Experimental study of oak seedling establishment

Marta Peláez, Rodolfo Dirzo (Stanford)

Graphical illustration of experimental design for study of oak seedling establishment

Summary

The purpose of this project is to improve the science underpinning conservation and restoration practices in oak savannas of California and other areas with a similar Mediterranean climate. California’s oak savannas and open woodlands are diverse ecosystems and valuable cultural landscapes. However recruitment of new seedlings is insufficient in many places to ensure a stable age structure and eventual replacement of mature trees. As part of a series of studies by Rodolfo Dirzo’s lab examining oaks from the stage of acorn germination and initial growth to the survival of young saplings exposed to herbivory or protected from it, this study specifically examines risks to seedlings that are planted at an age of 1-2 months.

Chrysanthe Frangos, Luisa Genes, Bohdan Kametts, and Marta Pelaez surveying oak seedlings Acorns from two oak species—Valley Oak (Quercus lobata) and Coast Live Oak (Quercus agrifolia)—were collected at Jasper Ridge in November 2022. They were placed in plastic bags, stored in the fridge at 3 °C for two weeks, float-tested, screened for insect damage, weighed, and planted in pots in a greenhouse. One to two months after emergence, seedlings were watered one last time and transplanted to 10 study sites at Jasper Ridge, with 5 sites close to a Q. agrifolia tree and 5 close to a Q. lobata. The study tests the effects on growth and survival due to acorn removal and aboveground clipping, alone and in combination, both under the cover of shrubs or in open grassland. The experimental design is illustrated in the graphic above.