Bringing Fire Back to the Kisatchie Sandstone Hills

by Sarah Farmer, Science Delivery Group
The Kisatchie Sandstone Hills of Louisiana provide habitat for many rare plants and animals, such as red cockaded woodpeckers and Louisiana pine snakes. Photo by Andy Scott.

The Kisatchie Sandstone Hills of Louisiana provide habitat for many rare plants and animals such as red-cockaded woodpeckers and Louisiana pine snakes. Photo by Andy Scott.

The hillside bogs, sandstone glades, and woodlands of the Kisatchie Sandstone Hills in Louisiana are potential homes to a number of rare and endangered animals such as the red-cockaded woodpecker and the Louisiana pine snake. However, in much of the Kisatchie Hills, the open woodlands these animals need have vanished amid a dense midstory of shrubs and small trees.

“Restoration of the Kisatchie Hills requires reintroduction of fire,” says U.S. Forest Service scientist Andy Scott. “Past fires, though, have resulted in high erosion rates and soil loss.” Scott is a research soil scientist at the Forest Service Southern Research Station (SRS) Southern Pine Ecology unit, and author of a paper about erosion and prescribed fire on a study area established in the Kisatchie Hills. The paper was recently published in the Southeastern Naturalist.

The Kisatchie Hills are part of the Kisatchie National Forest in west-central Louisiana and feature a number of fire-dependent ecosystems. Historically, the area was logged and open to cattle for grazing, but now it’s been about 65 years since the 4,000-acre study area was logged, and the last burn or cattle grazing was more than 20 years ago. Kisatchie Ranger District personnel conducted two prescribed burns – one in the growing season and one in the dormant season – on half the study area and compared vegetation, fuels, and erosion potential in similar areas of the burned and unburned sites.

After the fires, many of the shrubs and small trees in the midstory were top-killed, while grasses and wildflowers began to sprout and spread. Scott and his colleagues found that in the burned areas, 40 percent of the forest floor was covered with grasses and wildflowers, while only 7 percent of forest floor in unburned areas had herbaceous vegetation cover. Both red-cockaded woodpeckers and Louisiana pine snakes need a healthy herbaceous understory.

“Red-cockaded woodpeckers require old, widely spaced canopy pines for roosting and nesting, and open pine habitat for foraging,” says Scott. “Louisiana pine snakes prey on animals such as Baird’s pocket gophers, which in turn eat the roots of herbaceous plants. The presence of herbaceous vegetation is of prime importance for both red-cockaded woodpeckers and Louisiana pine snakes.”

Attempting to restore the Kisatchie Hills with prescribed fire is challenging because of the soil and geology of the area. “Soils on the study site are quite infertile,” says Scott. “They are also highly susceptible to erosion.” Much of the topsoil has already washed away, and the soil underneath it is very finely textured and prone to runoff. The prescribed fires reduced the thickness and density of the protective forest-floor layer, and elevated the erosion risk in the burned sites. However, the increased erosion risk may have been countered by the protective effects of a shorter midstory, and the recovery of the herbaceous community.

“Future management should consider erosion prevention,” says Scott. “The timing and intensity of additional burns should also be used to maximize plant cover on the forest floor and to improve the habitat by converting the woody understory to an herbaceous understory.”

Read the full text of the article.

For more information, email Andy Scott at andyscott@fs.fed.us

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Posted in Fire, Fish & Wildlife, Restoration, Southern Pines

Interrrupting an Invasional Meltdown

Research shows removing privet allows native earthworm communities to recover

by Zoё Hoyle, SRS Science Delivery Group
Southeastern forest infested with Chinese privet. Photo by David Moorhead, courtesy of bugwood.org.

Southeastern forest infested with Chinese privet. Photo by David Moorhead, courtesy of bugwood.org.

Earthworms have been described as “ecosystem engineers” because they can transform soil environments in ways – physical, chemical, and biological – that in turn lead to aboveground ecological changes. Most of the 8,000 species of the world’s earthworms stay in areas where they evolved, some occupying very narrow niches, but about 120 “cosmopolitan” or “peregrine” species have spread throughout the world, some invading and displacing native species.

A recent article by U.S. Forest Service and University of Georgia (UGA) researchers reports the effects of removing invasive Chinese privet on soil properties and earthworm communities in floodplain forests of the U.S. Southeast. Scientists found that removing privet disrupts the “invasional meltdown” that can occur when changes to soil due to privet infestation make it easier for exotic earthworms to invade — and allows native earthworm communities to recover.   

The Asian jumping worm (Amynthas agrestis) was one of the invasive earthworm species found in the experimental plots. Photo by National Park Service.

The Asian jumping worm (Amynthas agrestis) was one of the invasive earthworm species found in the experimental plots. Photo by National Park Service.

The researchers — Mac Callaham and Jim Hanula from the Forest Service Southern Research Station (SRS) with UGA graduate student and lead author Joshua Lobe and UGA professor emeritus Paul Hendrix – used the experimental forest plots established by Hanula for his long-term study on the effects of privet removal on aboveground native plant and pollinator communities. The team sampled every three months for a year, comparing soil characteristics and earthworm communities in plots with privet, those where privet had been felled, and those where privet had not yet invaded. 

