PRODUCTIVITY OF 2 DOUGLAS FIR SUBCLOVER/SHEEP AGROFORESTS COMPARED TOPASTURE AND FOREST MONOCULTURES/

Resource sharing between tree and forage plant components in silvopast oral systems includes a complex set of facilitative and competitive in teractions. To the extent that facilitation exceeds competition, agrof orests are expected to outyield monocultures of their components. Past ure and Douglas fir (Pseudotsuga menziesii) tree production of young a groforests was compared to pasture and forest monocultures under both grid and cluster patterns of tree planting near Corvallis, Oregon, USA , during 1983-1987, The height and diameter growth of forest and agrof orest trees was similar, regardless of tree planting pattern. Five-yea r average annual forage production was 6500, 5800, and 2800 kg ha(-1) on pasture, agroforest, and forest plots, respectively. The total cumu lative 1982-1987 above-ground phytomass yield of forage plus trees was similar for pasture and conventional grid forest monocultures. The to tal productivity of agroforests, however, was over 30% greater than ei ther pasture or forest components grown in monoculture. Approximately 1.6 ha (0.96 ha forest + 0.64 ha pasture) of monocultures would be nee ded to equal the productivity of 1 ha of agroforest.