2010

Amazonia through time: the effect of Andean uplift and climate change on landscape evolution and biodiversity

Hoorn, C.et al. Science. 330: 927-931.

The Amazonian rainforest is arguably the most species-rich terrestrial ecosystem in the world, yet the timing of the origin and evolutionary causes of this diversity are a matter of debate. We review the geologic and phylogenetic evidence from Amazonia and compare it with uplift records from the Andes. This uplift and its effect on regional climate fundamentally changed the Amazonian landscape by reconfiguring drainage patterns and creating a vast influx of sediments into the basin. On this “Andean” substrate, a region-wide edaphic mosaic developed that became extremely rich in species, particularly in Western Amazonia. We show that Andean uplift was crucial for the evolution of Amazonian landscapes and ecosystems, and that current biodiversity patterns are rooted deep in the pre-Quaternary.

Stropp, J., Ancieta, L., Ramirez, E., Brazão, R., van der Sleen, P. & ter Steege, H. (2010) Herbivoria e especifidade de habitat de árvores. Florestas de campinarana e de terra firme no alto Rio Negro. Pages 181-191 in: Cabalzar, A. (Ed.). Manejo do Mundo. Conhecimentos e práticas dos povos indígenas do Rio Negro. Foirn, ISA, São Gabriel da Cachoeira, Brazil.

Does neutral theory explain community composition in the Guiana Shield forest?

Olaf Banki, PhD Thesis, Utrecht University.

Recent years have seen a fierce debate about the causes of beta-diversity, the change in species composition over landscapes, in tropical rainforests. The introduction of neutral models has spurred this debate, by assuming that species composition changes randomly over landscapes with dispersal limitation as the driving ecological process. In this study the interaction between local and regional diversity of trees is investigated. We inventoried 61 1-ha plots in forests on brown and white sands, and on bauxite mountains in Guyana and Suriname. These data combined with earlier data led to the first biogeographical study on a species level involving 156 forest plots ranging from Venezuela to French Guiana. Forest composition changed dramatically between forest types, and at geographical distances. In general, forest composition followed geological patterns in the Guianas. Differences in plant attributes between the forest groups revealed a spectrum in covariation. On the one end of this spectrum a high dominance of trees with large seeds in dry fruits was combined with high wood densities in several forest types. On the other end a high dominance of trees and species with smaller seeds in fleshy fruits was combined with relatively low community averaged wood density. This spectrum could reflect different colonizing strategies of trees in the forest types, and could have an effect on potential dispersers. With neutral-like dynamical community models, different hypotheses on the low diversity of the white sand forest were evaluated. Forests on white and brown sands draw their species from different regional species pools. We provide strong evidence that asymmetric environmental filtering and a lower regional diversity (possibly due to the smaller size of the white sand area) could influence the lower diversity found in white sand forests compared with neighboring brown sand forests. White sand forests were not necessarily more dispersal limited than brown sand forests. Still within the white sand forests apparent changes in species abundance patterns occurred along geographical distances. Thus, we showed that a gradient in beta-diversity could occur in forests under similar climatic and soil conditions. The conservation value in terms of tree diversity of three bauxite mountains in Northeastern Suriname, was evaluated by placing 23 1-ha plots on the plateaus, slopes, and in the lowlands. These mountains are all destined for open-pit mining for aluminum ore, and may constitute a rare and endangered landscape type. Habitat type (e.g. the plateaus) explained more floristic similarity between plots than geographical distance. The plateaus also had the highest tree alpha-diversity currently found in Suriname. However, forest composition on the plateaus was also partly a random draw of species from the lowlands, and each of the mountains had its own specific species composition. Forests in the Guianas show evident differences in tree responses and composition, yielding little support for a neutral view. Most patterns are caused by small sets of common species that may dominate the forests, especially where the alpha-diversity of the forests is low. Striking biogeograpical patterns in the rainforests of the Guianas however remain unexplained by (current) environmental conditions.

download the thesis here

ATDN plots were also used in:

Malhado, A.C.M. et al. Are compound leaves an adaptation to seasonal drought or to rapid vertical growth? Evidence from the Amazon rainforest. Global Ecology and Biogeography 9: 852-862.

Gloor, M. et al. Does the disturbance hypothesis explain the biomass increase in basin-wide Amazon forest plot data? Global Change Biology 5: 2418-2430.

Saatchi, S. et al. Mapping landscape scale variations of forest structure, biomass, and productivity in Amazonia. Biogeosciences Discussions 6: 5461-5505.

ter Steege, H. ATDN, RAINFOR. (2010). Contribution of current and historical processes to patterns of tree diversity and composition of the Amazon. Pages 349-359 in: Hoorn, C., Wesselingh, F. & Vonhof, H. (eds.) Amazonia: Landscape and Species Evolution. Wiley-Blackwell, UK.

Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith