Resumen

HALLOY, Stephan. Exponential growth and survival in cardón (Echinopsis atacamensis subsp. pasacana) at its altitudinal limit (Tucumán, Argentina). Ecología en Bolivia [online]. 2008, vol.43, n.1, pp.6-15. ISSN 1605-2528.

Abstract The ‘cardón’ is a giant candelabra-shaped cactus reaching its altitudinal limit at somewhat more than 3,000 m in the Province of Tucumán, Argentina. Known scientifically as Echinopsis atacamensis subsp. pasacana (=Trichocereus atacamensis, =Trichocereus pasacana), cardón forms “forests” of relatively dense populations, with tall individuals reaching 12 m or more, often concentrated on archaeological sites. This note reports on the measurement of growth on a sample of cardones from 1982 to 2005 (9 measurements), to improve our understanding of its dynamics, regeneration, and its capacity to sustain impacts from harvesting and from climate change. Twenty one individuals were measured close to Infiernillo at 2,900 m, with sizes ranging from 3 to 800 cm, allowing for an almost continuous overlap of growth curves. Growth curves show acceleration from a few mm per year to 14 cm/year as the cardón grows in size. Because of this curve, exceptional in plants in general, cardón takes 30 years to reach 25 cm, while it reaches 95 cm by 60 years of age, and by 120 years it is reaching around 5 m. Growth can be interrupted or delayed through external factors, including drought, heavy frosts, mining insects and harvesting for wood. Four out of seven cardones measured in 1982 died, and one of three measured in 1984. Of the seven remaining individuals, all survived to 2005, but several have been damaged by frost. Due to delayed growth, the largest cardones possibly reach several hundred years of age.

Palabras clave : Growth curve; Longevity; Cactaceae; Subtropical Andes; Threatened species.

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