How california’s giant sequoia responds to draught

California recently experienced an unprecedented 5-year drought (2012-2016) that led to declining growth rates and increasing mortality levels in many trees and forests throughout the state.

APRIL 2018


In 2015 a research team launched a study to monitor and assess the impact of this historic drought on iconic giant sequoias, the largest and among the tallest and oldest trees in the world, found only in small, isolated groves in the Sierra Nevada mountains of California. This project involves measuring the water status and leaf physiology of ancient sequoia monarchs, and linking these measurements with field surveys and airborne data collected across the landscape. These leaf-to-landscape level measurements provide estimates of the intensity of drought-stress experienced by these trees and insights into the mechanisms and spatial patterns of sequoia drought response within and across groves. We found that during the drought giant sequoia trees suffered water stress at levels that approached or exceeded several physiological thresholds.

Au chevet des séquoïas de Californie

However, sequoias not only closed the tiny pores in their leaves (called stomata) but also produced tougher, more drought resistant leaves and shed unusual amounts of foliage. These leaf and crown-level adjustments allowed sequoias to effectively reduce water loss to the atmosphere, which helped them to maintain their overall health and avoid widespread mortality. Giant sequoia drought responses varied spatially and corresponded to site water balance characteristics. Recent measurements indicate that sequoias appear to be recovering from the drought after a wet 2016-2017 winter, but additional measurements are needed to evaluate long-term drought impacts on tree health. Understanding the effects of severe drought, including where on the landscape forests are more or less vulnerable to these events, is critical to help resource managers proactively prepare for the future.

Anthony Ambrose, project leader:

Anthony Ambrose

“Giant sequoia trees are precious natural treasures and have awed and inspired generations of people from all over the world. The support of the Petzl Foundation in 2017 has been essential to our project by allowing us to continue to monitor and assess drought impacts on giant sequoias during a critical post-drought recovery period. This information forms the basis for understanding and mapping giant sequoia drought responses which will help managers to effectively protect and conserve these iconic trees into the future.”

Uploaded in April 2018


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