Native plant species richness in non-native Pinus contorta forest

Abstract

Pinus contorta (lodgepole pine) is invasive in many southern hemisphere countries, having spread extensively from original plantings. It is widely controlled to limit its spread and negative impacts, and is generally assumed to have little value for native plant biodiversity. We surveyed vegetation in two stands of montane wilding P. contorta forest, and recorded a subcanopy of more than 50 native plant species from 35 genera, including trees, shrubs, ferns, and orchids. Canopy openness ranged between 5 and 20% and was positively related to native plant species richness at both sites. Native plant species richness was negatively related to P. contorta stem density at one site but not the other, where richness was positively related to soil available phosphorus concentrations. A diverse native subcanopy in wilding P. contorta forest may represent an important seed source for further native regeneration in invaded areas. Pinus contorta control methods that minimise disturbance to the native subcanopy may be prudent if a return to native vegetation is a long-term management goal.