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Posts Tagged: oaks

Oaks in vineyards a ‘win-win’ for bats and growers

A blue oak stands in a vineyard. The bat echolocation microphone and yellow sticky card (to sample insects) at the top of the telescoping pole are attached to a vine post at the edge of the tree canopy.

Californians love their oak trees. During vineyard development, Central Coast grape growers often feel compelled to leave an old iconic oak standing, even if it ends up right in the middle of their vineyard. While driving through the Central Coast, it's not unusual to see the pattern of vineyard rows broken by a majestic oak tree. Aside from their beauty, what are some of the ecosystem services that these majestic trees provide?

Author Anne Polyakov sets up bat echolocation recorder at a tree site.
To find answers, a UC Cooperative Extension scientist in San Luis Obispo County collaborated with a U.S. Forest Service scientist to study how bats use blue oak and valley oak trees in vineyards. UC Cooperative Extension specialist Bill Tietje, a co-author of the study, says they focused on bats that eat insects because bat populations have declined dramatically in some areas due to habitat loss and disease. “And bats don't hurt grapes. As a matter of fact, thanks to the huge number of bugs they consume—bats could be very good for a vineyard.”

To understand the potential value of remnant oak trees for insectivorous bats, the researchers placed microphones to detect bat calls within 14 Central Coast vineyards. The recordings revealed 11 species of insectivorous bats foraged within the vineyards and bat foraging activity was 1.5 times greater at the trees compared to open, tree-less areas within the vineyard. And the bigger the tree, the bigger the number of bats it attracted.

“The study results suggest that the large oak tree in my vineyard not only increases the beauty and biodiversity of the agricultural landscape, but also attracts insect-eating bats that can provide natural pest control—a win-win,” said grape grower Jerry Reaugh, who cooperated with the researchers.

Bat echolocation recording device is solar-powered at a tree in a vineyard.
In fact, the presence of insectivorous bats called woodland-adapted bats more than doubled within the vineyards with trees. The study indicates that the oak trees attracted woodland-adapted bats that would normally be absent from vineyards. 

Tietje hopes that the free insect-reduction services provided by bats will increase grape growers' incentive to manage and maintain the trees, and even to plant new oak trees in suitable areas around their vineyard, in mutual benefit to both agriculture and biodiversity.

“In addition to their value for insectivorous bats, remnant trees maintain bird and insect diversity by providing food, habitat, cover and stepping stones that facilitate the movement of wildlife within agricultural landscapes,” said Tietje.

This study comes at a time when declining blue oak and valley oak populations are of great concern.

“We hope the study will increase awareness of these beautiful and beneficial trees and make the case for conservation and restoration,” Tietje said. “Preserving and enhancing biodiversity in the midst of climate change is key to ensuring resilience in our landscapes and communities.” 

Western red bats, which resemble this eastern red bat, were one of 11 bat species found at oak trees. Photo by Merlin Tuttle
The study by University of Washington graduate student Anne Polyakov, Theodore Weller of USDA Forest Service and Tietje is published in the September 2019 edition of Agriculture, Ecosystems and Environment.

Posted on Monday, August 26, 2019 at 3:24 PM
Tags: bats (16), Bill Tietje (4), oaks (9)
Focus Area Tags: Natural Resources

Hybrid oak trees muddle identification at California Naturalist Regional Rendezvous

Knowing the names of trees is a point of pride for many California Naturalists. So a walk among the diversity of oaks at the Pepperwood Preserve left many feeling humbled.

The three-hour excursion was part of the UC California Naturalist Regional Rendezvous in October at the 3,200-acre nature preserve nestled in the foothills between Napa Valley and Santa Rosa.

Excursion leader Steve Barnhart, academic director emeritus at Pepperwood, said there are 500 oak species in the world; 21 in California. But cohabitating on the rolling hills and valleys of the Golden State, many oaks have produced hybrids that combine characteristics, making identification challenging.

Steve Barnhart opens the 'Oaks of Pepperwood' excursion during the California Naturalist Regional Rendezvous.

Doctoral candidate Phrahlada Papper, who is studying oak tree genetics, said, “I'm of the mind that you shouldn't ever name an oak.”

