Weedy and secundary palm species in central amazonian forest Fragments

Aldicir Scariot

doi:10.1590/s0102-33062001000200012

Abstract

Forest fragmentation may affect the abundance and distribution of organisms. Some species populations decrease being eventually driven to local extinction while other species may experience population increase. In a survey of the composition and abundance of secondary and weedy palms in eight forest fragments (three of 1-, three of 10- and two of 100-ha), in three sites (Dimona, Porto Alegre and Esteio) in central Amazonia, five native palm species which do not occur in the continuous forest were identified. Three were secondary species (Astrocaryum acaule Mart., Bactris maraja Mart. var. maraja and Bactris sp), one weedy (Lepidocaryum tenue Mart.), and one of unknown status (B. oligocarpa Barb. Rodr. & Trail). The highest abundance was found in the 1-ha fragments which had 172 of the 206 palms found compared with 33 in the 10-ha and one in the 100-ha fragments. However, most of these palms occur in the Dimona site, which accounted for 195 of the 206 of the individuals, compared with seven in Esteio and four in Porto Alegre. The weedy L. tenue, which forms clonal populations, although occurring only in Dimona, accounted for 91% of the individuals recorded. It is possible that with increased habitat degradation of small fragments, some populations of secondary and weedy species will also increase, what may be detrimental to the closed forest plant species populations occurring in forest fragments.

Highlights

Over 15 x 104 km2 yr-1 of tropical forests is being deforested each year (Whitmore 1997), and an additional 1% of the total area is being degraded (Myers 1988)
Most of the Amazonia is going to be subject to development, leaving a mosaic of forest fragments whose areas may range over several orders of magnitude (Bierregaard et al 1992)
The eight forest fragments used for this study are isolated by 100 - 350 m of cleared land from the continuous forest, and are located in the Dimona, Porto Alegre and Esteio ranches

Summary

Introduction

Over 15 x 104 km yr-1 of tropical forests is being deforested each year (Whitmore 1997), and an additional 1% of the total area is being degraded (Myers 1988). Deforestation leaves a fragmented habitat, which represents breaks in the continuity of the distribution of original vegetation, reduces the habitat available to wild plants and animals, and adds edges into a formerly continuous landscape. Most of the Amazonia is going to be subject to development, leaving a mosaic of forest fragments whose areas may range over several orders of magnitude (Bierregaard et al 1992). This development can lead to losses in biological diversity and changes in the distribution and abundance of organisms within and among fragments. The population response of a given species to fragmentation depends on the relative size of habitat fragments, the spatial scale on which the fragments are arrayed, and how fragments mediate dispersal success across the landscape (Doak et al 1992, Fahrig & Merrian 1994)

Methods

Results

Conclusion