By Steven S. Perakis and Julie C. Pett-Ridge
Tree species that form symbioses with nitrogen-fixing bacteria can naturally fertilize forests by converting atmospheric nitrogen gas into plant-available forms. However, other mineral nutrients that plants require for growth are largely locked in bedrock, and are released only slowly into soil. We used strontium isotopes to trace nutrient sources for six common tree species in a temperate rainforest, including one species from a globally widespread genus known for high rates of biological nitrogen fixation. We found that trees capable of fixing atmospheric nitrogen gas were also best able to directly access mineral nutrients from bedrock. This gives nitrogen-fixing trees the unique ability to provide the full suite of essential nutrients required to fuel growth and carbon uptake in forest ecosystems.
In the Microbial Sciences Building at the University of Wisconsin-Madison, the incredibly efficient eating habits of a fungus-cultivating termite are surprising even to those well acquainted with the insect’s natural gift for turning wood to dust.
According to a study published today (April 17, 2017) in the journal Proceedings of the National Academy of Sciences, when poplar wood undergoes a short, 3.5-hour transit through the gut of the termite, the emerging feces is almost devoid of lignin, the hard and abundant polymer that gives plant cells walls their sturdiness. As lignin is notorious for being difficult to degrade, and remains a costly obstacle for wood processing industries such as biofuels and paper, the termite is the keeper of a highly sought after secret: a natural system for fully breaking down biomass.
“The speed and efficiency with which the termite is breaking down the lignin polymer is totally unexpected,” says John Ralph, a UW-Madison professor of biochemistry, researcher at the Great Lakes Bioenergy Research Center (GLBRC) and lignin expert. “The tantalizing implication is that this gut system holds keys to breaking down lignin using processes that are completely unknown.”