Even the tan oak, long thought to be misnamed, is coming under new scrutiny.

“It's not an oak,” Barnhart said. “It has acorns, male and female flowers on the same stalk, but tan oaks are insect pollinated. True oaks are wind pollinated. Tan oaks are closer to chestnuts.”

But Papper raised his hand. “Genetically, it might be an oak,” he said.

Barnhart laughed. “So tan oak is up in the air. That's why it's so much fun to be in science,” he said. “I learned something today.”

Doctoral student Phrahlada Papper discusses oak tree genetics.

In popular culture, oaks are thought to be majestic, towering trees, with wide spreading branches. However, Barnhart said, most California oaks are shrubs, including the leather oak.

Leather oaks grow in serpentine soils and have the ability to produce two types of flowers, one in the spring and another quite different in the fall. Leather oaks are monoecious, they have both male and female flowers on the same plant. On a particular leather oak at Pepperwood, Papper was surprised to find male and female flower parts in one bract and surmised that weather patterns may be responsible.

“California has weird weather and with climate change, it's getting even more weird,” Papper said.

Leather oak details.

Papper believes tracking phenology, the cyclic and seasonal changes in plants, is an ideal citizen science project for California Naturalists. One such project underway at Pepperwood is led by Wendy Herniman. A University of Edinburgh, Scotland, master's student, Heniman is documenting the phenology of 10 Pepperwood oak trees: 2 blue oaks, 3 coast live oaks, 2 black oaks and 3 Oregon oaks.

“Pepperwood is looking at climate change. It's a designated sentinel site. We're monitoring fog, we have soil probes, and we're collecting all weather and climate information. We can tie that to phenology,” she said. “We're trying to find out if phenophases are changing.”

Understanding the changing phenophases is important, Barnhart said.

“Everything is connected,” he said. “If acorns are produced early, animals species that depend on the food source will be disrupted. You have imbalances in the timing of the natural world. With climate change, what are the effects we'll be seeing?”

Wendy Heniman talks about her research near a hybrid Oregon-blue oak.
 
The acorn shape is Oregon oak-like. The leaf contours are blue oak-like. The specimen is evidence of hybridization in oaks.
 
California native poison oak is also found on the Pepperwood Preserve. It is unpopular with humans, but birds like the golden berries.
A 15-year-old Douglas fir was mechanically removed to stop it from crowding a 50- to 60-year-old oak tree, Steve Barnhart said. Fire suppression is giving oak competitors like firs a greater foothold in oak woodlands. "Fire suppression was an unhealthy thing to do," Barnhart said.
Posted on Monday, October 16, 2017 at 1:30 PM
Tags: California Naturalist (27), oaks (9)

Sudden oak death moving to urban areas; 3 steps to protect oaks

Doug Schmidt, standing, and Matteo Garbelotto examine a bay laurel on the UC Berkeley campus.
Drought is decreasing but not defeating the pathogen that causes sudden oak death, according to a citizen science-assisted survey conducted this spring by a UC Agriculture and Natural Resources forest pathologist.

Results of the 2015 Sudden Oak Death Blitz survey reveal coastal mountain infestations in areas such as Big Sur (19% infection), the Santa Cruz Mountains (13% infection), and western Sonoma County (12% infection) remain high despite an overall decline in infection rates from 4.4% to 3.7% across California's 15 infested counties.

Sudden oak death (SOD) symptoms have been seen in Alameda, Contra Costa, Humboldt, Lake, Marin, Mendocino, Monterey, Napa, San Francisco, San Mateo, Santa Clara, Santa Cruz, Solano, Sonoma and Trinity counties.

“Understanding the current disease distribution is key to preventing sudden oak death spread. Citizen scientists have been an invaluable help with this task over the last decade,” said Matteo Garbelotto, UC ANR Cooperative Extension specialist in the Department of Environmental Science, Policy and Management at UC Berkeley, who organizes the annual SOD Blitz.

Several new SOD outbreaks of note were identified during the blitzes. Two infected California bay laurel trees were confirmed near UC Berkeley's West Gate, a high-traffic, high-risk area with many heritage oaks. An infected California lilac shrub was found in the Presidio of San Francisco's (part of the Golden Gate National Recreation Area) southeastern quadrant. An infected California bay laurel tree was confirmed in Danville (eastern Contra Costa County) in an area where SOD had not previously been reported, and an urban park in Saratoga was found infested for the first time.

