Influence of soils and topography on Amazonian tree diversity: a landscape-scale study

Laurance, Susan G.W., Laurance, William F., Andrade, Ana, Fearnside, Philip M., Harms, Kyle E., Vicentini, Alberto, and Luizão , Regina C.C. (2010) Influence of soils and topography on Amazonian tree diversity: a landscape-scale study. Journal of Vegetation Science, 21 (1). pp. 96-106.

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Question: How do soils and topography influence Amazonian tree diversity, a region with generally nutrient-starved soils but some of the biologically richest tree communities on Earth?

Location: Central Amazonia, near Manaus, Brazil.

Methods: We evaluated the influence of 14 soil and topographic features on species diversity of rain forest trees (≥10 cm diameter at breast height), using data from 63 1-ha plots scattered over an area of ∼400 km2.

Results: An ordination analysis identified three major edaphic gradients: (1) flatter areas had generally higher nutrient soils (higher clay content, carbon, nitrogen, phosphorus, pH and exchangeable bases, and lower aluminium saturation) than did slopes and gullies; (2) sandier soils had lower water storage (plant available water capacity), phosphorus and nitrogen; and (3) soil pH varied among sites. Gradient 2 was the strongest predictor of tree diversity (species richness and Fisher's α values), with diversity increasing with higher soil fertility and water availability. Gradient 2 was also the best predictor of the number of rare (singleton) species, which accounted on average for over half (56%) of all species in each plot.

Conclusions: Although our plots invariably supported diverse tree communities (≥225 species ha−1), the most species-rich sites (up to 310 species ha−1) were least constrained by soil water and phosphorus availability. Intriguingly, the numbers of rare and common species were not significantly correlated in our plots, and they responded differently to major soil and topographic gradients. For unknown reasons rare species were significantly more frequent in plots with many large trees.

Item ID: 10986
Item Type: Article (Research - C1)
ISSN: 1654-1103
Keywords: tropical biology; density dependence; distributional ecology; fishers; permanent plots; rare species; soil chemistry; soil texture; soil water; species diversity; species richness; tropography; tropical trees
Date Deposited: 09 Aug 2010 03:23
FoR Codes: 05 ENVIRONMENTAL SCIENCES > 0502 Environmental Science and Management > 050202 Conservation and Biodiversity @ 100%
SEO Codes: 96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960899 Flora, Fauna and Biodiversity of Environments not elsewhere classified @ 100%
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