georg-August-University [Göttingen], University of Oxford [Oxford], École normale supérieure - Paris (ENS Paris), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École des hautes études en sciences sociales (EHESS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
P33 - Chimie et physique du sol, 0106 biological sciences, pan-tropical, 010504 meteorology & atmospheric sciences, P40 - Météorologie et climatologie, REDD, Rainforest, F50 - Anatomie et morphologie des plantes, 010603 evolutionary biology, 01 natural sciences, Basal area, [SDV.SA.SF]Life Sciences [q-bio]/Agricultural sciences/Silviculture, forestry, K01 - Foresterie - Considérations générales, Quadratic mean diameter, Ecology, Evolution, Behavior and Systematics, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Changement climatique, Global and Planetary Change, Biomass (ecology), Tree canopy, Ecology, carbon, Diameter at breast height, large trees, Tropics, 15. Life on land, Structure du peuplement, séquestration du carbone, climate change, 13. Climate action, Forêt, Environmental science, Physical geography, tropical forest ecology, REDD+, Woody plant, forest structure
Abstract

© 2018 John Wiley & Sons Ltd Aim: Large tropical trees form the interface between ground and airborne observations, offering a unique opportunity to capture forest properties remotely and to investigate their variations on broad scales. However, despite rapid development of metrics to characterize the forest canopy from remotely sensed data, a gap remains between aerial and field inventories. To close this gap, we propose a new pan-tropical model to predict plot-level forest structure properties and biomass from only the largest trees. Location: Pan-tropical. Time period: Early 21st century. Major taxa studied: Woody plants. Methods: Using a dataset of 867 plots distributed among 118 sites across the tropics, we tested the prediction of the quadratic mean diameter, basal area, Lorey's height, community wood density and aboveground biomass (AGB) from the ith largest trees. Results: Measuring the largest trees in tropical forests enables unbiased predictions of plot- and site-level forest structure. The 20 largest trees per hectare predicted quadratic mean diameter, basal area, Lorey's height, community wood density and AGB with 12, 16, 4, 4 and 17.7% of relative error, respectively. Most of the remaining error in biomass prediction is driven by differences in the proportion of total biomass held in medium-sized trees (50–70 cm diameter at breast height), which shows some continental dependency, with American tropical forests presenting the highest proportion of total biomass in these intermediate-diameter classes relative to other continents. Main conclusions: Our approach provides new information on tropical forest structure and can be used to generate accurate field estimates of tropical forest carbon stocks to support the calibration and validation of current and forthcoming space missions. It will reduce the cost of field inventories and contribute to scientific understanding of tropical forest ecosystems and response to climate change.

Published
2018
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8. Using volume-weighted average wood specific gravity of trees reduces bias in aboveground biomass predictions from forest volume data

Author

Moses Libalah, Bonaventure Sonké, Vivien Rossi, Pierre Ploton, Narcisse Guy Kamdem, Nicolas Barbier, Le Bienfaiteur Takougoum Sagang, Gislain Ii Mofack, Victor François Nguetsop, Stéphane Takoudjou Momo, Noël Fonton, Plant Systematic and Ecology Laboratory (LaBosystE), Department of Biology, Higher Teachers’ Training College, Université de Yaoundé, University of Dschang, Botanique et Modélisation de l'Architecture des Plantes et des Végétations (UMR AMAP), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut National de la Recherche Agronomique (INRA)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), Commission des Forêts d’Afrique Centrale (COMIFAC), Faculté des Sciences - Université de Dschang [Cameroun], Université de Dschang, Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de la Recherche Agronomique (INRA)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD [France-Sud]), and Université de Yaoundé I

Subjects
0106 biological sciences, 010504 meteorology & atmospheric sciences, Linear model, télédétection, [SDV]Life Sciences [q-bio], Tree allometry, Management, Monitoring, Policy and Law, 010603 evolutionary biology, 01 natural sciences, remote sensing, cameroun, Statistics, 0105 earth and related environmental sciences, Nature and Landscape Conservation, Mathematics, Biomass (ecology), Forest inventory, Terrestrial LiDAR, Cameroon eastern forest, Diameter at breast height, Aboveground biomass, Forestry, 15. Life on land, Wood specific gravity, Weighting, Tree (data structure), Error propagation, Volume (thermodynamics), Specific gravity
Abstract

