Long term observation has found that one native plant from the Mojave Desert, the brittlebush, has exhibited remarkable adaptation capabilities despite rising temperatures.
A new study from the University of Utah has tracked the brittlebush's ability to adapt to increased aridity and temperature levels. Published in the latest Proceedings of the National Academy of Sciences, the study is a long-term project supported by the National Science Foundation.
A Forty-Year Study
The dataset used by the University of Utah researchers is from two long-term research sites in the American Southwest. One site is situated in Death Valley, in the northern part of the Mojave Desert, while the other is near Oatman, Arizona.
The sites, both about a few hundred square meters in area, were established in the early 1980s by American biologist and University of Utah Distinguished Professor James "Jim" Ehleringer. Professor Ehleringer, also an elected member of the U.S. National Academy of Sciences and a Fellow of the American Geophysical Union, among others, have proposed the sites in recognition of long-term observations.
The article from the University of Utah also noted that for almost 40 years, Jim Ehleringer and his research team had visited both sites to collect plant samples and to survey the vegetation.
Last July 6, 2020, a scaled-down team of three members continued a previously-postponed survey trip. Study co-author Darren Sandquist wrote on Twitter: "DEPRAVED 2020 was unlike any other - delayed to June, and with a crew of but three. Easy to distance 6 m when working in the wide-open of the Mojave."
DEPRAVED 2020 was unlike any other - delayed to June, and with a crew of but three. Easy to distance 6 m when working in the wide-open of the Mojave. We missed you Jim @ehleringer #Encelia #covidsafe #fieldwork pic.twitter.com/LFwj5epuHm — Sandquist Lab (@SandquistLab) July 5, 2020
The focus of the study, scientific name Encelia farinosa, is better known as brittlebush or incienso. It posts an average lifespan of 30 years. Characterized by its silver leaves and yellow flowers, the E. farinosa is endemic to northern Mexico and the southwestern U.S.
Its English name is taken from its brittle stems, while its Spanish name is a reference to its early use as incense.
Tracking Brittlebush Growth
In biologists and foresters, the most common method of reviewing a tree's age and climate history is through its tree rings. However, the same is not applicable in arid environments with different types of plants - such as the brittlebush. The research team used the multi-decadal record of carbon isotope ratio collections and 39 years of population survey data for brittlebush species in the two sites.
The carbon isotope present in the brittlebush leaves discloses information such as the width of the plants' stomatal opening, which in turn describes the response to water availability. Brittlebush stomata are found underneath its leaves.
From the data, the brittlebush has apparently increased their water use efficiency by up to 58 percent over the 39-year period. It was noted being double compared to forests' efficiency increase of 20 to 30 percent over the same period. The observed changes were credited with increasing carbon dioxide concentrations and water stress levels.
Avery Driscoll, lab technician and lead author for the study, noted that their research directly related variations in plant ecophysiology to changing climate over a relatively short timescale. Driscoll added that while the study does not conclude anything regarding shrub growth, it does point out that the increase in water-use efficiency was higher in deserts compared to forests.
