Modelling Spanish black pine postdispersal seed predation in Central-eastern Spain

Abstract

A comprehensive knowledge of species ecology and ecosystem dynamics is required when regenerating stands, either naturally or artificially. Silvicultural practices based on forester´s ecperiencies and applied forestry studies had ensured successful forest growth and regeneration over large periods for pine species in the Mediterranean areas. Nevertheless, since the end of the 19th century seedling establishment failures have been reported for Pinus nigra in Central-Eastern Spain regions. The main factors affecting seedling recruitment are diverse and include seed production, seed post-dispersal and predation, and site and physiographic factors. In this research work, we specifically address post-dispersal Spanish black pine seed predation at two different locations, one being the most common and representative location for the species and the other located on areas at their ecological limit of distribution. A modelling approach was employed to analyze the effect of stand and site characteristics and climate variables on the post-dispersal predation process. The generalist feeding habits of post-dispersal seed predator groups (e.g. ants, birds and rodents) and the limited ability of plants either to compensate for or to respond to post-dispersal seed losses indicate that post-dispersal seed predation have a considerable impact on plant population and therefore on the capacity of the stand to preserve its regeneration ability. Our study demonstrates that mast seeding and relative air humidity have significant impact on seed removal by the predators depending on forest location. Further developments include the construction of stochastic models to predict the effects of climate-related variables on seed losses, contributing to reduce uncertainty in post-dispersal Spanish black pine seed predation dynamics and to provide instructive and credible tools to decision-makers and forest managers.