With the improvement of remote sensing techniques for forest inventory application such as terrestrial LiDAR, tree volume can now be measured directly, without resorting to allometric equations. However, wood specific gravity (WSG) remains a crucial factor for converting these precise volume measurements into unbiased biomass estimates. In addition to this WSG values obtained from samples collected at the base of the tree (WSGBase) or from global repositories such as Dryad (WSGDryad) can be substantially biased relative to the overall tree value. Our aim was to assess and mitigate error propagation at tree and stand level using a pragmatic approach that could be generalized to National Forest Inventories or other carbon assessment efforts based on measured volumetric data. In the semi-deciduous forests of Eastern Cameroon, we destructively sampled 130 trees belonging to 15 species mostly represented by large trees (up to 45 Mg). We also used stand-level dendrometric parameters from 21 1-ha plots inventoried in the same area to propagate the tree-level bias at the plot level. A new descriptor, volume average-weighted WSG (WWSG) of the tree was computed by weighting the WSG of tree compartments by their relative volume prior to summing at tree level. As WWSG cannot be assessed non-destructively, linear models were adjusted to predict field WWSG and revealed that a combination of WSGDryad, diameter at breast height (DBH) and species stem morphology (Sm) were significant predictors explaining together 72% of WWSG variation. At tree level, estimating tree aboveground biomass using WSGBase and WSGDryad yielded overestimations of 10% and 7% respectively whereas predicted WWSG only produced an underestimation of less than 1%. At stand-level, WSGBase and WSGDryad gave an average simulated bias of 9% (S.D. = ±7) and 3% (S.D. = ±7) respectively whereas predicted WWSG reduced the bias by up to 0.1% (S.D. = ±8). We also observed that the stand-level bias obtained with WSGBase and WSGDryad decreased with total plot size and plot area. The systematic bias induced by WSGBase and WSGDryad for biomass estimations using measured volumes are clearly not negligible but yet generally overlooked. A simple corrective approach such as the one proposed with our predictive WWSG model is liable to improve the precision of remote sensing-based approaches for broader scale biomass estimations.

Published
2018
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9. Shift in functional traits along soil fertility gradient reflects non-random community assembly in a tropical African rainforest

Author

Olivier J. Hardy, Duncan W. Thomas, Thomas Drouet, Bonaventure Sonké, Pierre Couteron, George B. Chuyong, Vincent Droissart, David Kenfack, Moses Libalah, David S. Pescador, Botanique et Modélisation de l'Architecture des Plantes et des Végétations (UMR AMAP), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut National de la Recherche Agronomique (INRA)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), Université de Yaoundé, Université Libre de Bruxelles [Bruxelles] (ULB), Universidad Rey Juan Carlos, Smithsonian Tropical Research Institute - CTFS ForestGEO, Smithsonian National Museum of Natural History (NMNH), Washington State University (WSU), University of Buea, Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de la Recherche Agronomique (INRA)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD [France-Sud]), Université de Yaoundé I, Université libre de Bruxelles (ULB), and Universidad Rey Juan Carlos [Madrid] (URJC)

Subjects
0106 biological sciences, Specific leaf area, [SDV]Life Sciences [q-bio], Species distribution, Plant Science, Rainforest, Biology, Abiotic filtering, 010603 evolutionary biology, 01 natural sciences, INTRASPECIFIC TRENDS, cameroun, Cameroon, Abiotic component, KORUP NATIONAL PARK, Ecology, ABIOTIC FILTERING, LEAF TRAITS, Edaphic, 15. Life on land, Intraspecific trends, Korup National Park, Leaf traits, Trait, CAMEROON, Soil fertility, Quadrat, Biologie, 010606 plant biology & botany
Abstract

