Production and interaction of pastures and shelterbelts in the central North Island

Abstract

Many New Zealand farms contain shelterbelts which have generally been unmanaged, resulting in dubious shelter benefits and poor log values at harvest. The effect of a 6- and 7-row Pinus radiata shelterbelt on adjacent pasture production was monitored at Matea, Taupo during 1992193. Pasture production was measured at a range of distances parallel'to the shelterbelts on both sides and on open pasture. A 15% increase in pasture production was recorded at 0.7 tree height distance on both sides of the shelterbelts. There was also a gradual trend of increasing dry matter production as distance from the shelterbelts increased. However, on average, the sheltered zone produced slightly less dry matter than the open pasture. Increases in soil and herbage nutrient levels close to the shelterbelt suggest nutrient transfer by animals to the sheltered zones may have occurred. Shelterbelt tree growth was assessed and projected forward to maturity. Merchantable log volume at age 28 years was predicted to be 2300 m3/km of shelterbelt. Based on current log prices the 7-row shelterbelt was estimated at age 28 years to have a net value of $130 000/km Keywords: log value, nutrients, pasture production, pasture composition, Pinus radiata, shelter, shelterbelt, wood yields