Field of Science

Trees changed almost everything

A recent publication in geology (this link takes you to the SciAmer news, not the publication directly) reports that rivers changed significantly because of the evolution of trees. Although rivers vary significantly, they were broad and shallow with wandering courses prior to the evolution of trees where upon these larger plants with deeper roots which could hold more soil began restricting rivers to narrower, and therefore deeper, channels. So it comes as no great surprise that many flood prone areas are often the result of deforestation. Rivers are certainly not the Phactor's cup of tea, but trees are. It's hard to imagine Earth without its mantle of forests and soil, although it certainly isn't what it used to be. This story takes you back to the Devonian, a smallish geological period, just under 60 million years in duration beginning 416 million years ago. At the beginning of the Devonian one group of vascular plants existed and they ranged in size from about the length of your little finger to a full hand span, tip of the thumb to tip of the little finger, and they were the biggest plants on land! But by the end of the Devonian not only had plants diversified considerably, but the first aborescent plants appear, pseudosporochnalean cladoxylopsids. About 10 million years later the first true trees (Archaeopteris) appeared right at the end of the Devonian. The former grew like tree ferns while the latter had a branching crown, and you need more an more anchoring to keep bigger plants standing upright. The next geological period, the Carboniferous, the dominate land plants were aborescent forms of clubmosses, horsetails, and ferns, and these, along with the early seed plants, pteridosperms, formed the forests that changed the form of rivers.


Colin Wilson said...

In case you haven't heard, woody plants older than the one you referenced have recently been identified.

The Phytophactor said...

Thanks for the heads up. I had not seen that report of early Devonian woody plants, not trees, but certainly woody.