Background and aims – There is increasing recognition that plant traits mediate environmental influence on species distribution, justifying non-random community assembly. We studied the influence of local scale edaphic factors on the distribution of functional traits in a tropical rainforest of Cameroon with the aim to find correlations between the main edaphic gradient and community functional trait metrics (weighted mean trait, functional divergence and intraspecific variation). Methods – Within the Korup Forest Dynamics Plot (50 ha), we randomly selected 44 quadrats of 0.04 ha each, collected soils and analysed 11 topography and soil variables. Leaves were harvested from all 98 tree species found in the quadrats to calculate community trait metrics [quadrat-level weighted mean (qk) and functional divergence (FDivk)] for leaf area (LA), specific leaf area (SLA), leaf phosphorus (LPC), leaf nitrogen concentration (LNC) and nitrogen to phosphorus ratio (N:P ratio). We examined relationships between the main edaphic gradient with qk, with FDivk and with intraspecific variation and interpreted correlations as the effects of abiotic filtering and competitive interaction. Key results – Soil fertility was the main edaphic gradient and was significantly correlated with qk for LPC, LNC and LA and with FDivk for LPC, N:P ratio, LA and SLA, confirming the influence of abiotic filtering and competitive interaction by the soil fertility gradient, respectively. For a given trait, quadrats were either over-dispersed or under-dispersed, accounting for 7–33 % of non-random trait distribution along the soil fertility gradient. Trends in intraspecific traits variation were consistently lower than quadrat-level mean traits along the soil fertility gradient. Conclusions – This study demonstrates the influence of soil fertility gradient on local scale community trait distribution and its contribution to non-random community assembly., SCOPUS: ar.j, info:eu-repo/semantics/published

Published
2017
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10. Field and Morphometric Studies ofPhyllobotryonMüell.Arg. (Salicaceae) in the Korup Forest Area of Cameroon

Author

Augustina G. N. Fongod, Marie Claire Veranso, Moses Libalah, and David Kenfack

Subjects
Morphometric analysis, Salicaceae, biology, Botany, Principal component analysis, Taxonomy (biology), Plant Science, Phyllobotryon, biology.organism_classification, Tropical forest, Calyx
Abstract

Morphometric analysis of Phyllobotryon Muell.Arg. in the Korup Forest Area of Cameroon recognizes three distinct morphospecies (1-3), which show significant variation in several leaf and fruit characters. In order to clarify the taxonomy of Phyllobotryon, we conducted univariate and multivariate analyses on sixteen quantitative and four qualitative characters scored from 111 fresh samples. Analysis of Variance revealed nine significant quantitative characters from which the first three Principal Components accounted for 74.6 % of the total variation. Results from Discriminant Analysis strongly support the existence of two groups (96.2 % and 100 %) representing Morphospecies 2 and 3, but morphospecies 2 is only weakly supported (88.9 %) as distinct from morphospecies 1. Characters such as petiole length, fruit surface ornamentation, style & calyx persistence, flower and fruit orientation and leaf shape are of

Published
2014
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11. Biodiversity and Conservation of Tropical Montane Ecosystems in the Gulf of Guinea, West Africa

Author

Gail W. Hearn, Drew T. Cronin, Moses Libalah, and Richard A. Bergl

Subjects
0106 biological sciences, 0301 basic medicine, Global and Planetary Change, Ecology, Biodiversity, 010603 evolutionary biology, 01 natural sciences, 03 medical and health sciences, Overexploitation, Critically endangered, 030104 developmental biology, Ecoregion, Geography, Habitat destruction, Refugium (population biology), Species richness, Endemism, Ecology, Evolution, Behavior and Systematics, Earth-Surface Processes
Abstract

Mount Cameroon (4095 m), the highest peak and only active volcano in West Africa, is located in the center of the Gulf of Guinea Pleistocene refugium. The associated forests and highlands along the southern Nigerian-Cameroon border and on the island of Bioko, known as the Biafran forests and highlands, are important formations of the Cameroon Volcanic Line owing to their wide elevational range, and on Mount Cameroon, a continuous gradient of unbroken vegetation from sea level to over 4000 m. The montane zones in the region begin 800 m above sea level forming the critically endangered Mount Cameroon and Bioko Montane Forests ecoregion. The broad elevational gradient of the region has resulted in high habitat diversity, leading the region to be a center for species endemism and richness across many taxa. Some of the densest human populations in Africa also occur in this region, putting intense pressure on the forests and highlands mostly due to overexploitation and habitat loss. The governments of ...

