Do Saguaros Grow Older in Higher Elevations?

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Do Saguaros Grow Older in Higher Elevations?

• Erin Benjamin
• Brian Block

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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

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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

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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)

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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

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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

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Catalina Foothills Elevation 2559 Feet
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Apache Junction Elevation 1758 Feet
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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

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Results

• Reject Hypothesis
• Create New Hypothesis

Saguaros grow better at lower elevations
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Overview

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

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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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Thank You