Story and photos by Conservation Science Manager Mitchell Coleman
Fall foliage, primarily senescing black oak (Quercus kelloggii) overlooking Lopez Flats toward Middle Ridge, Blue Ridge, and the head of El Paso Canyon.
I recently heard a neighbor, who is originally from the East Coast, remark that California does not have much of a fall season. While it’s true that autumn in California is quite different from back east, it is nothing to shake a stick at (ha ha), a point I gently relayed to my easterly neighbor.
Fall has descended upon Tejon Ranch and the change of season can be felt, seen, heard, and smelled.
Hot summer temperatures have diminished to a pleasant cool. Daylight lengths are shorter, and angles are more subdued. Once-green hills are now burned browns, golds, and grays. Deciduous plants are beginning to change color. Some plants, interestingly, even wait until the fall season to flower, even though it is the driest time of year. Some of these flowers are quite aromatic and showy, and to me, signal that fall on Tejon has truly arrived. Let’s consider some of the ecological changes taking place right now.
A flower of California fuchsia (Epilobium canum), which blooms on Tejon starting in September. Fun fact: In California, red tubular flowers are usually pollinated by hummingbirds!
We all know the basic science behind deciduous color change. As fall days grow shorter, not as much sunlight is available for plants to carry out photosynthesis. Deciduous plants, which produce leaves afresh every season, sense this change and begin to restrict water and nutrient flow via their conductive vessels, xylem and phloem, initiating the familiar seasonal changes. The green hue of the chlorophylls begins to recede, making visible yellow and orange pigments, such as flavonoids and carotenoids, which were always present yet in smaller quantities (thus drowned out by the chlorophylls). As the season proceeds, other pigments, like the sugary and reddish anthocyanins, begin to form. Eventually, a hormonal cascade signals the plants to begin dropping leaves.
Changing leaf colors of black oaks on Winters Ridge. The greens, yellows, and oranges are a mix of chlorophyll, flavonoid, and carotenoid pigments. Photo by Laura Pavliscak.
Now, megaflora on Tejon are still mostly evergreen, albeit diverse, given the region’s mixing of four major ecoregions in the context of a Mediterranean climate. Depending on your location on the Ranch, your landscape view will be dominated by foothill pines (Pinus sabiniana), white fir (Abies concolor), incense cedar (Calocedrus decurrens), Joshua tree (Yucca brevifolia), many evergreen live oaks like canyon oak (Quercus chrysolepis), and many evergreen chaparral shrubs, like manzanita (Arctostaphylos sp.). These evergreen species tend to have thick, leathery, sclerophyllous leaves, which aid in the retention of water and nutrients, among other functions. This makes sense given that such leaves are long-lived. Partly related to resource conservation, the photosynthetic mechanism of evergreen leaves occurs year-round with varying degrees of efficiency, yet in general have a lower rate than deciduous plants.
Evergreen chaparral vegetation in the fall on Bronco Ridge looking over the Antelope Valley. Visible in the frame are big berry manzanita (Arctostaphylos glauca) and chamise (Adenostoma fasciculatum).
In contrast, deciduous plants have a different sort of leaf economy. Carbon assimilation for deciduous leaves must have a faster rate of return over a shorter period, since the leaves effectively have between early spring and late fall to get their job done. It is less about resource conservation and more about efficiency.
Leaves of fragrant sumac (Rhus aromatica), a deciduous chaparral shrub, showing off their fall colors.
Flowers of the common sunflower (Helianthus annuus) in Sacatara Canyon. This is another fall bloomer. Fun fact (same for many asters, though not all): Each yellow “petal” is actually an individual flower of smaller fused petals (ray flowers), while the smaller brown pieces in the middle are also individual flowers (disc flowers). Thus, each “sunflower” is actually a composite of hundreds of smaller flowers; the old family name was Compositaceae.
There will be many opportunities to see fall foliage this season. Join us for cross-ranch tours on October 12 or November 10, or if you’re feeling adventurous (and fit), the annual 12-mile hike down El Paso Canyon! Fall foliage aside, it’s a great time of year to observe the California condors in their natural habitat. Just sayin’.