Published
2014
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12. Toward a general tropical forest biomass prediction model from very high resolution optical satellite images

Author

Christophe Proisy, Pierre Couteron, Cécile Antin, David Kenfack, S.T. Momo, Duncan W. Thomas, Gislain Ii Mofack, Nicolas Barbier, Maxime Réjou-Méchain, Jean-Philippe Gastellu-Etchegorry, Jean-François Bastin, N. Barathan, Narcisse Guy Kamdem, P. Petronelli, N. Balachandran, P. Verley, Uta Berger, Gilles Dauby, D. Zebaze Dongmo, Pierre Ploton, S. Pargal, Nicolas Texier, Raphaël Pélissier, Moses Libalah, Vincent Droissart, Georges Chuyong, Bonaventure Sonké, N. Ayyappan, Botanique et Modélisation de l'Architecture des Plantes et des Végétations (UMR AMAP), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut National de la Recherche Agronomique (INRA)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), AgroParisTech, Institut Français de Pondichéry (IFP), Ministère de l'Europe et des Affaires étrangères (MEAE)-Centre National de la Recherche Scientifique (CNRS), Research Unit of Landscape Ecology and Plant Production Systems, Université libre de Bruxelles (ULB), University of Buéa, Diversité, adaptation, développement des plantes (UMR DIADE), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), Evolutionary Biology and Ecology [ULB], Herbarium et Bibliothèque de Botanique africain, Centre d'études spatiales de la biosphère (CESBIO), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Laboratoire de Botanique systématique et d'Ecologie [ENS Yaoudé], Université de Yaoundé I-École normale supérieure [ENS] - Yaoundé 1, Smithsonian Tropical Research Institute, Ecologie des forêts de Guyane (UMR ECOFOG), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut National de la Recherche Agronomique (INRA)-AgroParisTech-Université de Guyane (UG)-Centre National de la Recherche Scientifique (CNRS)-Université des Antilles (UA), Washington State University (WSU), Technische Universität Dresden = Dresden University of Technology (TU Dresden), ANR-12-EBID-0002, European Project: 266546,EC:FP7:ENV,FP7-ERANET-2010-RTD,BIODIVERSA2(2010), Institut des sciences et industries du vivant et de l'environnement (ISIVE), Centre National de la Recherche Scientifique (CNRS)-Ministère de l'Europe et des Affaires étrangères (MEAE), Université Libre de Bruxelles [Bruxelles] (ULB), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Université de Yaoundé I [Yaoundé]-École normale supérieure [ENS] - Yaoundé 1, Technische Universität Dresden (TUD), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de la Recherche Agronomique (INRA)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD [France-Sud]), Institut de Recherche pour le Développement (IRD [France-Sud])-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), and Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)

Subjects
0106 biological sciences, Canopy, 010504 meteorology & atmospheric sciences, Tropical forests, forêt tropicale, Imagerie par satellite, Residual, [SDV.BID.SPT]Life Sciences [q-bio]/Biodiversity/Systematics, Phylogenetics and taxonomy, 01 natural sciences, Basal area, [SDV.SA.SF]Life Sciences [q-bio]/Agricultural sciences/Silviculture, forestry, Lacunarity, K01 - Foresterie - Considérations générales, Biomasse, Dynamique des populations, Satellite imagery, ComputingMilieux_MISCELLANEOUS, U10 - Informatique, mathématiques et statistiques, Inventaire forestier, Geology, Tropical forest biomass, Forêt, Fourier transform, Ordination, Passive optical imagery, Télédétection, REDD, Soil Science, Structural basin, 010603 evolutionary biology, Texture, Computers in Earth Sciences, Ressource forestière, 0105 earth and related environmental sciences, Remote sensing, model, Méthode statistique, Tropics, Modèle de simulation, 15. Life on land, Forest carbon, Environmental science, U30 - Méthodes de recherche, Canopy structure, satellite images
Abstract

