Science

USU scientists study how climate change could affect where plants get their water

Utah Public Radio | By Ryan Helcoski

Published May 31, 2024 at 3:45 PM MDT

Researchers Nizhonii Begaye (left) and Faraz Rehman (right) are pictured in the desert standing near a blackbrush (a small bush) outside Monticello, UT. They are injecting hydrologic tracers to target depths beneath the plant using small tools placed in and around the plant — Nizhonii Begaye (left) and Faraz Rehman (right) inject hydrologic tracers to target depths beneath a blackbrush outside Monticello, UT

Andrew Kulmatiski is an associate professor in Wildland Resources at USU. One of the topics he and his team study is something seemingly basic, but actually quite complex.

“We're examining where plants get their water from. It's a surprisingly simple question, but really hard to figure out," Kulmatiski said. "We really don't know what's going on underground, because when you dig a hole, you've killed everything you want to look at. “

A researcher, Andrew Kulmatiski, in field gear stands in the field holding the drill that is similar to large power drill with a very long bit that he and his team use to drill holes into the soil around target plants — Andrew Kulmatiski stands in the field holding the drill that he and his team use to drill holes into the soil around target plants

Granted, the general process of root water absorption is understood, but the precise relationship between, say, woody and grassy vegetation is not fully fleshed out. Though it has been studied for over 100 years, ecologists in the past often investigated the topic by looking primarily at root biomass.

“But what we learned in the past 10 or 15 years, in part due to some of my research, is that plant root biomass doesn't really tell you what plant roots are doing, because some roots are very active, and some roots just sit there and don't really do anything," Kulmatiski said. "And so, I've developed a technique using isotope tracers, in order to figure out exactly how much water plants are accessing from different soil depths.”

To carry out his technique, Kulmatiski and his team drill thousands of holes in the ground around a plant, then drill a pilot hole and inject a small amount of a harmless isotope tracer. Then they wait and collect the water the plant transpires and measure the concentration of the tracer within it.

“And then I can measure how much water different species absorb from different soil depths, I can then use that in soil water flow models to predict how different species will respond to different precipitation regimes, different climates on the landscape, or different anticipated climates," he said.

Researcher Krishaunna Riggs knees in the field placing a bag on a grass to collect transpiration water. There are many bushes around her, the soil is red, and there are notable geological formations in the background, outside Monticello, UT — Krishaunna Riggs places a bag on a grass to collect transpiration water. A tracer was injected into the soil beneath this plant and the concentration of tracer in the transpired water will indicate how much tracer was absorbed from the injection depth. Outside Monticello, UT

And that, of course, matters, given the reality of climate change. States like Utah are going to get less rain, but bigger rain events when it does happen. That means some plants, like juniper, may gain a competitive advantage over others.

“So if we want to manage the landscape for forage production, or diversity or productivity, understanding how different plants access water is really basic," Kulmatiski said. "And we just don't know how plants do it. It's surprisingly tricky to figure out these very simple problems.”

Which is why Kulmatiski and his team are seeking answers.