A grant of $263,600 could help put the green back into dying oaks on University of California land.
Sudden Oak Death Syndrome (SODS) has turned California’s hills into killing fields of dead and dying trees. Along a 1,500-mile stretch of California and Oregon coastline, large numbers of tan oaks, coast live oaks and black oaks are dying off, threatening wildlife and increasing the risk of forest fires.
Recently, the David and Lucile Packard Foundation gave $263,600 to help the UC Natural Reserve system study and attend to its 33 reserves over the next 5-10 years. UCSB scientists oversee Sedgwick Reserve, a 5,600-acre plot of land in the Santa Ynez Valley.
“The study is [stimulated] by the need to identify the different plant life along with the cause of [SODS], and the unknown cause for the decline of native grasses,” said Jim Reichman, director of UCSB’s National Center for Ecological Analysis and Synthesis.
Oaks are vital to the woodland ecology of California, providing food and shelter to wildlife. The trees’ roots prevent soil erosion. Dead trees, while a boon to insects and fungi, are a fire hazard.
Every year since 1995, SODS killed an increasing number of trees. First, a tree’s shoots – new growth at the top of the oak – droop, as older leaves became pale green. Two to three weeks later, every leaf announces the death of the tree by turning brown. While the tree is dead or dying, parasitic insects bore into it, sucking out its sap. In the summer, heat bakes the tree and splits its bark. Eventually, rotting roots fail to support the tree, and it crashes to earth.
David Rizzo, the assistant plant pathologist at UC Davis’ reserves, said SODS could permanently alter California’s ecology.
“[SODS] has the potential to change oak woodlands forever,” he said. “Some of the affected areas have had from 80 percent to 90 percent of their oaks die. These oaks are a huge habitat for significant wildlife such as the spotted owl. If the oaks were to disappear, other problems such as erosion and fire hazards could also ensue.”
So far, pathologists have determined the cause of the SODS to be phytopthora, a fungus that enters into the outside and inside bark of a tree’s trunk and limbs – possibly through raindrops. Once this fungus enters the tree, it produces an enzyme that cuts through the outer and inner layers of the bark by breaking down the cell walls. This breakdown causes the tree to “bleed” or ooze out dark brown sap. The weakening of the tree by the fungus makes the tree vulnerable to ambrosia beetles and western oak bark beetles. The insects feed off of the tree’s sap, sucking it dry.
Reichman said, “the [fungus] appears to be transmitted in the air [because] the entirety, and not just the base of the tree is affected. The blocking of the tree’s vessels inhibits the tree from receiving water and nutrients, which then results in its death.”