International audience; Very high spatial resolution (VHSR) optical satellite imagery has shown good potential to provide non-saturating proxies of tropical forest aboveground biomass (AGB) from the analysis of canopy texture, for instance through the Fourier Transform Textural Ordination method. Empirical case studies however showed that the relationship between Fourier texture features and forest AGB varies across forest types and regions of the world, limiting model transferability. A better understanding of the biophysical mechanisms on which canopy texture – forest AGB relation relies is a prerequisite to move toward broad scale applications. Here we simulated VHSR optical canopy scenes in identical sun-sensor geometry for 279 1-ha tropical forest inventory plots distributed across the tropics. Our aim was to assess the respective merits and complementarity of two types of texture analysis techniques (i.e. Fourier and lacunarity) on a set of forests with contrasted structure and geographical origin, and develop a general texture-based approach for tropical forest AGB mapping. Across forests, Fourier texture captured a gradient of stands mean crown size reflecting well the progressive changes in stand structure throughout forest aggradation phase (e.g. Pearson's r=−0.42 with basal area) while lacunarity texture captured a gradient of canopy openness (, i.e. Pearson's r=−0.57 with stand gap fraction). Both types of texture indices were highly complementary for predicting forest AGB at the global level (so-called FL-model). The residual error of the FL-model was structured across sites and could be partially captured with a bioclimatic proxy, further improving the performance of the global model (so-called FLE-model) and reducing site-level biases. The FLE model was tested on a set of real Pleiades images covering a mosaic of high-biomass forests in the Congo basin (mean AGB over 49 field plots: 359±98Mgha−1), leading to a significant relationship (R2=0.47 on validation data) with reasonable error levels (

Published
2017
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13. Using terrestrial laser scanning data to estimate large tropical trees biomass and calibrate allometric models: A comparison with traditional destructive approach

Author

Bonaventure Sonké, Raphaël Pélissier, Gilles Le Moguédec, Gislain Ii Mofack, Stephane Momo Takoudjou, Jan Hackenberg, François de Coligny, Nicolas Barbier, Narcisse Guy Kamdem, Moses Libalah, Pierre Ploton, Sébastien Griffon, Université de Yaoundé, Botanique et Modélisation de l'Architecture des Plantes et des Végétations (UMR AMAP), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut National de la Recherche Agronomique (INRA)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), Unité de recherche Biogéochimie des Ecosystèmes Forestiers (BEF), Institut National de la Recherche Agronomique (INRA), Global Environment Facility, Université de Yaoundé I, and Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de la Recherche Agronomique (INRA)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD [France-Sud])

Subjects
0106 biological sciences, tropical forest, Accuracy and precision, afrique centrale, 010504 meteorology & atmospheric sciences, Mean squared error, REDD, [SDV]Life Sciences [q-bio], Tree allometry, forêt tropicale, 010603 evolutionary biology, 01 natural sciences, allometric equation, tropical forest trees, Calibration, biomasse aérienne, Ecology, Evolution, Behavior and Systematics, lidar, 0105 earth and related environmental sciences, Remote sensing, above-ground biomass, Biomass (ecology), arbre tropical, Central Africa, Ecology, Ecological Modeling, terrestrial-laser scanner, 15. Life on land, equatorial africa, K10 - Production forestière, Tree (data structure), Lidar, Congo Basin, optical radar, équation allométrique, Environmental science, Allometry, U30 - Méthodes de recherche
Abstract

1. Calibration of local, regional or global allometric equations to estimate biomass at the tree level constitutes a significant burden on projects aiming at reducing Carbon emissions from forest degradation and deforestation. The objective of this contribution is to assess the precision and accuracy of Terrestrial Laser Scanning (TLS) for estimating volumes and above-ground biomass (AGB) of the woody parts of tropical trees, and for the calibration of allometric models. 2. We used a destructive dataset of 61 trees, with diameters and AGB of up to 186.6 cm and 60 Mg respectively, which were scanned, felled and weighed in the semi-deciduous forests of eastern Cameroon. We present an operational approach based on available software allowing the retrieving of TLS volume with low bias and high accuracy for large tropical trees. Edition of the obtained models proved necessary, mainly to account for the complexity of buttressed parts of tree trunks, which were separately modelled through a meshing approach, and to bring a few corrections in the topology and geometry of branches, thanks to the amapstudio-scan software. 3. Over the entire dataset, TLS-derived volumes proved highly reliable for branches larger than 5cm in diameter. The volumes of the remaining woody parts estimated for stumps, stems and crowns as well as for the whole tree proved very accurate (RMSE below 2.81% and R-2 above of .98) and unbiased. Once converted into AGB using mean local-specific wood density values, TLS estimates allowed calibrating a biomass allometric model with coefficients statistically undistinguishable from those of a model based on destructive data. The Unedited Quantitative Structure Model (QSM) however leads to systematic overestimations of woody volumes and subsequently to significantly different allometric parameters. 4. We can therefore conclude that a non-destructive TLS approach can now be used as an operational alternative to traditional destructive sampling to build the allometric equations, although attention must be paid to the quality of QSM model adjustments to avoid systematic bias.

