Invasive Tallowtree Widespread in the Mississippi Alluvial Valley and Gulf Coast

by Maureen Stuart, SRS Science Delivery Group
:Chinese tallow tree seeds resemble popcorn. Photo by Jim Miller.

Chinese tallow tree seeds resemble popcorn. Photo by Jim Miller.

Nonnative, invasive plant species pose a threat to forest resources throughout the South.

Increasingly, nonnative plants infiltrate landscapes, eroding and replacing native plant communities. This can have irreversible and degrading effects on critical, human-sustaining ecosystems.

Tallowtree (Triadica sebifera) is one of the most pervasive exotic tree species in the South and is known to replace entire stands of forests. Sometimes called popcorntree due to the resemblance of its seeds to popcorn, tallowtree was first introduced to coastal South Carolina and Georgia in the late 1700s. Then, in the early 1900s, the U.S. Department of Agriculture (USDA) promoted planting of tallowtree along the Gulf Coastal Plain in Texas as a source of oil for industrial applications. The USDA has long since abandoned this program, but the tree continues to be planted as an ornamental and by beekeepers.

Following its introduction in the late 1700s, tallowtree rapidly took over the Gulf Coast that stretches from Florida to Texas, covering over 500,000 acres in Texas and Louisiana alone. U.S. Forest Service Southern Research Station (SRS) Forest and Inventory Analysis (FIA) data suggest that tallowtree has increased 174 percent in east Texas and more than 500 percent in Louisiana since the early 1990s; this aggressive invasive is now the fifth most common tree species in east Texas and Louisiana, and the most widespread and abundant nonnative tree in the Mississippi Alluvial Valley, according to a newly published report.

Tallowtree is a hardy plant. It can grow in almost every habitat type, from streambanks and wetlands to grassland prairies and other upland sites. It also thrives in various soil types, including both freshwater and saline soils. Tallowtree is shade-tolerant and can withstand periodic floods. In addition to these ecological characteristics, warming temperature trends and an increase in major destructive weather events facilitate and even accelerate the plant’s rate of invasion.

“Tallowtree has a tremendous capacity to change whole ecosystems,” says Sonja Oswalt, forester with the SRS FIA unit. This species can be particularly problematic in that it can move into native prairies and convert them to monoculture tallowtree forests.

In 2010, SRS published A Field Guide for the Identification of Invasive Plants in Southern Forests. Jim Miller, lead author of the guide, is one of the foremost authorities on invasive plants in the South; co-authors are SRS research technician Erwin Chambliss and Auburn University research fellow and extension specialist Nancy Lowenstein. The book provides information on accurate identification of the 56 nonnative plants and groups that are currently invading the forests of the 13 Southern States. It lists other nonnative plants of growing concern.

The information included in the guide is now available as a free application for iPhones, iPods, and iPads called Invasive Plants in Southern Forests.

Recommendations for prevention and control of invasive species are provided in a companion booklet, A Management Guide for Invasive Plants of Southern Forests, which Miller co-authored with Steven Manning, president of Invasive Plant Control, Inc., and Stephen Enloe, Auburn University weed management extension specialist.

For more information, email Sonja Oswalt at soswalt@fs.fed.us or Jim Miller at jameshmiller@fs.fed.us.

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Posted in Forest Inventory & Analysis, Invasive Plants, Threats

Mississippi Alluvial Valley Forests: The Next 50 Years

Subregional report from the Southern Forest Futures Project

by Zoё Hoyle, SRS Science Delivery Group
Range and extent of the Mississippi Alluvial Valley (red outline) and the counties it encompasses (white outlines). The yellow line separates the Holocene Deposits section from the Deltaic Plain section. Photo courtesy of the U.S. Forest Service.

Range and extent of the Mississippi Alluvial Valley (red outline) and the counties it encompasses (white outlines). The yellow line separates the Holocene Deposits section from the Deltaic Plain section. Photo courtesy of the U.S. Forest Service.

The Southern Forest Futures Project (SFFP) started in 2008 as an effort to study and understand the various forces reshaping the forests across the 13 states of the Southeast. Chartered by the U.S. Forest Service Southern Region and Southern Research Station (SRS) along with the Southern Group of State Foresters, the project examined a variety of possible futures and how they might affect forests and their many ecosystems and values.

Because of the great variations in forest ecosystems across the South, the Futures Project produced separate findings and implications for each of five subregions, including the newly published report for the Mississippi Alluvial Valley, a 24.9-million-acre area in the floodplain and delta of the lower Mississippi River.

“This report identifies findings from the Futures Project relevant to the Mississippi Alluvial Valley and expands those findings further through additional synthesis and analysis,” said Emile Gardiner, author of the report and research forester for the SRS Center for Bottomland Hardwoods Research. “It also outlines implications of the alternative futures developed for the Futures Project for the forest-based resources and ecosystem services of the Mississippi Alluvial Valley.”