These bay laurel leaves show P. ramorum symptoms.
“In an effort to protect habitat restoration in the Presidio, we are working to strengthen Best Management Practices to prevent the spread of SOD based on the Garbelotto lab recommendations,” said Christa Conforti, integrated pest management specialist at Presidio Trust in San Francisco. “In partnership with UC, the National Park Service, and the Golden Gate National Parks Conservancy, we are developing a Phytophthora prevention, detection and control strategy, which includes active participation in SOD Blitzes.”

Nineteen citizen science-based SOD Blitzes (largest number of blitzes to date) were held this spring, two of which were new this year – one in Trinity County and one on Kashia Band of Pomo Indian land in Mendocino County. The 504 volunteers surveyed nearly 10,000 trees from San Luis Obispo County, north to Mendocino and Trinity counties. Each volunteer was trained to identify Phytophthora ramorum (the plant pathogen known to cause SOD) symptoms on California bay laurel and tanoak leaves. “Blitzers” had up to three days to collect and record locations of symptomatic samples, which were then sent to the Garbelotto lab for DNA analysis to determine the presence or absence of the pathogen.

The SODMap mobile app shows a map of sampled trees.
SOD management workshops

Garbelotto is sharing results from the spring blitzes as well as new recommendations for SOD management at workshops being held around the Bay Area. Workshops will be held in Sebastopol on Nov. 3, in Berkeley on Nov. 4, and in San Rafael on Nov. 13. For details, see “Community meetings” at sodblitz.org.

For landowners in infested areas concerned about protecting their oak trees, Garbelotto will reveal his updated three-step SOD management plan. He will show them how to:

  1. Use the SODMap mobile app to help assess risk of oak infection (see sodmapmobile.org).
  2. Determine if California bay laurel trees near high-value oaks should be considered for removal (using a new buffer zone new chart - http://nature.berkeley.edu/garbelottowp/?page_id=2345).
  3. Apply phosphonates to high-value oak and tanoak trees to boost immunity (updated dosages and application frequencies at http://nature.berkeley.edu/garbelottowp/?page_id=2348).

Infection on California bay laurel and tanoak leaves indicates arrival of P. ramorum to an area, but true oak (California black oak, coast live oak, canyon live oak and Shreve's oak) infection typically requires a couple of years with wet conditions after pathogen arrival. Therefore, preventatively treating oaks to help ward off infection is best done when early indicator species first show symptoms, prior to oak infection and optimal conditions for the pathogen – cool and moist.

These surveys are made possible thanks to funding from the USDA Forest Service and the PG&E Foundation as well as help from the California Native Plant Society.

For more information on the workshops, go to sodblitz.org or contact Katie Harrell at (510) 847-5482 or kpalmieri@berkeley.edu. For more information on sudden oak death and P. ramorum, visit the California Oak Mortality Task Force website at suddenoakdeath.org.

 

Posted on Friday, September 25, 2015 at 11:38 AM

Give oaks water once a month

Even though California's majestic oak trees are generally considered drought tolerant, the last four years of well-below-average rainfall are taking a toll, reported the Sierra Sun Times.

"In some parts of the state, oaks are being deprived of water for as long as nine months, creating extreme water stress," said Greg Giusti, a forest and wildlands advisor for UC Agriculture and Natural Resources. Giusti is headquartered in the UC ANR Cooperative Extension office in Mendocino County. 

Giusti and Kris Randal, the UC Master Gardener coordinator for Mariposa County, suggest that California residents with oaks on their property give the trees a good soaking once a month during the summer.

The water should be applied around the drip line - the area below the outstretched branches - but not near the trunk. A permeable soaker hose is an ideal tool for slow application over the wide area. Allow the water to run until it has soaked down to a depth of 12 to 18 inches, which can be detected with a long probe such as a screwdriver. "If it comes up with signs of moisture at the tip, you're good," the article says.

Randal said it is important to let the soil dry out completely between waterings, because oaks are susceptible to root fungus that can grow in warm, damp soil.

