Belowground Experimental Approaches for Exploring Aboveground–Belowground Patterns

Experiments in aboveground–belowground community ecology are challenging, usually because manipulation and observation of the belowground component is problematic. Problems arise because the soil is an opaque, tri-phasic medium which restricts access and visualisation. While pot studies are commonly used to investigate aboveground–belowground interactions, they have inherent problems including a tendency to cause hypoxic conditions and elevated temperatures. A range of other techniques has been used by ecologists to manipulate belowground factors, in particular. In the laboratory, controlled manipulation includes simulated root damage experiments, split-root experiments and aboveground–belowground olfactometers. Observing belowground components in the laboratory has been achieved using slant boards, rhizotrons, rhizotubes, X-ray tomography and isotope labelling. Manipulation of belowground communities in field experiments either relies on supplementation (e.g. adding organisms) or exclusion (e.g. insecticides), both of which can have confounding effects of experimental manipulations. Observing belowground communities in the field either relies on chemically based and destructive sampling or non-destructive methods (e.g. metal tagging). Researchers continue to innovate with new techniques such as meta-barcoding showing great potential.