Distribution of pteridophyte communities along environmental gradients in Central Amazonia, Brazil

Abstract

Extrapolation of local abundance-environment relationships to broader scales provides species distribution models used for conservation planning. We investigated the importance of environmental heterogeneity and geographic distance on pteridophyte species spatial distribution on 38 plots of 250 x 2.5 m distributed over 90 km 2 in Central Amazon. Inclusion of canopy openness in our models increased the capacity of predicting community composition even under the narrow range of canopy openness found in our plots. Nevertheless, there was still a large amount of unexplained variance (55-65%). The response of the community to the light gradient was hierarchical and we did not find evidences of light partitioning. Most species were concentrated in low light plots but a few common and abundant occurred along the entire gradient. Soil properties were the major determinants of community composition. Contrary to similar studies, slope was not a good predictor of pteridophyte community composition, indicating that this relationship may be site-specific. There was no correlation between Boristic distances and geographic distances. We concluded that mesoscale turnover is low, although locally environmental variation determines high turnover of species. Studies among different Amazonian physiognomies tend to find high levels of beta-diversity. However, coarse comparisons can not reveal subtle patterns that are relevant for biodiversity conservation planning. This study found

The Need for Large-Scale, Integrated Studies of Biodiversity - the Experience of the Program for Biodiversity Research in Brazilian Amazonia

“…The Brazilian acronym for LTER is PELD; hence the name for the method, RAPELD. there were no light measurements in the plots, but they are now being done at some of the sites (Zuquim et al 2009). All of these measures are summarized as the mean of the 6 sub-samples per plot.…”

Different slopes of a mountain can determine the structure of ferns and lycophytes communities in a tropical forest of Brazil

“…Recent findings point out the important role of the environment component in structuring plant communities and how it can vary according to the scale evaluated, underlying geology and topography. The environmental determinism over plants distribution has thus received increasing attention and is considered essential towards the evaluation and comprehension of species coexistence models (Svenning et al 2004, Karst et al 2005, Jones et al 2008, Zuquim et al 2009, Li et al 2011. Therefore, it is reasonable to think that the ferns and lycophytes community differentiation pattern that we found may have emerged from environment variation related to the slope topographic orientation.…”

“…Some studies argue that topographic patterns are site-specific and slope effects seem to be a bad surrogate for the prediction of community structure because it is probably a synergistic response of the community to variable factors (Vormisto et al 2004, Zuquim et al 2009). We agree with this viewpoint, but slope topographic orientation may influence factors that are knowingly more important than others to a specific biological group.…”

“…Ranging from local to regional scales, several studies have shown that plant species composition and abundances answer to some common environmental variables such as topography (Vormisto et al 2004), soil characteristics (Jones et al 2006, Tuomisto et al 2003, length of the dry period and moisture availability (Engelbrecht et al 2005). Although there is considerable debate as to what degree floristic distributional patterns depend on environmental factors relative to other processes (Hubbell 2001, Dalling et al 2002, Wyatt and Silman 2004, findings appear to show that the major role is played by environmental factors (Karst et al 2005, Jones et al 2006, 2008, Zuquim et al 2009). …”

“…Not only do they have high richness and endemism levels (Tryon and Tryon 1982), but they are known to have had a large part of its floristic variation consistently predicted by environmental variation. Among the array of environmental factors, topographic and edaphic factors appear to be noticeably important at different scales (Karst et al 2005, Jones et al 2006, 2008, Zuquim et al 2009). It is thus reasonable to think that ferns exposed to the geomorphologic heterogeneity along the Atlantic Forest would be influenced by environmental variation.…”