Is the zone of influence colonized by roots of neighboring species? Field tests in a Patagonian steppe

In general, there is more knowledge about aboveground structure and processes than about those belowground. It has been proposed that plants are belowground territorial and root segregation explains species coexistence. We explored this idea by studying root intermingling of perennial graminoid plants in an arid Patagonian steppe. We extracted soil samples under target species. Additionally, we buried root traps filled with sieved soil to quantify root colonization close to plants (zone of high influence), of five dominant graminoid species. We sorted root biomass by species from samples and traps using a root-trait taxonomic key with 95% accuracy. Both studies indicated that the zone of high influence is occupied by roots of target and neighbor species (1–4 species) but showed differences in relative biomass of species. After 4 months, species with high root RGR show dominance in traps. This soil pre-emption seems transitory because in the descriptive study dominant species predominated independently of target species. We propose that coexistence among active roots of several species could be explained by different soil occupation rates in the zone of high influence. More studies are needed in relation with resource use in order to comprehend relationship between above and belowground biomass distributions. •Roots of different species occupied the same soil volume in a zone of high influence.•In the short-term, root intermingling resulted from fast-growing species colonization.•In the long-term, aboveground dominant species also dominated belowground.•The same soil volume is exploited by active roots of several species according to RGR.•Species differ in root biomass accumulation under or close to the aboveground portion.