South SFV Today

Sitting atop the land of the Muwekma Ohlone Tribe, in the Santa Cruz Mountains near Stanford University, is the Jasper Ridge Biological Preserve. This site has served as a key location for scientific studies aimed at understanding natural ecosystems since 1965.

Rodolfo Dirzo, a professor of biology, began research in 2009 on the impact of herbivores like deer on oak seedlings. He protected some seedlings from deer while leaving others as controls. Initial results showed a decline in oak seedlings due to deer, but changes occurred with the return of mountain lions, leading to increased vegetation abundance and oak regeneration.

Dirzo's research has expanded, unveiling complexities in oak survival. Key species, including valley oak and blue oak, face threats from climate change, pests, disease, and drought. These species are particularly vulnerable compared to coast live oaks, whose loss could have significant ecological repercussions.

Dirzo emphasized the cultural importance of these plants, stating, "These plants have significance for the cultural and traditional views and cosmovision of the local people here."

Research by Dirzo's scholars, Ramon Perea and Marta Peláez, explored how nurse plants protect oak seedlings. Their 2015 study surveyed oak regeneration under coyote brushes. In 2023, experiments showed nurse plants aided oak survival in drought but had less impact in normal conditions. "Traditionally, we ecologists have always thought of plant-animal interactions to be negative in nature," Dirzo remarked, noting the research challenges this view.

Chrysanthe Frangos discovered deciduous oaks struggling compared to evergreens under nurse plants. Concerns arise as their loss would impact biodiversity and soil chemistry. "Losing deciduous oaks could have huge ecological impacts on biodiversity," Frangos noted.

Further experiments by Perea and Peláez suggested deer might aid seedlings during drought by reducing leaf surface water loss. "These herbivores might be detrimental for oak saplings, but our main takeaway was that, at the seedling stage, they can play a positive role too," Peláez explained.

The studies offer insights into preserving oaks under climate change threats. Dirzo's team suggests pilot studies for oak conservation, balancing deer and predator populations for survival.

Tadashi Fukami, JRBP faculty director, highlighted the preserve's role as a resource for studying complex ecological interactions. He remarked, "This research is a good example of how long-term research can accumulate."

Dirzo, also involved with Stanford's environmental programs, continues to advance these studies, supported by the preserve's rich history of research.

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