Demographic model for Aleppo pine invading Argentinean grasslands

Abstract

Biological invasions represent one of the most significant threats to the conservation of biological diversity. Understanding the population dynamics of an invasive species is essential to detecting key components that allow the development of an effective management strategy. South American Pampas are particularly vulnerable to the invasion by alien woody plants that threaten the last remnants of native biodiversity. Aleppo pine (Pinus halepensis) invades mountain grasslands in southern Buenos Aires province, Argentina, where it changes the structure and dynamics of the whole ecosystem. We combined information on the biology of the species in its native range with our data in the invaded area to develop a population model aimed at understanding the invasion process and detecting key parameters associated with its success. A 12 × 12 stage-structured matrix model was used to describe the dynamics of the species in the area, through deterministic and stochastic projections. Population growth rates were greater than one for both types of projections, in accordance with its invasive capacity in the area. Elasticity analysis highlights the contribution of survival at the first adult stage (seven to 14 years) to the population growth rate, and in this way, draws attention to this stage when developing a species control strategy. Aleppo pine shares key biological characteristics with other high-impact invasive pine species in Argentina and other countries in the Southern Hemisphere. These similarities include the presence of serotinous cones and an abundant seed bank in the canopy, recruitment conditioned by competition in the regeneration niche, and a relatively short juvenile period. In this way, the model developed in this work could be easily adjusted for similar situations involving invasive congeners in other grassland ecosystems.