Naturalised status of exotic conifers in New Zealand

Abstract

ABSTRACTThis paper provides an assessment of the naturalisation status all exotic conifers present in New Zealand using existing herbarium specimens as qualifiers. A total; of 371 exotic taxa are confirmed as having been introduced for cultivation which represents 63% of world conifers that are non-native to New Zealand. In strong contrast to indigenous conifers, introduced conifers are predominantly from the Pineaceae and Cupressaceae families. Naturalised conifers are a major issue for southern hemisphere countries, this paper confirms a total of 57 exotic conifer taxa as wild in New Zealand, including 15 new taxa described as wild since the last comprehensive update. Conifers from the Rocky Mountain and Eastern Asiatic Botanical Regions are prominent among introduced taxa, but naturalised taxa frequently originate from Madrean and Circumboreal Regions. Many of the taxa previously reported as wild have expanded their New Zealand range considerably since their distributions were last described. Despite these increases, most exotic conifers in New Zealand likely occupy a relatively small proportion of the area in which they could establish. The ongoing naturalisation and spread of exotic conifers illustrate the significant environmental weed threat posed by this group.