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Restoring wetlands can lessen soil sinkage, greenhouse gas emissions, study finds

Restoring wetlands can help reduce or reverse soil subsidence and reduce greenhouse gas emissions, according to research in California’s Sacramento-San Joaquin River Delta by Dartmouth College researchers and their colleagues.

The study, which is one of the first to continually measure the fluctuations of both carbon and methane as they cycle through wetlands, appears in the journal by Global Change Biology.

Worldwide, agricultural drainage of organic soils has resulted in vast soil subsidence and contributed to increased atmospheric carbon dioxide concentrations. The California Delta was drained more than a century ago for agriculture and human settlement and has since experienced subsidence rates that are among the highest in the world. It is recognized that drained agriculture in the Delta is unsustainable in the long-term. To help reverse subsidence and capture carbon, there is interest in restoring drained agricultural land-use types to flooded conditions, but flooding may increase methane emissions. Carbon dioxide is the primary greenhouse gas emitted through human activities, but pound for pound, methane’s impact on climate change is more than 20 times greater than carbon dioxide.

Researchers at Dartmouth, UC-Berkeley and UC-Davis installed monitoring equipment on three moveable four-meter towers, measuring carbon dioxide and methane concentrations above a pasture and a cornfield that had been drained and a flooded rice paddy, a newly restored wetland and a wetland that underwent restoration in 1997. They found that the drained sites were net carbon and greenhouse gas sources. Conversely, the restored wetlands were net sinks of atmospheric carbon dioxide, but they were large sources of methane emissions, says co-author Jaclyn Hatala Matthes, an assistant professor an assistant professor in Dartmouth’s Department of Geography. “However, we do expect that the methane emissions will stabilize over time,” she says. “We’ve seen that emissions tend to increase for the first few years, and that this increase is correlated with the increase in wetland plant growth and spread during this time.”

In another recent paper published in the Journal of Geophysical Research-Biogeosciences, Matthes and her co-authors analyzed the correlation between wetland methane emissions and vegetation around the towers, where more plants resulted in an increase in the methane emissions. Where the vegetation patches had more “edges” — convoluted borders — the methane emissions were lower. “We are looking at the structure of vegetation patterns that might help to inform management goals for a restored wetland, how big do you want the vegetation patches to be, how much edge they should have,” Matthes says. “It’s a little bit tricky in ecosystem engineering, but we are hoping to learn some things about how people might plan wetland vegetation in order to maximize carbon dioxide uptake but to minimize methane release.”

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The above story is based on materials provided by Dartmouth College. Note: Materials may be edited for content and length.

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