Pantropical variability in tree crown allometry
Authors: Loubota Panzou Grace Jopaul , Fayolle Adeline , Jucker Tommaso , Phillips Oliver L. , Bohlman Stephanie , Banin Lindsay F. , Lewis Simon L. , Affum‐Baffoe Kofi , Alves Luciana F. , Antin Cécile , Arets Eric , Arroyo Luzmila , Baker Timothy R. , Barbier Nicolas , Beeckman Hans , Berger Uta , Bocko Yannick Enock , Bongers Frans , Bowers Sam , Brade Thom , Brondizio Eduardo S. , Chantrain Arthur , Chave Jerome , Compaore Halidou , Coomes David , Diallo Adama , Dias Arildo S. , Dimobe Kangbéni , Djagbletey Gloria Djaney , Domingues Tomas , Doucet Jean‐Louis , Drouet Thomas , Forni Eric , Godlee John L. , Goodman Rosa C. , Gourlet‐Fleury Sylvie , Hien Fidele , Iida Yoshiko , Ilondea Bhely Angoboy , Ilunga Muledi Jonathan , Jacques Pierre , Kuyah Shem , López‐Portillo Jorge , Loumeto Jean Joël , Marimon‐Junior Ben Hur , Marimon Beatriz Schwantes , Mensah Sylvanus , Mitchard Edward T. A. , Moncrieff Glenn R. , Narayanan Ayyappan , O’Brien Sean T. , Ouedraogo Korotimi , Palace Michael W. , Pelissier Raphael , Ploton Pierre , Poorter Lourens , Ryan Casey M. , Saiz Gustavo , dos Santos Karin , Schlund Michael , Sellan Giacomo , Sonke Bonaventure , Sterck Frank , Thibaut Quentin , Van Hoef Yorick , Veenendaal Elmar , Vovides Alejandra G. , Xu Yaozhan , Yao Tze Leong , Feldpausch Ted R. 
Published: December 2020

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.