Plant-soil interactions in a serpentine neotropical forest

Abstract

Serpentine soils are those with high levels of high metals and occur spontaneously through limited areas of the world, imposing many environmental restrictions to the organisms inhabiting those soils. Regarding the soil microbes in serpentine soils, there‟s divergence between the authors, with some areas exhibiting adaptations and resistance to heavy metals, with high diversity of soil microbial structure, and other areas with the opposite pattern. Despite serpentine soils are being studied for decades in temperate and Mediterranean areas, we have few studies concerning the topic in tropical areas. As a central paradigm for the vegetation associated to serpentine soils, there‟s usually vegetation with lower biomass, lower tree‟s height and lower species number, leading to a depleted flora with many degrees of nutritional imbalance, high rates of endemic and/or heavy metal hyperacummulator species. However, new evidence seems to indicate that this pattern might be different for serpentine tropical flora, indicating that other mechanisms could be involved in the permanence of a higher species number in those areas despite the excess of heavy metal. Regarding the serpentine microbial structure, there‟s little specific information for the neotropical areas. In this sense, our study aims to fill this gap, aiming to understand the interactions between soil microbes and plants in a neotropical serpentine area. Our study focused in five main questions: A) the interactions between soil microbes-plants will be negatively affected by the presence of heavy metals in the soils, as well as the functional traits; B) higher C:N ratio in serpentine soil areas; C) total PLFAs and total fungi will be lower in serpentine areas; D) there will be higher amounts of total gram positive bacteria and lower gram negative bacteria in serpentine soils and E) functional traits will have a tendency to dwarfism in serpentine areas, while the functional traits leaf thickness, xylem and phloem area will exhibit a tendency to xeromorphism. As a general pattern, we found that gram positive bacteria interact with iron in the leaves; the C:N ratios are higher in serpentine 1 than serpentine 2, but the two areas are similar to the non-serpentine area; there was no difference between total PLFAs, total fugi, total gram positive bacteria and total gram negative bacteria in our study areas and finally, there‟s a tendency to dwarfism and xemorphism in the functional traits of Copaifera langsdorffii Desf. in serpentine soils.