Live Fast and Die Young: Another Message from Fluff the Cottonwood Tree

This is Fluff the cottonwood tree (she/her/hers). I think this is my fifth message that Stan has agreed to post for me on his blog. I live about a half block away from his house in Oklahoma.

I know Stan is the one with the botany Ph.D., but I know a thing or two myself. And today I am going to tell you about the evolution of life cycles.

Cottonwoods like me are the James Deans of the tree world. We live fast and die young. In contrast, many of the oak trees that grow here in Oklahoma, like the post oaks up on Turkey Mountain, live for several centuries. They grow slowly and invest in the future: they have strong wood, for example. They produce large seeds (acorns). They grow in stable forests where long life and big seeds are important in winning the game of competition. But us cottonwoods live along rivers, creeks, and lakes. I live near Joe Creek, a quintessentially Okie name, although it is a rip-rap lined drainage ditch. We cottonwoods do not have a future to invest in.

The margins of rivers, creeks, and lakes are very unstable habitats. Every few years, a major flood will come along and sweep many of us away into the oblivion of death. I am a little luckier than most; I live far up on the bank. But the flood waters almost got me—and Stan’s house—in 2019. Still, the cumulative risk of death from flooding is very great, and it is a rare cottonwood that is able to enjoy his or her hundredth birthday. Why build strong wood, when we do not live very long? And why invest in big seeds to compete against trees, most of which will get swept away in a flood anyway? We live fast and die young. We reach our full height after maybe fifty years. After that, our trunks keep growing but our roots are not very deep. We are just asking to get knocked over in a flood. But even if we do not, we fall over as our weak wood rots away. From where I stand, I can see a house with a new roof. The old one was damaged by one of my fellow cottonwoods falling on it during an unremarkable storm. If you want to plant a tree near your house, you should probably choose an oak instead of a cottonwood.

We reproduce like crazy as soon as we are about fifteen years old, which is young for a tree. We need to get as much reproduction finished as possible, in case we die even sooner than we expect. Stan took this photo of some of my seeds in 2019.

All these characteristics fit together. In order to grow fast, we have large xylem vessels in our wood, which conduct water rapidly to the leaves at the top of the tree. The very fact that we have lots of big, hollow vessels in our wood is what makes the wood weak. Oak trees have stronger wood, but the price they pay for it is slower growth.

I do not recommend the James Dean strategy in general, but my species lives in a habitat in which trees get destroyed quite often. For us, the James Dean approach works very well. The same is true for all species. If a disaster happens frequently, it is better to grow up fast and reproduce early. One such disaster is predators. Research has shown that fishes that live where there are predators will grow fast and reproduce young. But in the absence of predators, they grow larger and more slowly, reproducing later. The same pattern has been observed in opossums. It sounds like a law of nature, a spectrum of life cycles, and I am at the James Dean end of it.

Despite this, trees almost always live longer than animals, even most tortoises. I will probably outlive Stan.

Evotour, part ten. Among the Ancients

I went to Sequoia Park to feel small; I went to the Ancient Bristlecone Pine Reserve to feel young. These bristlecone pine trees (Pinus longeava) are the champions of a type of survival in which organisms live in hostile environments, are just barely alive, grow slowly, but stay alive for a long time. At least, they are the multicellular champions; there are apparently some bacteria that live miles down into the crust of the Earth and metabolize atoms and inorganic molecules and divide once a century. But you will never see them. But you can walk right up to a bristlecone pine that was 2000 years old when Jesus was born, and 1000 years old when Moses fled into the wilderness.

Sequoia trees (see earlier essay) grow quickly when they are young. Bristlecone pines, however, grow slowly from the very start. The park ranger at the reserve showed me a 10-cm-tall eight-year-old bristlecone seedling.

Of course, not all of the bristlecones are over 4000 years old. They represent a whole range of ages, though mostly measured in centuries or millennia. The park personnel do not identify which trees are the oldest, because they do not want humans taking home little souvenirs of the ancient world.

The trees are barely, but very much, alive. Find me a piece of intact 4000-year-old wood that is not inside of a bristlecone pine tree. Of course, their dry, often cold environment helps to preserve them; it is not a place fungi would prosper. But through the ancient trunks there are still xylem rays—with living cells and cell membranes and active transport—that are alive and preserve the wood.

There is a price to pay for rapid metabolism, the kind us mammals have. Our intelligence consumes a lot of food and oxygen, as does our movement and warm blood. That price is a short life. But none of us would trade places with the bristlecones. Disregarding for the moment the Tolkeinian vision of Ents, trees (especially the slowest growing ones) have no awareness or memory of their environments; no wisdom. The idea of a long-lived human (a Methuselah, for example) is a biological fantasy. But as humans we do have some advantages. We live far longer than do other mammals with similar metabolism, and not just because of recent medical advances. We start to fall apart after age 30, which was when most prehistoric people died, but amazingly enough our minds do not fall apart right away. Many of us actually grow more wise and intelligent as we get older, until senescence at last gets us.

I came neither to envy nor to gloat over the bristlecones. I came to humbly experience the possibility of an almost completely different kind of life than my own.