Within the desert vegetation of the South American coast, the lomas, also known as fog oasis, are isolated vegetation communities along the Chilean and Peruvian coast (Fig 1) occurring on small mountains or steep coastal slopes (
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The lomas is an ecosystem with two distinct seasons, a dry season and a humid season (mostly between May and October) where elevational fog condenses to provide moisture for vegetation [28,33]. However, during El Niño events, high precipitation occurs throughout the year, causing constant vegetation presence, especially of ephemeral herbs [14]. Most studies that recorded El Niño event effects on lomas plant communities have focused on quantifying species richness [14,16,19,34], primary productivity [35] or abundance [36,37] separately. Recent studies have considered a more integrative assessment of lomas plant communities [24,38]. However, there are fewer studies that evaluate multiple plant community characteristics together during the ENSO.
In order to assess the ecological importance of the species in the lomas we calculated an importance value index (IVIi) per sampling campaign. This index can use one, or combinations of two or three, of the following parameters: relative frequency, relative abundance and relative vegetation cover depending on the objectives of the study [46,47]. Historically the most noticeable response of the vegetation of the South American coast to El Niño events has been the extensive blooming of the desert [48], therefore we chose to combine the relative vegetation cover and relative abundance because the first one can be interpreted as a proxy of biomass and the latter of regeneration. These two variables were weighted for each species as shown in Eq 1 per sampling campaign:
Unlike most studies which surveyed study sites in the arid ecosystems of the west coast of South America only during the growing season, we have surveyed our study sites at four points in time throughout the whole annual cycle of vegetation. Thus, our results could be used as baseline for comparisons with lomas that are unprotected and subject to grazing after the El Niño event.
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