Distribution and Diversity of Pteridophytes and Melastomataceae along Edaphic Gradients in Yasuní National Park, Ecuadorian Amazonia¹

Abstract

We documented the floristic composition of pteridophytes (ferns and fern allies) and Melastomataceae in Yasuní National Park, Amazonian Ecuador. Our main questions were: (1) Are the density of individuals, species richness, and/or species diversity (measured with Shannon's H′) of the two plant groups related to edaphic differences? and (2) How many of the pteridophyte and Melastomataceae species are non–randomly distributed in relation to a soil base content gradient within terra firme (non–inundated forest). To answer these questions, we sampled 27 line transects of 500 × 5 m distributed in an area of ca 20 × 25 km. The study area included a permanent 50 ha plot established to monitor forest dynamics; thus, our results also provide information on landscape–scale floristic variability to which results from within the plot can be compared. A total of 45,608 individuals and 140 species of pteridophytes, and 4893 individuals and 89 species of the Melastomataceae, were counted in the transects. Both with pteridophytes and with Melastomataceae, a clear negative correlation was found between the amount of extractable bases in the soil and the number of plant individuals encountered in a transect. With Melastomataceae, species richness and species diversity also were negatively correlated with soil base content, but with pteridophytes they were not. More than 50 percent of the common species of both pteridophytes and Melastomataceae were nonrandomly distributed along the soil cation content gradient within terra firme. We conclude that while the species richness patterns observed in one plant group are not indicative of similar patterns in other plant groups, it seems likely that a substantial (but unknown) proportion of species belonging to other plant groups will be found to show distribution patterns that reflect edaphic preferences within terra firme forests.

Habitat niche partitioning by 16 species of Myristicaceae in Amazonian Ecuador

“…Within this broad forest type, however, species associations with minor variation in topography and soils are apparent (Phillips et al 2003). Significant non-random distribution of stem density with respect to two or three microhabitats has been demonstrated for 25% of the tree species > 1 cm dbh occurring on a large permanent plot in western Amazonia (Valencia et al 2004a) and for palms, pteridophytes and species of the Melastomataceae in similar forest (Svenning 1999;Duque et al 2002;Tuomisto et al 2002Tuomisto et al , 2003. However, these studies are correlative and provide no mechanistic understanding of the factors influencing the spatial distributions of tropical trees.…”

A composição florística e a diversidade de pteridófitas diferem entre a Floresta de Restinga e a Floresta Ombrófila Densa das Terras Baixas do Núcleo Picinguaba/PESM, Ubatuba/SP?

“…As pteridófitas possuem capacidade de dispersão e migração pouco variáveis (Tryon 1986), fazendo com que tenham elevado potencial como indicadoras ambientais (Tuomisto & Poulsen 1996). Pesquisas têm revelado que estas plantas podem indicar diferentes condições edáficas (Tuomisto & Ruokolainen 1994, Tuomisto et al 1995, Tuomisto & Poulsen 1996, ambientes alterados (Tuomisto et al 1995, Ruokolainen et al 1997) e estágios distintos de regeneração florestal, mediante a associação da comunidade a diferentes tipos de vegetação (Poulsen & Baslev 1991, Paciência 2008.…”

Soil nutrients influence spatial distributions of tropical tree species

“…The clearest evidence for the effects of habitat and soil factors on species distributions comes from studies conducted at mesoscales (Ϸ1-100 km 2 ) (17, 18) and landscape scales (10 2 to 10 4 km 2 ) (19)(20)(21)(22)(23)(24). At these scales, tropical forest landscapes are a mosaic of edaphic types (25,26), with levels of heterogeneity and spatial segregation that allow the effects of dispersal and habitat factors on species distributions and community structure to be relatively easily quantified.…”