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...1. 非生物因子（abiotic factors）、生物相互作用（biotic interactions）与扩散能力（dispersal ability）共同决定了物种的空间分布格局。现有理论预测，在严酷气候条件下，非生物限制因素将划定物种的分布边界；而在温和气候条件下，分布边界则由生物相互作用决定；扩散能力则会限制物种分布范围的两端。然而，目前针对这三类因子如何共同作用于环境梯度上的物种的实证研究仍较为匮乏。2. 本研究联合考察上述三类因子，以探究瑞士阿尔卑斯山脉境内及超出其海拔分布范围的瑞士石松（Pinus cembra）的更新限制机制。我们既开展了该松树的自然更新调查，同时辅以种子移植实验，以检验非生物因子（夏季与冬季平均气温、土壤湿度）、生物相互作用（林下植被盖度、林冠盖度、种子捕食）以及/或星鸦（Spotted nutcrackers）的种子沉积对其更新的影响程度……