The Tejon Ranch Exclosure Experiment (TREE) aims to understand how changes in large mammal assemblages in the Anthropocene, namely wildlife loss and substitution of wildlife by livestock, impact ecological communities, through direct and indirect pathways. The experiment uses 27 one-hectare experimental plots (about 2.47 acres each) across sites that range in climatic conditions (minimum and maximum air and ground temperatures, humidity, soil moisture and solar radiation); it builds on work done through the NSF-funded M2M project. Plots consist of three treatments: all ungulates (mammals with hooves) domestic and wild allowed; only wildlife allowed (no domestic ungulates); and no ungulates (domestic or wild) allowed.

TREE was established in 2016 by University of California, Santa Barbara, Principal Investigators Devyn Orr and Hillary Young, and is managed in collaboration with the Conservancy. Since establishment, a number of questions have been investigated, including how do changing herbivore assemblages and climate impact herbaceous plant diversity and composition, floral resource availability (i.e., amount of pollen and nectar available to insect pollinators), oak seedling establishment and survival, and tick-borne disease dynamics.