Heterogeneity has a critical influence on biodiversity and ecosystem processes. While the influence of heterogeneity on species diversity and abundance is well documented, how heterogeneity influences the distribution and arrangement of necessary resources across a landscape is still unclear. Heterogeneity in vegetation structure and composition is often cited as an important factor in the near‐ground thermal environment; however, because of a paucity of comparative studies across landscapes that differ in their degree of vegetation heterogeneity, researchers lack knowledge of the underlying mechanisms that influence variation in the thermal environment. Particularly, we do not have a clear understanding of the relative contribution of structural and compositional vegetation heterogeneity to thermal patterns. Therefore, we assessed the thermal environment in nine grassland landscapes that differed in their degree of structural and compositional heterogeneity. At the landscape level, we used a variance partitioning approach with linear mixed models to measure the link between four metrics of vegetation heterogeneity and temperature variability. At the microsite level, we used piecewise structural equation models to assess the fine‐scale drivers of temperature in these landscapes and develop a causal model describing the relationship between vegetation variables and temperature. We found that temperature variance at the landscape scale was strongly related to the diversity of plant functional groups, heterogeneity in plant species composition, and variation in vegetation height. At finer scales, species richness, vegetation height, and overhead obstruction were the best predictors of temperature once weather was accounted for. Vegetation composition variables indirectly influenced fine‐scale temperature variation through their effects on vegetation structure. These results suggest that scale has a strong influence on the observed relationship between temperature variance and different metrics of vegetation heterogeneity. Our results provide support for the role of landscape heterogeneity in shaping the thermal landscape and offer insights into the possible impacts of habitat homogenization on the thermal environment.

中文翻译：

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结构和成分的异质性在多个尺度上影响热环境

异质性对生物多样性和生态系统过程具有至关重要的影响。尽管异质性对物种多样性和丰富度的影响已得到充分证明，但异质性如何影响景观中必要资源的分布和安排仍不清楚。植被结构和组成的异质性经常被认为是近地热环境中的重要因素。然而，由于缺乏针对植被异质性程度不同的景观进行的比较研究，研究人员对影响热环境变化的潜在机制缺乏了解。特别是，我们对结构和成分植被异质性对热型的相对贡献没有清晰的了解。因此，我们评估了9个草地景观的热环境，这些草地的结构和成分异质性程度不同。在景观水平上，我们使用带有线性混合模型的方差分区方法来测量植被异质性和温度变化的四个指标之间的联系。在微型站点级别，我们使用分段结构方程模型来评估这些景观中温度的精细尺度驱动因素，并建立描述植被变量与温度之间关系的因果模型。我们发现景观尺度的温度变化与植物功能群的多样性，植物物种组成的异质性以及植被高度的变化密切相关。在更细的尺度上，物种丰富度，植被高度，一旦考虑到天气因素，顶置障碍物就是温度的最佳预测指标。植被组成变量通过影响植被结构而间接影响了精细尺度的温度变化。这些结果表明规模对观测到的温度变化与植被异质性的不同度量之间的关系有很大的影响。我们的结果为景观异质性在塑造热景观中的作用提供了支持，并提供了对栖息地均质化对热环境的可能影响的见识。这些结果表明规模对观测到的温度变化与植被异质性的不同度量之间的关系有很大的影响。我们的结果为景观异质性在塑造热景观中的作用提供了支持，并提供了对栖息地均质化对热环境的可能影响的见识。这些结果表明规模对观测到的温度变化与植被异质性的不同度量之间的关系有很大的影响。我们的结果为景观异质性在塑造热景观中的作用提供了支持，并提供了对栖息地均质化对热环境的可能影响的见识。