Marin County 

A couple of months ago, I was on a large ranch near Boonville in Mendocino County, walking back from a plot where we have been counting and measuring trees killed by P. ramorum. As I came out of the drainage where most of the dead trees were, I was suddenly walking through a white oak woodland.

Here the trees were statelier, they were widely spaced, and everything felt drier. Besides the white oaks, huge bay laurels shaded the leaf litter and flowering plants in the understory. I looked down and saw this:

This is Lithophragma, aka the "woodland star." It was waving in the breeze, so I didn't get a very clear picture. I'm a sucker for all those delicate-looking flowers with complicated petals so often found in oak woodlands. Here's another one, Silene:

One of the interesting things about our oak woodlands is the variety to be found among them, even in just the northern part of the state. In Humboldt County, many of our coastal ridges and "bald hills" are crowned by open stands of white oaks. Driving past Laytonville in Mendocino County, one passes majestic stands of long-limbed valley oaks. Along Highway 20 from Lake into Colusa County, blue oak savanna with golden grass and plenty of other oak species carpets the tall rolling hills. On the way into the Bay Area from the north, the driver can't miss the coast live oaks lining the ridges near the road, heavy branches dipping down to the ground. In all these habitats, oaks have evolved to take advantage of relatively little water and thin soils, factors that make these places dicey, at best, for Douglas-fir or other conifer survival.

But Douglas-firs will try to survive there if they can get a foothold. In the eras of Native American use and European settlement, fires were either started or allowed to burn through many of these woodlands to maintain their open character. This kept conifers out. But beginning in the twentieth century, fires were kept out, and the conifers started to come in.

In the north coast, we are losing many oak woodlands and historically open prairie areas to Douglas-fir encroachment--and also to encroachment by some hardwood species that like the increased shade, such as bay laurel.

Interestingly, in many of these places it's easy to tell that the Douglas-firs don't really like it there. Here's a picture of one of the sites where we have installed some experimental silvicultural treatments to try to limit slow the spread of P. ramorum. It's an old prairie that has been under Douglas-fir invasion for a very long time. Note the crowded conditions and sickly-looking conifers. The Douglas-firs here are suffering from heavy infestations of two root diseases, Phaeolus schweinitzii (the velvet-top fungus) and Armillaria.

Bay laurel, though, is not as particular as Douglas-fir. If it can get established,it can grow surprisingly well even in places that seem as though they should be too dry. And in an area where P. ramorum has also become established, it will find the bay laurel--the tree is like a P. ramorum magnet.