Below ground transfer of carbon between trees and common mycelial networks
Paper birch and Douglas-fir form the mycorrhizas with many of the
same fungi both in the field (Jones et al. 1997) and in the greenhouse
(Simard et al. 1997c). In her Ph.D. thesis, Suzanne Simard established
that 13C or 14C fixed by young Douglas-fir and paper birch was
transferred below ground between the two species in the field (Simard
et al. 1997a). Although transfer occurred in both directions, net
transfer was from paper birch to Douglas-fir and this was accentuated
by shading Douglas-fir. Ecologically significant amounts of C were
transferred from birch to Douglas-fir. This challenges many of our
assumptions of how plants interact belowground.
Ectomycorrhizal fungi appeared to facilitate this transfer because lower levels of isotope were detected in western redcedar planted equidistant from birch and Douglas- fir. The western redcedar had arbuscular but not ecto-mycorrhizas. A laboratory study on the same two plant species found that carbon transfer was reduced three-fold when hyphae growing between the two root systems were severed. Due to high variability, this difference was not significant (Simard et al. 1997b).
There are many unresolved questions about below ground carbon transfer in this system.
- How much of the transfer occurs entirely within common mycelial networks vs via a soil route?
- Which compounds are transferred?
- Is the direction of transfer influenced by the phenology, size, and distance apart of the two trees?
- To what extent does below ground carbon transfer occur amongst other ectomycorrhizal tree species in the Interior Cedar Hemlock zone?
- How important are common mycelial networks in seedling establishment in dry interior zones?
- How extensive are mycelial networks in forests of different ages?
Last reviewed 4/8/2015 12:31:10 PM