Spatial patterns of tree recruitment in a relict population of Pinus uncinata: forest expansion through stratified diffusion

The dynamics of tree populations depend on spatial patterns of seed production and recruitment. These patterns result from the succession of different processes, including seed arrival, seedling emergence, establishment and growth (Schupp & Fuentes, 1995). While spatial patterns of seed arrival are determined by the mechanisms of seed dispersal (Nathan & Muller-Landau, 2000), those related to recruitment depend on the interaction of multiple abiotic and biotic factors (Clark et al., 1998, 1999). For instance, spatial patterns of seed rain may depend on the location of parents, but seedling distribution will be affected more by the presence of suitable microsites that control germination and seedling survival. The seminal work of Grubb (1977) emphasized the relevance of the regeneration niche for understanding how Unidad de Recursos Forestales, CITA, Gobierno de Aragón, Zaragoza, Spain, Departament d’Ecologia, Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain, Department of Zoology, University of Toronto, Toronto, Ontario, Canada and Department of Biology, Western Illinois University, Macomb, IL, USA