A tree requires air, water and sunlight to live.
Trees filter carbon dioxide (CO2) from the air and release oxygen. Their leaves use sunlight in a process called photosynthesis to convert sunlight into glucose, a sugar and food for the tree. Trees draw water from the ground through their roots to provide necessary water and soil minerals for the tree’s life cycle. CO2, glucose and water are food for the tree.
As you may know, trees and other plants are necessary to sustain our atmosphere. All animals, humans included, breath in oxygen and breathe out carbon dioxide. CO2, higher air temperatures and fossil fuel emissions add to the CO2 in our atmosphere. Too much CO2 can be lethal to most animals on the planet. Trees and other plants take in carbon dioxide, removing vast quantities, and release oxygen. They remove the bad and deliver the good.
As fall advances in the Sierra foothills of Nevada County, some plants, most noticeably trees, begin to change color in a spectrum from faded brown to glowing yellow. While some trees are evergreen year-round, other trees are deciduous and their leaves change color and drop off in the fall.
“Evergreen” is self-explanatory; these trees stay green year-round. However, evergreens do shed more needles in the fall. As those of us who live amongst the Ponderosa Pines know full well, old needles fall off as they are replaced by new needles.
Most evergreen trees are conifers — cone-bearing trees. We have pine cones, fir cones and cedar cones, each an identifying feature of the particular tree. Our conifers have needles for leaves. A brown conifer is usually a dead conifer. The most common foothill conifers are the Ponderosa pine (Pinus ponderosa), grey pine (P. sabiniana) and western cedar (Calocedrus decurrens). Note: scientific names are in parentheses.
The term “deciduous” comes from the Latin meaning “tending to fall, to fall, falling.” Deciduous trees by definition lose their leaves.
Deciduous trees and shrubs are responsible for most of our fall colors. Common deciduous trees in the foothills include blue oak (Quercus douglasi), black oak (Q. kelloggii), bigleaf maple (Acer macrophyllum), Pacific dogwood Cornus nuttallii), California sycamore (Platanus racemosa), several different species of poplar including a generic (Populus spp. X) and at higher elevations, the quaking aspen (Populus tremuloides). All of these trees are broad-leaved, meaning their leaves are broad, as opposed to having needles for leaves.
Note: The Sierra foothills are the exception to the deciduous/broad-leafed rule; other than the black oak (Quercus kellogii), our other native broad-leafed trees, the interior live oak and canyon live oak are broad-leafed and evergreen.
The deciduous trees display most of our fall color. The blue oak turns brown as the leaves fall. The black oak is one of our better fall colors — the leaves turn a rusty yellow/red. The most spectacular fall colors come from the bigleaf maple — deep, glowing yellows. These maples light up the fall forest. The dogwood has a rich yellow/orange-colored leaf and the sycamore turns brown. The sycamore leaf is huge, larger than even the big leaf maple, and a popular table or mantle decoration. Watch out, they crumble easily.
It is the combination of all these things that make the beautiful fall foliage colors we enjoy each year.
The dormant period starting in the fall is part of the plant life cycle. The days become shorter as fall approaches. The shorter days signal to the trees that soon winter will be here and there will not be enough light for photosynthesis.
Photosynthesis is made possible by chlorophyll, a chemical found on the surface of leaves that gives them their green color. The trees begin to go dormant and photosynthesis stops. They stop growing for the season, living off stored food. The green chlorophyll begins to disappear as the trees shut down, causing the leaves to begin to change color — and some very pretty colors indeed, from subdued brown to vibrant yellow.
There are many great spots in Nevada County to see the fall colors. The bigleaf maples are lighting up the Hardrock trail in Empire State Park. There are a myriad of colorful trees, native and non-native, in downtown Grass Valley, Nevada City and the surrounding areas. You will see a wide range of fall colors traveling north on Highway 49 in spots such as the Independence Trail and the old Highway 49 pullout, both in South Yuba State Park.
Get out and enjoy the beautiful fall colors of Nevada County and the surrounding Sierra foothills.
Robert Kelly lives in Grass Valley.