title: Pine invasions in treeless environments: dispersal overruns microsite heterogeneity.
abstract: Understanding biological invasions patterns and mechanisms is highly needed for forecasting and managing these processes and their negative impacts. At small scales, ecological processes driving plant invasions are expected to produce a spatially explicit pattern driven by propagule pressure and local ground heterogeneity. Our aim was to determine the interplay between the intensity of seed rain, using distance to a mature plantation as a proxy, and microsite heterogeneity in the spreading of Pinus contorta in the treeless Patagonian steppe. Three one-hectare plots were located under different degrees of P. contorta invasion (Coyhaique Alto, 45° 30'S and 71° 42'W). We fitted three types of inhomogeneous Poisson models to each pine plot in an attempt for describing the observed pattern as accurately as possible: the "dispersal" models, "local ground heterogeneity" models, and "combined" models, using both types of covariates. To include the temporal axis in the invasion process, we analyzed both the pattern of young and old recruits and also of all recruits together. As hypothesized, the spatial patterns of recruited pines showed coarse scale heterogeneity. Early pine invasion spatial patterns in our Patagonian steppe site is not different from expectations of inhomogeneous Poisson processes taking into consideration a linear and negative dependency of pine recruit intensity on the distance to afforestations. Models including ground-cover predictors were able to describe the point pattern process only in a couple of cases but never better than dispersal models. This finding concurs with the idea that early invasions depend more on seed pressure than on the biotic and abiotic relationships seed and seedlings establish at the microsite scale. Our results show that without a timely and active management, P. contorta will invade the Patagonian steppe independently of the local ground-cover conditions.
authors: Laboratorio de Invasiones Biológicas Facultad de Ciencias Forestales Universidad de Concepción Victoria 631, Casilla 160-C Concepción Chile; Institute of Ecology and Biodiversity (IEB) Las Palmeras 3425 Ñuñoa, Casilla 653 Santiago Chile.
authors: Aníbal
authors: A
authors: Pauchard
authors: Biodiversity and Conservation Unit Department of Sciences King Juan Carlos University c/Tulipán s/n. 28933 Móstoles Madrid Spain.
authors: Adrián
authors: A
authors: Escudero
authors: Laboratorio de Invasiones Biológicas Facultad de Ciencias Forestales Universidad de Concepción Victoria 631, Casilla 160-C Concepción Chile; Institute of Ecology and Biodiversity (IEB) Las Palmeras 3425 Ñuñoa, Casilla 653 Santiago Chile.
authors: Rafael A
authors: RA
authors: García
authors: Biodiversity and Conservation Unit Department of Sciences King Juan Carlos University c/Tulipán s/n. 28933 Móstoles Madrid Spain.
authors: Marcelino
authors: M
authors: de la Cruz
authors: Programa Conservación de Flora Bioforest SA Camino a Coronel km 15 S/N Concepción Chile.
authors: Bárbara
authors: B
authors: Langdon
authors: Institute of Ecology and Biodiversity (IEB) Las Palmeras 3425 Ñuñoa, Casilla 653 Santiago Chile; Departamento de Botánica Facultad de Ciencias Naturales y Oceanográficas Universidad de Concepción Casilla 160-C Concepción Chile.
authors: Lohengrin A
authors: LA
authors: Cavieres
authors: Laboratorio de Invasiones Biológicas Facultad de Ciencias Forestales Universidad de Concepción Victoria 631, Casilla 160-C Concepción Chile; Institute of Ecology and Biodiversity (IEB) Las Palmeras 3425 Ñuñoa, Casilla 653 Santiago Chile.
authors: Jocelyn
authors: J
authors: Esquivel
keywords: Invasibility; Pinus contorta; plant–plant interactions; propagule pressure; spatial patterns; tree invasions