music; ambience: birds, wind in leaves; rope whizzing
“Here it is probably about 8:30 in the morning. It’s really neat this time of day; the trees are just starting to get cranking.”
Two-hundred ninety-five feet above the forest floor, ecologist Steve Sillett is near the top of a Redwood: one of the world’s tallest trees. Welcome to Pulse of the Planet’s Science Diaries, a glimpse of the world of science from the inside. This month, a look back and an update on some of our favorite stories.
“The pores in their leaves are opening up. They’re photosynthesizing with the morning light. And they’re evaporating water because the pores are open to take in CO2. Depending on how warm of a day and how much wind there is and if there’s very low humidity, the trees will actually have to shut down to prevent losing too much water, because if they lose so much water the stress inside their sap wood becomes so much that air bubbles will form and shut the tree down and the top will die. So that’s one of the things we’re looking at is how far the trees can push it before they have to shut down. And ultimately the taller the tree, the earlier in the day it has to do this. So eventually there’s going to be a height beyond which the tree can’t really grow and still have a positive carbon balance, meaning it cannot produce enough sugars through photosynthesis to continue growth. Pretty neat.”
After collecting his data at the top of the tree, Steve is ready to descend with the help of ropes and a harness.
“Okay, on the way down, starting at 90 meters (Rappelling and whizzing sound of rope) Thirty Ten Touchdown.”
Steve Sillett’s latest research shows that as a tree ages, its proportion of disease-resistant heartwood increases, meaning that older forests are more effective than younger ones at pulling carbon from the atmosphere, debunking a commonly held belief that trees become unproductive with age.
Pulse of the Planet’s Science Diaries are made possible by the National Science Foundation. I’m Jim Metzner.