Differences in plant composition in an Araucaria araucana (Molina) K.Koch and Nothofagus antarctica (G. Forst.) Oerst. forest in a Pinus contorta Douglas ex Loudon invasion gradient

Abstract

Conifers are the most studied group of plants in invasion biology. Outside their natural range, they are capable of causing major community and ecosystem impacts. Pinus contorta, is currently considered one of the world’s most invasive tree species, especially in temperate ecosystems. This study aims to determine if the invaded vegetation differ along a P. contorta invasion gradient in the Malalcahuello National Reserve, located in the Andes of the Araucania Region, south-central Chile. 18 rectangular plots of 100 m2 were established in the invaded area in transects from the seed source to the native forest. Within each plot all pines were tallied when larger than 50 cm in height and their crown projection was recorded, as well as the presence and coverage of all plant species present and their life forms. The results indicate to the establishment of a gradient of invasion and increased richness, abundance and diversity of plant species from the areas closest to the source of seeds (higher invasion) to the native forest. In relation to life forms, only chamaephytes and hemicryptophytes show a significant association to the pine invasion, with lower richness and abundance in areas with higher pine cover. The establishment of pines seems to follow a dispersal Kernel, because the highest density occurred near the original stands and a steady decrease occurs with distance from the seed source. The invasion process in the area is still in development, so it is possible to infer that to progress this situation is expected to reduce species diversity even when the canopy of pines begins to close. This study indicates that P. contorta is capable of reducing plant diversity in mountain areas, especially when invades in high densities. These findings should be considered when controlling th is species. A restoration plan will be required in the areas of the gradient where P. contorta has displaced native species.