EFFECT OF NATURAL ROOT GRAFTING ON GROWTH RESPONSE OF JACK PINE (PINUS BANKSIANA; PINACEAE)

Premise of study: Trees are traditionally considered as distinct entities even though they can share a communal root system through root grafts, which are morphological unions between two or more roots. Little is known regarding the ecological significance of natural root grafting, but because grafted trees can share resources and secondary compounds, growth of linked trees can be affected directly by the presence of root grafts. Traditional forest ecology concepts may have to be revised to include direct interactions between connected trees. Methods: We hydraulically excavated six 30-50-m(2) plots (three natural stands and three plantations). We measured yearly radial growth and determined the influence of root grafting on radial growth of grafted trees. Key results: During periods of root graft formation, root grafting tended to reduce radial growth of jack pine trees, after which growth generally increased. The influence of root grafting on growth was more significant in natural stands, where root grafting was more frequent than in plantations. Conclusions: These results suggest that root grafting initially is an energetically costly process but that it is afterward nonprejudicial and maybe beneficial to tree growth. The use of a communal root system allows for a maximum use of resources by redistributing them among trees, leading to increased tree growth.