“…They may also act as seed traps or protect the seedlings of other species from herbivory (Callaway and Walker, 1997;Holmgren et al, 1997;García et al, 2000). The importance of plant-plant interactions appears to vary according to environmental heterogeneity (Hartgerink and Bazzaz, 1984;Kitzberger et al, 2000;Tielbörger and Kadmon, 2000;Beckage and Clark, 2003) and the intensity of abiotic stress experienced by the interacting species (Bertness and Callaway, 1994), as well as the life stages, size and physiologies of the interacting species (Callaway and Walker, 1997;Holmgren et al, 1997;Rodríguez-García et al, 2011).…”