Trees Opitimal Life-form
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Are Trees the Optimal Life-form?

385 Million Years of Evolution and Still Going Strong

We turned one of our side lawns into a garden this summer and included two trees in the design — one was a seven-gallon Parrotia. The root ball was not huge, but poor drainage in the clay-bound soil required an extra-large hole. I marveled at both the simplicity and complexity of the tree as we planted it. Roots attach it firmly to mother earth for water and nutrients, and above ground, its leaves harness the energy of the sun to grow. I wondered about the origins of these ubiquitous plants and recalled an article on aspens saying whole groves of them were actually a single living organism springing from a common root mat.

Life crept out of the oceans and onto dry land about 470 million years ago during the Ordovician period. But don’t imagine jungles teeming with tall, exotic trees, vines, and lush flowering plants. Instead, picture a Martian-like landscape with the rocks covered by moss and liverworts. The first Ordovician plants were simple nonvascular organisms, but they had a major impact on the world and may have played a role in the Ordovician-Silurian mass extinction.

Trees, structured like the ones we know today, didn’t appear on the scene until about 385 million years ago — deep roots, a stout bark-covered trunk, and branches supporting a thick cover of green leaves. They probably didn’t look much different from the trees in your backyard or a city park. The period was the middle Devonian, some 130 million years before dinosaurs arrived.

Precisely 384 million years after the first trees evolved, Homo sapiens managed to struggle onto the evolutionary stage. Trees came and stayed, watching millions of animal species arrive and then disappear into the void of extinction. Perhaps they are the optimal complex life-form.

Characteristics of Success

Trees evolved during a period when the climate was warm and relatively stable. Plant evolution was experimenting with various strategies for surviving away from bogs and open water. Competition for resources sparked new approaches, simultaneously sending trees higher above ground and deeper below the surface.

Access to direct sunlight was essential, with fierce competition to grow tall and wide. But extra height induced structural instability, making it difficult for the plants to stay upright. This problem with the physics of gravity facilitated growing both upward and downward, and developing deep root systems to keep the growing mass above the ground from toppling over.

The deep roots also allowed trees to excel at capturing water and nutrients deep below the surface. This deep-root strategy is why mature grapevines send roots as deep as ninety feet into the ground. Well-developed vineyards in the Willamette Valley of Oregon don’t need irrigating during the summer dry season because their deep roots tap into water stored during the previous wet season.

The earliest trees developed survival strategies that were so successful they are still in use 385 million years later. If Homo sapiens are victims of the Anthropocene mass extinction, there is a good chance trees will carry on, thriving in the absence of chainsaws and agricultural deforestation. Poor forest management by incompetent human caretakers will be a problem of the past.

Pinpointing the Change

The rise of trees in the middle to late Devonian was a turning point in Earth’s history. Terrestrial ecology was forever changed, along with climate and geochemical cycles — trees shaped the surface of our planet.

Investigations into paleosol (fossil soil) in the New York Catskill mountains recently uncovered definitive evidence of fossilized root systems from the genus Archaeopteris, Earth’s earliest-known true tree. The preserved evidence shows a highly evolved root system similar to modern-day trees.

The Devonian paleosol, found in an abandoned quarry, provided direct visual evidence of Earth’s first trees. Mapping the spectacular in situ root systems let researchers trace the roots in three dimensions, much like uncovering live tree roots in a roadcut. Outcrops like this one give geologists direct insights into a world long past, providing our own short-lived species with an evolutionary perspective on the importance of the trees we destroy globally at an ever-increasing pace. If Homo sapiens want to be here in another 385 million years, perhaps we should undertake studies on how trees have survived for so long in a sustainable balance with Earth’s ecosystems.

Related Articles:

Invasion of the Ordovician plants (by WM House; ArcheanWeb) 

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Reflections on life’s journey and thoughts on the Tao Te Ching — In Search of a Path

A fictional adventure about the origins of life — The Strings of Life


The 385 Million-Year-Old Tree Roots That Rewrite History (by Richard Milner; Grunge) 

Rise of Trees (Source: Plant Evolution & Paleobotany) 

How Grapevine Roots Grow (Source: Lodi Wine Growers) 

Mid-Devonian Archaeopteris Roots Signal Revolutionary Change in Earliest Fossil Forests (by William E. Stein, Christopher M. Berry, Jennifer L. Morris, Charles H. Wellman, David J. Beerling, and Jonathan R. Leake; Current Biology) 

William House
William is an earth scientist and writer with an interest in providing the science "backstory" for breaking environmental, earth science, and climate change news.