Even if water is unavailable and the leaves begin to turn brown or fall, the experts suggest waiting for spring before considering removing the tree.

"If you tree leafs out, it's still alive," Randall said. "And in this drought, give it extra time to leaf out."

A large blue oak in Mariposa County.

 

Posted on Friday, August 21, 2015 at 12:58 PM
Tags: drought (163), Greg Giusti (14), Kris Randal (2), oaks (9)

Native oaks stressed by drought may recover

Bill Tietje is a UC Cooperative Extension area natural resources specialist in the Department of Environmental Science, Policy and Management at UC Berkeley. He is based in San Luis Obispo.

Along with insects and disease, the drought of 1987-1992 apparently contributed to the decline and death of these California live oak trees.
UC Cooperative Extension's Master Gardeners have received many calls during the past few months concerning the poor condition of many California native oak trees, in both urban and rural landscapes. Many evergreen oaks, including coast live oaks, have brown leaves and thin foliage. Adding to the unattractiveness, a deciduous oak, the blue oak, dropped its leaves ahead of schedule. Although a tree may look unhealthy, it can recover.

Early leaf drop is a deciduous tree's adaptation for conserving water that it otherwise would lose through transpiration from its leaves, which can occur as long as the leaves are green.

More recently, another deciduous oak, the valley oak, kept its brown, dead leaves longer than usual. This could be due to the virtual lack of rainfall and wind last fall and early winter, both of which typically contribute to an earlier leaf drop.

So why are these things happening?

Sergio Garcia, UCCE advisor emeritus, examines blue oak that died during the 1987-1992 drought . Many of the trees that died were on sites with shallow soil and southern exposure.
The situation

As you know, it's dry out there! In fact, the past 12 months have been the driest on record, going back to 1870. Not surprisingly, many oaks are under water stress—and they show it.

This situation reminds one of the conditions during the drought of 1988-1990, one of the most widespread and severe droughts in the state's history. Coincidentally during that time in three counties on the Central Coast, UC Cooperative Extension was conducting a study that included the monitoring of coast live oak, blue oak, and valley oak trees on study plots scattered throughout Monterey, San Luis Obispo and Santa Barbara counties. Many of the oaks looked stressed. Some of the trees succumbed to the drought. Small oak trees in the undergrowth and on steep terrain with southern exposure, and shallow, infertile soil, were most vulnerable. Such sites are typically drier than other slopes and orientations. However, large, mature trees—or, large branches on these trees—on more gentle slopes, also died. Usually there is not only a single factor that causes the decline and mortality of oak trees. Drought stress lowers the trees' defense, making the trees more susceptible to mortality factors such as decay fungi and boring beetles. Most likely the drought caused early death of some oak trees that would have persisted otherwise.

What can be done?

Surely our native oaks have been through droughts before. So the oak trees, other than the very small or very old trees, should be okay. Nonetheless, given the very low rainfall this year it may be prudent to give a valued tree in the urban landscape a “deep watering”.

The entire tree may not die. Here a large branch of a valley oak tree died.
A deep watering can be accomplished by moving a hose around under the tree's canopy during the day for a day or two at a low flow or a trickle stream, such that the water percolates into the soil, not simply run down the hill. Water a few feet away from the base of the tree to avoid inviting damage from crown rot caused by the fungi Phytophthora cinnamomi. Water-saturated soil increases the chances of infection of the tree trunk.

A deep watering followed by soil drying for a month or two should not harm the tree. In fact, a deep watering may be the best recommendation for invigorating your thirsty oak tree, thus providing some insurance that the tree will survive this current drought.

I should mention that unless California receives normal or better rainfall the rest of the rainfall season, it is likely that early leaf drop will occur next summer. Remember, as suggested above, the early browning and fall of leaves does not mean that your tree will die. This is simply the tree's way of adapting to conserve water when soil moisture is low. Unless the tree is severely weakened by some other cause, it will leaf out normally the following spring.

For more information: Tietje, W., W. Weitkamp, W. Jensen, and S. Garcia. 1993. Drought takes toll on Central Coast's native oaks. California Agriculture 47(6):4-6.

 
Posted on Friday, January 31, 2014 at 12:11 PM
Tags: drought (163), oaks (9)

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