Giant Sequoia trees can be thousands of years old, are the most massive organisms on Earth, and reach astounding heights. But they can’t just keep on getting taller indefinitely, it seems. There are limits. Figuring out these limits and how they shape these giant forests is a main focus of Professor George Koch’s research, featured on the cover of this month’s issue of the prestigious journal, Oecologia. At the tops of the trees, the leaves have just as much nitrogen as leaves lower in the canopy, they have the capacity to photosynthesize at high rates, and they are equally efficient with water. So, what’s missing? It turns out that lifting water against gravity is hard, and it gets harder and harder the higher you go. So at the tops of the giant redwood trees, the leaves are water stressed, and tree height approaches the physical limits imposed by gravity. Confronting such a force of physics, it’s not clear there’s anything these trees can do to grow any taller. Yet, like many humans, their girth continues to increase long after they reach maximum height.
Read the full paper here