Press Release 1
Press Release 2

FOR IMMEDIATE RELEASE: May 11, 2006
CONTACT: Janet Byron, (510) 987-0668 or janet.byron@ucop.edu

April-June 2006 California Agriculture magazine

Press Release 1:

Lake Tahoe air pollution not linked to out-of-basin sources; scientists explore causes, solutions for lake clarity decline
Although scientists know that Bay Area and Sacramento emissions contribute to Central Valley smog, the same plumes of pollution rarely reach Lake Tahoe. A review of air-quality research in the UC peer-reviewed journal California Agriculture concludes, “Pollutants most closely connected to the decline in Lake Tahoe’s water quality originated largely from within the [Tahoe] basin.”
Lake Tahoe has suffered a 30 percent decline in its famed clarity since the first ”Secchi disk” measurements were taken in 1964. Soil erosion and nutrient runoff into the lake, coupled with air-pollution deposition, are responsible for scattering light particles and spurring algae growth.
In a special section, “Restoring clarity: The search for Tahoe solutions,” California Agriculture presents five peer-reviewed research and review articles on air quality, runoff controls and biodiversity in the Tahoe Basin, as well as related news and editorial coverage of Lake Tahoe’s environmental history, research facilities, clarity modeling and weed control efforts.

The full articles are posted online at http://californiaagriculture.ucop.edu
According to the air-pollution study led by Alan Gertler, professor at the Desert Research Institute in Reno, the Bay Area and Sacramento create plumes of nitric acid, phosphorus, ozone and other pollutants, but the levels dissipate almost entirely in the Sierra foothills and they do not reach the Tahoe Basin. Rather, local road dust, soil, vehicle exhaust and wood smoke are the major sources of airborne pollutants that end up in the lake.
“The most effective strategy to reduce the impact of atmospheric deposition on the lake’s clarity and in-basin forest health would be to control local pollutant emissions,” writes Gertler, who collaborated with scientists from UC Davis, the USDA Forest Service and the National Park Service on the study.
Other Lake Tahoe studies in California Agriculture include the first comprehensive study of how urbanization and remnant forests are affecting biodiversity in the Lake Tahoe Basin; a unique on-the-ground study of how wildfire influences nutrient runoff into the lake; and several studies on how well commonly employed erosion-control measures, as well as a newer method called “mechanical mastication,” are helping to control runoff and improve forest health. Scientists from UC, the University of Nevada, and federal, state and regional agencies conducted the multidisciplinary research.
In a related editorial overview published in California Agriculture, pioneering UC Davis limnologist Charles Goldman explains the history of environmental impacts to the lake, which have contributed to its precipitous decline in clarity. The first Western settlers arrived in 1844, Goldman writes, and the discovery of gold near Virginia City in 1857 led to clear-cutting of most of the Tahoe Basin’s old-growth timber.
The forests grew back and the lake apparently recovered by the late 1880s, but residential, commercial and recreational development — and the resulting nutrient-laden runoff — took their toll through the 1950s and 1960s. “Small particles remain suspended in the water column for years, adding to the gradual but relentless transparency loss,” Goldman writes.
The Tahoe Regional Planning Agency was formedin 1969, providing a strong central authority to coordinate the lake-related activities of two states, five counties and local agencies. In 1984, a federal judge halted development in the basin for 2 years, and the first Tahoe Summit was held in 1997 with President Clinton in attendance.
At the same time, multifaceted scientific research has helped to inform regulatory decision-making in order to protect and improve the lake. UC Davis and Sierra Nevada College will complete a new state-of-the-art research facility, the Tahoe Center for Environmental Sciences (http://terc.ucdavis.edu), in Incline Village this summer, and the next biennial Lake Tahoe science conference will convene in October 2006.
“Strong, science-based evidence has been the decisive factor in successfully defending the Tahoe Regional Planning Agency from assaults over the years,” Goldman writes. “New scientific discoveries on lake temperature and nutrients, and watershed ecology, together with developments in adaptive management, give further promise for the future of the lake.”

