After the Acid Rain

Tools for identifying and restoring affected Southern Appalachian watersheds

by Sarah Farmer, SRS Science Communications
Although acid rain, fog, and mist have become less common in recent decades, many high elevation watershed streams in the southern Appalachians are still acidic due to past deposition. Photo by Brian Stansberry, courtesy of Wikimedia Commons.

Although acid rain has become much less common in recent decades, many high elevation watershed streams in the southern Appalachians are still acidic due to past deposition. Photo by Brian Stansberry, courtesy of Wikimedia Commons.

“Rain has become much less acidic since the Clean Air Act was strengthened in the 1990s,” says U.S. Forest Service Southern Research Station (SRS) soil scientist Jennifer Knoepp. “However, some high elevation streams still have chronic or episodic acidity.”

Acid rain, as well as other forms of acidic deposition such as acid fog and acid mist, can still occur at high elevations in the southern U.S. Additionally, the acid rain of decades past has left a chemical legacy in high elevation soils.

Acids can be stored in soils for long periods of time before leaching out and making their way to rivers and streams. The acids do not move alone, either. Because of their powerful negative electronic charge, acids attract positively charged molecules. These positively charged molecules are often critical to plant growth, and their loss can weaken trees and slow growth.

Land managers need tools for identifying which watersheds are still affected by past acidic deposition, as well as strategies for restoring such watersheds. Knoepp and her colleagues addressed both of these issues in a recent study that was published in the Journal of Forest Ecology and Management.

The scientists studied high elevation watersheds in three national forests in the southern Appalachians, all in North Carolina: the North River in Cherokee National Forest; Santeeetlah Creek in Nantahala National Forest; and the North Fork of the French Broad in Pisgah National Forest.

High elevation watersheds are especially susceptible to acid deposition from rain, fog and mist. Knoepp and her colleagues studied individual catchments within each watershed to represent a gradient in elevation as well as a range of acidic deposition histories.

High elevation watersheds in the southern Appalachians tend to have deep, rocky soils with more organic matter than their lower elevation counterparts. They also have different vegetation communities and get far more acidic deposition.

As long as streams are not overwhelmed by acidic deposition, they can naturally neutralize some acids. Knoepp and her colleagues wanted to identify measurements that would help managers rank streams by their ability to resist acidification, or their acid-neutralizing capacity. The scientists also wanted to identify catchment and soil metrics that managers could use to rank streams by their sensitivity to acidity.

Knoepp and her colleagues found that the height of trees and the thickness of their trunks, or their basal area, were indicators of watershed acidity. Acid rain triggers a cascade of chemical reactions in soils that can last for years, and scientists identified a number of belowground indicators, such as soil mineralogy, total carbon content, and the depth and chemistry of specific soil layers.

The scientists also estimated the amount of lime it would take to restore acidic watersheds. “The lime requirements we identified were within the broad range found in other studies,” says Knoepp. “However, the amount required varied by watershed, and the effectiveness would likely vary by watershed as well.”

Read the full text of the article.

For more information, email Jennifer Knoepp at jknoepp@fs.fed.us.

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Posted in Forest Watersheds, National Forests

My City’s Trees

New app helps people learn about the values of urban trees

by Tom Brandeis, SRS Forest Inventory & Analysis
FIA data from the forest inventory assessment of Austin, Texas, shown on My City's Trees.

FIA data from the forest inventory assessment of Austin, Texas, shown on My City’s Trees.

The Texas A&M Forest Service has developed a web-based application, My City’s Trees, designed to give the public easy access to information from the urban forest inventories conducted by the U.S. Forest Service Forest Inventory and Analysis (FIA) program.

The application, hosted at the Texas Forest Info website, currently shows results from FIA’s first urban forest assessment for Austin, Texas, but the inventories of many more cities are in progress and will be online when data is available.

