Pantropical variability in tree crown allometry

Grace Jopaul Loubota Panzou (1) , Adeline Fayolle (2) , Tommaso Jucker (3) , Oliver Phillips (4) , Stephanie Bohlman (5) , Lindsay Banin (6) , Simon Lewis (7) , Kofi Affum‐baffoe (8) , Luciana Alves , Cécile Antin (9) , Eric Arets (10) , Luzmila Arroyo (11) , Timothy R. Baker (4) , Nicolas Barbier (9) , Hans Beeckman (12) , Uta Berger (13) , Yannick Enock Bocko (14) , Frans Bongers (15) , Sam Bowers (16) , Thom Brade (16) , Eduardo Brondizio (17) , Arthur Chantrain (2) , Jérôme Chave (18) , Halidou Compaore (19) , David Coomes (20) , Adama S. Diallo , Arildo Dias (21) , Kangbéni Dimobe , Gloria Djaney Djagbletey , Tomas Domingues , Jean‐louis Doucet (2) , Thomas Drouet (22) , Eric Forni (23, 24) , John Godlee (16) , Rosa Goodman , Sylvie Gourlet‐fleury (23, 24) , Fidele Hien , Yoshiko Iida , Bhely Angoboy Ilondea , Jonathan Ilunga Muledi , Pierre Jacques (2) , Shem Kuyah , Jorge López‐portillo , Jean Joël Loumeto , Ben Hur Marimon‐junior , Beatriz Schwantes Marimon , Sylvanus Mensah , Edward Mitchard , Glenn Moncrieff , Narayanan Ayyappan (25) , Sean O’brien , Korotimi Ouedraogo , Michael W. Palace , Raphaël Pélissier (9) , Pierre Ploton (9) , Lourens Poorter (15) , Casey Ryan (16) , Gustavo Saiz , Karin dos Santos , Michael Schlund , Giacomo Sellan , Bonaventure Sonke , Frank Sterck , Quentin Thibaut (2) , Yorick van Hoef , Elmar Veenendaal , Alejandra Vovides , Yaozhan Xu , Tze Leong Yao , Ted Feldpausch (1)

1 University of Exeter
2 Université de Liège - Gembloux
3 University of Bristol [Bristol]
4 University of Leeds
5 UF - University of Florida [Gainesville]
6 Smithsonian Tropical Research Institute
7 Centre for Ecology & Hydrology - Lake Ecosystems Group [Lancaster, U.K.]
8 UCL - University College of London [London]
9 UMR AMAP - Botanique et Modélisation de l'Architecture des Plantes et des Végétations
10 Wageningen Environmental Research (Alterra)
11 UAGRM - Universidad Autonoma Gabriel René Moreno
12 RMCA - Royal Museum for Central Africa [Tervuren]
13 TU Dresden - Technische Universität Dresden = Dresden University of Technology
14 UMNG - Université Marien Ngouabi [Brazzaville]
15 WUR - Wageningen University and Research [Wageningen]
16 Edin. - University of Edinburgh
17 Indiana University [Bloomington]
18 EDB - Evolution et Diversité Biologique
19 INERA - Institut de l'Environnement et Recherches Agricoles [Ouagadougou]
20 CAM - University of Cambridge [UK]
21 Goethe University Frankfurt
22 ULB - Université libre de Bruxelles
23 UPR Forêts et Sociétés - Forêts et Sociétés
24 Cirad-ES - Département Environnements et Sociétés
25 IFP - Institut Français de Pondichéry

Aim: Tree crowns determine light interception, carbon and water exchange. Thus, understanding the factors causing tree crown allometry to vary at the tree and stand level matters greatly for the development of future vegetation modelling and for the calibration of remote sensing products. Nevertheless, we know little about large-scale variation and determinants in tropical tree crown allometry. In this study, we explored the continental variation in scaling exponents of site-specific crown allometry and assessed their relationships with environmental and stand-level variables in the tropics. Location: Global tropics. Time: period Early 21st century. Major taxa studied: Woody plants. Methods : Using a dataset of 87,737 trees distributed among 245 forest and savanna sites across the tropics, we fitted site-specific allometric relationships between crown dimensions (crown depth, diameter and volume) and stem diameter using power-law models. Stand-level and environmental drivers of crown allometric relationships were assessed at pantropical and continental scales. Results: The scaling exponents of allometric relationships between stem diameter and crown dimensions were higher in savannas than in forests. We identified that continental crown models were better than pantropical crown models and that continental differences in crown allometric relationships were driven by both stand-level (wood density) and environmental (precipitation, cation exchange capacity and soil texture) variables for both tropical biomes. For a given diameter, forest trees from Asia and savanna trees from Australia had smaller crown dimensions than trees in Africa and America, with crown volumes for some Asian forest trees being smaller than those of trees in African forests. Main conclusions: Our results provide new insight into geographical variability, with large continental differences in tropical tree crown allometry that were driven by stand-level and environmental variables. They have implications for the assessment of ecosystem function and for the monitoring of woody biomass by remote sensing techniques in the global tropics.

Mots clés: Crown allometry; Environment; Forest; Precipitation; Savanna; Soil; Stand‐level variable; Tropical biomes

Domaines: Systématique, phylogénie et taxonomie; Biodiversité et Ecologie; Botanique; Ecosystèmes

Grace Jopaul Loubota Panzou, Adeline Fayolle, Tommaso Jucker, Oliver Phillips, Stephanie Bohlman, et al.. Pantropical variability in tree crown allometry. Global Ecology and Biogeography, 2021, 30 (2), pp.459-475. ⟨10.1111/geb.13231⟩. ⟨hal-03103872⟩