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• 1 media/SouthernCalOakWoodlandMontecito.jpg media/Savannah_Pan_Crop_Sm.jpg 2018-12-02T17:47:50-08:00 Of Oaks, Floods, Fires, Famine, Feasts and Giants 102 gallery 2019-12-05T13:38:38-08:00

  Quaerite quercu

  Oaks, genera Quercus, are the ancient monarchs of the California landscape.   Oak species native only to California are the oldest (over 500 years) and largest oaks on Earth. Its qualities as a tree are the work of evolution, but its predominance on the landscape of Southern California is the clever work humans, who cultivated these giants and suppressed their competitors on multigenerational scale.  The ancient oaks of California deserve narration at two different time scales: that of millions for evolution, and that of thousands for distribution and magnification.
  
  Let us meet two of these old oaks, of the species called Ku'w in Chumash; Encino in Spanish; Coast live oak in English; and Quercus agrifolia in scientific Latin.  They live in the ancient Chumash territory of Topanga Canyon.  At least 250 years of age, each has witnessed the entire modern human world, from from the years before Spanish conquest of 1769-1824.  
  
  As toothsome acorn nuts and as seedlings, these oaks at infancy hid from deer and other browsers inside the cracks of the boulders that are now splayed open by their powerful roots.  By the time they fell as acorns into those boulder-cracks, this canyon, Topa'anga, had been cultivated for thousands of years by the Chumash and later Tongva who depended upon them.  Every mature oak and walnut had a name, as villages and families laid claim to specific trees, inheriting them and passing them down for generations. Producing bushels of nutritious acorn meat each year, each mature oak was cherished and defended; young oaks were encouraged and tended. 
  
  Seeing them now in the 21st century, they exhibit their evolutionary super-powers. Their ancestors survived by adapting to the four great hazards of the region: floods, droughts, fires, and predation by giant herbivores.  Each, gripping boulders with its feet and soaring 50 feet into the air, clings tenaciously just above the walls of a canyon that is scoured by flash floods during winter rains. The unstable climate of Soutehrn California alternates floods and droughts, so the leaves of Ku'w are also drought-adapted, coated by a reflective waxy surface to deflect a portion of the sun's rays and to retain water.  Scarred by fire, these trees have survived the regular wildfires of the Mediterranean dry seasons.   "As summer rainfall disappeared" in the late Miocene, circa 5.3 million years ago, "most deciduous broadleaf species went locally extinct, but California’s oaks survived."
  
  Predation by giant herbivores was the fourth great danger that shaped the oak species into giant survivors.  Ancestors of the oaks began to appear during the Cretaceous period about 100 million years ago in North America, fed upon by dinosaurs such as sauropods. The great height and strength of these trees, along with the spiny needles on their small, hard leaves, are defenses against powerful, tree-ripping herbivores.  Long after the age of dinosaurs, oaks faced the largest land mammals ever known.  The Giant ground sloth Paramylodon, weighing 1,000 kg / 2,200 lbs could reach 10 feet to tear at the branches of trees to consume its foliage, small branches, and acorns.  The prized strength of oak for shipbuilding and architecture evolved to resist even the voracious browsing of 10,000 Kg / 22,000 lb Columbian mammoth, which needed to consume 250 kg, 500 lbs of vegetation per day.

  "Big herbivores have big effects on plants. Beyond the direct impacts of herbivory on the physiology, form and growth of individual plants, herbivores shape plant communities in many ways: by reducing vegetation density and creating gaps; facilitating species coexistence; dispersing seeds; suppressing sensitive species; reducing fire potential by preventing accumulation of dry plant tissue; and accelerating nutrient recycling via urine"Note.

  Quercus forbears of  "today's native species must have been pre-adapted to summer drought and were able to persist in the region as summer rainfall diminished and the climate became more Mediterranean."Note

  Despite its great persistence, oaks did not dominate among the trees of the woodlands of the foothills or the plains of Southern California until the Holocene, with the arrival of Homo sapiens after 10,000 years ago.  “The pattern of nearly continuous expanses of oak woodlands in the Coast Ranges and around the Central Valley is a recent phenomenon. During ice ages low elevation California would have been characterized by coniferous forest. The characteristic Mediterranean climate of California with its oak covered rolling hills has only existed for brief periods during interglacial cycles like the one we enjoy today. " (Mensing 2014: 41).

  Thousands of years of human husbandry alone can explain the oak-dominant foothill woodlands and riparian woodlands. By burning prairie and plains annually to every few years, indigenous Californians created ideal, sub-climax environments for the oaks upon which they came to rely. Especially at the edges of the mountains, fire-husbandry prevented conifers from advancing to lower elevations, where they would otherwise succeed the oaks, overtopping them and blocking their sunlight.  Human fire management not only kept spaces open around oaks: it also increased the reach of the oaks into the open valleys, where savannas (widely-spaced trees) emerged.
  
  The fruit of the oak is the acorn, large meaty and very nutritious, although too bitter with tannic acid  for human consumption until rinsed in water.  Non-human mammals and birds evolved to feed on the abundant acorns throughout the Pleistocene, and the giant canopies of the oaks, like coral reefs or the kelp forests of the coast, became hot-spots of animal diversity.  “Oak woodlands support thousands of under-story plant species, over three hundred species of vertebrates, and thousands of invertebrate species, hosting "complex networks of species interactions and interdependence.”Note. "Valley oaks [Quercus lobata] also created a microclimate for many kinds of understory plants and fungi that only survived under the trees."  One observer reported in 1915 counting "fifty to seventy-five nests of American egrets in the tops of large oak trees along a tributary to the San Joaquin Valley." (Anderson, M. Kat. 2005: 31).   Drawn to the herbaceous open fields for grazing, Deer and other large browsing mammals, such as elk and pronghorns in turn, were attractive prey for larger carnivores such as mountain lions, bobcats, and the omnivorous grizzly bear.
  
  By the time Europeans reached California in the 16th-18th centuries, the landscape and ecology they encountered reflected the ancient work of mammals: first megafauna and then Humans.  European conquerors were amazed by Southern California's open, verdant, park-like appearance, by its large herds of elk and antelope, by the ease of hunting bear, deer, small mammals, and birds.  They thought they were seeing wilderness in a pristine state, a beautiful garden.   A garden it quite literally was: a cultivated, husbanded, tended, and managed ecology, which intensified the biomass and productivity of the region.  The long-lived oak forests of human craft still testify to the grand temporal scale on which this garden had long been tended.