Data from: Spatiotemporal scaling of plant species richness and functional diversity in a temperate semi-natural grassland

The accumulation of biodiversity in space and time has been modelled extensively using the species-area relationship and the species-time relationship, respectively. Recently, these models have been combined into time-area curves in order to investigate spatiotemporal scaling of species richness. This study expands on previous research by applying these spatiotemporal models to functional diversity. Understanding spatiotemporal dynamics of ecological traits is important due to their crucial role in ecosystem functioning and mediating species responses to environmental change. We present a new function based on the semi-logarithmic species-area relationship, which was applied with a power function to vegetation survey data from Scottish machair grassland for both species richness and two measures of functional diversity. When taking a whole-study approach using non-linear mixed effects models, the semi-logarithmic function used here shows a positive time-area interaction for species richness, contrasting with the negative interaction of the power law found in previous investigations. Although there was a negative time-area interaction for functional diversity measures at the whole-study scale, parameter estimates were inconsistent at the individual site level. Overall, the results reveal differing spatiotemporal dynamics of species and their traits and suggest that the appropriate scale for space-for-time substitutions depends on the aspect of biodiversity being investigated. The new model developed in this study, and the novel application to functional diversity, opens up future possible research into spatiotemporal dynamics of biodiversity.生物多样性在空间与时间维度上的积累规律，已分别通过物种-面积关系（species-area relationship）与物种-时间关系（species-time relationship）得到了广泛建模研究。近期，为探究物种丰富度的时空尺度规律，上述两类模型被整合为时间-面积曲线（time-area curves）。本研究将此类时空模型拓展应用至功能多样性（functional diversity）领域，以此丰富既有研究成果。理解生态功能性状的时空动态至关重要，因其在生态系统功能维持以及调控物种对环境变化的响应中发挥着关键作用。本研究基于半对数物种-面积关系（semi-logarithmic species-area relationship）构建了全新的模型函数，并结合幂函数（power function），将其应用于苏格兰滨海砂质草原（Scottish machair grassland）的植被调查数据，同时分析了物种丰富度与两项功能多样性指标。当采用非线性混合效应模型（non-linear mixed effects models）开展全研究尺度分析时，本研究所用的半对数模型函数在物种丰富度维度呈现出正向的时间-面积交互效应，这与既往研究中幂律（power law）所揭示的负向交互效应形成鲜明对比。尽管在全研究尺度下，功能多样性指标的时间-面积交互效应为负，但在单个样地尺度上，参数估计结果并不一致。综合来看，研究结果揭示了物种及其功能性状的时空动态存在差异，并表明：空间替代时间法（space-for-time substitutions）的适宜尺度，取决于所研究的生物多样性维度。本研究构建的全新模型及其在功能多样性领域的创新性应用，为未来生物多样性时空动态相关研究开辟了新的方向。