Zoom the camera in tight enough and there are spots an hour east of Sacramento that could be mistaken for the surface of Mars, with bare rock poking up through rust-red soil.

Widen the view a bit, though, and you might see something more rare: one of a handful of endangered plants that grow in the unusual soils of western El Dorado County and, as far as science knows, pretty much nowhere else.

Beyond the rare flora, the blue oak foothills and chaparral of Pine Hill Preserve offer the sounds of 100 bird species at one time or another during the year. You might also hear a coyote, spot signs of a gray fox or even – as a couple of people have learned to their surprise over the past year – come quite a bit closer than you expected to a mother black bear and her cub.

The preserve covers more than 4,100 acres in five units spread out from Cameron Park to beyond the northeast end of Folsom Lake. It is run cooperatively by the U.S. Bureau of Land Management, the American River Conservancy and seven other local, state and federal agencies.

"It's a wild area close to Sacramento, which is where I live," said Chris Conard, a longtime volunteer at the preserve.

On this recent Saturday morning he led a 20-member group into the preserve to spot birds.

"There's this mix of bird and habitat types that's really interesting, especially this time of year when you have both the native and migrating species."

A wild tom turkey kept up a running commentary from the ground as Conard led the group up a private road that scales the side of Pine Hill into one of the preserve areas, but he was looking up the hill.

"That chk-chk-chk-chk, that's a Bullock's oriole," Conard said.

A dozen pairs of binoculars scanned the treetops. Some spotted the orange-and-black visitor, which migrates between Central America and its breeding grounds in Washington state, atop a pine, just to the left of a chattering bunch of acorn woodpeckers.

Plants, rare and delicate

The mission of the Pine Hill Preserve, however, is found at ground level, and the reason is the ground itself. The geology of the area includes a belt of gabbro, a granular igneous rock that's chemically similar to basalt, the dark stone common on the sea floor. It's rich in iron and magnesium compounds, weathers to a rusty hue and forms relatively poor soils that many plants won't tolerate.

Pine Hill was set up to protect some of those that do.

Of eight rare plant species in the preserve, five have been listed since 1996 under the federal Endangered Species Act as either threatened or endangered.

Four of the eight, it's believed, grow nowhere else:

• The Pine Hill ceanothus, a low shrub with white flowers that spreads and sets roots where its branches touch the soil. Federal officials list it as endangered and the state calls itrare.

• El Dorado bedstraw, which grows in tufts a few inches high, often at the base of live oaks or black oaks. Also listed as endangered on the federal rolls and rare by the state.

• Pine Hill flannelbush, a sprawling low shrub with hairy leaves and orange flowers. It's unclear how it's related to dwarf flannelbush specimens in three other counties; it also is endangered at the federal level and rare in the state's eyes.

• El Dorado mule-ears are a form of sunflower with large, triangular leaves that dies back each winter, raising yellow flower heads as much as 3inches across that are made up of much smaller flowers. Though not endangered, it is listed as "rare, threatened or endangered"by the California Native Plant Society.

Protection efforts date back to the 1980s, with work to design a preserve system starting in 1992. The preserve is still growing toward its target size of 5,000 acres; it added 80 acres in the past year, said preserve manager Graciela Hinshaw.

But it's tricky, she said: "Some of the units are almost completely surrounded by development."

The field trip group at Pine Hill this daypassed hillside homes with lush lawns on its way up to the preserve, and the crown of the hill sprouts cell phone towers and telecommunications equipment behind chain-link and barb-wire fences; turkey vultures perch near the top before returning to the thermals rising from the hillside.

Land acquisition depends on willing sellers and the availability of cash to make a purchase, Hinshaw said. That's also a factor in why parts of the preserve are hard to reach.

"Since we have limited resources, if you have 20 acres of prime habitat vs.20 acres that provide access, the habitat has to take priority."

The long-term goal is to set aside enough habitat to give the plants a viable shot at survival and to manage it for their benefit. That includes developing a plan for using fire to rejuvenate the chaparral, where the plants have evolved to use periodic wildfires as a jumping-off point for renewed growth. That's not now possible in the areas near development, Hinshaw said, although volunteers do clear brush to restore the open space favored by the plants and burn some of it in piles.

The preserve also is preparing a 10-acre parcel to reintroduce the Pine Hill flannelbush.

"It's one of the plants in deep, deep trouble," Hinshaw said. "The finest specimen I've ever seen is on private land. The owner is very proud of it. He prunes it and waters it … his neighbors are jealous."

Many of those on the bird walk were neighbors, some with homes that back up to preserve land.

"This is neat, because now that I know what's endangered I won't weed it," said Paula Agostini, who moved with her husband, Ramon Lopez, to Rescue a little more than three years ago; the nearby preserve was a selling point for the house.

David Fischer brought his children from Shingle Springs. Both Jonathan, 11, and Mary, 9, were impressed, even after a couple of hours of walking and nature.

"There's lots of flowers that we've never seen before," Jonathan said. "It's just a whole different world from where we live."