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Balancing birds and biofuels: Grasslands support more species than cornfields

In Wisconsin, bioenergy is for the birds. Really.

In a study published today in the journal PLOS ONE, University of Wisconsin-Madison and Wisconsin Department of Natural Resources (DNR) scientists examined whether corn and perennial grassland fields in southern Wisconsin could provide both biomass for bioenergy production and bountiful bird habitat.

The research team found that where there are grasslands, there are birds. Grass-and-wildflower-dominated fields supported more than three times as many bird species as cornfields, including 10 imperiled species found only in the grasslands. These grassland fields can also produce ample biomass for renewable fuels.

Monica Turner, UW-Madison professor of zoology, and study lead author Peter Blank, a postdoctoral researcher in her lab, hope the findings help drive decisions that benefit both birds and biofuels, too, by providing information for land managers, farmers, conservationists and policy makers as the bioenergy industry ramps up, particularly in Wisconsin and the central U.S.

“As bioenergy production demand increases, we should pay attention to the ecological consequences,” says Turner.

This is especially true for grassland birds, as populations of species like the eastern meadowlark, dickcissel and the bobolink have declined in recent decades.

The study began when UW-Madison’s Carol Williams, coordinator of the Wisconsin Grasslands Bioenergy Network, and the DNR’s David Sample approached Turner and asked for her help. They wanted to know: “What are the implications of the decisions we make about how we use our lands?” says Turner.

The research team carefully selected 30 different grassland sites — three of which are already used for small-scale bioenergy production — and 11 cornfields in southern Wisconsin. Over the course of two years, the researchers characterized the vegetation growing in each field, calculated and estimated the biomass yields possible, and counted the total numbers of birds and bird species observed in them.

According to Blank and Turner, the study is one of the first to examine grassland fields already producing biomass for biofuels and is one of only a few analyses to examine the impact of bioenergy production on birds.

While previous studies suggest corn is a more profitable biofuel crop than grasses and other types of vegetation, the new findings indicate grassland fields may represent an acceptable tradeoff between creating biomass for bioenergy and providing habitat for grassland birds. The landscape could benefit other species, too.

Because they are perennial, the grassland fields can also be used year after year, following best management practices that preserve the health of the soil and provide reliable habitat for migratory birds.

“Plant diversity is good for wildlife diversity,” says Blank. “Our study suggests diverse bioenergy crop fields could benefit birds more so than less diverse fields.”

Among the grasslands studied, the team found monoculture grasses supported fewer birds and fewer bird species than grasslands with a mix of grass types and other kinds of vegetation, like wildflowers.

… new findings indicate grassland fields may represent an acceptable tradeoff between creating biomass for bioenergy and providing habitat for grassland birds.

The team found that the presence of grasslands within one kilometer of the study sites also helped boost bird species diversity and bird density in the area.

This is an opportunity, Turner says, to inform large-scale land use planning. By locating biomass-producing fields near existing grasslands, both birds and the biofuels industry can win.

Incentives for a conservation-minded approach could be used to help offset potential differences in profit, the researchers suggest. They also add that the biomass yields calculated in the study may represent the low end of what is possible, given that one of the two study years, 2012, occurred during a significant drought period in the state.

“The study shows species generally really benefit from the practice,” says Blank. “We really can produce bioenergy and provide habitat for rare birds in the state.”

Agriculture and Food News — ScienceDaily

Restoring grasslands: Ant diversity indicates restored grasslands

When it comes to restoring grasslands, ecologists may have another way to evaluate their progress — ants.

The more diverse the ant population, the closer a restored section of grassland is to its original state, according to Laura Winkler, who recently completed her master’s degree in plant science, specializing in entomology, at South Dakota State University. When it comes to native grasslands, ants are “ecosystem engineers.”

Ecological role of ants

Ants play many ecological roles, Winkler explained. “They aerate the soil, cycle nutrients and play a role in plant defense and seed dispersal. Ants move more soil than earthworms, plus they are food for lots of reptiles and birds.”

Some ant species support colonies of plant-feeding insects, such as aphids or plant hoppers, even protecting them from predators. “It’s like having dairy cattle,” Winkler said. Through this technique, the ants consume the sugar-rich honey dew the aphids secrete, much as humans use cow’s milk. When the ants are in need of protein, they simply eat the aphids.

Ants also distribute organic matter by moving dead insects into the colonies and their dead nest mates away from the colonies, Winkler added.

Comparing restored, undisturbed grasslands

Winkler compared tracts of restored grasslands to undisturbed ones at three sites in eastern South Dakota–Sioux Prairie in Minnehaha County, Oak Lake Field Station in Brookings County, and Spirit Mound in Clay County. The U.S. Fish and Wildlife Service manages the restored areas, while the undisturbed area at Sioux Prairie is managed by the Nature Conservancy, Oak Lake by SDSU and Spirit Mound by the S.D. Game, Fish and Parks Department.

