The authors also discovered that trees which would later form root grafts tended to have better growth rates compared with trees that did not form root grafts, even prior to graft formation. Individuals may need to become large enough in order to have enough energy to complete a root graft, or so their root systems are able to come into contact with those of other trees. Conversely, smaller, weaker trees may lack energy to form root grafts, or they may not have very extensive root systems.
So what are some of the advantages of joining root systems with another tree?
"Root grafting could give an evolutionary advantage to the species," said DesRochers. "For example, it could allow well-located trees to support trees that grow in drier or poorer environments. This has been known for herbaceous species that propagate vegetatively, but has rarely been addressed in trees."
Indeed, if the larger trees facilitated acquisition of resources among conspecifics in the stand, they could maintain stand integrity; supplying carbohydrates to suppressed trees could deter tree death that would create gaps in the stand which would then allow other species to invade. Such root grafting behavior could be viewed as the formation of a communal root system, enhancing conspecific growth within the stand. This challenges the typical competition outlook, and could be interpreted as an intraspecific cooperative behavior that maintains stand integrity.
"Interestingly, we also found a couple of root grafts between jack pine and black spruce during the excavation of the sites,"
|Contact: Richard Hund|
American Journal of Botany