Program Methods, Procedures & Protocols:

1. Establish study areas and transect grids for researchers. Groups of 4-5 students will be assigned to a study area.

2. Researchers will measure and tag focus plants in their transect grid areas. Focus plants will include:

  • Bigberry manzanita
  • Blackbrush
  • California buckwheat
  • Catclaw acacia
  • Creosote
  • Desert willow
  • Holly-leaf cherry
  • Honey mesquite
  • Ironwood
  • Juniper
  • Jojoba
  • Joshua tree
  • Mojave yucca
  • Nolina
  • Paperbag Bush
  • Pinyon pine
  • Scrub oak
  • Cactus species
  • Other plants may be measured and tagged.

3. One linear transect will be established for each study site. From a known landmark, an 80-foot (24-meter) linear transect will be established. Along that transect, perpendicular transects will be measured out every 20 feet at a 90o angle in each direction. Along each 20-foot perpendicular transect, all focus plants within arm’s length (3 feet) in each direction along the perpendicular transect line will be recorded and measured.

4. All plants measured will be tagged.

5. Measurements will be recorded on data log sheets and entered into a website database.

6. Tagged plants will be re-measured every two years. New plants will be added in study areas when found.

7. Results will be regularly compared to determine if patterns are evident and if estimates of growth rate can be determined.

Measurement Tools Used:
Measuring tapes, clinometers, calculators, time reader cards.

Location of Study and Vegetation Class/Type



  • Sheep's Pass
  • Stirrup Tank
  • Barker Dam
  • Black Rock Canyon
  • Keys View
  • Porcupine Wash
  • N/A
    (Future Program Expansion)
  • N/A
    (Future Program Expansion)

Vegetation Class/Type

  • Blackbrush Scrub
  • Mojave Creosote Bush Scrub
  • Mohave Mixed Steppe
  • Mojave Mixed Woody Scrub
  • Mojavean Pinyon--Juniper Woodlands
  • Sonoran Creosote Bush Scrub
  • Sonoran Mised Woody
    & Succulent Scrub
  • Stabilized & Partially Stabilized Desert Dunes

Length of Research:
Long-term study of at least 6 years, extended in 6-year increments with evaluation at the end of each 6-year period, for a target study period of 24 years.

Predicted outcome:
We expect to see growth patterns become apparent as measurements are collected, producing estimates of the growth rates of sampled desert plants.

Cornett, James, W. JWC Ecological Consultants. 20-Year Joshua tree study in the Mojave Desert.

Vasek, Frank. 1995. “Ancient Creosote Rings and Yucca Rings,” The California Desert: An Introduction to Natural resource and Man’s Impact. June Latting and Peter Rowlands, Editors

LaPre, Lawrence. 1979. “The Physiological Ecology of the Mojave Yucca.” Dissertation, University of California, Riverside.

Kobaly, Robin. 2006. “Age determination of ancient southwest desert plants using growth ring data of cleared vegetation”. Study for The SummerTree Institute to develop age estimation tools and curriculum for their “Saving The Ancients” program and “Discovering The Ancients” program.

Various studies at Joshua Tree National Park, Joshua Tree National Park


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A brief description of Joshua Tree National Park, including weblinks for the U.S. National Park Service site as well as other sites of interest regarding the park.

Official NPS Web site:
Joshua Tree National Park

When you go out in the desert and actually look at the plants, and I mean sit and look at them, you begin to see the diversity and complexity this land has to offer. When you walk next to the plants and rocks of the desert, you begin to feel connected to them, as your grandparents would have felt, if they had lived here. It is not a harsh place, if you slow down and listen.

Curt Sauer, Superintendent
Joshua Tree National Park