Exploring the fossilized root network of a 385-million-year-old forest has recently helped scientists reimagine what the world’s first forests might have looked like.
Near the small town of Cairo in New York’s suburbs, beneath a quarry, researchers have reconstructed the remnants of a majestic and mature ancient forest. This was home to at least three of the earliest plant species on Earth.
Some of the initial trees, known as cladoxylopsids, resembled large celery stalks, reaching heights of 10 meters and pointing skyward. Other trees looked like conifers but had fern-like foliage, such as Archaeopteris. The third plant species featured a bulbous base and a crown of fern-like branches, known as Eospermatopteris.
Fossilized tree roots in Cairo, New York.
The seven parallel sections of the Cairo site led researchers to believe that these primitive trees were quite old and large. Consequently, they were not densely packed but rather scattered across a floodplain that was subject to seasonal erosion and flow.
Dry periods were a regular part of the cycle, but the Cairo forest, situated along the Catskill River, appeared to be home to these primitive trees, which were once thought to survive only in swamps or river deltas.
These tree-like plants belonged to the genus Eospermatopteris, resembling tall ferns standing on bulbous trunks.
Because these towering trees had shallow, unbranched roots, they may not have adapted well to drier conditions. Therefore, their presence in the ancient floodplains of Cairo is puzzling.
Previously, scientists had only found evidence of Eospermatopteris in low, wet soil conditions, such as the prehistoric site of Gilboa, also in New York.
However, unlike the swamps of Gilboa, the Cairo site is estimated to be 2 to 3 million years old, and its landscape is quite diverse.
Researchers believe it was once formed from an abandoned channel with a depression that only filled with water during certain seasons.
Eospermatopteris appears to have thrived here for possibly over 16,000 years. Researchers noted that their roots adapted to semi-arid conditions and the potential for brief flooding.
At the research site in Cairo, scientists also found evidence of deeper root systems from extinct conifer-like plants belonging to the genus Archaeopteris. These were more advanced trees than Eospermatopteris, with woody branches and true leaves capable of photosynthesis. They also had deeper roots, sometimes spreading 11 meters wide and reaching depths of 7 meters.
These features were thought to have allowed primitive fern-like trees to escape lowland swamps hundreds of millions of years ago, eventually moving into drier areas like floodplains, where groundwater levels could fluctuate.
However, new findings suggest that even primitive Eospermatopteris, lacking true leaves or deep roots, may have left swamps under drier conditions.
Evolutionary ecologist Khudadad from Binghamton University in New York stated: “This discovery shows that the earliest coniferous trees could thrive in a variety of environments and were not limited to wet conditions. Not only could these trees endure drier environments, but they also adapted to the harsh conditions of the vast clay lands that once dominated the Catskill plains.”
So why do we often see Eospermatopteris dominating prehistoric delta regions while Archaeopteris dominated floodplains?
The reason is that these plants still reproduced using spores rather than seeds, making them more likely to thrive near rivers or water sources that could disperse their genes further.
The authors of the new study suggest that fossil records may be misleading. The prehistoric Cairo forest is believed to have vanished after a prolonged flooding event that submerged the trees and killed them. However, the sediment created afterward may have preserved their roots in a way that is rarely seen in floodplain regions and more commonly found in other areas.
Given the absolute age of the prehistoric Cairo forest, researchers suspect that its structure is unusual. They believe it likely represents mature forests from a time that has not been preserved or explored.