Published
2017
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14. Contrasted allometries between stem diameter, crown area, and tree height in five tropical biogeographic areas

Author

Vincent Droissart, Vanessa Hequet, Nicolas Texier, Philippe Birnbaum, Hervé Vandrot, Narcisse Guy Kamdem, Donatien Zebaze, Robin Pouteau, Pierre Couteron, Pierre Ploton, Thomas Boutreux, Moses Libalah, Elodie Blanchard, Thomas Ibanez, Cécile Antin, Nicolas Barbier, Grégoire Vincent, Bonaventure Sonké, Institut Agronomique Néo-Calédonien (IAC), Botanique et Modélisation de l'Architecture des Plantes et des Végétations (UMR AMAP), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de la Recherche Agronomique (INRA)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD [France-Sud]), Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Collège de France (CdF (institution))-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA), Laboratoire de Botanique et Ecologie, Université de Yaoundé I, Laboratoire de Botanique systématique et d'Ecologie [ENS Yaoudé], Université de Yaoundé I-École normale supérieure [ENS] - Yaoundé 1, Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut National de la Recherche Agronomique (INRA)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Collège de France (CdF)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Institut National de la Recherche Agronomique (INRA), Université de Yaoundé I [Yaoundé], Université de Yaoundé I [Yaoundé]-École normale supérieure [ENS] - Yaoundé 1, and Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Lumière du jour, 0106 biological sciences, Canopy, 010504 meteorology & atmospheric sciences, Physiology, F62 - Physiologie végétale - Croissance et développement, forêt tropicale, Plant Science, [SDV.BID.SPT]Life Sciences [q-bio]/Biodiversity/Systematics, Phylogenetics and taxonomy, F50 - Anatomie et morphologie des plantes, 01 natural sciences, Allométrie, Tree architecture, K01 - Foresterie - Considérations générales, Tronc, Crown light exposure, Ecology, Forestry, [SDV.BV.BOT]Life Sciences [q-bio]/Vegetal Biology/Botanics, Houppier, Anatomie végétale, Forêt, Ontogeny, Écosystème forestier, Tree species, Rainforest, F40 - Écologie végétale, Biogéographie, Biology, 010603 evolutionary biology, [SDV.EE.ECO]Life Sciences [q-bio]/Ecology, environment/Ecosystems, Stem size, Croissance, Power function, Scaling, 0105 earth and related environmental sciences, Allometry, Morphologie végétale, Ecologie, Niche differentiation, 15. Life on land, Tropical forest, Physical geography, [SDE.BE]Environmental Sciences/Biodiversity and Ecology
Abstract

Across five biogeographic areas, DBH-CA allometry was characterized by inter-site homogeneity and intra-site heterogeneity, whereas the reverse was observed for DBH-H allometry. Tree crowns play a central role in stand dynamics. Remotely sensed canopy images have been shown to allow inferring stand structure and biomass which suggests that allometric scaling between stems and crowns may be tight, although insufficiently investigated to date. Here, we report the first broad-scale assessment of stem vs. crown scaling exponents using measurements of bole diameter (DBH), total height (H), and crown area (CA) made on 4148 trees belonging to 538 species in five biogeographic areas across the wet tropics. Allometries were fitted with power functions using ordinary least-squares regressions on log-transformed data. The inter-site variability and intra-site (sub-canopy vs. canopy trees) variability of the allometries were evaluated by comparing the scaling exponents. Our results indicated that, in contrast to both DBH-H and H-CA allometries, DBH-CA allometry shows no significant inter-site variation. This fairly invariant scaling calls for increased effort in documenting crown sizes as part of tree morphology. Stability in DBH-CA allometry, indeed, suggests that some universal constraints are sufficiently pervasive to restrict the exponent variation to a narrow range. In addition, our results point to inverse changes in the scaling exponent of the DBH-CA vs. DBH-H allometries when shifting from sub-canopy to canopy trees, suggesting a change in carbon allocation when a tree reaches direct light. These results pave the way for further advances in our understanding of niche partitioning in tree species, tropical forest dynamics, and to estimate AGB in tropical forests from remotely sensed images.

