2.1. Study site

Tejon Ranch, located in southern California, contains 97,124 hectares of conserved lands that are jointly managed by the Tejon Ranch Company, Tejon Ranch Conservancy, and two grazing lessees. Cattle grazing is the most widespread land management practice affecting riparian areas on the ranch. The Ranch encompasses areas of California's San Joaquin Valley, Sierra Nevada Mountains, Mojave Desert, Tehachapi Mountains, and South Coast Ranges. This study is limited to major streams with well‐developed woody vegetation, in the San Joaquin Valley portion of the ranch. Despite large‐scale conversion of riparian forests in California's Central Valley, these areas provide a wide array of ecosystem services (Vaghti & Greco, 2007); due to its extent and management history, Tejon Ranch provides an ideal location to study a relatively intact network of Central Valley riparian forests.

Five creek segments were selected for study within the area of interest: Chanac Creek (CH), El Paso Creek (EP), Lower Tejon Creek (LT), Tunis Creek (TU), and Upper Tejon Creek (UT)—hereafter referred to as “creek segments.” Within each of these creek segments, three locations were selected randomly within areas with woody vegetation for a total of 15 study reaches—hereafter referred to as “study reaches” (Figure 1). In the winter of 2014–2015, one study reach on each stream segment was randomly chosen to receive a cattle exclosure. The exclosures were in place for the remainder of the study. Reaches that received exclosures were CH2, EP3, LT1, TU2, and UT3.

Map of study reaches on Tejon Ranch

Although somewhat drier than the “true” Mediterranean climate (Aschmann, 1984), the study area is in a Mediterranean‐type region of California, with hot dry summers and cool wet winters. Mean annual precipitation is 21 cm. Eighty‐nine percent of this falls between November and April (http://ipm.ucanr.edu/WEATHER/wxactstnames.html). Mean maximum summer daily temperatures are between 32 and 35°C, and mean minimum summer temperatures are between 15 and 19°C. Mean maximum winter daily temperatures are between 15 and 21°C, and mean minimum daily winter temperatures are between 3 and 8°C. The 4 years encompassed by this study had below‐average rainfall. Between 2012 and 2015, the average annual precipitation was only 15.7 cm. The 2015–2016 rain‐year had approximately average rainfall (20 cm).