Forest Discovery: Trees Trade Carbon Among Each Other
Forest trees use carbon not only for themselves; they also trade large quantities of it with their neighbours. Botanists from the University of Basel report this in the journal Science. The extensive carbon trade among trees – even among different species – is conducted via symbiotic fungi in the soil.
It is well known that plants take up carbon dioxide from the air by photosynthesis. The resulting sugar is used to build cellulose, wood pulp (lignin), protein and lipid – the building blocks of plants. While growing, the tree transports sugar from its leaves to the building sites: to the branches, stems, roots and to their symbiotic fungi below ground (mycorrhizal fungi).
Carbon dioxide shower for trees
Dr. Tamir Klein and Prof. Christian Körner of the University of Basel together with Dr. Rolf Siegwolf of the Paul Scherrer Institute (PSI) now report, that this sugar export goes further than previously thought. In a forest near Basel the researchers used a construction crane and a network of fine tubes to flood the crowns of 120 year old and 40 meter tall spruce trees with carbon dioxide that carried a label. The researchers used carbon dioxide that, compared to normal air, contains less of the rare and heavier 13C atom.
While this modification made no difference for the trees, it allowed the botanists to track the carbon through the entire tree using an atomic mass spectrometer. This way they were able to trace the path of the carbon taken up by photosynthesis from the crowns down to the root tips. The researchers found the labelled carbon not only in the roots of the marked spruce trees. The roots of the neighbouring trees also showed the same marker, even though they had not received labelled carbon dioxide. This included trees from other species.