Vegetation successions over 30 years of high country grassland invasion by Pinus contorta

Abstract

The invasion of a high country grassland site (850 m asl) by lodgepole or contorta pine (Pinus conforta, Dougl.) wildings was monitored over 32 years in the Craigieburn Range, Canterbury. The first wildings appeared in 1975. By 1985, density had reached 34,550 stems/ha, with a mean height of 1.85 m and a basal area of 17 m2/ha. By 2007, stocking had dropped to 11,400 stems/ha, with a mean top height of 14.3 m and a basal area of 104 m2/ha. Thirty-eight plant species were present 10 years after wilding invasion started. Twenty-six species (68%) were indigenous. By 2007, the number of species present had dropped to seven, none of which were indigenous. The introduced tussock hawkweed (Hieracium lepidulum) featured in both assessments. It was concluded that more species are likely to invade as the canopy opens up, but if native species are wanted they may have to be introduced by artificial seeding.