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ºÙºÙÊÓƵ and the USDA Forest Service's Center for Urban Forest Research are collaborating on two new research programs on the Davis campus. One is a test of an "engineered" soil for parking lots; the other is a study of a new, disease-resistant breed of elm tree.

Parking-lot soil: Scientists from the urban-forest center and the ºÙºÙÊÓƵ Department of Land, Air and Water Resources recently finished installation of a new, lighter kind of soil engineered specifically for parking lots. Trees, their root systems, and the new soil that supports them combine to form a mini-reservoir for capturing stormwater.

The "Davis soil" is made with materials that are naturally available and inexpensive. It traps, cleans and slowly releases stormwater, reducing pollutant loads, runoff flooding. At the same time, the trees shade the parking lot, lowering pollutant emissions from cars and reducing the ambient temperature; absorb pollutants from the air; capture additional stormwater; and beautify their environment.

The mini-reservoir design and the Davis soil are being tested under everyday conditions in ºÙºÙÊÓƵ' parking lot 47A, at the corner of LaRue Drive and Dairy Road. Sixteen "treated" parking spaces are being compared with 16 parking spaces designed according to campus standards.

Elm trees: Scientists from the center and the ºÙºÙÊÓƵ Department of Plant Sciences are testing 17 new cultivars of American elm as part of a national trial to find replacements for the huge trees that once shaded many American cities but were killed by Dutch elm disease. (A cultivar is a cultivated variety of plant species or hybrid that has unique, desirable characteristics that persist when it is propagated.)

They have planted 74 elms at the campus's Bowley Plant Science Teaching Center that are expected to be good performers in northern California. The trees include the disease-tolerant American elm cultivar "Valley Forge" and hybrids such as "Accolade," mostly of Asian heritage, whose vase shape duplicates the American elm. Other promising cultivars offer elm leaf beetle resistance, ornamental bark, and a wide range of environmental tolerances.