Press Release 2:

Yellow starthistle marches across 14 million acres of California
Yellow starthistle has invaded more than 14.3 million of California’s 101 million acres, making it by far the fastest-spreading and most-invasive nonnative plant the state has ever seen, according to a peer-reviewed study published in the April-June 2006 issue of the University of California’s California Agriculture journal.
Now commonly found in rangelands and along roadsides statewide, yellow starthistle —native to southern Europe and northern Africa — grows in bushy patches and has 1-inch-long spines emanating from its flower heads, which irritate hikers and discourage grazing animals. It is also poisonous to horses, and can harm the local landscape and ecology.
“Once this weed gains a foothold, it can build up dense populations that displace native and other desirable vegetation,” wrote Michael Pitcairn, lead author of the study and a scientist with joint appointments at the California Department of Food and Agriculture and the UC Davis department of plant sciences.
Pitcairn and his colleagues conducted a township study in 2002, the first comprehensive statewide survey of yellow starthistle since 1985, when California’s gross yellow starthistle acreage was an estimated 7.9 million acres.
The full article, and the entire April-June 2006 issue of California Agriculture, is posted online at http://californiaagriculture.ucop.edu.
The article includes a county-by-county table of yellow starthistle infestation levels. In 2002, Monterey County had the largest gross acreage (1.65 million acres), followed by Siskiyou and Mendocino counties (about 1 million acres each) and Fresno County (925,000 acres). The largest proportional increase in infestation occurred in Ventura County, which went from 5 acres in 1985 to 250,000 acres in 2002.
When evaluated by region, the Sacramento Valley had the largest gross acreage of yellow starthistle with more than 5.8 million acres, followed by the San Joaquin Valley (3 million acres), the North Coast (2.8 million acres) and the Central Coast (2.3 million acres). These four regions account for 98% of the total gross acreage of yellow starthistle in California. The far northeast corner of California and southeast coast and interior regions still remain largely unaffected, although limited starthistle infestations do occur in these regions.
“It is not certain how far east and southeast yellow starthistle will spread in the future because the environmental factors that limit its distribution (such as low annual rainfall) are not yet known,” the authors wrote. “However, we anticipate yellow starthistle continuing to increase its density and distribution in both Northern and Southern California, with the highest rates of increase in the southern coastal counties.”
The first record of yellow starthistle in California was made in Oakland in 1869, and it was subsequently introduced many times as a contaminant of alfalfa seed. Using herbaria records and a comprehensive literature review, the authors map out the weed’s spread throughout the state over the past 135 years. It increased slowly through 1960, but then exploded in numbers, invading an average of 335,000 acres per year.
“Since 1960, the rate of spread of yellow starthistle has been steady, almost linear, and there is no indication of it slowing down,” the authors wrote.
Management programs for yellow starthistle are in place regionally and locally, and a biological control agent has been released in numerous locations around California. The authors urge land managers to eradicate new infestations when they are “small and easy to control.”
Contact: Michael Pitcairn, (916) 262-2049, mjpitcairn@ucdavis.edu.

Note to editors: California Invasive Weeds Awareness Week is July 17-23, 2006; for more information, go to the California Invasive Plant Council Web site at www.cal-ipc.org.

Also in the January-March issue of California Agriculture:

• Bat houses: An 8-year study evaluated the occupancy rates of 186 bat houses installed in rural areas around California’s Central Valley. Colonies of bats preferred houses mounted on structures such as buildings, with shade or morning sun only, within one-quarter mile of water.
  Contact: Rachael Long, (530) 666-8734, rflong@ucdavis.edu.
• Tomato water use: Processing tomato yields have increased 53 percent during the past 35 years, but critical data concerning crop water use has not been evaluated since the 1970s. A 4-year study of water use by processing tomatoes, conducted from 2001 to 2004 in the Central Valley, provides important information that growers can use to schedule more-efficient crop irrigation.
  Contact: Blaine Hanson, (530) 752-4639, brhanson@ucdavis.edu.
• Boron deficiency in grapes: Boron deficiency can reduce grape yields in certain areas of California. Foliar boron applied to vines at the right time during the fall was an effective treatment.
  Contact: Peter Christensen, 559-449-8220, CHRISTEN@uckac.edu.