“Other than a couple of studies on root biomass and soil properties, there have been surprisingly few studies on the effects of privet on belowground biotic communities,” said Callaham, research ecologist for the SRS Center for Forest Disturbance Science. “This is the first study to look at the effects of removing an invasive plant on soil properties and earthworm communities in these southeastern riparian forests.” 

Researchers found 14 different species of earthworms in the privet experiment plots, five native to North America, the others originating from Europe and Asia. Overall, they found the lowest abundance of native earthworms in the plots with privet, greater abundances in reference plots and in plots where privet was felled and cleared. Analysis showed that the soil pH was significantly higher (i.e., less acidic) in the privet plots than that in reference plots and those where privet was felled.

“More research is needed, of course, but we speculate the presence of privet caused pH to rise, favoring some exotic earthworm species and potentially leading to an invasional meltdown,” said Callaham. “We found that where privet was removed, pH was as low as reference plots, and exotic earthworms seemed to lose their competitive advantage and so native earthworm communities began to recover.”

“The study supports the idea that by removing a key invasive species like privet, land managers could decrease interactions with other exotics and short-circuit the invasional meltdown process,” added Callaham. “It also shows that native earthworm species have the potential to recover after the removal of an invasive plant despite the continued presence of exotic earthworm species.”

 Read the full text of the article, published online in April 2014.

For more information, email Mac Callaham at mcallaham@fs.fed.us.

Read more about recent SRS research on privet removal effects

Read more about about Callaham’s research on invasive earthworms.

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Posted in Bottomland Hardwoods, Forest Operations, Invasive Plants, Restoration, Threats

The Invasion of Southern Forests by Nonnative Plants

Key Findings from the Southern Forest Futures Project Technical Report

by Zoё Hoyle, SRS Science Delivery Group
Princesstree (Paulownia tomentosa), invades widely after wildfire, timber harvesting, and other disturbances. Photo by Leslie Mehrhoff, courtesy of Bugwood.org.

Princesstree (Paulownia tomentosa), invades widely after wildfire, timber harvesting, and other disturbances. Photo by Leslie Mehrhoff, courtesy of Bugwood.org.

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 along with the Southern Group of State Foresters, the project examines a variety of possible futures and how they might shape forests and their many ecosystems and values.

Invasive plants increasingly infiltrate southern forests, eroding landscapes and replacing native communities while degrading critical human-sustaining ecosystems. The SFFP technical report chapter on nonnative invasive plants summarizes information for 56 of the most damaging trees, shrubs, vines, grasses, and forbs currently invading forests, pastures, rights-of-way, orchards, grasslands, wetlands, and yards in the South. 

Key findings from the chapter:

  • Invasive plants continue to escape into and spread through southern forests to eventually form exclusive infestations nd replace native communities to the detriment of forest productivity, biodiversity, ecosystem services, and human use potential.
  • Over a 300-year period, invasive plants have been increasingly imported into the South, despite public policies and warnings by professional ecologists and plant experts of long-term irreversible ecosystem damage.
  • Approximately 9 percent of southern forests – or about 19 million acres — are currently occupied by one or more of the 300 invasive plants in the region.
  • The invasion process is accelerated by greater forest disturbance, fragmentation, parcelization, and urbanization needed to accommodate and support an increasing population and is by climate warming.
  • The annual spread of invasive plants in southern forests is conservatively estimated at 145,000 forested acres.
  • Given the current occupation and spread of invasive plants and the increasingly common infestations by multiple species, eradication appears only probable on specific lands unless awareness and strategic programs are greatly enhanced.
  • Over a 20-year period, research has developed effective control treatments and integrated approaches that can eradicate or replace invasive plants, while a more robust, coordinated, and focused effort will be required to stem and turn the tide of invasion.
  • Model projections show high-threat invasive plants have not reached their potential range or density limits within the region under current conditions. A predicted warming climate will permit northward range extensions for some, while range extensions can be restricted by a simultaneous drier climate.
  • Increased occupation by invasive plants would diminish the variety and abundance of current wood-based products from the “wood basket” of the United States. Some invasive species may find use in biomass and composite products if harvesting and processing become more efficient.
  • Most plants escaping into southern forests have been imported, hybridized, sold, and planted for yard and garden beautification, soil stabilization, wildlife habitat enhancement, and livestock production.
  • Stricter controls for importing species are pending, but their effectiveness will be hampered as long as garden centers continue to market invasive plants as ornamentals.
  • Limiting the degree of occupation and impact depends on the development of adaptive management programs and actions that are coordinated across political boundaries and engage all ownerships. Piecemeal and splintered actions by agencies and ownerships, if continued, cannot dwarf the destructive impacts of this invasion.
  • Public awareness campaigns, cooperative spread abatement networks, collaborative programs of detection and eradication, dedicated research and extension programs, and employment of new land restoration options have been found to slow the spread of invasive plants and prevent them from destroying critical habitats.

Access the Southern Forest Futures Project Technical Report.

 Access the Summary Report of the Southern Forest Futures Project.

 Access the latest publications by SRS scientists.

 

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Posted in Climate Change, Invasive Plants, Threats