On a flat expanse of land 10 miles south of Dixon, the Jepson Prairie Preserve is among the best of the few remaining vernal-pool habitats in California as well as a prime example of the native bunchgrass prairie that once covered much of the state. With winter rains, the prairie’s impermeable layer of clay soil holds rainwater in shallow pools and small lakes (the largest, Olcott Lake, is 93 acres) that slowly evaporate through the spring. During that time, dozens of species of plants and animals that depend on the water in the ephemeral pools complete their brief life cycles. Fairly shrimp and other aquatic invertebrates are abundant in the pools early in the season. Then, as the pools begin to dry, wildflowers bloom in sequence, often forming colorful concentric rings around the edges of the shrinking pools.
The best way to see and learn about the prairie and its plant and animal inhabitants is through a docent-led tour, offered on weekends in the spring (usually beginning in early March and ending on Mother’s Day). Although most of the prairie is only accessible through the tours, there is a short self-guided nature trail open to visitors during daylight hours. Dogs are not allowed anywhere on the preserve.