By Darrell J. Pehr
Giant Lab Helps Scientists Understand Changes over Past Century
Picture a scientific laboratory, a place where careful, detailed, significant research has been conducted for almost a century. What do you see? Spotless beakers and test tubes, polished stainless steel countertops, and regular use of the autoclave, just for good measure … Right?
Well, not exactly.
The reality? It’s a massive outdoor lab covering an expanse of desert, savannah and mountains, where violent downpours whisk precious, life-giving water across the parched soil too quickly, and searing droughts return every 20 or 30 years.
Since 1912, the 192,000-acre Jornada Experimental Range, just north of Las Cruces, has served as an ideal outdoor lab for studying the processes that shape similar arid and semiarid lands across the globe.
And what better place to study these harsh places than in a landscape that has seen its share of harshness? Change has been a constant companion to this northern fringe of the Chihuahuan Desert, from the consumption of once abundant grasslands by vast cattle herds of the late 1800s to the creeping effects of climate change and, now, the shadow of urbanization, literally just around the corner. Research at the Jornada Experimental Range is conducted by scientists and technicians with the U.S. Department of Agriculture’s Agricultural Research Service with four areas of focus: methods for assessment and monitoring of rangelands; ecologically based technologies for remediation of degraded rangelands; animal behavior-based strategies for livestock management; and predictive models of ecosystem responses to changes in climate and other management-dependent and independent drivers.
The Jornada Experimental Range’s mission expanded in 1981, when it was selected as one of the original sites of the National Science Foundation’s network for long-term ecological research (LTER) in the U.S.
As an LTER site, research is collaborative with other institutions and agencies with an interest in deserts, desert agriculture, desert ecology and the management of desert rangelands. The JER program is part of a global desert research effort that includes USDA, New Mexico State University, and other scientists’ work. That collaborative spirit extends to its neighbor, the adjacent Chihuahuan Desert Rangeland Research Center, operated by NMSU (formerly known as the College Ranch).
Of course, some JER research does demand modern lab facilities … and spotless beakers. In 2000, the JER headquarters – Wooton Hall – was constructed on the NMSU campus. It houses labs, offices and conference facilities. Not long after that a change in focus took place among JER research. Until about 2002, research had focused on desertification: the process a landscape goes through as it becomes a desert.
“It’s becoming more desert-like. If you go back to the 1850s, you can see that it actually was almost all grasslands,” said Deb Peters as she looked over maps designating the type of vegetation on the Jornada at various times in history. Peters is a JER research scientist and, as a faculty affiliate in the departments of Biology and Plant and Environmental Sciences at NMSU, the lead principal investigator for the Jornada Basin LTER. “There is a shift from grass-dominated to shrub-dominated.”
Research had focused on how that happened, with the understanding that it happened worldwide during the same time.
At the Jornada, “It involves extreme disturbances, such as periodic droughts,” Peters said. “But exactly what happens in that sequence of events is a little complicated.” Peters said a common belief in Las Cruces is that a drought in the 1950s was a major cause, but records show the process already was under way decades earlier.
Fellow scientist Al Rango, a JER research hydrologist, said millions of cattle grazed New Mexico in the late 1800s.
“People at that point thought it was such a lush area, that they could exploit it, but those millions were munching away,” Rango said. “There was a big drought in the late 1880s that coincided with those animals being in there. They ate what they could and were partially the cause (of desertification). It’s difficult to say that it wouldn’t have happened if the livestock weren’t there, but there certainly were a lot of livestock.”
Peters said the combination of animals eating the grass and drought created conditions that accelerated the disappearance of grasslands and encroachment of shrubs.
“Once the shrubs start getting established, there’s even more erosion of the soil, so the grasses are going to have an even tougher time,” Peters said. “So a positive feedback is set up that is going to make it more likely the shrubs will get established. In these systems, because of the soil properties – they’re fairly fragile – so you move that topsoil and the shrubs are much more likely to maintain themselves. It’s much harder for the grasses to come back.”
As researchers gained an understanding of how desertification took place, they turned their attention to researching methods to restore and remediate the landscape. Some work already had been tried, like removal of shrubs, but those efforts hadn’t followed a definite strategy and results, if any, sometimes didn’t show up for years.
“They’d pull them all up and then the shrubs would come back even denser. A lot of stuff didn’t work,” Peters said. “So we’ve tried to be more strategic about where and how would you do these things.”
A project now under way by JER ecologist Brandon Bestelmeyer is examining the plant-animal interactions in the transition areas – called ecotones – between grasslands and shrublands. Osvaldo Sala, a professor of biology at Brown University in Providence, R.I., is creating artificial droughts and rainy seasons on small plots at the JER to gauge the nuances of rainfall. A researcher from UCLA, Greg Okins, is investigating wind erosiondeposition and vegetation interactions.
Future research is likely to have more focus on the effects of climate change.
One area of interest for Peters is how seasonal distribution of precipitation that could accompany climate change would affect grasslands and shrublands.
“If there’s a shift to more winter precipitation, then the shrubs have more of an advantage,” Peters said. “If there’s a shift to more summer precipitation, it’s better for grasses. But we don’t know what will happen. There is no consistency among the models for this.”
Being able to look at the long history of research at the JER will help researchers understand such future changes, and how to monitor those changes. One method used to look at long-term climate change at the JER is to investigate soil.
As Curtis Monger, a professor in NMSU’s Department of Plant and Environmental Sciences, put it, “Soils have a memory, so to speak, of past climates. The depth to caliche (calcium carbonate), the amount of organic matter, and the ratio of carbon-12 to carbon-13 all provide clues about former rainfall, temperatures, and vegetation (desert shrublands vs. grasslands vs. woodlands).
“In addition to these features, the thickness and sequence of sedimentary layers and soil horizons contain a record of erosion, which is highest when plant cover is sparse, like today. We are always on the lookout for buried charcoal,” Monger said, “because it can be C-14 dated and tell us when climate change occurred. For example, a recent study revealed that erosion was very active in parts of the Jornada during the Medieval Warm Period (around 1200 AD).”
As Peters notes, “Our depth of knowledge provides us insight on what would happen, not only here, but in other dry rangelands around the U.S., North America, and the world. This is one reason why we are working in many other areas around the globe.”
Rango, too, thinks of climate change, but other factors must be considered.
“The climate change effect is one of the things that potentially could cause changes like desertification to happen, but other things, like the overgrazing, and the normal drought cycle are more significant. When the normal drought is a big one and it coincided with all the cattle being there, that impact is a heck of a lot more than the climate change impact.”
Nevertheless, researchers must be ready to factor in climate change as an agent of change.
“Somewhere down the road, in climate change, droughts are going to become more severe, as are flood events, because of the way it all takes place, so at this point I don’t think we can attribute too much of it to climate change that is ongoing, but in the future, it could be more important,” he said.
Regardless of which direction the future will take their investigations, range researchers in southern New Mexico can count on two things: change is inevitable, and an ideal place to study that change will be the Jornada Experimental Range.
“Although it seems the desert is static, things happen over short periods of time that have big impacts, like flooding events, drought events and wind erosion events,” Peters said. “It is a very dynamic system.”