Trees, microbes, and molecules: Understanding the role of tree biodiversity in the microbial carbon fluxes of Amazonian agroforest soils

Abstract

Microbial activity in soils is driven by the compositions of the soil-dissolved organic matter (DOM) that diffuses from the litter layer or the roots directly into the soil. However, the chemical diversity of the organic molecules transferred into the soil solution can vary depending on the tree community composition and plant diversity. In agroforest systems (AFS), the plant diversity and the system composition can vary to meet the farmers environmental and socio-economic needs. Thus, it is unclear to what extent AFS plant diversity affects the soil DOM and how these changes can influence microbial activity. For this reason, this project's purpose is to extract the dissolved organic matter from the litter and soils of agroforests in the Amazon region that were designed with increasing native tree diversity to assess the role of the molecular composition of the DOM in the interactions between aboveground tree diversity and the belowground microbial processes. For that, we will have the collaboration of the Prof. Gerd Gleixner and the Molecular Biogeochemistry research group from the Max Planck Institute for Biogeochemistry (MPI-BGC), which possesses state-of-art analytical chemistry facilities and have accumulated great knowledge with the different techniques needed to further study the DOM. In the MPI-BGC we will employ High-Resolution Mass Spectrometry (HR-MS) with sufficient mass resolving power over a wide mass range (from a hundred to several thousand daltons) to separate the closely spaced m/z peaks that are usually found in a typical DOM mass spectrum. The molecular characteristics of the DOM will be cross validated with functional predictions from the data generated through Next-Generation Sequencing (NGS) of the soil total DNA and will be coupled through different bioinformatic and statistical techniques in order to fully unravel the complex interaction between above- and belowground processes in Amazonian soils.