Long-term growth rates of cirio (Fouquieria columnaris), a giant succulent of the Sonoran Desert in Baja California |
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| Authors: | Martín Escoto-Rodríguez Stephen H Bullock |
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| Institution: | a Facultad de Ciencias, Universidad Autónoma de Baja California, 22860, Ensenada, Baja California, México;b Departamento de Ecología, Centro de Investigación Científica y de Educación Superior de Ensenada, Apartado Postal 2732, 22800, Ensenada, Baja California, México;c Department of Biology, San Diego State University, San Diego, CA, 92182-4614, U.S.A. |
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| Abstract: | Factors affecting temporal and spatial variations of growth were studied in cirio, a succulent often surpassing 10 m in height. Measurements were obtained for intervals of 3–93 years at 14 sites in Baja California. Height tended to be asymptotic but total plant length (i.e. including all succulent stems) increased in linear relation to trunk diameter. Growth in length showed an overall average of 4·6 cm year−1 but ranged from 0·3–16·7 cm year−1 (annualized from data for intervals >34 year). Most of the variation was among individuals, but some differences between sites were also significant. Growth was clearly and strongly related to size only for individuals less than 1 m in height. Repeated measures on the same individuals showed that the autocorrelation of growth was about 0·8 between intervals of 3 or more years. Differences among individuals were related to physiographic position, the presence of caliche and the density of neighboring plants, which together explained 43% of the variation. We discuss the implications of these results for age estimates, indicators of site quality and studies of similar plants. |
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| Keywords: | growth analysis age estimation autocorrelation size dependence site index |
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