changing leaves, changing landscapes

9/13/2018

by Trevor George

The days are shortening and the light feels different. The nightly low temperatures are dipping into the 40s and the sun is still hot, but it feels cool in the shade. Acorns are starting to fall and woodpeckers appear to be snatching them before they hit the ground. Fall is around the corner.

Some trees around town are already beginning to display their annual fall brilliance, like this one by our office.

Chinese pistache tree near Cherry Street, Santa Rosa.

In natural areas, some native species are also beginning their transformation. Changes in light and temperature are causing the bright green chlorophyll that colored our forests through the summer to break down. As the chlorophyll fades, yellow and orange pigment already in the leaf are revealed. Unlike yellow and orange, the red and purple you sometimes see was not already in the leaf. Red and purple coloring is a result of sugar that is created during the day and then trapped in the leaf during cool nights.

As the weather changes, a new layer of cells develops at the point between the leaf and where it attaches to the tree. Eventually, that connection is severed and the tree seals the cut so that a scar is already in place when the leaf falls under or is blown away. This is the process that results in countless hours of raking and gutter clearing.

Here are a couple species that you can already see changing.

Big Leaf Maple (Acer macrophyllum) turns a bright yellow and can be picked out easily in riparian environments. Photo taken at Laufenburg Ranch.

Poison oak (Toxicodendron diversilobum) turns a bright red color, which makes it much easier to avoid! It’s already heading toward winter dormancy when it fully loses its leaves. The loss of oily leaves means less surface area for you to come in contact with, but those dormant branches and vines will still give you a nasty rash. Photo taken at Laufenburg Ranch.

At Sonoma Land Trust, these colors are the early signals of upcoming tasks on the land. Soon, we’ll begin preparing our roads and trails for rain, using straw mulch and native grass seed to cover bare soils. We’re working hard to finish restoration projects by the October permit deadlines and we’re maintaining structures on our preserves for storms to come. Fire season is far from over, but it’s never too early to get ready for whatever this fall and winter brings us.

This time of year, I’m missing the rain and ready for its return. But for now, I’ll enjoy the final month or so of sunny, 70-something degree weather that we are lucky to enjoy where we live.