Questions: (1) What are the roles of regional climate and plant growth rate for seedling establishment during ENSO rainy pulses along the western coast of South America? (2) What is the water threshold for tree seedling establishment in these arid ecosystems?
Location: Atacama Desert, western South America: Piura (5°10’ S, 80°37’ W), Mejia (17°00’ S, 71°59’ W), Fray Jorge (30°41'S,71°37'W).
Methods: We experimentally simulated a gradient of ENSO rainfall in three locations encompassing the total extent of the Atacama Desert to test the relative importance of regional climate for seedling establishment during rainy pulses. We also carried out a common garden experiment to test the role of potential interspecific differences in growth rate among two Prosopis tree species.
Results: Water threshold for seedling survival increased towards the south with less than 27 mm required in Piura, 100 mm in Mejia and 450 mm in Fray Jorge. We found that seedling survival and growth rate (shoots and roots) were much higher in Piura than in the other two sites for both Prosopis species.
Conclusions: Our results indicate that tree establishment during rainy pulses is more likely to be successful in regions where rain falls during warm months and stimulates fast plant growth, and where loose soil texture facilitates deep root growth and therefore access to more stable water sources.
Diferentes revisiones coinciden en señalar 2 o 3 especies de Prosopis para el sur de Ecuador y norte de Perú: P. juliflora (SW) DC, P. pallida (Humb. et Bonpl. ex Willd.) Kunth y P. affinis Sprengel. En el presente trabajo se informa del análisis cuantitativo de caracteres foliares de especímenes del genero Prosopis, recolectados a lo largo de la costa desde Arequipa (Perú) a Manta (Ecuador). Los resultados señalan tres grupos bien definidos. Del análisis comparativo de los tipos y ejemplares de herbario de todas las especies y sinónimos citados para la zona de estudio surge que los taxones existentes son: P. pallida, P. limensis Bentham, ambos de amplia distribución, y P. chilensis (Molina) Stuntz emend Burkart restringido al valle del río Camaná. Estos tres taxones se corresponden con los tres grupos obtenidos del análisis numérico. Debe señalarse la exclusión del área de P. juliflora y P. affinis. Se sugiere no utilizar las numerosas variedades señaladas para P. pallida.
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