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Saguaro ( Carnegiea gigantea , Cactaceae) age–height relationships and growth: the development of a general growth curve
Author(s) -
Drezner Taly Dawn
Publication year - 2003
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.3732/ajb.90.6.911
Subject(s) - biology , population , cactus , linear regression , statistics , growth curve (statistics) , regression , ecology , demography , mathematics , sociology
Because the growth rate of saguaros varies across different environments, past studies on saguaro population structure required extensive data collection (often over many decades) followed by site‐specific analysis to estimate age at the sampled locale. However, when height–growth data from different populations are compared, the overall shape of the growth curves is similar. In this study, a formula was developed to establish saguaro age–height relationships (using stepwise regression) that can be applied to any saguaro population and only requires a site‐specific factor to adjust the curve to the local growth rate. This adjustment factor can be established more efficiently and requires less data than the full analyses required for previous studies. Saguaro National Park East (SNP‐E) was used as the baseline factor, set to 1.0. Results yielded a factor of 0.743 for SNP West. When the formula was applied to 10‐yr interval data from Organ Pipe Cactus National Monument (OPCNM) in Arizona, USA, this location had a factor of 0.617 (relative to SNP‐E). With this formula and relatively little field sampling, the age of any individual saguaro (whether the individual was sampled or not) in any population can be estimated.