This is Science Friday. I'm John Dankosky. I'm in for I Reflated this week.

Big trees are incredibly important to forest ecosystems, capturing carbon, housing animals,

propelling new tree growth and providing much-needed shade. But when I say big trees,

you might be thinking about the biggest trees. You know, giant sequoias or redwoods,

trees that can grow to roughly 25 stories tall. Well, big trees are an essential part of every forest.

These are considered the top 1% of trees in each forest ecosystem, and they play an integral role

in preserving forests all over the world. To help us better understand the wonderful world of

big trees, his ecologist Jim Lutz. He's an associate professor of forest ecology at Utah State

University in Logan, Utah. He also manages three forest dynamics plots in the American West

through the Smithsonian Network. Jim Lutz, welcome to Science Friday. Thanks so much for being here,

and thanks for talking about big trees with us. Well, John, thanks for having me. Let's start off

with some of the basics here. When we're talking about a big tree, what exactly are we talking about

from your perspective? Well, when we look at forests around the world or even around the country,

we have trees of different sizes. Every forest actually has big trees. A good guideline for

where a big tree starts would be about two feet in diameter, but that's not really

always a great comparison. The best comparison is with the trees that are around it,

and really a big tree might be the ones that are the biggest 1% in any forest.

So how old are the oldest big trees, or does it vary widely by the type of tree?

Some of the very long-lived species like the giant Sequoia, or Douglas Farr, or even some oaks,

can live hundreds or thousands of years. Whereas some big trees, perhaps in

eastern US forest, might only be a hundred years old or 150. Why is it that some trees

get much, much bigger while they're neighbors of the same species stay relatively small?

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