Natural View: Many shades of green after wildfires

We’ve driven several times through the recently burned Tehachapi Mountains since early winter. After the rain, some hillsides quickly turned bright green, while others remained mostly brown dirt, covered with blackened remains of shrubs. Many shrubs on the brown hillsides are sprouting from their bases, and there are wildflowers, but the overall effect is still sparse.

Which hillsides are in good shape?

Most motorists zipping by, if they even notice the colors, would likely say that the green hills are doing better than the brown ones. After all, green is the color of living plants. But they would be wrong — a consequence of trying to botanize at 70 mph.

After a wildfire, annual plants recover fast. The soil contains a bank of dormant seeds, which sprout as soon as the rains come, and sometimes before. Ten days after the 1993 Laguna fire, the first blades of annual grass appeared.

The bright green hillsides are actually covered with introduced European grasses and weeds, not native plants and shrubs. The grasses are the legacy of 100 years of ranching history, when native shrubs were chained off to create rangeland for sheep and cattle; topped with a recent history of too-frequent wildfires.

On the brown hillsides, other plants are stirring: Shrubs are slowly regrowing, and dormant seeds of native wildflowers are resprouting. The seeds have waited patiently under the coastal shrubs and are now exposed to sunlight, nutrients from the ashes and rain. They create a colorful display the first spring following a fire.

Coastal sage shrubs need at least several years to mature, flower and produce seeds. A second wildfire a few years after the first one can eliminate shrubs that have not had time to drop seeds into the soil.

In the foothills of the Santa Ana Mountains, some areas have burned three times in the last 10 years, far too often for the shrubs to recover. This spring, and every spring after this, those hillsides will be covered with nonnative grasses, and weeds like wild mustard and tree tobacco.

Every winter, fire or no fire, many hillsides and canyons of the Greenbelt glow with that same particularly vibrant emerald green that signals nonnative grasses.

Not all bright green signals alien plants; hillsides covered in native shrubs also turn green in winter. The native coastal sage shrubs come out of their summer dormancy and sprout new green leaves after the rains. This green is softer and deeper.

The easiest way to tell what’s happening on a hillside is to watch whether the color changes between now and late May. As they set seed and die, exotic annual grasses will turn from green to California’s famous “gold.� If the view out your window stays green, your favorite hillside is probably doing all right!

ELISABETH M. BROWN is a biologist and the president of Laguna Greenbelt Inc.