Biotic interactions and seed deposition rather than abiotic factors determine recruitment at elevational range limits of an alpine tree

1. Abiotic factors, biotic interactions and dispersal ability determine the spatial distribution of species. Theory predicts that abiotic constraints set range limits under harsh climatic conditions and biotic interactions set range limits under benign climatic conditions, whereas dispersal ability should limit both ends of the distribution. However, empirical studies exploring how these three components jointly affect species across environmental gradients are scarce. 2. Here we present a study that jointly examines these factors to investigate the constraints of the recruitment of Swiss stone pine (Pinus cembra) across and beyond its elevational range in the Swiss Alps. We investigated the natural recruitment of pines and additionally conducted seed transplant experiments to test how much abiotic factors (mean summer and winter temperatures, soil moisture), biotic interactions (understorey vegetation cover, canopy cover, seed predation) and / or seed deposition by the Spotted nutcrack...