Divergent ecological effects of oceanographic anomalies on terrestrial ecosystems of the Mexican Pacific coast

Abstract

Precipitation pulses are essential for the regeneration of drylands and have been shown to be related to oceanographic anomalies. However, whereas some studies report increased precipitation in drylands in northern Mexico during El Niñ o years, others report increased drought in the southern drylands. To elucidate the effect of oceanographic/atmospheric anomalies on moisture pulses along the whole Pacific coast of Mexico, we correlated the average Southern Oscillation Index values with total annual precipitation for 117 weather stations. We also analyzed this relationship for three separate rainfall signals: winter-spring, summer monsoon, and fall precipitation. The results showed a distinct but divergent seasonal pattern: El Niñ o events tend to bring increased rainfall in the Mexican northwest but tend to increase aridity in the ecosystems of the southern tropical Pacific slope. The analysis for the separated rainfall seasons showed that El Niñ o conditions produce a marked increase in winter rainfall above 22°latitude, whereas La Niñ a conditions tend to produce an increase in the summer monsoon-type rainfall that predominates in the tropical south. Because these dryland ecosystems are dependent on rainfall pulses for their renewal, understanding the complex effect of ocean conditions may be critical for their management in the future. Restoration ecology, grazing regimes, carrying capacities, fire risks, and continental runoff into the oceans could be predicted from oceanographic conditions. Monitoring the coupled atmosphere-ocean system may prove to be important in managing and mitigating the effects of large-scale climatic change on coastal drylands in the future.coastal drylands ͉ deserts ͉ El Niñ o ͉ rainfall pulses ͉ tropical dry forests

GRACE satellite observed hydrological controls on interannual and seasonal variability in surface greenness over mainland Australia

“…Res. Biogeosci., 119, 2245-2260, doi:10.1002 researchers [Canon et al, 2011;Caso et al, 2007;Forzieri et al, 2013;Fang et al, 2001;Knapp and Smith, 2001;Mendez-Barroso et al, 2009]. One reason was ascribed to the relatively short length of data records, but more essentially, because precipitation only provides an indirect observation of water availability.…”

The Flora of Greater San Quintín, Baja California, Mexico (2005–2010)

“…The CFP is mostly in the United States, from southern Oregon through California including the Pacific drainages, but extends south to near El Rosario, Baja California, Mexico (Howell 1957;Raven and Axelrod 1978;Thorne 1993;Peinado et al 1994). The distribution of the CFP essentially coincides with the presence of winter-spring rainfall and the absence of summer rainfall (Minnich and Franco-Vizcaíno 1998;Caso et al 2007). CFP vegetation once occupied 324,000 hectares of land; today, however, only 80,000 hectares (less than 25%) remain naturally vegetated (Myers et al 2000).…”

“…The southern limit of the CFP in Baja California is related to water availability (Shreve 1936). Winter rainfall decreases rapidly at around 32u latitude (Caso et al 2007); however, CFP vegetation continues to occur where coastal fog augments water availability (and in disjunct higherelevation ''sky islands'' further south on the peninsula). Fog moisture extends CFP vegetation into areas with relatively low winter rainfall where desert vegetation would otherwise occur.…”

The Vascular Flora of Greater San Quintín, Baja California, Mexico

“…The southern limit of the CFP in Baja California corresponds to water availability (Shreve 1936). Winter rainfall decreases rapidly at around 32º latitude (Caso et al 2007); however, in the summer rain shadow caused by the Sierra San Pedro Martir, CFP vegetation occurs where coastal fog augments water availability. This extends CFP vegetation into areas with relatively low winter rainfall where desert vegetation would otherwise occur.…”

“…The CFP is mostly in the U.S. and extends from southern Oregon through California including all of the Pacific drainages, south to near El Rosario, Baja California (Howell 1957, Thorne 1993, Peinado et al 1994, Raven & Axelrod 1995. The distribution of the CFP essentially coincides with the presence of winter-spring rainfall and the absence of summer precipitation (Caso et al 2007, Minnich & Franco-Vizcaíno 1998. CFP vegetation once occupied 324,000 hectares of land; however, today only 80,000 hectares (less than 25%) remain naturally vegetated (Myers et al 2000).…”