A Look Back On the Decade: California Oaks and the Drought
Oak trees are one of the most prolific and common trees throughout California, finding home primarily throughout the northern valley and foothills, be it the endemic blue, canyon-live, or valley variety. With twisting, mighty limbs that extend to curled tendrils, and trunks like that of an ocean liner anchor, residents of the Golden State recognize these trees as a symbol of the state, unlike the palm trees that arise in nearly every media bit about the state. Hardy and enduring, California’s native oaks are no stranger to drought, and tolerate them well. With roots that can reach fifty plus feet deep into the soil, California oaks are able to access underground aquifers when water runs scarce. Though despite the brute-like strength and tolerance these trees possess, the record breaking drought experienced from 2011 until March 15th, 2019 saw a die-off of many oaks throughout the state.
As water reservoir levels hit record lows in 2015 and 2016, underground water simultaneously disappeared. The sources of water that oaks could once depend on even in the worst of drought situations by reaching down their roots, sometimes as far as 80 feet, had essentially been depleted. As years accumulated with not enough rain to replenish these underground aquifers, the trees began to produce signs of stress, some of which were surprising. Blue oaks in some groves were found to have produced a physiological stress signal in response to the drought by dwarfing their leaves. Others became infested with bark beetles as the population of the pest exploded due to the dry weather, perfect for reproduction.
Ring studies conducted on these trees indicated that the 2012-2015 portion of the drought was the most severe drought California had experienced in more than 600 hundred years. From atmospheric scientists to plant scientists to hydrologists, these endemic trees to California served as an important climate signal. They indicated to atmospheric scientists that drought such as the period of 2012-2015 was unprecedented and that the like had not been seen centuries before. Plant and environmental scientists warned that the lack of groundwater supply for the oaks and their subsequent die-off could signal a change in the California vegetation. If extended and record-breaking drought conditions were to continue and be the norm for the areas in which the trees grew, the vegetation would change drastically. The oaks that once signaled the mediterranean climate of the region would cease to exist, with drought-tolerant shrub and bush overtaking such as mesquite. The landscape would slowly turn to become more of a chaparral like that of Southern California as opposed to the temperate mediterranean climate of valley and foothills that Californians knew.
In total, it was estimated that nearly 100 million trees died off in the nearly decade-long drought of California, the majority lying with the different species of oak throughout the state. From a complete dry-out of the underground aquifers to the infestation of bark beetles, oaks suffered from multiple angles and consequences of the drought. Moving forward, as the climate is expected to warm and these periods of extreme drought come to be more commonplace, mass die-offs of these stately organisms are feared, and expected. Climatologists warn that periods of extremes, from wet to dry, will be further and further apart, and more impactful as they do occur resulting from the imbalance. One may deduce that this may spell disaster for the stately trees.
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© 2019 Weather Forecaster Alexis Clouser
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