New Kind of WoodCould Be the Climate Hero We’ve Needed
- Trees are typically organized into two categories: hardwoods (angiosperms) and softwoods (gymnosperms).
- A new study suggests that there is a third type of wood—known as “midwood”—that could explain the nanoscale architecture of the tulip tree (Liriodendron tulipifera), which contains structural elements whose size is squarely in between hardwood and softwood.
- Because tulip trees grow quickly and are surprisingly efficient at storing carbon, the researchers hope that further study could help us unlock their secrets and potentially breed tulip tree-like wood into other species for carbon capture purposes.
Liriodendron tulipifera, more commonly known as the tulip tree or yellow poplar, is one of the most beautiful trees in North America. A member of the magnolia family, this fast-growing tree—putting on average 25 inches per year until reaching a height of around 150 feet—sports distinctive leaves, and its wood is used purposes ranging from furniture to toys and musical instruments. Most importantly, the tree is a carbon capture champion, and is estimated to soak up two to six times more carbon in forests where it is the predominant species. But what exactly makes it so carbon hungry?
To answer this question, scientists from the University of Cambridge and Jagiellonian University in Poland analyzed the nanoscale architecture of the secondary cell wall (read: wood) in hydrated samples of the tree using a technique called “low-temperature scanning electron microscopy.” What they discovered upends the very basics of how scientists identify trees. The results of the study were published in the journal New Phytologist.
“Our survey data has given us new insights into the evolutionary relationships between wood nanostructure and the cell wall composition, which differs across the lineages of angiosperm and gymnosperm plants,” Raymond Wightman, a co-author of the study from the University of Cambridge, said in a press statement. “Angiosperm cell walls possess characteristic narrower elementary units, called macrofibrils, compared to gymnosperms.”
Angiosperms—usually deciduous trees (oaks, birches, and maples) that produce seeds protected by fruit—are considered hardwoods. Gymnosperms, on the other hand, are softwoods, include such categories as cone-producing conifers. According to this study, hardwood angiosperms typically have macrofibrils (filaments made of cellulose) around 15 nanometers in diameter, whereas macrofibrils in softwoods measure around 25 nanometers.
The tulip tree, along with its Chinese native relative (Liriodendron chinense), are usually considered hardwoods. But, strangely, both species have macrofibril sizes that fit squarely in the middle of these two tree types.
“We show Liriodendrons have an intermediate macrofibril structure that is significantly different from the structure of either softwood or hardwood,” Jan Łyczakowski, a co-author of the study from Jagiellonian University, said in a press statement. “Liriodendrons diverged from magnolia trees around 30-50 million years ago, which coincided with a rapid reduction in atmospheric CO2. This might help explain why tulip trees are highly effective at carbon storage.”
Sticking with the traditional naming convention, the researchers propose the existence of a third type of wood, known as “midwood.” In an article published in The Conversation this week by Łyczakowski and Wightman, they explain that when these trees first evolved, atmospheric CO2 fell from 1,000 parts per million (ppm) to roughly 500 ppm. This likely caused the tree to develop methods for more effective carbon capture, essentially transforming it into the perfect tree to help combat our current climate crisis.
This insight could help scientists more effectively capture carbon in plantation forests, or even breed tulip tree-like wood into other species to increase their carbon appetite. For now, this new type of wood raises questions about what other trees might have similar “midwood” attributes, and if they too hold secrets that could help us battle against a warming world.
“We can no longer assume, when looking at a previously unstudied tree, that it falls into the same two categories (softwood or hardwood) scientists have placed trees in for years,” the researchers wrote for The Conversation. “We are now looking at whether its seemingly unique wood structure is the sole reason it is king of carbon capture, and we are widening our search to find out if there are any more midwood trees—or even more new wood types out there.”
Darren lives in Portland, has a cat, and writes/edits about sci-fi and how our world works. You can find his previous stuff at Gizmodo and Paste if you look hard enough.