Influence of “El Niño Southern Oscillation” periods on plant density of Hoffmannseggia aphylla (Fabaceae) an endangered species

Backgrounds and aims: Studies on the natural regeneration of plant species under hyperaridity conditions have been scarce, mainly because of the low germination percentage of the species under these conditions. Presumably, sporadic phenomena such as the El Niño Southern Oscillation (ENSO) could have a positive effect on the natural germination of these species, although this effect has not yet been satisfactorily explored. M&M: To test the crucial assumption of our statement, a hyperarid region (average rainfall below 5 mm/year) was used as a model to determine the effect of ENSO years on the natural regeneration rate of adult individuals of the endemic legume Hoffmannseggia aphylla (retama) in the Atacama Desert, northern Chile. Thus, the vegetation density of an endemic leguminous species in a sector of the Pampa del Tamarugal, Tarapacá Region, northern Chile, was analyzed for six years. Results: The density of this species increased during ENSO years, mainly due to water flows from the highest sectors of the Tamarugal pampas, such as the town of Pica, in addition to the increase in humidity and summer rainfall. Conclusion: Our results highlight the transcendence of the ENSO in the regeneration of leguminous plants.