Invasion of Ligustrum lucidum (Oleaceae) in Southern Yungas of Argentina. Changes on microhabitat properties and avian communities.

AYUP, M; MONTTI, L; ARAGON, MR; GRAU, HR

Mar del Plata

Congreso; 2nd World Conference on Biological Invasions and Ecosystem Functioning; 2011

Ligustrum lucidum is the most important exotic tree in NW Argentina montane forests (Yungas). We assessed the effects of its expanding invasion on avian communities by (1) measuring different habitat properties (forest vertical structure and composition, vegetation cover, light availability, air temperature, air relative humidity and soil litter depth), (2) comparing bird species composition and diversity in Ligustrum-dominated and native-dominated secondary forests and (3) analyzing seasonal patterns and changes in these variables between forest types. The study was conducted during 2010-2011 wet and dry seasons, at two altitudinal zones: 500-800 and 1100-1450 masl. Ligustrum dominated forests had a more homogeneous vertical forest structure with a denser canopy cover (resulting in lower understory solar radiation), a significantly lower understory cover and lower litter depth. Air temperature and relative humidity did not differed between forests in either season. Solar radiation was higher in the dry season in both forest types, but litter depth showed opposite patterns between seasons depending on forest types. We recorded 59 bird species of 21 families. Bird species abundance, richness and diversity indexes were significantly lower in Ligustrum- dominated forests relative to native forests of similar successional age, which had almost twice as many species as the former. Avian community differed between altitudinal levels, but this difference was stronger between Ligustrum and native-dominated forests. Avian community composition was less variable in time and space in native forests than in Ligustrum-dominated forests. Our results suggest that L. lucidum invasion generates structurally homogeneous and simpler forests that represent a less suitable habitat for a diverse avifauna. Our results exemplify the wide range of ecological changes (from habitat properties and ecosystem functioning to large vertebrates’ composition) that subtropical mountain forests of Argentina are experiencing as a result of this invasion.