The Mississippi Alluvial Valley, subdivided for the report into an upper Holocene Deposits section and a lower Deltaic Plain section, supports a robust agricultural economy and provides significant recreational resources to residents of nearby urban centers. Although forests make up only 28 percent of the subregion, the bottomland forests and coastal swamps of the area provide habitat for diverse plants and animals, produce valuable forest products, and provide innumerable ecosystem services, including water quality and flood mitigation.

A few of the many key findings included in the report:

  • Average annual temperatures within the Mississippi Alluvial Valley are projected to rise by 1.2 to 2.9 °C through 2060, while average annual precipitation is forecasted to decrease by 1 to 24 percent during the same period.
  • Deforestation will continue in the Mississippi Alluvial Valley, but future clearing will be driven not by agricultural development but by urbanization, which is expected to drive the largest shift in land use over the next 50 years.
  • Nonnative insects and diseases will likely create more forest health issues within the Mississippi Alluvial Valley within the next 50 years. Once established in the area, emerald ash borer and other specialized nonnative insect pests could cause acute damage and the widespread elimination of their host trees.
  • Coastal baldcypress-water tupelo swamps of the Deltaic plain section are vulnerable for nearly complete degradation and loss from urbanization as well as altered hydrologic and sediment regimes, land subsidence, and sea-level rise.
  • As many as 21 high-priority nonnative plants now cover over 3.1 percent (206,782 acres) of all the area’s forests. Japanese honeysuckle, at 112,000 acres, is the most pervasive nonnative plant, and tallowtree (occupying 37,000 acres) the most widespread and abundant nonnative tree.
  • The area experiences a low incidence of wildfire compared to the rest of the South, but forecasted shifts towards a hotter and dryer climate through 2050 raise the potential for wildfire in the upper Holocene Deposits section, particularly in Arkansas.

For more findings and analyses, access the full text of the report.

For more information, email Emile Gardiner at egardiner@fs.fed.us.

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Posted in Bottomland Hardwoods, Climate Change, Economics & Policy, Forest Products, Forest Watersheds, Insects and Diseases, Invasive Plants, Recreation

Health Benefits of Green Spaces Not Shared Equally

by Sarah Farmer
Urban trees provide cooling and shade, make neighborhoods and parks more walkable, and ultimately help protect humans from obesity, heart disease, depression, and other issues.  Photo by the International Society of Arboriculture, courtesy of Bugwood.org.

Urban trees provide cooling and shade, make neighborhoods and parks more walkable, and ultimately help protect humans from obesity, heart disease, depression, and other issues. Photo by the International Society of Arboriculture, courtesy of Bugwood.org.

Without forests, parks, gardens, and other green spaces, some people may be at a higher risk of health challenges such as heart disease, obesity, depression, and heat-related illness. “Decades of research suggest that the natural environment can play an important role in sustaining public health,” says U.S. Forest Service Southern Research Station (SRS) scientist Viniece Jennings. “In some contexts, simple exposure to green spaces may improve human health.”

Jennings, a biological scientist at the SRS unit Integrating Human and Natural Systems, is lead author of a review article that evaluates the influence of green spaces on public health. The article was recently published in the International Journal of Environmental Research and Public Health.

Jennings and coauthor Cassandra Johnson Gaither focused on the link between green spaces and health disparities, which are often correlated with race or ethnicity, and income. Groups that are economically or socially disadvantaged tend to have poorer health outcomes, and while there are probably multiple causes of such disparities, the lack of access to urban green spaces may be a key reason. Several researchers have found that green spaces in the urban core of many American cities – areas often inhabited by minorities and people with low incomes – are rare or poorly maintained.

“In this article, we wanted to highlight how the pattern of inequitable access to green spaces is linked to health disparities,” says Jennings. “A number of research articles were pointing in the same direction, so we sought to connect the dots and invigorate the conversation on this topic.”

For example, trees can alleviate summer heat and reduce temperatures by providing shade. This is particularly important for city dwellers, as they are vulnerable to the urban heat island effect. This effect could be exacerbated by climate change. Extreme heat causes a number of preventable deaths, especially in minority and low-income communities.

A neighborhood with trees and parks is also a more walkable neighborhood, with implications for heart disease and obesity.  Living within a half mile of a park or some other green space seems to help reduce obesity rates and the presence of parks and green spaces can also lower blood pressure and reduce the risk of heart disease. Heart disease is a leading cause of death in the United States and rates differ among racial/ethnic minorities.

Urban green spaces can also help reduce stress and protect people from depression and other mental health challenges. Without trees around, people seem more prone to stress, sadness, and even lower attention capacity and cognitive ability. “This article presents an opportunity for ecosystem services to be further integrated into the public health dialogue,” says Jennings. “Natural sciences and public health can be complex fields, but we can articulate the commonalities to promote their partnership. “

Read the full text of the article.

For more information, email Viniece Jennings at vjennings02@fs.fed.us.

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Posted in Economics & Policy, Ethics & Values, Urban Forests