The Mojave desert is a tough place to live by any measure. Receiving less than 13.7 cm (6 in.) of rain per year, it is the driest of all North American deserts. Spanning a range of elevations, the Mojave is prone to extreme temperatures, from sub-freezing conditions at night and in winter up to 49 °C (120 °F) or higher in the summer. Without any natural cover, a relentless sun beats down on plants and animals alike.

One species thrives in the Mojave, however: the creosote bush (Larrea tridentata). Creosote is an evergreen shrub that grows 1 to 3 m (3-10 ft) in height and boasts bright yellow flowers. It is one of the most dominant species in the Mojave landscape, and it provides most of the scenery on the drive from Los Angeles to Las Vegas.


The dark green creosote leaves are full of resins (plant oils), making the plant inedible to all but very specialized insects and contributing to the shrub’s common nickname, ‘greasewood.’ Creosote releases these oils into the air after a precipitation event, and they permeate the desert with a distinct smell that long-time desert dwellers associate with the smell of rain.

A fascinating aspect of older plants is the propensity to form rings. Creosote shrubs can live a long time, and as they age, their oldest, most central branches die off and the crown splits apart into a ring pattern. These rings appear to march, spreading out over the years; however, each new plant is actually the same genetic individual -- meaning they’re clones.


The oldest known creosote clones are in the Lucerne Valley, California. Referred to locally as the ‘King Clone,’ this ring has been estimated by scientists to be over 11,000 years old and spans over 40 ft (15 m) in average diameter.



Figure 1.  The ‘King Clone’ of creosote (Larrea tridentata) in Lucerne Valley, California, is the large ring near the center of the map.  Note the black car on the road shown for scale.

Recently, I headed to the Mojave with the Parrot Sequoia camera, one of the smallest, lightest multispectral sensors on the market. In a single flight, Sequoia captures images across four defined visible and non-visible spectral bands, plus RGB imagery. 

I used Sequoia to help address ecological questions about these ancient desert shrubs. Specifically, I was interested in whether ancient rings vary in productivity compared to their younger counterparts? If estimates are correct, the King Clone germinated when wooly mammoths still roamed the earth. Now that’s impressive, for sure, but I also wonder what that kind of aging might mean for the plant itself.

I mounted Sequoia on a 3DR Solo drone and using the free, open source Tower app to plan a fully autonomous mapping mission, I was able to map the King Clone and surrounding shrubs in a 10-minute mission at 30 m altitude. Though it was a single, short flight, the drone-mounted Sequoia captured data for a variety of ring sizes. I then linked up with the Pix4D team in Lausanne to collaborate on data analysis.  

Pix4D stitched the Sequoia imagery into a high resolution orthomosaic in both color (RGB) and multispectral data layers. Focusing on a sub-sample of 60 shrubs that ranged from 1.2 to 23.5 m in diameter,we then used the Sequoia’s multispectral data to calculate the average normalized difference vegetation index (NDVI) across the different ring sizes.


Figure 2.  NDVI map showing multispectral data from the Parrot Sequoia camera of the clonal rings of creosote (including the King Clone) in Lucerne Valley, California.


The conclusion? There was no relationship between ring size and NDVI (Figure 1), without or without the King Clone included in the dataset as a statistical outlier (r  = 0.005, P = 0.96).




Figure 3.  Relationship between the diameter (measured at the widest point in meters) of creosote shrub rings and the average (shrub level) NDVI.


Its a a cool result, as it suggests that the physiology of ancient shrubs, or how they function in this extreme environment, may be similar to shrubs several millennia younger. Mark Twain said that age is an issue of mind over matter: If you don’t mind, it doesn’t matter. That certainly seems to be the case with creosote in the Mojave.

Drones have already transformed the way ecosystems are studied and monitored. It’s easier and faster than ever to get a large amount of rich, accurate and actionable data. And with the Sequoia camera in particular, scientists now have an incredibly powerful tool to complement traditional vegetation data collection on the ground.

 You can learn more about Sequoia here and Parrot Education herehere.

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  • https://www.youtube.com/watch?v=mthztW9EE0o

    Here is the how-to integration video for Phantom 3 and Sequoia.  In this case, I would use Pix4D Capture app for the waypoints.

  • I have been selecting the default settings for Canon S110 with 80% front and side lap (its a bit overkill but the stitching is good, so I stopped experimenting).   Then I go into Parameters and slow the Waypoint navigation speed down to 200 cm for 30 meter altitude, 500 cm per sec or so for 100 m.  This helps some with the rolling shutter on the RGB.

    We have talked to both the Tower and Mission planner folks and have gotten them Sequoia specs. So you should be able to select Sequoia from the cameras in the next versions of the software.  This will be awesome.

    Next, I go log into Sequoia, typically from my phone while I use a tablet to plan the mission (I like not having to flip back and forth between connections).  I use the calculator to estimate triggering by distance using the Sequoia GPS (e.g. 100m altitude x 80% overlap = ________).  I velcro the GPS in the center of Solo (velcro so I can swap batteries easily).  Then I use a light velcro strap to wrap around the vehicle for cable management.  

    Upload the mission to Solo with the tablet.  Hit 'Start Capture' with the phone.  And you are in business.  Pretty easy actually.

    You just need the power adapter cable from MicaSense:


  • Howdy and thanks for sharing. 

    Was the Tower app able to trigger the camera according to the planned mission or did you set the Sequoia to interval picture capture? 

    We been using standard RGB imagery to create canopy structure models in Northern Hardwood forest in Michigan. We have a new Sequoia and are searching for the right flight platform. 


  • Pretty common in arid environments that NDVI doesn't work too well. C4 rather than C3. NDVI and my other vegetation indices fall down in these environments. To go with that, sparse actual % cover doesn't help.

  • Yes, checking for dispersion would be a nice application.  Supposedly Larrea is allelopathic, though I am not sure how much empirical support there is for that.

    What would be great for academic teaching use would be a drone field lab where students mapped using Sequoia and then estimated plant cover, diversity, distribution, and some different vegetation indices. 

  • Greg, thanks for sharing these results. Very interesting indeed!

    Another application of your data that could be interesting is to examine the spatial distribution of creosote plants. Based on a calculation of average distance between individuals you may be able to determine if the distribution is random, dispersed, or clustered. I would expect to see a dispersed pattern because of inter-individual competition in the root zone. I did this on a population near ST George in SW Utah (using a Sony RX100 on an Iris+), and the pattern was clearly dispersed.

  • Hi Greg,

    40 years ago I spent a fair amount of time in the desert and frequently encountered more or less circular plant rings as you have described.

    Creosote bush was certainly common, but there are lots of other species as well.

    I thought they were interesting but had no knowledge of the underlying cause.

    It will definitely be interesting to see what information we can now get with more advanced imaging techniques.

    Best Regards,


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