Scientific evidence of a changing climate in California and across the globe is clear, but the impacts on ecosystems and agriculture are still difficult to predict, according to the University of California Agriculture & Natural Resources (UCANR).

Sophisticated computer models are used to forecast future climate, the university said, but understanding that temperature and precipitation levels will change in the future does not tell the full story; researchers also want real-world experience under those future conditions.

Moreover, some agricultural operations have higher sensitivity to these changes than others, UCANR said. Rangeland forage is particularly sensitive to climate changes since, unlike irrigated agriculture, ranchers rely solely on precipitation and have no control over how much and when it rains.

"It's tricky business," said rangeland expert Jeremy James, director of the University of California Sierra Foothill Research & Extension Center (SFREC) in Browns Valley, Cal. "It's not easy to forecast. We have to address the uncertainty in a realistic manner."

In order to study different climate projections on rangeland, James and Maggi Kelly, director of the UCANR Informatics & Global Information Systems special program, have begun developing a research site that will allow researchers to manipulate the temperature and rainfall on sections of rangeland to understand what would happen under predicted weather scenarios.

With a $220,000 National Science Foundation grant, construction is now underway on a four-acre site at SFREC that will help scientists learn how temperature and precipitation affect the growth and diversity of forage ranchers use to raise their livestock, UCANR said.

"We need to know how rangelands will respond when conditions change," James said. "Will we grow more but dry out earlier? Will we have more medusahead (an undesirable rangeland weed) or more soft chess (a high-quality forage)?"

When completed, 16 shelters on steel tracks will be connected to computer systems and hydraulic motors to move them up or down a research plot. The shelters and other equipment will allow scientists to precisely control the amount of precipitation (or irrigation water) that rains onto the plot. Other systems will give researchers control of air temperature.

"This facility isn't designed for one type of research," James said. "It is designed to conduct a wide variety of research by scientists over the next several decades. With this setup, we can look at the effect of climate change on soil biological communities, soil carbon, insect communities, plant-insect interactions and oak seedling recruitment."

UCANR said the research results from the project should give ranchers and land managers a better understanding of how climate change may affect agriculture and ecosystem function on rangeland while also providing important information on how to minimize impacts of these changes.

Some aspects of the research facility's development are not covered with the National Science Foundation funding, the university said. The researchers are looking for additional support to complete the project.

Related work underway

During a recent workshop, scientists from the University of California-Davis, the University of California-Berkeley and the University of California Cooperative Extension (UCCE) shared a sampling of current research at SFREC.

UCCE livestock and natural resources advisor Dan Macon described a project aimed at helping ranchers make decisions about maintaining a cattle herd when faced with impending drought.

"Science tells us you shouldn't feed your way out of a drought, but you want everything to stay the same. You want to maintain your genetic potential and keep cows that are familiar with the area," Macon said.

Working with ranchers, the research project compares management practices to determine the best way forward when the future looks meteorologically bleak, the announcement said.

"We're assigning cows to a traditional weaning and early-weaning groups," Macon said. "They'll be out on the range from March to early September under different parameters. We're also tying in economics, the value of genetic potential and the value of having cows who know the landscape."

Research by University of Oregon post doctorate researcher Ashley Shaw is looking into whether applying compost to rangeland will help mitigate climate change by sequestering more carbon and also if it will benefit forage under drought by increasing the soil's water holding capacity and improving nutrient delivery.

A defining research tool at SFREC is a data set that includes information on monthly rainfall and forage production going back 40 years.

A review of the data shows surprising variations and correlations at the center, where forage production averages 3,000 lb. per acre but has ranged from about 1,000 lb. per acre in 1987 to more than 5,000 lb. per acre in 2018, when there was so much growth that "we didn't have enough animals to graze" all of it, James said.

The data set paints a spectrum of the variation ranchers across the state must navigate to manage their livestock and rangeland in a way that is profitable and ecologically sound, UCANR said.