Published
2016
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15. Closing a gap in tropical forest biomass estimation: accounting for crown mass variation in pantropical allometries

Author

Raphaël Pélissier, Donatien Zebaze, Maxime Réjou-Méchain, Adeline Fayolle, Vincent Droissart, Gilles Dauby, F. Boyemba Bosela, Vivien Rossi, Alfred Ngomanda, Matieu Henry, Moses Libalah, Nicolas Texier, Narcisse Guy Kamdem, Georges Chuyong, J. Katembo Mukirania, Nicolas Barbier, Uta Berger, Pierre Ploton, Duncan W. Thomas, Rosa C. Goodman, Bonaventure Sonké, David Kenfack, Pierre Couteron, and Stéphane Takoudjou Momo

Subjects
Estimation, Biomass (ecology), Crown (botany), Mass variation, Pantropical, Forestry, Biology, Tropical forest, Closing (morphology)
Abstract

Accurately monitoring tropical forest carbon stocks is an outstanding challenge. Allometric models that consider tree diameter, height and wood density as predictors are currently used in most tropical forest carbon studies. In particular, a pantropical biomass model has been widely used for approximately a decade, and its most recent version will certainly constitute a reference in the coming years. However, this reference model shows a systematic bias for the largest trees. Because large trees are key drivers of forest carbon stocks and dynamics, understanding the origin and the consequences of this bias is of utmost concern. In this study, we compiled a unique tree mass dataset on 673 trees measured in five tropical countries (101 trees > 100 cm in diameter) and an original dataset of 130 forest plots (1 ha) from central Africa to quantify the error of biomass allometric models at the individual and plot levels when explicitly accounting or not accounting for crown mass variations. We first showed that the proportion of crown to total tree aboveground biomass is highly variable among trees, ranging from 3 to 88 %. This proportion was constant on average for trees < 10 Mg (mean of 34 %) but, above this threshold, increased sharply with tree mass and exceeded 50 % on average for trees ≥ 45 Mg. This increase coincided with a progressive deviation between the pantropical biomass model estimations and actual tree mass. Accounting for a crown mass proxy in a newly developed model consistently removed the bias observed for large trees (> 1 Mg) and reduced the range of plot-level error from −23–16 to 0–10 %. The disproportionally higher allocation of large trees to crown mass may thus explain the bias observed recently in the reference pantropical model. This bias leads to far-from-negligible, but often overlooked, systematic errors at the plot level and may be easily corrected by accounting for a crown mass proxy for the largest trees in a stand, thus suggesting that the accuracy of forest carbon estimates can be significantly improved at a minimal cost.

Published
2015
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16. Seeing Central African forests through their largest trees