The application allows users to zoom in to specific areas of interest such as their own neighborhoods and generate maps and reports with tables, figures, and explanatory text about their urban forests and the ecosystem services they provide. This information includes:

  • Distribution of the forest area, tree population, and land cover classes,
  • Numbers of trees by species and other attributes,
  • Urban forest carbon stocks and leaf biomass,
  • Compensatory values, which are estimates of the value of the forest as a structural asset, meaning a compensation amount for the physical loss of the trees,
  • Residential energy savings due to tree shading and microclimatic effects of urban trees (currently in development),
  • Surface water runoff that was avoided because of urban trees, and
  • Air pollution removed by trees, plus the economic value of avoided human health impacts from pollution removal by trees.

For more information about the My City’s Trees app, email Chris Edgar at cedgar@tfs.tamu.edu or Rebekah Zehnder at rzehnder@tfs.tamu.edu.

For more general information on Urban FIA, contact Tom Brandeis at 865-862-2030 or tjbrandeis@fs.fed.us.

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Posted in Forest Inventory & Analysis, Urban Forests

In South Carolina, Coyotes Not a Threat to Adult Deer

Study finds coyotes kill fewer adult female deer than expected

by Sarah Farmer, SRS Science Communications
Although coyotes kill large numbers of fawns, they are not always a threat to adult female deer. Photo by Steve Hillebrand, U.S. Fish and Wildlife Service, courtesy of Wikimedia Commons.

Although coyotes kill large numbers of fawns, they are not always a threat to adult female deer. Photo by Steve Hillebrand, U.S. Fish and Wildlife Service, courtesy of Wikimedia Commons.

In parts of the northeastern U.S., white-tailed deer populations have ballooned. Not so in parts of the southeastern U.S., such as South Carolina, where the statewide deer population has been declining for about 12 years.

“In the Southeast, coyotes often prey on white-tailed deer fawns,” says U.S. Forest Service research wildlife biologist John Kilgo. “There are also reports of coyotes attacking and killing adult female deer.”

Kilgo has been studying white-tailed deer for years, and recently led a study on deer survival patterns. The study was published in the Wildlife Society Bulletin, and took place at the Savannah River Site, a 310 square-mile nuclear reservation in South Carolina. The study involved 138 female deer that were fitted with radio collars to track their movements. The deer were monitored from 2006 through 2013.

Each year, 87 percent of the deer that Kilgo and his colleagues were studying survived. “Some studies have reported yearly survival rates as low as 57 percent,” says Kilgo. “Compared to deer in other parts of South Carolina, the deer at our study site are long-lived.”

During the course of the study, 30 of the 130 deer studied died. Hunting season had the most impact on deer survival, as 43 percent of deer that died did so during November and December. “Although harvest rates were low, harvest was the most frequent cause of deer mortality,” says Kilgo. Collisions between deer and vehicles were also a significant cause of death, and were responsible for 27 percent of the deer mortality.

The scientists were unable to determine a cause of death for 23 percent of the deer mortalities, although 6 out of 7 of these deaths occurred during summer, so diseases or other causes could have killed them. Theoretically, it is also possible that coyotes killed some of these deer.

However, the overall results strongly suggest that coyotes prey very infrequently, if at all, on adult deer. “Even if all unknown mortalities were caused by predation, the overall effect of these mortalities on annual survival was low,” says Kilgo. “It doesn’t appear that coyotes are a major threat to the adult deer we studied.”

“Coyotes are known to kill adult deer in some parts of the Southeast, but they did not have a significant impact in our study,” says Kilgo. “However, previous studies have shown that coyotes do kill significant numbers of fawns.”

At the Savannah River Site, only 22 percent of fawns survive. Most of them are killed by coyotes. Because of the low fawn survival, wildlife managers had already reduced harvest limits for adult female deer, so although hunting was a primary cause of deer mortality, the overall number of deer harvested by hunters was low. In areas where hunting limits and coyote predation are both high, limiting harvest could have a greater impact.

Controlling coyote populations is expensive, and the study suggests that adult female deer will not benefit from it, at least at the Savannah River Site.

Read the full text of the article.

For more information, email John Kilgo at jkilgo@fs.fed.us.

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Posted in Fish & Wildlife, Forest Watersheds
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