Invasive Species

Invasive plants and animals have been recognized as playing a large part in the loss of wetland and coastal habitats. Along with the projects detailed below, NWRC has been researching the impacts of exotic grasses on native plants and investigating the interactions between wild land fires and exotic invasive plants.

Research

Ecology, Management, and Control of Chinese Tallow in Coastal Prairie. NWRC scientists teamed with USFWS refuge managers to conduct prescribed burns in the rare coastal prairie communities of Texas and Louisiana to control an exotic tree species, Chinese tallow. By investigating the effects of burning on the survival and growth of these invasive species, researchers were able to show that effects of fire on Chinese tallow are size- and age-dependent, allowing refuge managers to focus their management dollars and labor effectively. An additional component of this work has been conducted in conjunction with researchers at Rice University and supported by the USEPA to look at the potential for fire to affect the initial colonization of prairie by Chinese tallow. In FY02, four publications, including a strategic plan for USGS research currently in review and three presentations, including one at the USFWS-sponsored workshop on invasive plants held at the Southern Weed Society Annual Meeting, Houston, TX, and the Symposium on Fire and Invasive Species held in conjunction with Ecological Society of America meeting in Tucson, AZ. (Dr. James B. Grace)

Satellite Mapping of the Distribution of the Exotic Tree, Chinese Tallow. In a progression of four papers in FY 2002, researchers at the National Wetlands Research Center described newly developed remote sensing tools to map the localized occurrences and regional distribution of the widespread and gregarious invasive species Chinese tallow; one article was published in Photogrammetric Engineering & Remote Sensing and the other three are in review. These developments relied on newly available Hyperion sensor hyperspectral data collected from the EO1 satellite platform Although directed at mapping and monitoring tallow, remote sensing hyperspectral technologies advanced here have decreased deficiencies that are at this time preventing widespread mapping of invasive plants in the United States and internationally. Researchers expect methods developed as part of this project will provide a template for mapping and monitoring other invasive species within the native landscape in differing geographic areas. This work is the result of a proposal submitted by scientists at NWRC in response to a NASA solicitation and subsequently accepted through open competition. Funding was received in part from the NASA-USGS Earth Observing-1 Mission Instrument Performance Evaluation and Data Validation Program. (Dr. Elijah Ramsey)

Impacts of the Exotic Mammal, Nutria, on Coastal Marsh Habitats. Scientists at NWRC continued conducting field experiments and developing and refining models to ascertain the potential impact of nutria on marsh habitat. The population density experiments have led to the testing and refinement of a new enclosure design that will assist other scientists in creating large scale mammal experiments on the marsh. Data from the experiments will help determine what levels of nutria density the marsh can sustain. The nutria model was originally designed to specifically link nutria population dynamics and feeding activity to marsh loss. Based on initial results, a new version of the model is being developed to more effectively model nutria induced marsh loss. This version is designed to understand the spatial extent of nutria damage and as well as to model various management options such as selective and regional trapping. The new version is being used to test different ideas about nutria dispersion and experiment with different trapping regimes. (Dr. Jacoby Carter)
For more information about the worldwide distribution of nutria, click here.
For more information about nutria, click here.

Surveying the Gulf of Mexico for Invasive Aquatic Plants: Scientists at NWRC surveyed the submerged aquatic vegetation in brackish waters along the Gulf of Mexico Coast from Anclote Key, just north of Tampa Bay, FL, to Laguna Atascosa National Wildlife Refuge, just north of Brownsville, TX. They found exotic invasives such as water hyacinth, hydrilla, and Myriophyllum in sites with salinities less than 1.0 parts per thousand but did not find exotics in either brackish or marine systems. (Dr. Jacoby Carter)

Interactions Between the Invasive Chinese Tallow and Migratory Birds. NWRC scientists teamed with USFWS refuge managers to determine the role birds play in the dispersal Chinese tallow. Researchers will also explore the value of tallow fruit to wintering birds. The USFWS refuge managers spend an increasing amount of time and money restoring coastal landscapes invaded by this species. This research combines field sampling of birds in tallow woodlands vs. native forests, laboratory analyses on nutritional aspects of tallow fruit and coexisting native fruits, and aviary experiments that will determine the ability of birds to metabolize the waxy fruit of Chinese tallow. Effects of differential avian use between habitat types may include changes in local bird communities, and differing tallow tree demographics and invasion patterns. In FY02, scientists produced two publications and provided two presentations on this topic. (Dr. Wylie Barrow)

Quantifying the Rate and Extent of Invasion of Chinese Tallow and Its Displacement of Native Plant Species. Researchers are working in the Barataria Unit ecosystems of Jean Lafitte National Historic Park and Preserve, LA, to establish a monitoring network of permanent plots that can be used to assess the rate and fate of tallow invasion on native habitats and tree species. They are also developing an individual-based forest simulation model of bottomland hardwood systems of the Mississippi River delta with and without control measures for the spread of Chinese tallow and to determine the role that rising sea level and surface water control will play in its future spread and eradication. (Dr. Tom Doyle)

Purple loosestrife volunteer Can Bingol holds a seed trap along the Porsuk River, Eskisehir, Turkey. The light gap behind him shows purple loosestrife in the center of the gap but because the photo was taken in the spring, the plants don't yet have their distinctive purple flowers.

Ecology of Purple Loosestrife. An NWRC scientist is building a team of researchers to study the growth, establishment, and genetic variation of purple loosestrife across latitudes in Eurasia and central North America. Their studies will focus on determining if the environmental factors that restrict distribution of purple loosestrife in Eurasia can also be used to control the species in North America. Furthermore, it is thought that the North American purple loosestrife may be a “superspecies” in the sense that it may have introgressed genes from closely related native species, so grant proposals have been submitted to study this possibility.(Dr. Beth Middleton)
For more information about invasive plant species in North America that are native to Turkey, click here.
For more information about how to help locate invasive purple loosestrife, click here.

Return to Forest Ecology Branch