PLANTS can adapt to extreme shifts in water availability, such as from drought and flooding, but their ability to withstand these extreme patterns will be tested by future climate change, according to a study by U.S. Department of Agriculture scientists and their cooperators.
The study was published in Nature by a team from USDA's Agricultural Research Service (ARS) led by Guillermo Ponce Campos and Susan Moran and an Australian team led by Alfredo Huete from the University of Technology-Sydney (UTS). This research included contributions from nine other ARS scientists, four U.S. Forest Service scientists and colleagues from the University of Arizona, the University of California-Irvine and UTS.
"In the U.S., much of our agricultural productivity has depended on long-term precipitation regimes, but those patterns are changing, and we need information for managing the effects of those shifts," ARS Administrator Edward B. Knipling said. "These findings can help managers respond to the challenges of global climate change with effective strategies for maintaining agricultural productivity."
The researchers conducted their investigation using measurements made during 2000-09 at 29 sites in the U.S., Puerto Rico and Australia. This provided data about precipitation patterns in environments ranging from grasslands to forests. Globally, 2000 through 2009 ranked as the 10 warmest years of the 130-year (1880-2009) record, ARS said.
The team compared these data with measurements taken from 1975 to 1998 at 14 sites in North America, Central America and South America.
To calculate ecosystem water use, the scientists used satellite observations to approximate above-ground net plant productivity at each site. Then, they combined these approximations with field data of precipitation and estimates of plant water loss to generate indicators of plant water use efficiency.
ARS said the researchers noted that ecosystem water use efficiency increased in the driest years and decreased in the wettest years. This suggests that plants' water demand fluctuated in accordance with water availability and that there is a cross-community capacity for tolerating low precipitation and responding to high precipitation during periods of warm drought.
However, the team observed that the water use efficiency data exhibited a trend of "diminishing returns." This suggests that plant communities will eventually approach a water use efficiency threshold that will disrupt plant water use and severely limit plant production when drought is prolonged.
The researchers also used the data to develop predictions about future plant responses to climate changes. Their results suggest that ecosystem resilience will decline as regions are subjected to continuing warming and drying trends. They project that this downturn will begin in grassland biomes because these plant communities are particularly sensitive to the hot and dry conditions of prolonged warm droughts.