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CU Boulder Ecology and Evolutionary Biology scientist Katharine Suding is leading ongoing research in partnership with City of Boulder Open Space

At first glance, grasslands may not display an obvious or flamboyant beauty.

Along the Front Range of Colorado, at least, they tend toward the scrubby and patchy—places of dusty, muted colors that can pale in comparison to nearby forests.

But in an area of grassland the size of a large room, there may be upward of 50 plant species. There may be pollinators and wildflowers, burrowing mammals, a rainbow array of reptiles and a universe of life in the soil itself.

“There’s incredible diversity in what can be really dry, harsh conditions,” explains Katharine Suding, a professor in the University of Colorado Boulder Department of Ecology and Evolutionary Biology. “Some of these grasses are rooting over 10 feet deep, so below ground there is this complexity that keeps the soils and the whole system super healthy. 

Katherine Suding is a plant community ecologist working at the interface of ecosystem, landscape and population biology.

“If we start losing that, we will see the effects in erosion, in a loss of capacity to hold water, in more flooding, in the loss of the system’s ability to support plants at all.”

Grasslands are increasingly at risk to climate change, which in the long-term may impact everything from local economies to food systems and regional biodiversity. To learn more about these grassland impacts fueled by climate change, particularly their response to drought, Suding and her co-researchers recently were  from the U.S. Department of Agriculture (USDA) National Institute of Food and Agriculture.

The aim of the grant is to fund research projects “that focus on the improvement of ecosystem health and output of ecosystem services in managed production systems—like croplands, forests and rangelands—that are currently under stress or at risk from climate change, pests, pathogens, invasive plants and increased environmental pressures. This program area priority calls for applied research that will advance scientific understanding of health functions, processes and management of sustainable agroecosystems,” according to the USDA.

Understanding grassland changes

The grant awarded to Suding and her co-researchers—who include Laura Dee, a professor in the CU Boulder Department of Ecology and Evolutionary Biology—will support the continuation of a drought and grazing study initiated six years ago in a partnership with City of Boulder Open Space and Mountain Parks. Concentrating on an area of open space south of Boulder, the research focuses on vegetation loss and how expanding patches of bare soil affect system resilience.

Grasslands are made up of grasses like the ones shown above. When large areas of grass cover the earth, they help midigate flooding and dry spells, decompose waste and stabilize the climate.

“When drought occurs, you get this patchy structure occurring and the development of open, bare patches,” Suding says. “That seems to generate this feedback loop where you have open patches start forming and then the grasses are not able to recolonize those patches. We see this pattern develop where drought starts making these patches, they get larger and larger and plants are unable to get back in because it’s really hot and really harsh in the center of these bare areas. So, more than just recovery is at stake. Once those patches are established and the bare areas get bigger and bigger, we start losing intact grassland.”

The researchers use thermal cameras to capture the large differences in soil temperature in vegetation and bare patches. They monitor the transition from many small bare patches to fewer but larger bare patches using aerial imagery. In doing so, they have observed a dieback of grasses, “which leads to the soil being easier to erode and blow away with huge wind events,” Suding says. 

“Then we start losing our soil structure, which may be telling us the grassland is starting to deteriorate and drought is pushing the system too hard. And then we need to take action and look to changing how we graze that system, changing how we manage the system. We don’t want those patches to get larger and larger, to the point that the grassland can’t recover.”

Long-term system health

The research partnership with City of Boulder Open Space is particularly important, Suding says, “because we can’t control the climate, but we can have input on policies at the local and state level.”

Grassland research in Colorado is especially important because millions of acres of public land are open to grazing. Grazing done with a conservation mindset can help keep grassland systems healthy, Suding says, adding that grasslands have adapted to the disturbances of grazing and fire to maintain biodiversity and health. 

However, with climate prediction models showing steadily increasing temperatures, “what is a little worrisome is we don’t know if the future of Boulder is going to be more like, say, Albuquerque in terms of climate and we don’t know how the grasslands are going to adapt to that,” Suding says.

The Boulder research site also is important because all three types of U.S grassland—tall grass, mixed grass and short grass prairie—are represented there. In particular, the site is home to xeric tall grass prairie, a type of grassland similar to that found in the U.S. Midwest, and is a conservation target for City of Boulder Open Space because of the incredible diversity of life found in it.

“This project will enable us to really look at spatial structures of how drought is changing where vegetation is and increasing the number and size of bare patches,” Suding explains. “We’re starting with relatively small-scale experiments and then using aerial imagery to scale it up. The ultimate goal is to be able to do this at scale, to understand changes in grasslands throughout the region and develop policies focused on long-term system health and resilience.” 

Postdoctoral scholar Elisa Van Cleemput is also a co-investigator on this research.