Fossils of ancient trees show they bizarrely ripped themselves apart

24 Oct 2017

An ancient tree, unrelated to this recent discovery. Image: HelloRF Zcool/Shutterstock

Fossils from the oldest known trees, dating back hundreds of millions of years ago, reveal a complex biology.

Just as our earliest ancestors looked considerably different to us today, the world’s oldest trees were equally as alien to what we see around us.

In a paper published to the journal Proceedings of the National Academy of Sciences, researchers from Cardiff University, Nanjing Institute of Geology and Palaeontology, and the State University of New York revealed findings from analysis of 374m-year-old tree samples.

Obtained from the oldest known tree in existence, the remains were discovered in north-west China and showed an interconnected web of woody strands within its trunk, much more complicated than any today.

These strands, known as xylem, are responsible for conducting water from a tree’s roots to its branches and leaves.

While most trees today form a single cylinder – leading to the formation of its famous rings – this ancient tree belonged to a group known as the cladoxylopsids, whose xylem was dispersed in strands in the outer 5cm of the tree trunk only.

Tree fossils

An illustrative transverse plane through the small trunk, showing the three naturally fractured parts. Image: Xu and Berry

No tree on Earth as complicated as this

In the middle of the tree trunk, it remained completely hollow with the narrow strands arranged in an organised fashion, interconnected like a finely tuned network of water pipes.

This meant that rather than the tree growing its rings outwards under bark each year, each of the hundreds of individual strands grew their own rings, like a large collection of mini trees.

In this somewhat bizarre and complex system, the tree would accommodate growth by allowing the volume of soft tissues between the strands to increase as they got bigger over time, thereby expanding the tree’s diameter.

As it expanded, another peculiar mechanism appeared in which the woody strands rolled out from the side of the trunk at the base of the tree, forming the characteristic flat base and bulbous shape synonymous with the cladoxylopsids.

Speaking of the research, study co-author Dr Chris Berry said: “There is no other tree that I know of in the history of the Earth that has ever done anything as complicated as this. The tree simultaneously ripped its skeleton apart and collapsed under its own weight while staying alive and growing upwards and outwards to become the dominant plant of its day.

“By studying these extremely rare fossils, we’ve gained an unprecedented insight into the anatomy of our earliest trees and the complex growth mechanisms that they employed.”

Colm Gorey was a senior journalist with Silicon Republic