USDA Forest Service (FS) researchers have provided the first proof of concept for a method that allows scientists to study below-ground carbon allocation in trees without destroying them. In the latest issue of the journal Plant, Cell & Environment, Kurt Johnsen and fellow researchers at the FS Southern Research Station unit in Research Triangle Park, NC, describe a reversible, non-destructive chilling method that stops the movement of carbon into root systems.
The photosynthetic process of plants has been estimated to account for almost half of the carbon circulating in the Earth's systems. Reliable data has been developed on carbon cycling in the above-ground processes of trees, but how much carbon is actually moved and stored below the ground has still not been determined. Most methods to study below-ground processes involve destroying the roots as well as the mycorrhizal communities that live symbiotically with root systems.
"Below-ground carbon allocation is one of the least understood processes in tree physiology," says Johnsen. "Being able to accurately measure it is essential for modeling forest and ecosystem productivity and carbon sequestration, but most methods disturb the root-mycorrhizal continuum that plays an essential role in nutrient transport."
One method of estimating below-ground carbon allocation involves girdling the tree, cutting through the phloem to stop the movement of carbon into roots. This method leaves the root-mycorrhizal continuum intact, but still destroys the tree. Johnsen and his fellow researchers decided to try chilling the phloem to temporarily interrupt carbon movement and leave the tree alive. Though the technique has been used on herbaceous plants in controlled environments, Johnsen's experiment represents the first test of the method on trees and, in particular, on large trees in the field.
The researchers chilled the phloem of 10 loblolly pine trees in a stand that receives annual
Contact: Kurt Johnsen
Southern Research Station - USDA Forest Service