When lightning caused fires around California's Big Basin Redwoods State Park north of Santa Cruz in August 2020, the fire spread quickly. Mild fires strike coastal redwood （红杉） forests about every decade. The giant trees resist burning thanks to the bark （树皮）， up to about 30 centimetres thick at the base, which contains acids. Their branches and needles are normally beyond the reach of flames. But this time flames shot through the top of 100-metre- tall trees, burning the needles. "It was shocking, " says Drew Peltier, a tree expert at Northern Arizona University. "It really seemed like most of the trees were going to die.
Yet many of them lived. In a paper published yesterday in Nature Plants, Peltier and his colleagues help explain why: The survivors use long-held energy reserves-sugars that had been made from sunlight decades earlier—and poured them into buds （芽） that had been lying dormant （休眠的） under the bark for centuries.
"This is one of those papers that challenges our previous knowledge on tree growth, " says Adrian Rocha, an ecosystem ecologist at the University of Notre Dame. "It is amazing to learn that carbon taken up decades ago can be used to sustain its growth into the future. "The findings suggest redwoods have the tools to cope with big fires driven by climate change, Rocha says. Still, it's unclear whether the trees could cope with the regular infernos that might occur under a warmer climate environment.
The fire in 2020 was so intense that even the top branches of many trees burned and their ability to photosynthesize （光合作用） went up in smoke along with their pine needles. Trees photosynthesize to create sugars and other carbohydrates （碳水化合物）， which provide the energy they need to grow and repair tissue. Trees do store some of this energy, which they can call on during a drought or after a fire. Although the redwoods have sprouted （长出） new growth, Peltier and other forest experts wonder how the trees will cope with far less energy from photosynthesis, given that it will be years before they grow as many needles as they had before the fire. "They're alive, but I would be a little concerned for them in the future. "
