• Amazonia;
  • Tropical lowland rain forest;
  • Vegetation analysis
  • Mainly as in Tuomisto & Poulsen (1996), but in addition to Salpichlaena volubilis, S. hookeriana is recognized here (cf. Tuomisto & Groot 1995), and of the species lumped under Lomariopsis japurenis s.l., only L. nigropaleata Holttum is relevant. Voucher specimens from the Ecuadorian plot are deposited in herbaria in Aarhus (AAU), Quito (QCA) and Turku (TUR), those from the Peruvian transects in herbaria in Iquitos (AMAZ), Lima (USM) and Turku (TUR)

Abstract. Local variation in individual density, species composition, species richness and species diversity of terrestrial pteridophytes were studied at four sites in the tropical lowland rain forest of western Amazonia. 15 568 pteridophyte individuals representing 40 species were recorded in four plots. The variability among subplots within the same plot was considerable in all the characteristics measured (number of individuals, number of species, species diversity); the square 1-ha plot was more homogeneous in these respects than any of the three 5 m by 1300 m transects. Species richness was affected by the density of individuals both within and among plots. Density of individuals was not affected by topographical position within any of the plots, whereas in some of the plots both species richness and species diversity were. Clustering and ordination analyses showed that floristically similar subplots could be found in different plots: although there was a tendency for subplots from the same plot to be floristically similar and therefore to group together, many recognized groups included subplots from two or more plots. Both within and among plots, the floristic differences corresponded to topographic position and were probably related to soil drainage. This was also evident in that the abundance patterns of many species followed the topography.