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Aims Ligustrum lucidum, native to China, is one of the dominant exotic and invasive tree species in secondary forests in Argentina. (1) We assessed its invasion during 20 yr in post-agricultural secondary forests dominated by native tree species, and (2) evaluated tree demographic rates of native individuals under and away from L. lucidum trees that invaded these forests. Locations Four 1-ha permanent plots of secondary forests, subtropical Andes of Tucumán, Argentina. Methods We quantified the invasion of L. lucidum individuals (≥10-cm diameter) from 1991 to 2011 within four 1-ha plots of secondary forests and analysed annual growth and mortality rates of native tree individuals (≥10-cm diameter) under and away from L. lucidum trees. For this, we compared tree demographic rates of all native individuals together (community level) under and away from individuals of L. lucidum, referred to as exotic and native neighbourhoods, respectively. Then, we described the relative growth rate of native tree species in exotic/ native neighbourhoods (species level) and related them to their demographic life histories and morpho-physiological traits. Results Both density and basal area of L. lucidum increased from 0.1% to 4% between 1991 and 2011. Native tree individuals grew 65% less in exotic neighborhoods compared to native neighborhoods. Relative growth rate showed negative values under L. lucidum individuals for the abundant species Ocotea porphyria, Parapitadenia excelsa, Juglans austalis and Allophylus edulis, indicating competition; while less abundant species Terminalia triflora, Cupania vernalis and Blepharocalix saliscifolius showed positive growth values under L. lucidum, suggesting a facilitation process. Thus, L. lucidum competes efficiently with some native tree species, particularly with those abundant species that dominate the canopy. Conclusions Ligustrum lucidum is invading post-agricultural secondary forests dominated by native tree species. While invading, L. lucidum competes with native abundant tree species that dominate the main structure of the forest canopy. As this invasive trend will likely increase in the near future, L. lucidum may alter forest structure, composition and dynamics, as well ecosystem functioning. [ABSTRACT FROM AUTHOR]

Native and invaded secondary forests are present in sierra de San Javier, the latter dominated by Ligustrum lucidum, which exerts an influence on native biodiversity. We analyzed the influence of the forest dominated by L. lucidum over liana communities compared to native secondary forests without dominance of exotic species. Forests were compared in abundance, composition, climbing mechanisms and distribution in size classes of liana stems. For this, liana stems ⩾ 0.5 cm and the trees ⩾ 10 cm in diameter at height breast, were measured, identified and surveyed in 10 plots located in the yungas piedmont of sierra de San Javier. Native forests had four times more abundance and richness of liana stems than invaded forest of L. lucidum. Individual trees of L. lucidum hosted liana stems in very low abundance, and in the forest dominated by this exotic species, the liana hosts were mainly native trees. Besides the fact that they do not constitute suitable hosts for lianas, they have an indirect influence through the exclusion of native host trees of lianas. [ABSTRACT FROM AUTHOR]

The commensalistic interaction between vascular epiphytes and host trees is a type of biotic interaction that has been recently analysed with a network approach. This approach is useful to describe the network structure with metrics such as nestedness, specialization and interaction evenness, which can be compared with other vascular epiphyte-host tree networks from different forests of the world. However, in several cases these comparisons showed different and inconsistent patterns between these networks, and their possible ecological and evolutionary determinants have been scarcely studied. In this study, the interactions between vascular epiphytes and host trees of a subtropical forest of sierra de San Javier (Tucuman, Argentina) were analysed with a network approach. We calculated metrics to characterize the network and we analysed factors such as the abundance of species, tree size, tree bark texture, and tree wood density in order to predict interaction frequencies and network structure. The interaction network analysed exhibited a nested structure, an even distribution of interactions, and low specialization, properties shared with other obligated vascular epiphyte-host tree networks with a different assemblage structure. Interaction frequencies were predicted by the abundance of species, tree size and tree bark texture. Species abundance and tree size also predicted nestedness. Abundance indicated that abundant species interact more frequently; and tree size was an important predictor, since larger-diameter trees hosted more vascular epiphyte species than small-diameter trees. This is one of the first studies analyzing interactions between vascular epiphytes and host trees using a network approach in a subtropical forest, and taking the whole vascular epiphyte assemblage of the sampled community into account. [ABSTRACT FROM AUTHOR]