A new instrument on the International Space Station is helping scientists understand the inner workings of plant life by showing how different plants balance the tradeoffs between growth and water use. A team of scientists has now undertaken a major global study of these tradeoffs among nine different plant types in 11 ecosystems around the world.
In this first-of-its kind study, the authors found that plants of the same type, such as deciduous broadleaf trees, evergreen needle-leaf trees, tall or low shrubs, herbs and non-herbaceous grasses, often have similar water-use efficiency regardless of where they grow. The results indicate that it is the type of plants, rather than the climate in which they are growing, that dictates their efficiency. The results also indicate that plant types with longer lifespans, such as shrubs and trees, have higher water-use efficiency than types like grasses, which have shorter lifespans.
The study suggests how environmental conditions may shape current and future plant communities and the ecosystem services they provide, say the authors. The results were just published in the journal Nature Plants.
Plants both use and lose water when they take up carbon dioxide to photosynthesize and grow. Species capable of growing more while using less water may be more resilient to the increasing frequency, intensity and duration of droughts projected to occur in many regions with global climate change.
“Knowing how different plant types optimize the tradeoffs between growth and water use can inform plans to mitigate and adapt to a warmer and drier future,” said lead author Savannah Cooley, a PhD student at Columbia University and a contractor for NASA’s Jet Propulsion Laboratory.
The analysis was made possible by data from a new satellite instrument, the ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station, or ECOSTRESS. The instrument provides the most detailed temperature images of Earth’s surface ever acquired from space. These temperature images are used to estimate rates of evapotranspiration (the transfer of water from the surface to the atmosphere) and photosynthesis by plants. Previously, the lower resolution of available data and disagreements among different land-surface models led to wildly varying measurements of water-use efficiency.
ECOSTRESS revealed patterns that could not be observed with previous satellite instruments, and that would be impossible to measure on the ground, say the researchers. For instance, using images from the Brazilian Amazon, the study demonstrated significant variation in water-use efficiency by plant type over the scale of just a few miles of seemingly similar tropical rain forest, as well as abrupt changes where forests had been converted to pasture.
The system was built by the Jet Propulsion Laboratory, and launched in 2018 to provide information on global land surface temperature at unprecedented spatial and temporal resolutions. It sends images at a resolution less than that of a football field every two to three days.
“ECOSTRESS is remarkable in that it allows us to determine plant water use nearly anywhere on Earth at spatial scales that were unthinkable just a few years ago, all from an instrument that is traveling more than 17,000 miles per hour more than 250 miles above us,” said study coauthor Joshua Fisher of Chapman University. The measurements may also be useful for detecting wildfires, urban heat waves, volcanic activity, and for a number of other applications, the authors say.
The study was also coauthored by Gregory Goldsmith of Chapman University.
Adapted from a press release by Chapman University.
