The Midpeninsula Regional Open Space District removed about 150 eucalyptus trees in part of a nature preserve last month to replace them with native plants and improve the forest’s fire resilience.
The trees were cleared from a 2.5-acre portion of the Sierra Azul Open Space Preserve near Lexington Reservoir in Los Gatos as part of the district’s Wildland Fire Resiliency Program, which aims to promote healthy, resilient, fire-adapted ecosystems, reduce wildland fire risk and facilitate the response of fire agencies.
“As a land management agency, we have a responsibility to take care of these lands. These lands, these open spaces, they do so much to take care of us,” said Midpen spokesman Ryan McCauley. “So I think it’s really incumbent upon us as managers of these lands to really ensure that we’re doing everything we can to make sure it’s as resilient as possible.”
The eucalyptus trees were planted ornamentally by the land’s previous owner, said McCauley. They are considered invasive and can outcompete native plants and deplete water supplies. The can grow quickly and prevent sunlight from reaching lower levels of the forest. A reaction between the chemicals the trees exude and the earth also can acidify the soil, making them the predominant species in an area. They also pose a significant wildlife hazard due to their volatile oils and shedding bark and leaf litter.
South of the previously infested portion of land is Aldercroft Heights, a neighborhood that is prone to wildfires and part of the Wildland Urban Interface.
After taking note of the nearby native species and features of the region, Midpen forest ecologist Arianna Camponuri said they decided to plant coast live oak, California buckeye and Pacific madrone trees, among other shrubs and perennials, and restore the area to a native California oak woodland. Since the forest is near the reservoir, it is considered a riparian ecosystem, so McCauley said they had to be more intentional and take more ecological care to make sure their actions bolster the integrity of the forest.
“A major thing with eucalyptus stands is that you have a low level of biodiversity, and biodiversity is really important because it’s the building block or foundation of resilience,” Camponuri said. “With a more single species composition in a forest ecosystem, you really don’t have that diversity to withstand a number of disturbances.”
Camponuri said they decided against planting some species after finding that the area was affected by pests called invasive shot hole borers–beetles that can carry pathogens that affect several tree species.
Camponuri said it would take a few years for the new plants to grow, during which time Midpen will conduct active invasive species management. The removed eucalyptus trees will be turned into logs and woodchips to support erosion control and suppress weed growth.