CSU ecologists to track impacts of climate change on grasslands with USDA grant

large storm over grasslandsGrasslands play a large role in Colorado’s agricultural economy, and climate change is having unpredictable effects on them. Ranchers rely on these expansive natural ecosystems to support grazing and livestock production. Research suggests that current rainfall patterns will soon be changing with the addition of more sudden and severe rainfall events, resulting in an unknown future for these important ecosystems.

In an effort to learn more about these coming changes, Biology Professors Alan Knapp and Melinda Smith were recently awarded a four-year $498,500 grant from the United States Department of Agriculture (USDA) to fund their project “Foundational research for managing forage production in semi-arid grasslands: preparing for a future with increased climate variability.”

Big storms, bigger problems

Historically, the productivity of plant growth in grasslands has been very dependent on moisture fluctuations. Much like a typical suburban lawn, grassland productivity is low during dry years and increases during wet years. This relationship between rainfall and productivity has served as the basis for ecologists’ foundational knowledge of grasslands for decades.

“But we’re faced with this future – it’s actually the present – of our rainfall patterns happening differently than they have happened in the past,” said Knapp. “We are seeing a shift towards the same amount of rain falling on fewer days and in much bigger rainfall events.”

Knapp and Smith have been tasked with identifying how the basic understanding of grasslands must be altered in order to mitigate the potentially negative impacts of these changing rainfall patterns.

In the field

To better understand the impact of these changes that are already underway, Knapp and Smith will be conducting experiments over the next four years at the Central Plain Experimental Range, an agricultural research service facility in Northern Colorado dedicated to grassland and grazing research. The site was initiated by the federal government after the dust bowl, when farmers were concerned for the long-term security of their grasslands.

The grant will support the scientists as they experimentally manipulate the climate in small areas to mimic large rainfall events and measure how the ecosystem responds. They will also be paying close attention to the carbon budget of the system, whether it stores or releases carbon, and water use, the amount of water being used by the plants for photosynthesis as opposed to evaporating from the soil.

“We aren’t just interested in the pattern, we want to understand the mechanism,” said Knapp. “So you have to understand all of these other parts that help you understand why the functioning of the grassland might be changing.”

They will be joined by David Hoover, a research ecologist and ecohydrologist at the USDA Agricultural Research Service. He will be using a new hydro-meteorological sensor network of rain gauges and soil moisture probes at the Central Plains Experimental Range to track deluges in near-real time. When storms hit, Hoover and his crew will become “deluge chasers,” measuring the effects of these extreme events on carbon cycling and forage production across plant communities, soils and livestock management.

A hopeful hypothesis

increase in downpours graphKnapp predicts that the increase of large rainfall events could actually be beneficial for Colorado’s grasslands, at least under some conditions.

“We think that we may see a potential increase in productivity here,” said Knapp. “Our grasslands are dry most of the time, so having big rainfall events means that rain water penetrates deeper into the soil, meaning less evaporates away into the atmosphere and more is available for plant growth.”

The pursuit of knowledge

The new project fits in well with the University’s Land-grant mission. “Ultimately, I would hope that people realize this type of research is a great example of the value of Colorado State University,” said Knapp. “Faculty here have many roles – teaching and education and service and outreach.” In addition, he said, “a large part of what we do involves basic knowledge generation. The information that’s in textbooks, the information that land managers use, the information that we all use to increase our quality of life and deal with our changing planet. It has to come from people in the field, people designing the experiments, people trying to understand the world.”

Knapp joined the faculty of the College of Natural Sciences in 2004 and serves as a senior ecologist in the Graduate Program in Ecology. He was named a University Distinguished Professor and inducted as a fellow of the American Geophysical Union in 2017. Knapp earned his M.S. and Ph.D. degrees in botany from the University of Wyoming in 1981 and 1988, respectively.

Smith came to Colorado State University in 2012 and serves as a professor in the Department of Biology in the College of Natural Sciences. Smith’s expertise is in plant community ecology and ecosystem ecology. She served as director of the Semi-arid Grassland Research Center from 2013-2018. Smith earned her M.S. and Ph.D. degrees in from Kansas State University in 1998 and 2002, respectively.

Hoover has been a research ecologist and ecohydrologist for the USDA Agricultural Research Service since 2016. He earned his Ph.D. in ecology from Colorado State University in 2014.