Browsing by Autor "William E. Magnusson"

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Functional composition of the Amazonian tree flora and forests
(Nature Portfolio, 2025) Hans ter Steege; Lourens Poorter; Jesús Aguirre‐Gutiérrez; Claire Fortunel; William E. Magnusson; Oliver L. Phillips; Edwin Pos; Bruno Garcia Luize; Christopher Baraloto; Juan Ernesto Guevara
Hyperdominance in the Amazonian Tree Flora
(American Association for the Advancement of Science, 2013) Hans ter Steege; Nigel C. A. Pitman; Daniel Sabatier; Christopher Baraloto; Rafael P. Salomão; Juan Ernesto Guevara; Oliver L. Phillips; Carolina V. Castilho; William E. Magnusson; Jean‐François Molino
The vast extent of the Amazon Basin has historically restricted the study of its tree communities to the local and regional scales. Here, we provide empirical data on the commonness, rarity, and richness of lowland tree species across the entire Amazon Basin and Guiana Shield (Amazonia), collected in 1170 tree plots in all major forest types. Extrapolations suggest that Amazonia harbors roughly 16,000 tree species, of which just 227 (1.4%) account for half of all trees. Most of these are habitat specialists and only dominant in one or two regions of the basin. We discuss some implications of the finding that a small group of species--less diverse than the North American tree flora--accounts for half of the world's most diverse tree community.
Soil physical conditions limit palm and tree basal area in Amazonian forests
(Taylor & Francis, 2013) Thaíse Emilio; Carlos A. Quesada; Flávia R. C. Costa; William E. Magnusson; Juliana Schietti; Ted R. Feldpausch; Roel Brienen; Timothy R. Baker; Jérôme Chave; Esteban Álvarez‐Dávila
Background: Trees and arborescent palms adopt different rooting strategies and responses to physical limitations imposed by soil structure, depth and anoxia. However, the implications of these differences for understanding variation in the relative abundance of these groups have not been explored. Aims: We analysed the relationship between soil physical constraints and tree and palm basal area to understand how the physical properties of soil are directly or indirectly related to the structure and physiognomy of lowland Amazonian forests. Methods: We analysed inventory data from 74 forest plots across Amazonia, from the RAINFOR and PPBio networks for which basal area, stand turnover rates and soil data were available. We related patterns of basal area to environmental variables in ordinary least squares and quantile regression models. Results: Soil physical properties predicted the upper limit for basal area of both trees and palms. This relationship was direct for palms but mediated by forest turnover rates for trees. Soil physical constraints alone explained up to 24% of palm basal area and, together with rainfall, up to 18% of tree basal area. Tree basal area was greatest in forests with lower turnover rates on well-structured soils, while palm basal area was high in weakly structured soils. Conclusions: Our results show that palms and trees are associated with different soil physical conditions. We suggest that adaptations of these life-forms drive their responses to soil structure, and thus shape the overall forest physiognomy of Amazonian forest vegetation.