Hundreds of rainout shelters on the Jornada Experimental Range are helping researchers predict what arid and semi-arid ecosystems will look like in the future. The rainout shelters serve as simulators of climate change, and they are just one part of a 20-year and ongoing Chihuahuan Desert study.
Osvaldo Sala, the Julie A. Wrigley professor at Arizona State University, has been a part of this project for more than 10 years. He said the key to determining the future of ecosystems is using four complementary approaches to reach scientific answers.
“The four legs of our research approach are observation, experimentation, modeling and long-term data analysis,” Sala said.
The Jornada Basin Long Term Ecological Research principal investigators live in various locations. Among others, Sala is working with lead principal investigator and New Mexico State University adjunct plant and environmental sciences faculty member Debra Peters and Northern Arizona University Professor of Environmental Science Laura Huenneke, who have been a part of the project for almost 20 years. The research team is in the process of writing manuscripts about all of its discoveries, and various groups of researchers convened on the NMSU campus in February to discuss their findings.
“The writing process is finding a story,” Sala said. “We have a hypothesis, we collect all the data, we perform statistical analyses, and then we get together to look at the data and try to put together a scientific story.”
What exactly is the story?
For one, vegetation maps beginning in the 1850s have shown that the Southwest changed from perennial grasslands to shrublands. Also, there has been a cycle of long periods of drought years followed by periods of wet years.
While short-term experiments may provide valuable data about processes, accurate predictions are not possible without long-term data.
“The long-term data on plant production and diversity have allowed us to see changes between very wet years and very dry years, and between sequences of wet years and sequences of dry periods,” Peters said. “These comparisons allow us to look at vegetation patterns and make inferences about what our future is going to look like. It’s only using that long-term data that we can make those sort of effective predictions.”
The rainout shelter project is part of the long-term research. The distances between the shingles on these structures purposely vary, in order to control precipitation. Some shelters intercept 50 percent of incoming precipitation and some intercept up to 90 percent.
Acting as simulators, the shelters intercept precipitation representing drought conditions and route precipitation through pipes to a plot that is irrigated, simulating wet conditions.
“We’ve run this rainfall manipulation for almost 10 years now,” Sala said. “During the first four years of rainfall manipulation, we didn’t see any significant difference. But by year seven or eight, we started seeing that in the drought treatments, there was a sharp decline of the grasses.
That would have been impossible to predict based on the short-term experiments. What’s even more interesting is that declining grass was accompanied by an increase in shrub production. And that only could be seen after 10 years of manipulation.”
The data have also shown that the diversity in species is related to the availability of water. High temperatures cause evaporation in the soil, which leads to soil drying faster. And in drought situations, the ecosystems will have fewer species.
Huenneke participated in the initiation, design and first years of data collection at the Jornada Range during her career at NMSU in the late 1980s and 1990s.
“It’s wonderful to come back after 20 years – 25 years in some cases – of these studies, and to look at what the continuing results have been,” Huenneke said. “It’s really an exceptional opportunity to look at long-term change in desert systems, which are so hard to sample. That’s what makes this such an unusually valuable study.”
One of the next steps is to develop a simulation model that incorporates all of the water and vegetation data collected thus far. The NMSU College of Agricultural, Consumer and Environmental Sciences has committed to funding a two-year research assistant position to work on the simulation model.
Operated by the Department of Agriculture Agricultural Research Service, data have been collected on the Jornada Experimental Range since 1915. Data have been collected for the LTER project, administered by NMSU, since 1983. The Chihuahuan Desert Rangeland Research Center is operated by NMSU.
Author: Kristie Garcia – NMSU