ROOTING DENSITY AND TREE SIZE OF PINUS-RADIATA (D-DON) IN RESPONSE TO COMPETITION FROM EUCALYPTUS-OBLIQUA (LHERIT)

Nine plots were set up in even-aged Pinus radiata plantations invaded by Eucalyptus obliqua to investigate the effect of below-ground competition from E. obliqua on P. radiata. The plots had different densities of E. obliqua. Individual trees in each plot were measured and mapped. Density contour maps of E. obliqua were made to show four different levels in the stands. Samples at three soil depths from each density level were taken to estimate the rooting density of both species. As the rooting density of E. obliqua increased, the rooting density of P. radiata decreased. This happened at all soil depths. The decrease in rooting density was closely related to the decrease in above-ground tree size of P. radiata. The results highlighted the importance of weed control in the early development of P. radiata stands.