Originally from Des Moines, Iowa, she began working with ants as an undergraduate at Iowa State University focusing on how burning and grazing affect species diversity. Her SDSU graduate research assistantship on ant biodiversity and natural history was funded through the Meierhenry Fellowship. Her research adviser was entomologist Paul J. Johnson, professor of plant science.

Variation with age

The U.S. Fish and Wildlife Service sites that had once been crop or pasture land were restored anywhere from one to four years ago, according to Winkler. This involved taking the areas down to the bare ground and then seeding native grasses. Winkler used data from multiple sites taken over a one-year period.

As expected, the younger sites had fewer ant species, with the numbers and diversity increasing over time. The restoration areas at age 1 had seven different species, while at age 2, the number had increased to nine and by age 3 to 10 species, Winkler reported. She expected the fourth year restorations to be even closer to the 17 species present in the undisturbed remnants, but what she saw was a slight decrease to eight species.

“The drought last year and then a wet spring also affects that vegetation, what’s going to survive and how many of the ants are out foraging,” Winkler pointed out.

She suspects that management techniques may also have played a role. “Some sites may have been burned more frequently,” she noted, to control weeds.

“We’ve got a sneak peek of what can happen,” Winkler said, but more long-term research is needed. Based on other research, she anticipates that the restored areas should peak in terms of species diversity within seven to eight years.

Increased specialization

Winkler also looked at how these ant species function. The younger restorations areas tend to have ants that are generalists who can go anywhere, but the older restorations tend to have more specialists, such as soil-dwelling ants, who are more particular about where they live, Winkler explained. The more dominant specialists push out some of the generalists.

“You’ll have ants everywhere,” she pointed out, but the greater the diversity, the more niches are being filled, and the more successful the restoration effort.

Agriculture and Food News — ScienceDaily

Restoring grasslands: Ant diversity indicates restored grasslands

When it comes to restoring grasslands, ecologists may have another way to evaluate their progress — ants.

The more diverse the ant population, the closer a restored section of grassland is to its original state, according to Laura Winkler, who recently completed her master’s degree in plant science, specializing in entomology, at South Dakota State University. When it comes to native grasslands, ants are “ecosystem engineers.”

Ecological role of ants

Ants play many ecological roles, Winkler explained. “They aerate the soil, cycle nutrients and play a role in plant defense and seed dispersal. Ants move more soil than earthworms, plus they are food for lots of reptiles and birds.”

Some ant species support colonies of plant-feeding insects, such as aphids or plant hoppers, even protecting them from predators. “It’s like having dairy cattle,” Winkler said. Through this technique, the ants consume the sugar-rich honey dew the aphids secrete, much as humans use cow’s milk. When the ants are in need of protein, they simply eat the aphids.

Ants also distribute organic matter by moving dead insects into the colonies and their dead nest mates away from the colonies, Winkler added.

Comparing restored, undisturbed grasslands

Winkler compared tracts of restored grasslands to undisturbed ones at three sites in eastern South Dakota–Sioux Prairie in Minnehaha County, Oak Lake Field Station in Brookings County, and Spirit Mound in Clay County. The U.S. Fish and Wildlife Service manages the restored areas, while the undisturbed area at Sioux Prairie is managed by the Nature Conservancy, Oak Lake by SDSU and Spirit Mound by the S.D. Game, Fish and Parks Department.

Originally from Des Moines, Iowa, she began working with ants as an undergraduate at Iowa State University focusing on how burning and grazing affect species diversity. Her SDSU graduate research assistantship on ant biodiversity and natural history was funded through the Meierhenry Fellowship. Her research adviser was entomologist Paul J. Johnson, professor of plant science.

Variation with age

The U.S. Fish and Wildlife Service sites that had once been crop or pasture land were restored anywhere from one to four years ago, according to Winkler. This involved taking the areas down to the bare ground and then seeding native grasses. Winkler used data from multiple sites taken over a one-year period.

As expected, the younger sites had fewer ant species, with the numbers and diversity increasing over time. The restoration areas at age 1 had seven different species, while at age 2, the number had increased to nine and by age 3 to 10 species, Winkler reported. She expected the fourth year restorations to be even closer to the 17 species present in the undisturbed remnants, but what she saw was a slight decrease to eight species.

“The drought last year and then a wet spring also affects that vegetation, what’s going to survive and how many of the ants are out foraging,” Winkler pointed out.

She suspects that management techniques may also have played a role. “Some sites may have been burned more frequently,” she noted, to control weeds.

