Desert shrubs become more efficient as temperatures rise

In response to rising temperatures and extremely dry conditions, desert plants are forced to adapt in order to survive. A new study from the University of Utah has found that one shrub in the Mojave Desert, the brittlebush, is exceptionally talented when it comes to adaptation. 

Over the last four decades, the brittlebush has more than doubled its water use efficiency. The research suggests that some desert plants have the resiliency to endure future climate change.

“We were able to directly relate changes in plant ecophysiology to changing climate over a relatively short timescale,” said study lead author Avery Driscoll. “This shows us that desert shrubs can and do acclimate to changing environmental conditions.”

The study was focused on decades of data from two long-term research sites in Death Valley and near Oatman, Arizona. 

Professor Jim Ehleringer, who established the sites in the 1980s, led a team to survey the vegetation and collect plant samples every spring for 39 years.

Brittlebush, Encelia farinosa, is commonly found throughout the Southwest and northern Mexico. The shrub has bright yellow flowers and silvery leaves, and can live for more than 30 years. 

The leaves of brittlebush contain a record of the climate in carbon isotopes that make up the tissue. These isotopes can be used to assess a plant’s water use efficiency.

The researchers found that the brittlebushes sampled for the study increased their water use efficiency by 53 to 58 percent over the 39-year study period.

Driscoll noted that the temperature is rising and humidity is dropping in the Mojave Desert.”This increase in water use efficiency shows that the leaf physiology of these plants has adjusted in response to this added water stress and increased availability of CO2.”

Experts theorize that increasing CO2 levels may actually benefit plants like the brittlebush because it allows them to get the same amount of CO2 with smaller stomatal openings, which reduces water loss. By contrast, forests have not yet demonstrated an increase in water use efficiency.

“While we can’t say anything about the implications for shrub growth, we did find that increases in water-use efficiency were substantially larger in deserts than they are in forests.”

Driscoll said it is too soon to tell whether brittlebush and other desert shrubs will be able to survive future warming.

“While it’s possible that more efficient use of water could translate into growth, survival or flowering benefits for these plants, we don’t yet know if the change will confer advantages or mitigate potential declines in the population.”

The study is published in the Proceedings of National Academy of Sciences.

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By Chrissy Sexton, Earth.com Staff Writer