Aliens help each other: possitive associations between Pyracantha angustifolia and Ligustrum lucidum in Central Argentina

TECCO, PA; GURVICH, DE; PEREZ-HARGUINDEGUY, N; CABIDO, M; DÍAZ, S

Porto Alegre, Brasil.

Simposio; 45th Symposium International Association for Vegetation Science; 2002

International Association for Vegetation Science

We studied the influence of the invader shrub Pyracantha angustifolia on the recruitment of exotic and native woody species at mountain shrublands in central Argentina. The study was carried out in a shrubland dominated by P. angustifolia (PYR) and Condalia montana (CON). We recorded all woody species established under the canopy of both shrubs and in absence of shrubs. We compared microhabitat conditions under shrubs, and in absence of it. We found more density of exotic species (0.6 ind m-2) than of native species (0.2 ind m-2). Native seedlings grew mainly in absence of shrub cover (0.4 ind m-2), less under CON (0.24 ind m-2) and under PYR canopy (0.11 ind m-2). Exotic seedlings showed significantly higher density under PYR canopy (0.84 ind m-2), its density decreased under CON and in absence of shrub cover (0.25 and 0.24 ind m-2, respectively). The most abundant species recruiting was Ligustrum lucidum (LIG). The microclimate under shrub canopies differed with open ground in terms of temperature and photosynthetic active radiation. PYR offers a shadier microhabitat compared with CON. This microclimatic difference may explain the high recruitment of exotic shade-tolerant LIG associated with PYR. In other words, the invasion of this shrub in mountain shrublands would be catalyzing the recruitment of other exotic species.