Midwest perennial plants wait for cues, including sustained warming trends and day length, to know to unfurl tender leaves or flower buds.
So what happens to perennials when the sun tells them they should stay dormant, but warming soil tells them another story? A new study from the University of Illinois has some answers.
To look at the interplay between soil temperature, day length and dormancy in switchgrass and prairie cordgrass, U of I's D.K. Lee and his collaborators designed a study to trick the plants.
"We dug plants up from the field and brought them into warm greenhouses in Illinois and South Dakota every month from October through March," Lee said. "The only lighting was the sun, so the plants had to react to the ambient photoperiod, or day length."
The warm temperatures triggered plants to start growing, but some of them got confused by the short days after they emerged. The plants think it's weird, Lee said, so weird that they reentered a kind of dormancy. New switchgrass shoots stopped growing, but stayed green and alive. New shoots that prairie cordgrass produced died back completely.
Regardless of the study's intent to gather information for breeding purposes, Lee keeps coming back to what the results say about potential effects of climate change on perennial plants.
"We think of climate change as being a slow and steady process; it's possible that evolution could keep up with a pace like that. But we're seeing extreme and sudden temperature fluctuations. That's what we're worried about," he said.
If perennial plants come out of dormancy during an early thaw and then get hit by a late frost, the crop for that year could be lost. Even though prairie cordgrass is known to be cold tolerant, if short days force it back into dormancy after emergence, it still may have lower yields.
"What would happen if all the perennials die off or produce less biomass one year because of an early warm spell?" Lee said. "Would aggressive annual weeds take over? The perennial plant community might have a shock."
U of I researchers are harnessing satellite data for a more complete picture of cropland and to estimate crop yield in the U.S. Corn Belt.
"In places where we may see just the color green in crops, electromagnetic imaging from satellites reveals much more information about what's actually happening in the leaves of plants and even inside the canopy," said Kaiyu Guan, an environmental scientist and the lead author on the research.
Guan says this work is the first time that so many spectral bands, including visible, infrared, thermal and passive and active microwave, and canopy fluorescence measurements have been brought together to look at crops.
The study uncovers that many satellite data sets share common information related to crop biomass grown above ground. However, the researchers also discovered that different satellite data can reveal environmental stresses that crops experience related to drought and heat.
"This is an age of big data. How to make sense of all of the data available, to generate useful information for farmers, economists and others who need to know the crop yield, is an important challenge," Guan said. "This will be an important tool. And although we started with the U.S. Corn Belt, this framework can be used to analyze cropland anywhere on the planet."