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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]

Background and aims: Alien success has frequently been associated with changes in the concentrations of soil nutrients. We aim to investigate the effects of plant invasion on soil nutrients, potential enzyme activity and litter elemental composition and stoichiometry. Methods: We compared stands of secondary forest invaded by Ligustrum lucidum and those dominated by natives, and performed litter chemical analyses on 3 native and 2 exotic tree species. Results: Soils of invaded sites had 20 and 30 % increase in β-glucosidase and alkaline phosphatase activity, higher Olsen-phosphorus (P) and potassium (K) concentrations and lower nitrogen (N) concentration and N:P, N:K and ammonium:Olsen-P ratios. Invaded and non-invaded sites differed in their overall nutrient composition and enzyme activity. Natives and exotics differed in nine of the 16 litter elemental composition and stoichiometry variables analyzed. Conclusions: The low N:P ratio in litter, the decrease in soil N in invaded stands and the low N concentration of exotics suggest that N is the limiting nutrient and that exotic success is related to higher N uptake and use efficiency. The higher investment in the acquisition of soil resources, higher nutrient uptake and use efficiency of limiting nutrients contribute to the success of exotics in this subtropical forest. [ABSTRACT FROM AUTHOR]

Abstract: Invasions of exotic tree species can cause profound changes in community composition and structure, and may even cause legacy effect on nutrient cycling via litter production. In this study, we compared leaf litter decomposition of two invasive exotic trees (Ligustrum lucidum and Morus sp.) and two dominant native trees (Cinnamomum porphyria and Cupania vernalis) in native and invaded (Ligustrum-dominated) forest stands in NW Argentina. We measured leaf attributes and environmental characteristics in invaded and native stands to isolate the effects of litter quality and habitat characteristics. Species differed in their decomposition rates and, as predicted by the different species colonization status (pioneer vs. late successional), exotic species decayed more rapidly than native ones. Invasion by L. lucidum modified environmental attributes by reducing soil humidity. Decomposition constants (k) tended to be slightly lower (−5%) for all species in invaded stands. High SLA, low tensile strength, and low C:N of Morus sp. distinguish this species from the native ones and explain its higher decomposition rate. Contrary to our expectations, L. lucidum leaf attributes were similar to those of native species. Decomposition rates also differed between the two exotic species (35% higher in Morus sp.), presumably due to leaf attributes and colonization status. Given the high decomposition rate of L. lucidum litter (more than 6 times that of natives) we expect an acceleration of nutrient circulation at ecosystem level in Ligustrum-dominated stands. This may occur in spite of the modified environmental conditions that are associated with L. lucidum invasion. [Copyright &y& Elsevier]