Browsing by Autor "Nigel C. A. Pitman"

Now showing 1 - 9 of 9

Do species traits determine patterns of wood production in Amazonian forests?
(Copernicus Publications, 2009) Timothy R. Baker; Oliver L. Phillips; William F. Laurance; Nigel C. A. Pitman; S. Almeida; Luzmila Arroyo; Anthony Di Fiore; T. Erwin; Níro Higuchi; Timothy J. Killeen
Abstract. Understanding the relationships between plant traits and ecosystem properties at large spatial scales is important for predicting how compositional change will affect carbon cycling in tropical forests. In this study, we examine the relationships between species wood density, maximum height and above-ground, coarse wood production of trees ≥10 cm diameter (CWP) for 60 Amazonian forest plots. Average species maximum height and wood density are lower in Western than Eastern Amazonia and are negatively correlated with CWP. To test the hypothesis that variation in these traits causes the variation in CWP, we generate plot-level estimates of CWP by resampling the full distribution of tree biomass growth rates whilst maintaining the appropriate tree-diameter and functional-trait distributions for each plot. These estimates are then compared with the observed values. Overall, the estimates do not predict the observed, regional-scale pattern of CWP, suggesting that the variation in community-level trait values does not determine variation in coarse wood productivity in Amazonian forests. Instead, the regional gradient in CWP is caused by higher biomass growth rates across all tree types in Western Amazonia. Therefore, the regional gradient in CWP is driven primarily by environmental factors, rather than the particular functional composition of each stand. These results contrast with previous findings for forest biomass, where variation in wood density, associated with variation in species composition, is an important driver of regional-scale patterns in above-ground biomass. Therefore, in tropical forests, above-ground wood productivity may be less sensitive than biomass to compositional change that alters community-level averages of these plant traits.
Economically important species dominate aboveground carbon storage in forests of southwestern Amazonia
(Resilience Alliance, 2017) N. Galia Selaya; Pieter A. Zuidema; Christopher Baraloto; Vincent Antoine Vos; Roel Brienen; Nigel C. A. Pitman; Foster Brown; Amy E. Duchelle; Alejandro Araujo‐Murakami; Luis A. Oliveira Carillo
Selaya, N. G., P. A. Zuidema, C. Baraloto, V. A. Vos, R. J. W. Brienen, N. Pitman, F. Brown, A. E. Duchelle, A. Araujo-Murakami, L. A. Oliveira Carillo, G. H. Vasquez Colomo, S. Meo Chupinagua, H. Fuentes Nay, and S. Perz. 2017. Economically important species dominate aboveground carbon storage in forests of southwestern Amazonia. Ecology and Society 22(2):40. https://doi.org/10.5751/ES-09297-220240
Estimating the global conservation status of more than 15,000 Amazonian tree species
(American Association for the Advancement of Science, 2015) Hans ter Steege; Nigel C. A. Pitman; Timothy J. Killeen; Susan G. W. Laurance; Carlos A. Peres; Juan Ernesto Guevara; Rafael P. Salomão; Carolina V. Castilho; Iêda Leão do Amaral; Francisca Dionízia de Almeida Matos
Estimates of extinction risk for Amazonian plant and animal species are rare and not often incorporated into land-use policy and conservation planning. We overlay spatial distribution models with historical and projected deforestation to show that at least 36% and up to 57% of all Amazonian tree species are likely to qualify as globally threatened under International Union for Conservation of Nature (IUCN) Red List criteria. If confirmed, these results would increase the number of threatened plant species on Earth by 22%. We show that the trends observed in Amazonia apply to trees throughout the tropics, and we predict that most of the world's >40,000 tropical tree species now qualify as globally threatened. A gap analysis suggests that existing Amazonian protected areas and indigenous territories will protect viable populations of most threatened species if these areas suffer no further degradation, highlighting the key roles that protected areas, indigenous peoples, and improved governance can play in preventing large-scale extinctions in the tropics in this century.
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.
Mapping density, diversity and species-richness of the Amazon tree flora
(Nature Portfolio, 2023) Hans ter Steege; Nigel C. A. Pitman; Iêda Leão do Amaral; Luiz de Souza Coêlho; Francisca Dionízia de Almeida Matos; Diógenes de Andrade Lima Filho; Rafael P. Salomão; Florian Wittmann; Carolina V. Castilho; Juan Ernesto Guevara
More than 10,000 pre-Columbian earthworks are still hidden throughout Amazonia
(American Association for the Advancement of Science, 2023) Vinícius Peripato; Carolina Levis; Guido A. Moreira; Dani Gamerman; Hans ter Steege; Nigel C. A. Pitman; Jonas Gregório de Souza; José Iriarte; Mark Robinson; André Braga Junqueira
Indigenous societies are known to have occupied the Amazon basin for more than 12,000 years, but the scale of their influence on Amazonian forests remains uncertain. We report the discovery, using LIDAR (light detection and ranging) information from across the basin, of 24 previously undetected pre-Columbian earthworks beneath the forest canopy. Modeled distribution and abundance of large-scale archaeological sites across Amazonia suggest that between 10,272 and 23,648 sites remain to be discovered and that most will be found in the southwest. We also identified 53 domesticated tree species significantly associated with earthwork occurrence probability, likely suggesting past management practices. Closed-canopy forests across Amazonia are likely to contain thousands of undiscovered archaeological sites around which pre-Columbian societies actively modified forests, a discovery that opens opportunities for better understanding the magnitude of ancient human influence on Amazonia and its current state.
