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  November 13, 2000

UConn Scientists Combat Invasive
Plants with National Park Service

In the 18th century, New England farmers made a disturbing discovery. Their ancestors, from colonial times, had nurtured a plant called the common barberry. Hearty and able to survive tough northeast winters, the shrub was useful in several respects. Its red berries made delicious jelly, attractive foliage, and winter forage for native birds, which were undeterred by the fact that the plant bristles with needlelike thorns.

But there was a problem. Common barberry was a host for a pathogenic wheat rust that was devastating crops throughout the region.

The farmers' subsequent efforts to outlaw and eradicate the plant marked one of the first cases in the country of people dealing with plants creating unexpected problems. Lacking the kind of information needed to make scientifically astute decisions about importation of plants, the New Englanders were encouraged to replace the common barberry with an equally attractive alternative.

Japanese barberry seemed the ideal solution. It offered the benefits of its common cousin without harboring the wheat rust. But a decided disadvantage would soon become apparent. Japanese barberry spreads like wildfire.

"It was cultivated mostly in suburban areas and selected rural retreats," says John Silander, a professor of ecology and evolutionary biology. "From that foothold it began spreading in the 1920s. By the 1960s, it had dispersed widely throughout the northeast. By the 1970s, it was recognized as a problematic invasive species throughout the region."

Every bit as tenacious as the common species, it thrives in an extraordinary range of soil, moisture and light conditions. And thanks to birds, which spread the seeds in their droppings, it is constantly expanding its turf. Wherever it goes, it chokes out other plants.

A 'Growing' Problem
Japanese barberry is just one of an increasing number of non-native plants on which Silander and Leslie J. Mehrhoff, curator of the University's George Safford Torrey Herbarium, are focusing their attention as part of a recently signed cooperative agreement with the National Park Service. The relationship, which will have an impact on nearly 40 eastern parks in New England and south to the Virginias, is expected to last for a number of years and unfold through a series of phases.

Characteristics of Invasive Plants
Five key biologic traits characterize invasive species, says Mehrhoff, and account for the striking pace of their intrusion into the landscape.

  • Abundant fruits, seeds or vegetative reproductive structures
    Notable examples include Morrow's Honeysuckle, Autumn Olive, Multiflora Rose, Purple Loosestrife, and Oriental Bittersweet.

  • Effective dispersal mechanisms
    Many of the well-known invasive woody plants, including trees, shrubs, and vines, are dispersed by wind
    Most invasives have a high percentage of germination and seedlings with a wide range of biological tolerance.

  • Rapid growth
    Annuals produce a large number of seeds in one year and biennials in two. Some shrubs can produce flowers and fruits in just four to six years.

  • Aggressive competitors
    Imported plants often leave behind the predators, parasites and diseases that helped keep them in check in their natural ranges.

The first phase, for which the researchers will receive $30,000, is scheduled to last one and a half years. During this phase, they will bring scientists from all over the region to UConn. Silander and Mehrhoff hope that students will benefit from exposure to these scientists and that it may lead to some formalized relationships.

A major goal of the project is to help the Park Service learn how to identify and deal with invasive plants. To begin with, the two researchers will assist the Park Service in developing a list of plants to watch for and protocols for identifying and dealing with those plants. Through workshops, Silander and Mehrhoff will acquaint park personnel with the plants, assist them in establishing inventories, and help them develop plans for monitoring and remediation. Similar workshops have been held at UConn for federal, state and town government officials, land trusts and conservation organizations during the past four years.

Although other universities work with some of the parks, UConn is unusual in working with so many, over such a large area.

"Each park has different problems," says Silander, "but when they've been surveyed, most park managers cite the need to know more about these plants."

That's why education is central to the project, says Mehrhoff. "Most people have little interest in where these species come from or how they came to be part of the mosaic of species that make up a particular landscape," he notes. "But when you look closer, there are reasons for concern. Some non-native plants are altering our landscapes in unforeseen and possibly irreversible ways."

The word "some" belies the scope of the problem, however. Non-Native Invasive and Potentially Invasive Vascular Plants in Connecticut, a publication Mehrhoff produced last January in collaboration with the State Geological and Natural History Survey of Connecticut and the Connecticut Invasive Plant Working Group, lists nearly 100 plants, including trees, shrubs, vines, herbaceous plants, grasses and aquatics. Many are well known. They include watercress, gill-over-the-ground, several privets, Norway maple, yellow iris, and Asiatic bittersweet, whose bright orange and yellow berries, festooning roadside thickets, are prized for autumnal wreaths and seasonal centerpieces.

"Not all plants brought into the country become problems," says Silander. "But those that do can cause severe environmental damage."

Many Kinds of Damage
And the scope of damage is wide-ranging. A study published last spring in the journal Issues in Ecology notes, for instance, that "plant invaders can completely alter the fire regime, nutrient cycling, hydrology, and energy budgets in a native ecosystem, greatly diminish the abundance or survival of native species, and even block navigation or enhance flooding." They can also push out or hybridize with native plants. In the process they often eliminate food sources necessary for other species in the food chain.

"There has been an unprecedented influx of exotic plants in the last decade," says Wayne Millington, regional integrated pest management coordinator for the northeast region of the national parks. "The spread of these plants has increased sharply. Many of these plants have enemies in other places that are not present here. So they spread unchecked. In the process, we're losing native species, including insects and species that pollinate the native plants that are being pushed aside by these aggressive competitors.

"Early detection is the future of pest management in the parks," Millington adds. "The park service doesn't have enough human resources to do all that is needed, so on an individual level we need to become more effective. That's what this relationship with the University of Connecticut is about."

Students benefit from the relationship, as well. The knowledge Mehrhoff and Silander obtain through the project will, of course, help to inform their courses. But the two also expect project funding to allow them to employ students in many ways, including internships and assistantships. Students are also expected to be involved in creating a project website. Mehrhoff adds: "We hope this project will help encourage more students to embark on careers in the field."

Jim Smith