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 three. Parkfield Road, or, Skipping Across Crustal Plates

I spent the afternoon of my 55^th birthday driving up a lonely road between expansive cattle pastures in the coastal mountains of California. There were few other vehicles. As I climbed the hill, grasslands gave way to savannas of valley oak (Quercus lobata) interspersed with digger pine (Pinus coulteri). Some of the oaks were massive. My goal was near the town of Parkfield, which is so small that you cannot be sure if you have passed through it. I was looking for a little bridge.

I found the bridge. It spanned over what looked like a little arroyo with cattails and willows (Salix lasiolepis) in the tiny bit of water at the bottom. But it was no ordinary arroyo. It was the San Andreas Fault. According to geological websites, the Parkfield bridge is the only bridge in the world that connects two continental plates. This may or may not be true; several highways, including state routes 46 and 41, must also cross this fault. And the fault has several branches. But this is the only place where a sign proclaims, “San Andreas Fault: entering North American Plate” on the west side, and “entering Pacific Plate” on the east.

This was an irresistible geological and evolutionary pilgrimage, one at which I made one of my Darwin Youtube videos, because continental drift has revolutionized our understanding of the world. Crustal plates constantly move; the Pacific Plate is moving northwest at the pace that fingernails grow. Usually it does not move at all, but as pressure builds up the plate lurches, causing an earthquake. This has not happened recently at Parkfield. Therefore it is not a deep chasm into which you can look and see hell; its recent immobility has allowed sediments to fill it in. The continents, consisting of lighter rock, are thrown around by the crustal plates. Geology has never been the same since the discovery of continental drift. Neither has evolution. We now understand one of many processes that separate an ancestral species into separate populations, allowing them to diversify into new species. The population can be divided as a crustal plate carries part of it away.

There is a story of cultural evolution going on in nearby Cholame, which is just a restaurant on Highway 46. At this location in 1955, James Dean died in a car crash. To many of us, James Dean was not that great of an actor; a friend of mine said he always had a constipated look on his face. But he became a hero in Japan. A Japanese man, Seita Ohnishi, donated money to construct a granite monument around a tree-of-heaven near the restaurant. He compared Dean’s untimely death to the death of cherry blossoms (what else?) at the prime of their beauty. Seita Ohnishi was not speaking just for himself, but for thousands of Japanese. Now, you might guess I will tie this in with evolution somehow. James Dean left a cultural legacy, more so in Japan than in America, which has far exceeded any biological fitness he might ever have had. Culture is not unique to humans, but it is a unique form of human evolutionary fitness.

I found a restaurant in Paso Robles (El Paso de los Robles, Oak Pass), Big Bubba’s Bad BBQ (bad here meaning good, like a retinal afterglow), which offered a free birthday meal. What perfect timing. All I had to do was to allow myself to be regaled by a birthday chant and have my picture taken.

I have now posted the YouTube video of Darwin walking over the San Andreas fault.

Note: Someone posted a comment on a previous entry, but when I click on it, my computer goes into an unresponsive mode. I have not read the comment but I suspect that someone has inserted a virus. Beware!  Update: The problem was apparently a computer glitch caused by Google. The comment was not a virus.