Response of Araucaria angustifolia seedlings to root competition in three different plant communities of southern Brazil

Abstract

The mixed rainforests in southern Brazil are characterised by the presence of a canopy-emergent conifer, Araucaria angustifolia. Experiments were conducted to test the hypotheses that root competition reduces establishment and growth of A. angustifolia in a grassland, Pinus plantation and native forest, and that root competition is more pronounced in the two former communities than in the latter. Seedlings were grown in grassland under three neighbourhood conditions: no neighbours; neighbour roots; and neighbour shoots and roots. In the native forest and Pinus sites, soil trenching was used to alleviate root competition. Plant survival was little affected by treatments and was higher in the Pinussite (77%) than in the others, where ant herbivory (grassland) and pathogens (native forest) caused low survival (46% and 43%, respectively). Plant growth was increased by relief from shoot competition in the grassland and by trenching in the Pinus site.