Diversity Helps To Maintain Grasslands During Drought
August 9, 2012

Researchers Find That Diversity Could Help Save Drought-stricken Grasslands

Brett Smith for redOrbit.com - Your Universe Online

As drought ravages grasslands across the United States, a few American scientists are looking into how different species of grass endure these harsh conditions.

In a study that could impact everything from the beef industry to lawn care, a University of Kansas-led team examined the resilience of 426 species of grass from around the world and found that diversity is key in maintaining robust grasslands, according to their report published this week in the journal Nature.

Researchers planted grass species from six different continents, using seeds provided by the U.S. Department of Agriculture and collected from the Konza Prairie in Kansas, in a walk-in growth chamber equipped with high intensity lighting that simulated sunny conditions.

After a six-week growth phase, the scientists stopped watering the plants and began to observe how they would react to drought-like conditions.

"In the end they all succumbed to drought," said the paper´s lead author Joseph Craine, a biology professor at the University of Kansas. "But that was our goal: to stress them all enough to know at what point they give in.”

“What we saw was that some of grass species were about as tough as lettuce, meaning that after a day or two without water they would start to wilt and curl up,” he said. “Others, however, were able to go for a week or two without water."

The team, which included biologists from the University of Oregon and the Nature Conservancy in Minneapolis, analyzed the plants´ different degrees of drought resistance and found that hardier grasses are well distributed around the world. They concluded that because of the even distribution of grass species, global steppes and grasslands are well positioned to endure future droughts.

"If we still have grasslands that are diverse, the grasslands are going to continue to function relatively well and not change too much," Craine said. "But when we replace our prairies with ones that just have a few species in it, then it's less likely that grasslands will be able to function normally in the future. That affects the animals and other things that depend on grasslands, making it more likely that the whole ecosystem collapses."

In addition to calculating grasslands´ resiliency to climate change, the study also found that more drought-tolerant species had higher rates of water and carbon dioxide exchange than their less tolerant counterparts. This suggests that even in the face of severe droughts, grasslands would continue to maintain their function in the ecosystem, possibly through the localized expansion of more drought-tolerant species.

The study comes as good news for cattle ranchers, who have been selling off their herds in record numbers as a direct result of the lack of green grass. Some ranchers have estimated that pasture growth so far this year is about 25-percent of what it typically is. The lack of rain is also preventing the growth of hay, another staple in a common herd´s diet. Many supplements and feed products are commercially available, but they often don´t provide the nutrients that healthy green grass contains.