Data from: Performance of forest bryophytes with different geographical distributions transplanted across a topographically heterogeneous landscape

Most species distribution models assume a close link between climatic conditions and species distributions. Yet, we know little about the link between species' geographical distributions and the sensitivity of performance to local environmental factors. We studied the performance of three bryophyte species transplanted at south- and north-facing slopes in a boreal forest landscape in Sweden. At the same sites, we measured both air and ground temperature. We hypothesized that the two southerly distributed species Eurhynchium angustirete andHerzogiella seligeri perform better on south-facing slopes and in warm conditions, and that the northerly distributed species Barbilophozia lycopodioides perform better on north-facing slopes and in relatively cool conditions. The northern, but not the two southern species, showed the predicted relationship with slope aspect. However, the performance of one of the two southern species was still enhanced by warm temperatures. An important reason for the inconsistent results can be that microclimatic gradients across landscapes are complex and influenced by many climate-forcing factors. Therefore, comparing only north- and south-facing slopes might not capture the complexity of microclimatic gradients. Population growth rates and potential distributions are the integrated results of all vital rates. Still, the study of selected vital rates constitutes an important first step to understand the relationship between population growth rates and geographical distributions and is essential to better predict how climate change influences species distributions.多数物种分布模型均假定气候条件与物种分布之间存在紧密关联。然而，学界对物种地理分布与种群表现对局地环境因子的敏感性之间的关联仍知之甚少。我们以瑞典一处北方针叶林（boreal forest）景观内的南、北朝向坡地为移栽样地，开展了3种苔藓植物（bryophyte）的种群表现研究，并同步在上述样地测定了空气与地表温度。我们提出如下假说：南部分布的两个物种Eurhynchium angustirete与Herzogiella seligeri在南朝向坡地及温暖环境中表现更优；北部分布的物种Barbilophozia lycopodioides则在北朝向坡地与相对凉爽的环境中表现更佳。仅北部分布物种呈现出与坡向相符的预期关联，两个南部分布物种则未表现出该规律。但其中一个南部分布物种的种群表现仍会因温度升高而得到提升。导致该结果不一致的一个重要原因在于，景观内的微气候梯度极为复杂，且受诸多气候强迫因子的影响。因此，仅通过对比南、北朝向坡地，或许无法完整反映微气候梯度的复杂性。种群增长率与潜在分布是所有生活史参数的综合结果。不过，针对特定生活史参数的研究仍是理解种群增长率与地理分布之间关联的重要切入点，同时也可为更精准地预测气候变化如何影响物种分布提供必要支撑。