In some cultures, the oak tree is sacred – a symbol of strength and longevity – and a coast live oak restoration project is underway in Limestone canyon to bring more of these sprawling and majestic trees to the Irvine Ranch Natural Landmarks. After the first three years of growing seedlings through different methods, the Irvine Ranch Conservancy science team has found that the strength and longevity of a young oak is no match for a hungry mule deer.
The coast live oak (Quercus agrifolia) is one of just a few large trees native to the Irvine Ranch Natural Landmarks. They provide shelter and food to wildlife, and while people may see the spiky leaves as threatening, mule deer eat them right up. And now that the seedlings at the oak restoration trial area are about 3 to 4 feet high, the dark green leaves are at the perfect height for deer to wander by and take a nibble. With 160 trees initially planted at the site, the grouping of oaks has become a bit of a snack bar for mule deer. It’s one of the more surprising lessons from the project, which started in 2011.
“We’ve apparently been successful at growing some delicious oak seedlings,” said Lars Higdon, Irvine Ranch Conservancy Restoration Project Manager. “We knew the trees were at risk of attack from underground rodents, but we didn’t expect this level of mule deer foraging. It may be just that there are so many healthy, well-watered seedlings at the right height in one spot.”
Higdon and his team are now testing above-ground cages around the growing seedlings to keep the mule deer at bay, and the cages seem to be working well so far. Findings from the trial project are being analyzed by Higdon and two volunteers, Michael and Gretchen Mavrovouniotis, who are engineers trained in data analysis. Initial results show that the underground rodent barriers had the greatest effect on the survival of the seedlings, and while irrigation did have some effect on the height of the surviving trees, it did not directly affect survival overall.
While irrigation was available at the project site thanks to a leftover ranching water source nearby, irrigation lines aren’t as easy to find in the remote wilderness. It is the most expensive part of a restoration project, since water has to be brought in by installing irrigation lines along the ground. Higdon initially thought that irrigation would be critical, and the recent drought put that theory to the test.
“The oak restoration trial was conducted during a dry period, and irrigation had a negligible effect on the survival rate,” said Higdon. “This means that with decent soil conditions, in other areas of the land where the ground can retain rain water, we may be able to have a successful oak restoration with little to no need for irrigation.”
In the oak woodland habitat around the oak trial area, fall will bring a variety of activity to support the restoration. Native grasses will be planted in the mostly barren ground surrounding the project area. While the seedlings have been growing, Conservancy staff and volunteers have been removing invasive weeds on the ground around them. After a few years of consistent removal, few enough weeds remain that the native seeds can be planted.
In the stand of mature oaks near the project area, volunteers are needed to help collect acorns that will start to fall. There are volunteer activities planned in other parts of Limestone Canyon to help water and weed the oak seedlings as well. In November, there is even an educational hike in nearby Round Canyon that will help visitors understand the history and importance of acorns in different cultures.
All programs are free, and require advance registration atwww.LetsGoOutside.org.