“We’ve got a sneak peek of what can happen,” Winkler said, but more long-term research is needed. Based on other research, she anticipates that the restored areas should peak in terms of species diversity within seven to eight years.

Increased specialization

Winkler also looked at how these ant species function. The younger restorations areas tend to have ants that are generalists who can go anywhere, but the older restorations tend to have more specialists, such as soil-dwelling ants, who are more particular about where they live, Winkler explained. The more dominant specialists push out some of the generalists.

“You’ll have ants everywhere,” she pointed out, but the greater the diversity, the more niches are being filled, and the more successful the restoration effort.

Agriculture and Food News — ScienceDaily

In grasslands remade by humans, animals may protect biodiversity: Grazers let in the light, rescue imperiled plants

A comparative study of grasslands on six continents suggests there may be a way to counteract the human-made overdose of fertilizer that threatens to permanently alter the biodiversity of the world’s native prairies.

The solution is one that nature devised: let grazing animals crop the excess growth of fast growing grasses that can out-compete native plants in an over-fertilized world. And grazing works in a way that is also natural and simple. The herbivores, or grazing and browsing animals, feed on tall grasses that block sunlight from reaching the ground, making the light available to other plants.

That’s the key finding of a five-year study carried out at 40 different sites around the world and scheduled for online publication March 9, 2014 in the journal Nature. More than 50 scientists belonging to the Nutrient Network, a team of scientists studying grasslands worldwide, co-authored the study.

“This study has tremendous significance because human activities are changing grasslands everywhere,” said study co-author Daniel S. Gruner, associate professor of entomology at the University of Maryland. “We’re over-fertilizing them, and we’re adding and subtracting herbivores. We have a worldwide experiment going on, but it’s completely uncontrolled.”

Gruner, a member of the Nutrient Network (which participants have nicknamed NutNet) since its founding in 2006, helped plan the worldwide study and analyze its results. Elizabeth Borer of the University of Minnesota was the study’s lead author.

The U.N. Food and Agricultural Organization estimates that grasslands cover between one-fifth and two-fifths of the planet’s land area and are home to more than one-tenth of humankind. But like all plant communities, grasslands are suffering from too much fertilizer.

As humans burn fossil fuels, dose crops with chemical fertilizers, and dispose of manure from livestock, they introduce extra nitrogen and other nutrients into the soil, air and water. The excess is a special problem for grasslands, where many plants, like annual wildflowers and others, have adapted to low nutrient levels. They often struggle to compete against grasses that use the extra nutrients to grow faster and bigger.

At the same time, grasslands worldwide are being converted to pastures for domestic animals, with native grazers like elk and antelope giving way to cattle and sheep.

Ecological theory asserts that grazers can counteract the effects of over-fertilizing in most cases, but the theory has never been broadly tested, Gruner said. To do that, the NutNet scientists ran essentially the same experiment worldwide, marking off test plots in groups of four at each of 40 sites. In each group, one plot was fenced to keep grazing animals out. One was treated with a set dose of fertilizers, to mimic the effect of excess nutrients from human sources, but was not fenced so the animals could graze. One was both fenced and fertilized. And one was left alone.

The researchers did not try to alter the test sites’ animal populations. In some places native animals were abundant. At others they’d been mostly replaced by domestic animals like cattle, goats and sheep. And still others were former pastures where livestock had browsed in the past, but were no longer there.

In general, where fertilizer was added and grazing animals were kept out, the variety of plants in the experimental plots decreased. Where animals were allowed to graze in the fertilized plots, plant diversity generally increased. The researchers’ data analysis concluded that the grazers improved biodiversity by increasing the amount of light reaching ground level.

Grassland plants have evolved a variety of strategies to take advantage of a setting where nutrients are in short supply and inconsistently available. They may be ground-hugging, or ephemeral, or shoot up when they capture a nutrient pulse, Gruner explained. These differing strategies create a diverse grassland ecosystem.

In the human-altered world where nutrients are always plentiful, plants that put their effort into growing tall to capture sunlight have an advantage. They block the sunlight from reaching most other plant species, which cannot grow or reproduce. But grazing animals cut down the light-blocking plants and give the others a chance to bloom.

“Where we see a change in light, we see a change in diversity,” said Borer, the lead author. “Our work suggests that two factors which humans have changed globally, grazing and fertilization, can control ground-level light. Light appears to be very important in maintaining or losing biodiversity in grasslands.”

The effect was greatest where large animals, wild and domesticated, grazed on the test plots: cattle, pronghorn and elk on North America’s Great Plains; wildebeests and impala on Africa’s Serengeti; and horses, sheep and ibex in rural India. In places where the only grazers were small animals like rabbits, voles and gophers, the grazers’ effect was weak and variable.

Agriculture and Food News — ScienceDaily