Root grafting in Radiata pine stands in the Australian Capital Territory

Root grafting, as indicated by the number of living stumps in thinned stands, is widespread in radiata pine stands in the Australian Capital Territory. Grafting begins when the stands are about 10 years old and increases rapidly to at least 25 years. That live stumps are connected to live trees by root grafts was shown by excavation. Neither initial spacing of trees nor thinning influenced the incidence of root grafting but shallow soils appeared to inhibit it. The radioisotope 86Rb and the dye acid fuchsin were used to demonstrate movement of materials through root grafts from living stumps to living trees; this occurred at rates of 5-25 cm per hour. No movement in the opposite direction nor from live tree to live tree was detected. No evidence was obtained of living stumps affecting the growth of associated trees. Techniques for grafting seedling roots, and preliminary experiments on the movement of substances through such grafts, are described.