Silvicultural Lessons from the 1974 Windthrow in Radiata Pine Plantations near Canberra

Abstract

The extensive withthrow depended on the coincidence of three conditions: (1) the presence of extensive stands made vulnerable through recent clearfelling upwind or thinning after they had grown to a height of about 30 m, (2) the saturation of soils with water, and (3) the occurrence of prolonged, gusty moderately fast winds with gusts of over 50 km/hr and aggregate wind runs exceeding 800 km in two days or 1200 km in three days. Similar or worse weather conditions have occurred at Canberra 4 or 5 times during the 48 years for which meteorological records are available. Extensive windthrow had, however, not been experienced before 1974 because the extensive vulnerable stands had not then existed.