Plant-plant spatial interactions in the dry Puna (southern Peruvian Andes)

Plant-plant interactions play a key role in regulating the composition of communities. The outcome of interactions is the net effect of both positive and negative interactions. Positive interactions (facilitation) are defined as non-trophic interactions that increase the average individual fitness of at least one of the species involved. The study area was the Salinas and Aguada Blanca National Reserve, in the southern Peruvian Andes, composed of Festuca orthophylla grassland (dry Puna). The research goals were to ascertain whether spatial interactions act in this plant community, in order to determine whether beneficiary species have species-specific spatial associations. Our findings indicate that the most important nurses were the tall tussock species. A direct correlation was observed between the dimension of the F. orthophylla tussocks and the number of beneficiary species. Twelve species were closely associated with nurse species; five occurred in relation with nurse plants but without any preference for one of them; four species grew both isolated and in relationship with nurse plants and six species mostly grew isolated on bare soil. Because of the impact of grazers, some plants cannot grow on open ground; in fact, the species most in need of spatial interactions are those without avoidance strategies and/or with broad leaves. F. orthophylla is the core of a clumped spatial pattern of vegetation. The importance of spatial interactions for biodiversity conservation seems to be closely related to environmental amelioration and to grazer activity because plants of low palatability often serve as biotic refuges for palatable plants.