Do Saguaros Grow Older in Higher Elevations? Erin Benjamin Brian Block

Elevation Effect on Saguaro Growth Importance - Saguaros are losing habitat - Humans are developing further into the desert - Conservation - To improve knowledge on how and where to conserve the saguaro species

Elevation Effect on Saguaro Growth Hypothesis: Saguaros Grow Better at Higher Elevation Criteria to be Measured Number of Arms Older Saguaros Have a Greater Number of Arms

Elevation Effect on Saguaro Growth Background - Saguaros have a slow growth rate - Saguaros have a shallow root system and are less able to tolerate extended periods of drought - Saguaros are not frost resistant - The older a saguaro the more arms (Saguaros over 200 years old routinely have 5 or more arms)

Elevation Effect on Saguaro Growth Background - Environmental Variables - The higher the elevation the cooler the temperature - The lower the elevation the lower the amount of moisture in the air - The higher the elevation the stronger the intensity of the sun - The higher the elevation the colder the winters and the higher the chance of saguaro death - The higher the elevation the more rain the monsoon season brings

Elevation Effect on Saguaro Growth Methods Two Investigators Examined 200 Saguaros and Counted Arms in Separate Geographic Locations Locations Examined Apache Junction Elevation 1758 Feet Catalina Foothills Elevation 2559 Feet Data Compiled and Evaluated

Catalina Foothills Elevation 2559 Feet

Apache Junction Elevation 1758 Feet

Results Catalina Foothills 6% of cacti observed had 10 arms or more Apache Junction 38% of cacti observed had 10 arms or more Based on Hypothesis there is a greater percentage of older saguaros at lower elevation examined

Saguaros grow better at lower elevations Results Reject Hypothesis Create New Hypothesis Saguaros grow better at lower elevations

Overview Cooler temperatures effect growth rate The intensity of the sun effects saguaros growth Colder winters lead to saguaro death

Study Limitations Data compiled from different regions Only one investigator counted saguaros with no arms Uncontrolled variables - Death rates - Disease - Rainfall - Animal and human impact

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