Age estimation has been a limiting factor in the study of giant columnar cacti. In order to test the feasibility of using radiocarbon methods to estimate the age of the giant cardon cacti (Pachycereus pringlei), we selected six sites spanning the latitudinal and precipitation range of the species in the Baja California peninsula. In each site, we selected four individuals of different heights and sampled a spine from the lowest areole in the stem. The age of the spine was estimated using 14C dating, and the mean annual growth rate of the plant was calculated dividing the height of the lead shoot by the plant’s age. Mean annual growth rate was 0.098 m/yr, with values varying between 0.03 and 0.23 m/yr. Within the range of plants sampled, mean annual growth rates were significantly correlated with the height of the plant (r2=0.82, P<0.0001), and no other site-specific variable such as precipitation or latitude was a significant predictor of mean annual growth rates. A model integrating mean growth rate versus height showed that relatively small differences in growth rates between plants accumulate during the plants’ lifetime, so that plants of similar size may have very different ages. We conclude that 14C dating provides a robust method to explore the growth and demography of columnar cacti.
El bajapalos pecho canela (Sitta canadensis) es una especie de distribución amplia en Estados Unidos y Canadá. No obstante,debido a irrupciones y vagabundeos, se ha registrado en Chihuahua, Sonora, Sinaloa, Baja California, Nuevo León y en el occidentede México (Jalisco y Colima). En Baja California existen cuatro registros: (1) Isla Guadalupe (población que se consideraextirpada desde 1995) (2), Sierra San Pedro Mártir (3), Sierra Juárez y (4) Santa Rosaliíta, los últimos dos registros son de hacemás de 20 años. Registramos por primera vez un bajapalos pecho canela macho adulto en el bosque de Los Attenuatas durantela temporada de invierno de 2015.
El cardón gigante (Pachycereus pringlei (S.Watson) Britton & Rose) es una especie endémica del Desierto Sonorense que por su gran biomasa es reservorio de nutrientes, brinda refugio y es fuente de alimento para la fauna. Los objetivos del estudio fueron identificar el número de especies que interactúa con el cardón y determinar cómo lo hacen. Para ello se colocaron fototrampas cerca de las flores y frutos, se fotografiaron a las especies que se observaron en los cardones y se utilizaron los reportes de literatura. Se registraron 61 especies que interactúan con los cardones, 25 de ellas no registradas anteriormente. Se reportan 83 asociaciones, de las cuales el 45% ocurren en la temporada de floración y fructificación. Por lo antes expuesto, es necesario categorizarlo como una especie clave del Desierto Sonorense y tomar en consideración las interacciones que mantiene con la fauna al tomar decisiones acerca de su manejo y conservación.
Abstract:We report the presence of the Band-tailed Pigeon, which was not previously recorded in the Sonoran Desert in Baja California. The site was 140 km south of the nearest forest. The presence of the pigeon further documents the propensity of Band-tailed Pigeons to wander widely.
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