Demographic Changes and Epidermal Browning in Two Protected Populations of Saguaro Cactus (Carnegiea gigantea)
Turner DS. 2004. Demographic Changes and Epidermal Browning in Two Protected Populations of Saguaro Cactus (Carnegiea gigantea). Desert Plants. 20(1):16-23
We studied the demography and health of the saguaro cactus (Carnegiea gigantea) in Saguaro National Park, Tucson, Arizona. We gathered data on populations in both districts of the park for the years 2000-2001 and compared them to baseline collected in 45 plots during 1989-1990. During the past decade, epidermal browning of the surviving marked saguaros increased by 6%, with greater increases in those which were browner ten years ago. We also found evidence that epidermal browning has increased in the whole population, with a mean increase of 3.7% when comparing all saguaros in 18 plots. Among the marked population, 16.5% died during the decade. The 10-year survival rate declined with greater levels of browning and greater height. Recruitment exceeded mortality on all but one plot, with dramatic increases among plants <1 m tall making the populations significantly younger and with higher population densities in 2000-2001 than in 1989-1990. Based on our census efforts in 18 of the study plots, we estimate the total population within Saguaro National Park is approximately 1,625,000 saguaros, a 35% increase over the 1990 estimate. Examination of size classes suggests the park continues to recover from historic damaging influences such as grazing, mining, and wood harvesting.
- Type
- Journal Article
- Authors
- Turner, Dale
- Units
- SAGU
- Keywords
- epidermal browning, Inventory Natural Resources, Saguaro National Park