Jitka Klimešová, Jana Martínková and Gianluigi Ottaviani
In recent years belowground plant ecology has experienced an exciting time with booming research interest worldwide. This has resulted in major advances in our understanding of belowground plant and ecosystem functioning focused on fine roots, mycorrhizal associations, and hence resource acquisition. However, other important functions of plants, not directly associated with resource acquisition (e.g., in situ persistence, space occupancy, ability to recover after biomass removal) and provided by different belowground organs (e.g., thick roots, rhizomes, bulbs) remain largely unexplored. Here, we propose a framework tailored to providing a comprehensive perspective on the entire set of belowground plants organs and functions. We reviewed the relevant literature, showing examples of essential functions for which we would ignore information completely if focusing only on the acquisitive (i.e. fine root) function. As a solution, we suggest a compartment-based approach. We identify two major belowground compartments, that is, acquisitive and non-acquisitive, associated with biomass allocation into different plant organs and functions. We discuss methodological challenges involved with implementing such an approach. For example, we tackle issues posed by changes in biomass allocation across different plants’ growth forms and life stages, as well as challenges associated with belowground biomass partitioning and biomass turnover. Finally, we urge plant scientists to apply methods and approaches that take into account all the belowground organs of plants. This way, we could expand our ecological understanding of belowground plant functioning such as improving estimates of carbon sequestration – highly relevant for global change science.