US grasslands affected more by atmospheric dryness than precipitation
A new study showing dryness of the atmosphere affects U.S. grassland productivity more than rainfall could have important implications for predicting how plants will respond to warming climate conditions.
Published online March 6 in the journal Nature Geoscience, the study conducted by scientists at Stanford University and Columbia University looked at 33 years of climate and vegetation satellite data to determine how plants regulate water and carbon dioxide under dry conditions.
The study’s large-scale methods to understand plant behavior could be used to improve predictive models of how environments will respond to droughts, which are expected to intensify in the 21st century.
"Just looking at changes in precipitation isn’t going to tell you the whole story," said lead author Alexandra Konings, an assistant professor of Earth System Science in Stanford’s School of Earth, Energy & Environmental Sciences (Stanford Earth).
When its stomata are open, a plant can take up CO2 from the atmosphere to make energy but risks losing water in dry conditions.
The strategy different plants use — whether to risk drying out in order to keep taking up carbon, or to close up and stop growing — affects their productivity.
Variability in drought response Using statistical analysis, the researchers separated out the effect of the plants’ behavior from the impacts of regional conditions, such as differences in precipitation or temperature.
Understanding how plant stomata respond to changes in the atmosphere is especially important in U.S. grasslands, which are a predominant source of carbon uptake, or storage of carbon from the atmosphere.
Behavioral differences Analysis shows grasslands that respond to drought by keeping their stomata open (anisohydric behavior) are more sensitive to dryness of the atmosphere than those that close their stomata and stop growth to save water (isohydric behavior).
While previous methods for understanding drought response entailed on-the-ground measurements, the new metric enables researchers to measure these patterns across the globe.