The haunting of the Soul's hill: uncoupled responses of plant functional traits and soil microbes to serpentine soils lead to Bonsai effect in the Neotropics.

We investigated the plant-soil linkages of Copaifera langsdorffii Desf., a widely distributed species in the Neotropics, and how the serpentine syndrome leads to dwarfism by comparing soil microbes, soil properties and tree functional traits in serpentine and non-serpentine soils. For this study, we evaluated the presence of heavy metals in the soils and how they affect plant functional traits; differences in the C:N ratio between serpentine and non-serpentine sites as well as soil microbiome by using phospholipid fatty acid technique approach to assess microbial functional groups. We further explored the relations between soil microbes (by using phospholipid fatty acid, i.e., components of cell membranes in microbes used as an indicator of microbial biomass), soil properties, vegetation attributes, leaf nutrients and leaf functional traits. We found a correlation between soil Gram-positive bacteria and iron in the plant leaves; the C:N ratios are higher in serpentine sites, but the two areas are similar to the non-serpentine area; there was no difference between the soil microbes in our study areas, and finally, there is a tendency to dwarfism and xeromorphism in the functional traits of C. langsdorffii in serpentine soils. We found that even though there are differences when comparing C. langsdorffii plants in serpentine and non-serpentine sites regarding the functional traits analysed in our study, the only soil microbe that seems to be interacting with the heavy metals is the Gram-positive bacteria, possibly due to chelating mechanisms.