There is a new paper out in Science, led by Hans ter Steege and involving just about every tree ecologist who has worked in Amazonia. It compiles data from forest plots across the region to ask some basic questions: (i) how many individual trees are there? (ii) how many tree species are there? (iii) how are tree species distributed between common and rare tree species. It comes to the surprising conclusion that only 227 "hyperdominant" species out of the approximate 16,000 tree species in Amazonia account for half of the trees in Amazonia. We estimate there are about 390 billion individual trees in the Amazon, with a mean of 565 trees per hectare (> 10 cm dbh). This hyperdominance is intriguing as to its causes, and has the potential to simplifying our understanding of the ecosystem ecology of this, the world's most biodiverse region.
The paper is here, with supplementary material and data appendices
There is a BBC news story here
Below are parts of the summary:
Results: Our analyses suggest that lowland Amazonia harbors 3.9 × 1011 trees and ~16,000 tree species. We found 227 “hyperdominant” species (1.4% of the total) to be so common that together they account for half of all trees in Amazonia, whereas the rarest 11,000 species account for just 0.12% of trees. Most hyperdominants are habitat specialists that have large geographic ranges but are only dominant in one or two regions of the basin, and a median of 41% of trees in individual plots belong to hyperdominants. A disproportionate number of hyperdominants are palms, Myristicaceae, and Lecythidaceae.
Discussion: The finding that Amazonia is dominated by just 227 tree species implies that most biogeochemical cycling in the world’s largest tropical forest is performed by a tiny sliver of its diver- sity. The causes underlying hyperdominance in these species remain unknown. Both competitive superiority and widespread pre-1492 cultivation by humans are compelling hypotheses that deserve testing. Although the data suggest that spatial models can effectively forecast tree community com- position and structure of unstudied sites in Amazonia, incorporating environmental data may yield substantial improvements. An appreciation of how thoroughly common species dominate the basin has the potential to simplify research in Amazonian biogeochemistry, ecology, and vegetation map- ping. Such advances are urgently needed in light of the >10,000 rare, poorly known, and potentially threatened tree species in the Amazon.
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Yadvinder Malhi is an ecosytem ecologist and Professor of Ecosystem Science at Oxford University