title: Plant neighbour identity matters to belowground interactions under controlled conditions.
abstract: BACKGROUND
  Root competition is an almost ubiquitous feature of plant communities with profound effects on their structure and composition. Far beyond the traditional view that plants interact mainly through resource depletion (exploitation competition), roots are known to be able to interact with their environment using a large variety of mechanisms that may inhibit or enhance access of other roots to the resource or affect plant growth (contest interactions). However, an extensive analysis on how these contest root interactions may affect species interaction abilities is almost lacking.
  
  
  RESULTS
  In a common garden experiment with ten perennial plant species we forced pairs of plants of the same or different species to overlap their roots and analyzed how belowground contest interactions affected plant performance, biomass allocation patterns, and competitive abilities under abundant resource supply. Our results showed that net interaction outcome ranged from negative to positive, affecting total plant mass and allocation patterns. A species could be a strong competitor against one species, weaker against another one, and even facilitator to a third species. This leads to sets of species where competitive hierarchies may be clear but also to groups where such rankings are not, suggesting that intransitive root interactions may be crucial for species coexistence.
  
  
  CONCLUSIONS
  The outcome of belowground contest interactions is strongly dependent on neighbours' identity. In natural plant communities this conditional outcome may hypothetically help species to interact in non-hierarchical and intransitive networks, which in turn might promote coexistence.
authors: Grupo de Ecología Funcional, Departmento de Ecología Funcional y Evolutiva, Estación Experimental de Zonas Áridas, Consejo Superior de Investigaciones Científicas, Almería, Spain. cris@eeza.csic.es
authors: Cristina
authors: C
authors: Armas
authors: Francisco Ignacio
authors: FI
authors: Pugnaire
mesh_terms: D018533:Biomass; D017753:Ecosystem; D004777:Environment; D063245:Plant Development; D018517:Plant Roots / Q000254:growth & development*; D013045:Species Specificity