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UAlbany Biologists Testing New Ways to Map Purple Loosestrife

By Greta Petry (September 10, 2004)

Doctoral student Anna Hartwell and biology Pr0fessor Gary Kleppel are tracking the effect of purple loosestrife on wetlands in New York State through high-tech remote sensing equipment.

Doctoral student Anna Hartwell and biology Professor Gary Kleppel are tracking the effect of purple loosestrife on wetlands in New York State through high-tech remote sensing equipment.

Biologists at the University at Albany are developing high-tech ways to map the distribution of plants like the ubiquitous purple loosestrife in New York State wetlands.

Loosestrife is an invasive marsh plant from Europe that crowds out native plants and alters native ecosystems.

UAlbany Professor Gary Kleppel, director of the Biodiversity, Conservation and Policy program said, “We are studying the feasibility of using hyperspectral remote sensing to monitor wetlands in New York State for the Environmental Protection Agency.”

Kleppel’s research is funded by a $320,000 grant from the Environmental Protection Agency over two years.

“The remote sensing device, called a hyperspectral scanner, is mounted on the underside of a twin engine Apache and flown over two areas in New York (Saratoga and Orange counties) where we know there are many wetlands,” Kleppel said. The pilot flies low — at about 1,100 feet — over wetlands in the Town of Stillwater and City of Mechanicville in Saratoga County, as well as Luther Forest in Malta. Orange County sites include Stewart Forest near Stewart Airport and a site owned by the Audubon Society.

The scanner measures the amount of light coming back from the earth in 37 spectral, or color, bands.

“Some of these bands are invisible, near and far infrared, but taken all together they can tell us a great deal,” Kleppel said. “For instance, it is believed that each plant species has a unique spectral signature. If you can identify that signature, you can, in theory, map that plant’s distribution everywhere.”

UAlbany biologists are working with their colleagues at Clemson University to identify the spectral signature of purple loosestrife, which displaces native marsh species and modifies ecosystems. “How this will affect humans is not yet fully understood, but wetlands are very important for cleaning water, and anything that alters that capacity has potential implications for us because we drink water,” Kleppel said.

Kleppel’s fifth year doctoral student, Anna Hartwell, 28, of Verona, N.Y., collected soil from the wetland areas under study. The UAlbany alumna earned a Master of Science degree in biodiversity, conservation and policy with Kleppel as her mentor.

She said, “The sites without many adult purple loosestrife plants had few to no purple loosestrife seedlings in the trays. But, in the trays of soil from the invaded sites, more than 500 purple loosestrife seedlings sprouted per tray. Other plant species in the trays had from one to 100 seedlings per tray.”

Adult purple loosestrife plants can produce two to three million seeds per plant; the majority will germinate if grown in suitable conditions.

“These results show that not only does purple loosestrife dominate in certain wetlands, it also dominates the seed bank in invaded wetlands. Once purple loosestrife is established, it is very difficult to eliminate,” Hartwell said.

Just how does one get rid of the invading plant? “Biological controls can be used to reduce purple loosestrife populations. The main biocontrol that is used is to introduce insects from purple loosestrife’s native habitat that eat different parts of the plant,” Hartwell said.

While Hartwell’s research provides much-needed data on the mechanisms by which purple loosestrife spreads and its effects on native marsh flora, Kleppel and colleagues at Clemson University are optimistic the unique spectral signature they have identified for purple loosestrife will allow them to map distribution of the plant from the air.

“We are in the process of validating and ‘tuning’ the signature through an intensive ground truth campaign,” Kleppel said. “So far, the spectral ‘fingerprint’ seems to be confirmed. In mid-August, we replicated some earlier experiments by flying the instrument over the same wetlands we flew over last year. We want to determine how well our observations can be repeated from one year to the next,” Kleppel said.

The new technology makes monitoring largescale wetlands feasible. There are too many wetlands to appraise them the old-fashioned way – by sending people into the field – and the abundance of wetlands on private property renders them less accessible.

“This project is contributing to a new direction for technology at UAlbany,” Kleppel said. It enables scientists to work on jobs too expansive in scope for people to carry out alone. He concluded, “A cadre of biologists, ecologists, meteorologists, and geographers at UAlbany is well versed in this technology and is gaining a good reputation in remote sensing. I look forward to the day when nano- and macroscience converge here, as data from nanosensors deployed in the environment are telemetered to satellites and then to receivers here at the University.”