The state of Sonoma County’s forests
Arthur Dawson | For the Press Democrat | March 1, 2017
Editor’s Note: This is part two of a series about the indigenous forests that blanket Sonoma County — their past, present and threats to their future.
Our forests “are undergoing a sea change,” observes Mark Tukman, founder of Tukman Geospatial, who is spearheading the Sonoma County Agricultural Preservation and Open Space District’s development of a fine-scale vegetation map.
“I’ve spent over a year looking at aerial photos and coordinating field teams. Many of our oak woodlands are disappearing rapidly, transitioning to Douglas fir and California bay,” he said.
In many places this is visible at ground level — dead manzanitas scattered beneath oaks dying in the shade of Douglas firs — a century of change visible in a glance. Of course, oaks and firs represent just a few of our native trees. Sonoma County’s wide range of geology, soils, landforms and climate has been described as “where Alaska meets Mexico.” With 10 species of oaks and 19 conifers, our forests reflect this diversity.
Close up, they can seem infinitely complex. But if you pull back, larger patterns emerge. Moving west to east, conifers grow in parallel bands — Bishop pine along the cool coast, then redwoods, and finally Douglas fir reaching warmer areas far inland. Interspersed are woodlands of oak, bay, madrone and other hardwoods. There are no hard boundaries between any of these types — in fact mixed conifer-hardwood forests are more common than either alone.
By the early 20th century, forested lands had seen severe impacts. Logged-off tracts of redwood and Douglas fir were now brushy and crowded with young trees. Oak and madrone woodlands, leveled for firewood, had become grassland. Settlements replaced oak savannahs. By all indications, there were far less trees 100 years ago than today.
Even so, in some areas, a mix of surviving forest, brushy areas recovering from timber harvest, and chaparral stands created conditions ripe for catastrophe. One of the county’s first large-scale wildfires occurred in September 1923. Pushed by strong winds, it burned 10,000 acres, destroying many homes and structures in Sonoma Valley. Afterward, citizens formed several rural fire departments. Rather than treating it as a tool, as Native Americans had with intentional, frequent burning, fire became the enemy. Suppression was the goal.