Deep subsurface water can sustain giant sequoias

Giant sequoias (Sequoiadendron giganteum) are adapted to a narrow ecological niche where they endure long, dry summers, during which their water use may exceed ~2 m3/day. To meet this demand, sequoias rely on subsurface water stores, the volume and distribution of which remains uncharacterized. We use elastic full-waveform inversion and geostatistical rock physics modeling to map and quantify subsurface water content in the Mariposa Grove of Giant Sequoias in Yosemite National Park. Our results show zones of high water content within the upper 2 m of the subsurface near drainages, whereas on hillslopes and ridges, areas of high water content tend to occur deeper or in more isolated zones. Additional analysis of the water content models shows that to avoid water stress throughout the summer, hillslope and ridgetop sequoias probably access substantial volumes of deep ( > 2 m) rock moisture from weathered bedrock, implying that the extensive rooting systems of giant sequoias probe deeper into the subsurface than previously thought. Giant sequoias on hillslopes and ridgetops can access rock moisture stored in weathered bedrock over 2 m deep, helping them avoid summer water stress, suggests a study using hydrogeophysics to quantify subsurface water content in the Yosemite National Park, USA.