It's easy being green in SLO County after recent rainstorms
Last week’s rains managed to keep most of the Central Coast hills green, but a dramatic change will occur over the next two weeks.
Numerical models are not forecasting any additional rains through the end of April, which is typical for this time of the year. To further increase the rate of drying, a strong area of high pressure is expected to develop about 600 miles to the west of the Central California coast Sunday. This condition will produce moderate gale-force to fresh gale-force (32 to 46 mph) northwesterly winds along the coastal regions of the state during the afternoon hours through Friday, if not longer.
These relentless winds will evaporate huge amounts of moisture from the soil. To compound matters, as the days grow longer and the angle of solar incidence increases, the sun’s energy will further dry the ground while perennial (a plant that lives for more than two years) vegetation and trees will continue to suck up moisture to support increasing amounts of photosynthesis and growth.
All these conditions will come together this week to quickly turn our emerald-green hills to golden brown in a blink of an eye as the mostly non-native grasses die or become dormant. Well adapted to extended periods of dry conditions, these Mediterranean species of grasses will let their above-ground stems and leaves die while their root systems and seeds will wait for the rains to return.
Native perennial grasses, which stayed green through much of the summer, dominated the Central Coast and most of California before the arrival of the first Spanish colonists. Some of the native grasses have root systems that extend 2 to 3 feet into the soil, allowing them to tap moisture farther down in the ground.
The conversion from native species grasses to annual Mediterranean grasses was one of the quickest and most complete type of plant conversions known. Today, about 95 percent of California grasses are non-native.
It’s hypothesized that most of these plants arrived in tall sailing ship ballast, which was mostly rocks and dirt placed deep in the ship’s hull to increase stability by counteracting the ship’s mast. When these ships arrived in California, the vessel’s crew removed much of ballast by dumping it overboard. The grass seeds contained in the ballast floated to shore.
Before this invasion of non-native plants, Central Coast grasslands were shaped by grazing animals, including great herds of elk and deer, which had been a vital part of the state’s grassland ecology for thousands of years. Native grasses can still be found in soil that experience instances of disturbance, for example, near dirt roads or hiking trails.
There is also ample evidence that Native Americans changed the character of the Central Coast landscape with fire. Henry Lewis — an award-winning author, educator and historian — concluded that tribes used fire to burn vegetation for at least 70 reasons. The primary reasons were for hunting, crop management, improving growth yield and controlling pests. The use of fire by Native Americans tended to replace forested land with grassland.
Speaking of fires, this year’s massive amounts of grass and other seasonal vegetation will become abundant fuel for wildfires. For fire safety tips, please visit www.calfireslo.org.
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About 70 percent of the electricity PG&E delivered to its customers in 2016 came from greenhouse gas-free resources like nuclear (Diablo Canyon nuclear power plant) and large hydro. An average of 32.8 percent of its electricity in 2016 came from renewable resources including solar, wind, geothermal, biomass and small hydroelectric power plants.
John Lindsey’s column is special to The Tribune. He is PG&E’s Diablo Canyon marine meteorologist and a media relations representative. Email him at email@example.com or follow him on Twitter: @PGE_John.