Fig 1.
Location of study plots in the Rincon Mountain District of the Saguaro National Park (SNP-RMD) east of Tucson, AZ.
Census plots are located in Section 17, Township 14S, Range 16E, Gila and Salt River Base and Meridian. The base map for the middle panel is a June 1, 2015 Landsat 8 image and the base map for the bottom panel is May 30, 2015 NAIP JPG2000 aerial image, both from the United States Geological Survey EROS data center. The illustration of the Sonoran Desert in the upper panel is derived from the Natural Vegetation layer available in the public domain section of the AZGEO Clearinghouse.
Table 1.
Species of cover plants for saguaros in the census plots grouped into three classes.
Fig 2.
Photo taken in 2016 of four saguaros showing different growth rates.
The saguaros were discovered in 1986 when they were 1 to 2.5 cm tall. The tallest saguaro in the photo is 287 cm tall and was 1 cm tall in 1986.
Fig 3.
Cumulative percentage of saguaros discovered at ages four to thirty years.
The age is based on the height of the saguaro in the year it is found.
Fig 4.
Height structure of the saguaro population in the census plots in the flats of the Saguaro National Park, Rincon Mountain District from 1942 to 2015.
Fig 5.
Saguaro population regeneration.
The number of plants established each year based on plants found in the census plots during 1942–2015. The germination year was estimated based on the height in the year of discovery.
Fig 6.
Saguaro reproductive potential from 1942 to 2016.
Fig 7.
Survival curves from 1942 to 2016 for saguaros in height classes I through V in 1942.
Table 2.
Mortality following the freeze of 2011 as recorded in the Spring 2012 census.
Table 3.
The number of saguaros established under small shrubs, in the grass, or in the open (cover class C3) increased during the time of no catastrophic freezes after December 1978.
Fig 8.
Kaplan-Meier survival probability curves for saguaros that were established during the episode of regeneration between 1959 and 1993.
Table 4.
Mortality through 2016 of saguaros that germinated during the episode of population regeneration that occurred from 1959 through 1993 based on cover class.