Productivity in the first seven years of a Pinus radiata-annual pasture agroforest in Western Australia

Abstract

Pinus radiata seedlings were planted into an annual pasture at low, medium and high densities. The trees were pruned annually from year 4 and those with poor form were progressively culled until final stand densities of 75, 150 and 225 trees ha-1 were achieved 7 years after planting. The pastures were grazed by sheep from year 4. The sheep carrying capacities of the pastures declined as tree density increased because of competition between trees and pasture and also because of debris from thinning and pruning. In year 7, under the high density trees, the sheep carrying capacity of the pastures was 73% and light transmission was 69% of that of control pastures (no trees) and debris covered about 22% of the pasture. Diameter growth measurements from year 5 to 7 were 7.65, 7, 45 and 6.35 cm for low, medium and high density of trees respectively, which indicates that competition between trees had commenced at the high density (P<0.05). There was little conflict between the agricultural and forestry components at the low stand density with satisfactory production from both. This system has the potential to generate annual income to offset pine establishment and silvicultural costs while providing another source of income in the long term. It is being tried on farm scale by some landholders wishing to diversify from grazing-only enterprises.