Centuries Old and Busily Adapting

Peripheral (left) and axial (right) leaves - Chron photo

Redwood trees have been studied for over a century by scientists, lumber companies, and environmentalists. The groups have different agendas, of course, but no one was expecting surprising new knowledge to arise, such as the functioning of their leaves.

The trees’ peripheral leaves, like those on most trees, are food producers that convert sunlight into sugar through photosynthesis. But the axial leaves serve an entirely different role, researchers found — absorbing water...

According to the [UC Davus] study, published in the American Journal of Botany, a large redwood can absorb 14 gallons of water in just the first hour after its leaves become wet...

In some trees, when leaves get wet, they inhibit the photosynthesis process, the study found, But in redwoods, the different leaf types allow photosynthesis to continue — even in the rain and fog.

“Having leaves that aren’t for photosynthesis is in itself surprising,” said Alana Chin, a doctoral student in ecology at UC Davis and lead author of the study. “If you’re a tree, you don’t want to have a leaf that’s not photosynthesizing unless there’s a very good reason for it.”

The study also found that redwoods can change the location of their leaves depending on the climate. Along the west North Coast, water-absorbing leaves are found on the lower branches, leaving the upper branches for the sun-collecting and photosynthesizing leaves. In drier southern areas, the opposite is true with the water-gathering leaves near the tops of the trees where they can catch more rain and fog.

Muir Woods redwoods, 2007

Redwoods have not only developed specialized axial leaves to absorb water, but they move them higher or lower depending on climate conditions.

Walking through a redwood forest is a near-mystical experience. The coolness, the quiet, the towering trees, and even the forest smells are far removed from the urban and suburban worlds where most park-goers dwell.

But the interior life of the redwoods is not so quiet. They're observing and adapting to the changing weather in order to survive. To the science-minded, like your humble blogger fancies himself to be, that makes us appreciate them even more.