Crecimiento exponencial y supervivencia del cardón (Echinopsis atacamensis subsp. pasacana) en su límite altitudinal (Tucumán, Argentina)
Abstract
El cardón es un cactus gigante en forma de candelabro que en la provincia de Tucumán (Argentina) llega a su límite altitudinal a poco más de 3.000 m. Conocido científicamente como Echinopsis atacamensis subsp. pasacana (=Trichocereus atacamensis, =Trichocereus pasacana), el cardón forma "bosques" de poblaciones relativamente densas con plantas de hasta 12 m ó más, a menudo concentradas en sitios arqueológicos. Esta nota informa sobre las observaciones de crecimiento medido en una muestra de cardones desde 1982 a 2005 (nueve mediciones) con el fin de entender algo sobre su dinámica, regeneración y capacidad de soportar impactos como cosecha para madera artesanal y cambio climático. Se midieron 21 individuos cerca de Infiernillo a 2.900 m, de clases de tamaño desde 3 a 800 cm, permitiendo un traslape de curvas de crecimiento prácticamente continuo. Estas curvas muestran una aceleración de crecimiento desde pocos milímetros al año hasta 14 cm/año a medida que incrementa su tamaño. Debido a esta curva, excepcional en plantas en general, en sus primeros 30 años un cardón apenas llega hasta 25 cm, mientras que a los 60 años ya alcanza cerca de 95 cm y a los 120 años ronda los 5 m. Este crecimiento puede ser interrumpido o demorado por diversas causas, incluyendo sequía, heladas fuertes, insectos minadores y cortes para madera. Cuatro de los siete cardones medidos en 1982 murieron y uno de los tres medidos en 1984. De los siete cardones restantes todos sobrevivieron hasta 2005, pero varios están dañados por heladas. Por las demoras de crecimiento, los cardones de mayor tamaño posiblemente alcancen varios cientos de años.
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.
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.
Description
Vol. 43, No. 1