Author

Marc Dufrêne, Terese B. Hart, Corneille E. N. Ewango, Pierre Ploton, T. de Haulleville, Fidèle Baya, Jean-François Gillet, Sylvie Gourlet-Fleury, C De Cannière, Jean-Louis Doucet, Vincent Droissart, Gilles Dauby, Yadvinder Malhi, Duncan W. Thomas, Georges Chuyong, Jean-François Bastin, Adeline Serckx, Tariq Stévart, T. Kavali, David Kenfack, Hans Beeckman, Bonaventure Sonké, Jan Bogaert, Moses Libalah, D. Beina, C. H. Gonmadje, Pierre Couteron, Maxime Réjou-Méchain, Adeline Fayolle, Jean-Remy Makana, Danae Maniatis, Nicolas Barbier, Raphaël Pélissier, Research Unit of Landscape Ecology and Plant Production Systems, Université Libre de Bruxelles [Bruxelles] (ULB)-Université de Liège, Botanique et Modélisation de l'Architecture des Plantes et des Végétations (UMR AMAP), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut National de la Recherche Agronomique (INRA)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), Université de Liège - Gembloux, Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad), Oxford University Centre for the Environment (OUCE), University of Oxford [Oxford], Ministère des Eaux, Forêts, Chasse et Pêche, Royal Museum for Central Africa [Tervuren] (RMCA), Laboratoire de Biométrie et Biologie Evolutive - UMR 5558 (LBBE), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National de Recherche en Informatique et en Automatique (Inria)-VetAgro Sup - Institut national d'enseignement supérieur et de recherche en alimentation, santé animale, sciences agronomiques et de l'environnement (VAS)-Centre National de la Recherche Scientifique (CNRS), University of Buéa, Diversité, adaptation, développement des plantes (UMR DIADE), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), Laboratoire de Physique des Solides (LPS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Entomologie fonctionnelle et évolutive - Université de Liège, Wildlife Conservation Society, Smithsonian Tropical Research Institute, Laboratoire de Botanique systématique et d'Ecologie [ENS Yaoudé], Université de Yaoundé I [Yaoundé]-École normale supérieure [ENS] - Yaoundé 1, Institut de Mécanique des Fluides de Marseille, Herbarieum et Bibliothèque de Botanique africaine, Université Libre de Bruxelles [Bruxelles] (ULB), Sud Expert Plantes, ANR-12-EBID-0002,CoForTips,Forêts du Bassin du Congo: Biodiversité, Points de Basculement et Résilience des Systèmes Écologiques et Sociaux Forestiers.(2012), Université de Liège-Université libre de Bruxelles (ULB), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de la Recherche Agronomique (INRA)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD [France-Sud]), Biens et services des écosystèmes forestiers tropicaux : l'enjeu du changement global (UPR BSEF), Ministère des Eaux, Forêts, Chasse et Pêche [République Centrafricaine], Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11), Université de Yaoundé I-École normale supérieure [ENS] - Yaoundé 1, Université libre de Bruxelles (ULB), and University of Oxford

Subjects
tropical forest, Tropical and subtropical dry broadleaf forests, F40 - Écologie végétale, distributions, Tropical trees, Biodiversity, Climate change, Forests, [SDV.BID.SPT]Life Sciences [q-bio]/Biodiversity/Systematics, Phylogenetics and taxonomy, Models, Biological, size, Article, diversity, [SDV.EE.ECO]Life Sciences [q-bio]/Ecology, environment/Ecosystems, Phénomènes atmosphériques, Forest ecology, K01 - Foresterie - Considérations générales, Bosecologie en Bosbeheer, Stock (geology), Forest floor, Multidisciplinary, biomass, Ecology, Agroforestry, Forestry, dynamics, 15. Life on land, [SDV.BV.BOT]Life Sciences [q-bio]/Vegetal Biology/Botanics, PE&RC, Forest Ecology and Forest Management, Climatic change, Geography, Africa, Secondary forest, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, U30 - Méthodes de recherche
Abstract

Large tropical trees and a few dominant species were recently identified as the main structuring elements of tropical forests. However, such result did not translate yet into quantitative approaches which are essential to understand, predict and monitor forest functions and composition over large, often poorly accessible territories. Here we show that the above-ground biomass (AGB) of the whole forest can be predicted from a few large trees and that the relationship is proved strikingly stable in 175 1-ha plots investigated across 8 sites spanning Central Africa. We designed a generic model predicting AGB with an error of 14% when based on only 5% of the stems, which points to universality in forest structural properties. For the first time in Africa, we identified some dominant species that disproportionally contribute to forest AGB with 1.5% of recorded species accounting for over 50% of the stock of AGB. Consequently, focusing on large trees and dominant species provides precise information on the whole forest stand. This offers new perspectives for understanding the functioning of tropical forests and opens new doors for the development of innovative monitoring strategies., SCOPUS: ar.j, info:eu-repo/semantics/published

Published
2015
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