This knowledge led to the further hypothesis that the biotope space, for example the soil volume in which species can root, should also matter. With increasing biotope space more species occupying different niches can be "packed" into the environment. Therefore, complementarity and beneficial biodiversity effects should increase.
In a paper soon to appear in Ecology Letters, Dimitrakopoulos and Schmid tested this hypothesis by growing plant monocultures and mixtures on a gradient of increasing soil depths and volumes, offering increased rooting space to species.
The results supported the hypothesis and showed that the increase was linear. Scaled up to agricultural systems this means that benefits of intercropping may be greater on deep soils and that soil erosion may reduce intercropping benefits.
Ecology Letters