Multi-scale comparisons of tree composition in Amazonian terra firme forests
(Copernicus Publications, 2009) Eurídice N. Honorio Coronado; Timothy R. Baker; Oliver L. Phillips; Nigel C. A. Pitman; R. Toby Pennington; Rodolfo Vásquez; Abel Monteagudo; Hugo F. Mogollón; Nállarett Dávila; Marcos Ríos
Abstract. We explored the floristic composition of terra firme forests across Amazonia using 55 plots. Firstly, we examined the floristic patterns using both genus- and species-level data and found that the species-level analysis more clearly distinguishes among forests. Next, we compared the variation in plot floristic composition at regional- and continental-scales, and found that average among-pair floristic similarity and its decay with distance behave similarly at regional- and continental-scales. Nevertheless, geographical distance had different effects on floristic similarity within regions at distances <100 km, where north-western and south-western Amazonian regions showed greater floristic variation than plots of central and eastern Amazonia. Finally, we quantified the role of environmental factors and geographical distance for determining variation in floristic composition. A partial Mantel test indicated that while geographical distance appeared to be more important at continental scales, soil fertility was crucial at regional scales within western Amazonia, where areas with similar soil conditions were more likely to share a high number of species. Overall, these results suggest that regional-scale variation in floristic composition can rival continental-scale differences within Amazonian terra firme forests, and that variation in floristic composition at both scales is influenced by geographical distance and environmental factors, such as climate and soil fertility. To fully account for regional-scale variation in continental studies of floristic composition, future floristic studies should focus on forest types poorly represented at regional scales in current datasets, such as terra firme forests with high soil fertility in north-western Amazonia.
Relationships Among Ecologically Important Dimensions of Plant Trait Variation in Seven Neotropical Forests
(Oxford University Press, 2006) Ian J. Wright; David D. Ackerly; Frans Bongers; Kyle E. Harms; Guillermo Ibarra‐Manríquez; Miguel Martínez‐Ramos; Susan J. Mazer; Helene C. Muller‐Landau; Horacio Paz; Nigel C. A. Pitman
The dimensions represented by SLA, seed/fruit size and leaf size were essentially independent and thus conveyed largely independent information about plant strategies. To a lesser extent the same was true for plant height and WD. Our tentative explanation for negative WD-leaf size relationships, now also known from other habitats, is that the traits are indirectly linked via plant hydraulics.
Seasonal drought limits tree species across the Neotropics
(Wiley, 2016) Adriane Esquivel‐Muelbert; Timothy R. Baker; Kyle G. Dexter; Simon L. Lewis; Hans ter Steege; Gabriela López‐González; Abel Monteagudo Mendoza; Roel Brienen; Ted R. Feldpausch; Nigel C. A. Pitman
Within the tropics, the species richness of tree communities is strongly and positively associated with precipitation. Previous research has suggested that this macroecological pattern is driven by the negative effect of water‐stress on the physiological processes of most tree species. This implies that the range limits of taxa are defined by their ability to occur under dry conditions, and thus in terms of species distributions predicts a nested pattern of taxa distribution from wet to dry areas. However, this ‘dry‐tolerance’ hypothesis has yet to be adequately tested at large spatial and taxonomic scales. Here, using a dataset of 531 inventory plots of closed canopy forest distributed across the western Neotropics we investigated how precipitation, evaluated both as mean annual precipitation and as the maximum climatological water deficit, influences the distribution of tropical tree species, genera and families. We find that the distributions of tree taxa are indeed nested along precipitation gradients in the western Neotropics. Taxa tolerant to seasonal drought are disproportionally widespread across the precipitation gradient, with most reaching even the wettest climates sampled; however, most taxa analysed are restricted to wet areas. Our results suggest that the ‘dry tolerance' hypothesis has broad applicability in the world's most species‐rich forests. In addition, the large number of species restricted to wetter conditions strongly indicates that an increased frequency of drought could severely threaten biodiversity in this region. Overall, this study establishes a baseline for exploring how tropical forest tree composition may change in response to current and future environmental changes in this region.