Journal of Tropical Ecology

Are floristic and edaphic patterns in Amazonian rain forests congruent for trees, pteridophytes and Melastomataceae?

Kalle Ruokolainen a1c1, Hanna Tuomisto a1, Manuel J. Macía a1a2, Mark A. Higgins a1a3 and Markku Yli-Halla a4p1
a1 Department of Biology, University of Turku, FI–20014 Turku, Finland
a2 Real Jardín Botánico de Madrid, Consejo Superior de Investigaciones Científicas, Plaza de Murillo 2, E–28014 Madrid, Spain
a3 Center for Tropical Conservation, Box 90381, Duke University, Durham, NC 27708 USA
a4 MTT Agrifood Research Finland, FI–31600 Jokioinen, Finland

Article author query
ruokolainen k   [PubMed][Google Scholar] 
tuomisto h   [PubMed][Google Scholar] 
macia mj   [PubMed][Google Scholar] 
higgins ma   [PubMed][Google Scholar] 
yli-halla m   [PubMed][Google Scholar] 


Studies in western Amazonian forests have found that similarities in soil cation concentration and texture explain floristic similarities between sites, when these are measured using trees, pteridophytes or Melastomataceae. However, it is not known to what extent the three plant groups react to the same soil characteristics, because tree studies have almost always been conducted in different areas than studies on the understorey plant groups. We made inventories in 23 sites representing non-inundated rain forests on clayey to loamy soil in three regions of western Amazonia. Significant Mantel correlations between the floristic patterns of trees and pteridophytes were found in all three regions when floristic differences were measured with species presence–absence data. When species abundance data were used, and when the floristic patterns of trees and Melastomataceae were compared, significant correlations were found in one or two regions. Mantel correlations between plant groups were highest in the two regions where the observed variation in soil characteristics was largest. In all regions, the same soil variables emerged with significant Mantel correlations with trees, pteridophytes and Melastomataceae. Soil calcium and magnesium were most frequently retained in the models of multiple regression on distance matrices. On average, soil differences explained 50% of the variation in floristic differences (range = 14–84%), and geographical distances explained 16% (range = 0–64%). Our results demonstrate that beta diversities of the three plant groups are highly correlated, and that much of this congruence is explained by similar reactions to soil variation. These results support the idea that pteridophytes, and to a lesser degree Melastomataceae, can be used as indicators of general floristic and edaphic patterns in Amazonian rain forests. Since understorey plants are much quicker to inventory than trees, this would make it possible to recognize and map floristic patterns over huge areas of lowland Amazonia within a reasonable time.

(Accepted September 26 2006)

Key Words: Amazonia; beta diversity; indicator species; Melastomataceae; pteridophytes; soil; trees; tropical rain forest; vegetation inventory.

c1 Corresponding author. Email:
p1 Present address: Department of Applied Chemistry and Microbiology, Environmental Soil Science, University of Helsinki, FI-00014 Helsinki, Finland.