Early growth and quality of radiata pine in a silvopastoral system in New Zealand

The effect of different understoreys on the early growth and quality of radiata pine (Pinus radiata) in a silvopastoral system was evaluated in Canterbury, New Zealand. Fitted models successfully represented the effect of understorey on the growth (basal area and height) and a quality of trees (diameter over stubs). Basal area, diameter, height and volume growth were affected by understorey competition. Trees growing with no-understorey had 34%and 29% higher volume than trees growing with lucerne (Medicagosativa) and cocksfoot (Dactylis glomerata)understoreys, respectively. However, the height of trees at age 10 grown without understorey competition was only 9% and 15% more than trees grown with grass and lucerne understorey, respectively. Understorey competition effects on growth became more evident during the summer and early autumn months when water deficits occurred. The quality of trees was also affected by understorey competition. While trees grown in bare ground had higher growth than trees grown with understorey competition, they had the poorest stem quality with higher diameters over stubs, branch size, sweep and proportion of stem defects. This will have an impact on the agroforestry system profitability by affecting the net harvest revenue. This revised version was published online in June 2006 with corrections to the Cover Date.