Made for Managers: Research to help grassland productivity weather a variable climate

Photo Credit

USDA Forest Service photo by Erika Reiter

Researchers Jacqueline Ott (center, Rocky Mountain Research Station) and Amy Symstad (right, U.S. Geological Survey) work on building a rainout shelter with the research team.

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Dr. Jacqueline Ott, research ecologist with the USDA Forest Service Rocky Mountain Research Station, is partnering with Dr. Amy Symstad from the U.S. Geological Survey and Dr. Troy Ocheltree at Colorado State University on a four-year study on the Buffalo Gap National Grassland.

The study will use the grassland’s response to drought scenarios to offer tailored management tools to land managers seeking strategies for long-term resilience on these grasslands. Specifically, the researchers aim to provide managers with metrics they can use to determine whether they should adjust their grazing practices during or after a drought.

The Buffalo Gap National Grassland accounts for “some of the most intact grasslands in the world,” explains Ott. It offers recreational opportunities and critical forage for livestock and is home to diverse plant and animal species that are unique to the Great Plains region of North America.

Photo Credit

USDA Forest Service photo by Erika Reiter

A rainout shelter installed at the study site in the Buffalo Gap National Grassland.

The mixed grass prairies like those of the Buffalo Gap support some of the largest cattle production in the country. These prairies and their forage productivity are shaped by a highly variable climate, fire, and grazing. Understanding their effects on grasslands is critical for managers as they make future-driven decisions.

The timing and intensity of drought influences the productivity of grasses and other plants within this region of the world, but the exact patterns of these influences are not fully understood, especially within mixed grass prairies.

The experiment focuses on the different responses of cool-season grasses and warm-season grasses, which fill different roles within the Great Plains. Although all grasses are capable of growth throughout the growing season from March through October, cool-season grasses tend to grow more during the cooler periods of the season (spring and fall) while warm-season grasses tend to grow more during the warmer periods (summer and early fall).

Depending on the timing of a drought, these two groups of grasses may be affected differently, so much so that the overall forage production during and after drought will depend on which types of grasses are in a pasture.

At the beginning of the 2024 growing season, the research team set up 46 rainout shelters on 10-foot by 14-foot experimental plots at two sites on the Buffalo Gap National Grassland. The team then moved the shelters to other plots during the middle of the growing season. Each of these shelters functions as a partial roof that keeps half of all rainfall off the sheltered plots.

Photo Credit

Photo by Carston Chancellor

Researcher Jacqueline Ott rides Carbon, a Forest Service horse, over a study plot to model the impacts of livestock on droughted grasslands.

The team is also simulating grazing and trampling by livestock in the experimental plots to model the effects of two potential grazing strategies during and after a drought. To do this, Ott and her team first use lawnmowers to remove forage, then guide horses across the experimental plots to re-create the effects of cattle hooves on the plants and soil surface.

Throughout the growing season, the team has returned to the field to measure the response of the grasses and other plants to the simulated drought and grazing scenarios. The research team has been measuring plant community composition, forage productivity, belowground bud production, soil moisture, and stages of grass development.

Ott is looking closely at the impacts of partial-season and season-long droughts on the grasses using indicators like delays in plant development, the number of buds produced (buds are the primary source of grass regrowth following drought), and changes in stem recruitment. Research identifying and evaluating how grasslands will respond to major ecosystem drivers is critical for managing these landscapes.

“Our job as researchers is to provide the best available science for both public and private land managers,” says Ott. “Land managers often have to make difficult decisions on whether to maintain their herd size during drought conditions. Through this research, we can provide managers additional confidence in how their grasslands will recover forage productivity potential following drought.”

The study will be ongoing for the next few years. In addition to the field study, greenhouse studies will be led by Ocheltree to examine physiological responses of dominant grass species to drought.

To learn more about this research, view the Buffalo Gap National Grassland drought and grazing study video. In the video, which was filmed in March of 2024, Ott and Symstad talk about what inspired this collaboration, the design of the field experiment, and how the research will help managers navigate drought conditions. Little did they know that the 2024 growing season would provide an even greater variety of drought treatments than they had planned!

To see more photos from the installation of the study’s rainout shelters, visit: Buffalo Gap Drought Study | Flickr

Rangeland permitted land on national forests and grasslands make up about 13 percent of all rangelands in the United States. Forest Service scientists are working with rangeland managers to find solutions supporting grassland productivity and ecosystem services. Healthy grasslands provide more foraging opportunities for livestock and better tolerate and recover from disturbances like wildfire, drought, invasive species, and disease.