Carbon transfer

The classic method: feed a donor tree air enriched in the isotope ¹³C, then look for it in a nearby recipient tree.

The calculation

The share of recipient carbon that came from the donor is

$$f = \frac{\delta^{13}C_{\text{recipient}} - \delta^{13}C_{\text{control}}}{\delta^{13}C_{\text{donor}} - \delta^{13}C_{\text{control}}}$$

where the control is a similar tree with no network link to the donor.

The catch

A rise in $\delta^{13}C$ shows carbon arrived. It does not show it came through the fungus: it could move through soil water or root grafts instead. Studies that cut the hyphae with mesh barriers are the better test.

Back to Mycorrhizal networks · next: How nutrients move