Abstract
AimConservation and land-use planning require accurate maps of patterns in species composition and an understanding of the factors that control them. Substantial doubt exists, however, about the existence and determinants of large-area floristic divisions in Amazonia. Here we ask whether Amazonian forests are partitioned into broad-scale floristic units on the basis of geological formations and their edaphic properties.LocationWestern and central Amazonia.MethodsWe used Landsat imagery and Shuttle Radar Topography Mission (SRTM) digital elevation data to identify a possible floristic and geological discontinuity of over 300 km in northern Peru. We then used plant inventories and soil sampling to document changes in species composition and soil properties across this boundary. Data were obtained from 138 sites distributed along more than 450 km of road and river. On the basis of our findings, we used broad-scale Landsat and SRTM mosaics to identify similar patterns across western and central Amazonia.ResultsThe discontinuity identified in Landsat and SRTM data corresponded to a 15-fold change in soil cation concentrations and an almost total change in plant species composition. This discontinuity appears to be caused by the widespread removal of cation-poor surface sediments by river incision to expose cation-rich sediments beneath. Examination of broad-scale Landsat and SRTM mosaics indicated that equivalent processes have generated a north–south discontinuity of over 1500 km in western Brazil. Due to similarities with our study area, we suggest that this discontinuity represents a chemical and ecological limit between western and central Amazonia.Main conclusionsOur findings suggest that Amazonian forests are partitioned into large-area units on the basis of geological formations and their edaphic properties. The evolution of these units through geological time may provide a general mechanism for biotic diversification in Amazonia. These compositional units, moreover, may correspond to broad-scale functional units. The existence of large-area compositional and functional units would suggest that protected-area, carbon sequestration, and other land-use strategies in Amazonia be implemented on a region-by-region basis. The methods described here can be used to map these patterns, and thus enable effective conservation and management of Amazonian forests.
Highlights
Amazonian forests are globally important because of their role in nature conservation and climate regulation
The discontinuity identified in Landsat and Shuttle Radar Topography Mission (SRTM) data corresponded to a 15-fold change in soil cation concentrations and an almost total change in plant species composition
Main conclusions Our findings suggest that Amazonian forests are partitioned into large-area units on the basis of geological formations and their edaphic properties
Summary
Amazonian forests are globally important because of their role in nature conservation and climate regulation. Substantial doubt exists, about the existence and determinants of floristic divisions in Amazonian forests. The search for large-area divisions in Amazonia has generally focused on possible past or present dispersal barriers in these apparently uniform forests. Large-area floristic units have been delimited on the basis of postulated Pleistocene forest refugia (Prance, 1982, 1994). Find no evidence of Pleistocene forest fragmentation in the Amazonian lowlands, suggesting that Pleistocene climate change has not been a primary driver of contemporary floristic patterns (Colinvaux & De Oliveira, 2001; Colinvaux et al, 2001; Kastner & Goni, 2003)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
