Differences in root architecture influence the persistence time of competing species in simulated plant communities

Aims Although several studies have shown that species interactions can support coexistence of plant species, our understanding of the role of root traits and architecture in coexistence is limited, despite their key role in resource acquisition. Theory suggests two seemingly contrasting outcomes: (1) when species share similar traits, competitive exclusion is slowed and persistence is prolonged, or (2) when species differ greatly in their traits, niche separation reduces competition allowing longer persistence. Here, we ask: Does greater divergence in root architecture increase or decrease persistence time in simulated plant communities? Methods We use a functional-structural plant model to simulate the development of annual plant communities over time. The plants belong to one of five species that differ in root architecture, resulting from simulations of evolution under varying levels of competition. Results Our findings support both theoretical predictions, but through different mechanisms. Differences in root morphology increase persistence time, with the two most different species persisting indefinitely. This appears to result from a density-dependent effect that enables species to recover from low densities. In contrast, in communities composed of ecologically identical species, persistence time seems to be governed by neutral drift and increased with their population density and area size. Conclusions The magnitude of differences in root morphology of interacting species drive their expected persistence time through distinct mechanisms.