On the east side of Big Basin are forests of oak, bay leaf, madrone, and other trees that can tolerate the drier conditions of the rain shadow on that side of the Santa Cruz Mountains. The image here shows a transition region of forest along the summit area of the Santa Cruz Mountains within Big Basin.
It's a great idea to simply find a turn out in Big Basin and walk into the forest. Mature redwood forests have very little undergrowth and are easy to hike through. The charburned bark and clothespin break in a tree shown in these images shows how the forest survives even the most severe forest fire. While all other vegetation will be consumed by fire, the coastal redwood tree will not die in a forest fire. The redwood is also remarkable for being able to stand and grow on even the steepest terrain. Redwoods only rarely fall in the forest, usually from having roots undermined by erosion, and when they do fall, the trunk will not rot for centuries. Redwoods do die by being cut down for lumber by humans though, as this rot resistant wood is both beautiful and excellent for outdoor deck construction. Some old homes have no concrete foundation, but have redwood timbers laid directly on the soil, and water tanks and hand split fence posts over a century old are commonplace in Northern California agricultural areas.
The San Francisco Bay has a Summit Ridge Trail, the best part of which runs through the edge of Big Basin State Park. See the image for a rough sketch of the trail route, but bear in mind that this trail must be, in places at least, intersected by freeways and urban traffic. Big Basin and Castle Rock State Parks are connected by this ridge trail. Please NO SMOKING or campfires along this trail, as California forests are very dry and suseptible to forest fires.
Poison Oak is endemic throughout the Santa Cruz mountains, so avoid it or expect an uncomfortable rash. Sensitivity varies with individuals and exposure, but the immune response can actually get worse with repeated exposure to the active chemical ingredient. Some individuals severe response may require hospitalization. The plant is dormant in winter, so while it's possible to get a rash from dead twigs, it's less likely. During the active growing season, the leaves are green and tender, much like an oak leaf, and tend to be less potent. In my experience, the worse time of year to get a good rash is during the fall when the leaves turn fall colors. You can also get a good case of the rash by sleeping with a dog who has walked through the forest brush, while the animal itself will not be affected. Seek medical advice if the rash turns into serious swelling or persists for awhile, but often simply reducing the itchy feeling with vinegar will help. The best solution is to avoid walking through the brush. Trails are often cleared of the plant, and with practice, you will learn to identify and avoid it. See the photo and links...
When we visited the park in the mid 60s, there were warning signs, but you could still buy paper bags with deer food to feed them. You can still spot deer in the park. The Opal Creek area is a great place to look for Mule deer.
The park website says: "In fact, the park once had deer feeding stations where park visitors could hand feed the deer. The practice was discontinued in the 1970s when the park decided it was unsafe for both the deer and the visitors. Mule, or black tailed deer are still plentiful in the park. However, we recommend that you maintain a respectful distance. Though deer are beautiful and graceful animals, they are also very powerful"