Abstract Spatial environmental heterogeneity (EH) is an important factor determining species richness among many taxa across spatial scales. Increased EH may support higher diversity mainly by providing a higher number of ecological niches. However, the shapes of the EH-diversity relationships and their influence on diversity measures at landscape scales are poorly understood. We used random forests regression models to assess the relationships between different components of EH and bird species richness across Great Britain. Bird data were obtained using BTO/JNCC/RSPB Breeding Bird Survey methods across 335 UK Countryside Survey (CS) 1-km squares in 2000. Data on components of EH, including; vegetation, habitat diversity, and habitat structure were collected in associated field surveys. Using the results of our EH component-bird richness models, we applied the case of the likely decline of the ash tree, a species of conservation concern and a key component of British landscape complexity, to create predictive scenarios of future bird richness. We found that EH components had a strong positive effect on bird richness and identified six key components that explained over 70% of variance in bird richness. Bird richness responses were strongly dependent on the specific EH components and were generally non-linear, especially for habitat structural variables, such as lines of trees and hedges. Our predictive scenarios showed a decrease in bird species richness only for simulated ash tree decreases within the habitat structural variables of over 90%, and only for areas where this tree species was a particularly abundant component of the landscape. Our findings, showing that bird richness responses differ for EH components, and that non-linear responses are common, could help the ‘design’ of landscapes that enhance bird diversity. In particular, our study indicates that, in some cases, increasing the occurrence of key structural components of habitat (such as ensuring a minimum of 700 m of managed hedges or a minimum of 70 individual trees per km square), could have disproportionally positive impacts on bird richness.

中文翻译：

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栖息地多样性和结构调节英国鸟类丰富度：非线性关系对保护的影响

摘要 空间环境异质性（EH）是决定空间尺度上许多类群物种丰富度的重要因素。增加的 EH 可能主要通过提供更多的生态位来支持更高的多样性。然而，人们对 EH 多样性关系的形状及其对景观尺度多样性测量的影响知之甚少。我们使用随机森林回归模型来评估 EH 的不同组成部分与整个英国的鸟类物种丰富度之间的关系。鸟类数据是在 2000 年使用 BTO/JNCC/RSPB 育种鸟类调查方法在 335 个英国乡村调查 (CS) 1 平方公里范围内获得的。关于 EH 组成部分的数据，包括：在相关的实地调查中收集了植被、栖息地多样性和栖息地结构。使用我们的 EH 组件-鸟类丰富度模型的结果，我们应用了白蜡树可能衰退的案例，这是一种受保护的物种，也是英国景观复杂性的关键组成部分，以创建未来鸟类丰富度的预测情景。我们发现 EH 成分对鸟类丰富度有很强的积极影响，并确定了六个关键成分，可以解释超过 70% 的鸟类丰富度差异。鸟类丰富度响应强烈依赖于特定的 EH 成分，并且通常是非线性的，尤其是对于栖息地结构变量，例如树木和树篱的线条。我们的预测情景表明，鸟类物种丰富度仅在栖息地结构变量超过 90% 的模拟白蜡树减少，并且仅适用于该树种是景观中特别丰富的组成部分的区域。我们的发现，表明 EH 成分的鸟类丰富度响应不同，并且非线性响应很常见，可以帮助“设计”增强鸟类多样性的景观。特别是，我们的研究表明，在某些情况下，增加栖息地关键结构组成部分的出现（例如确保至少 700 m 的管理树篱或每平方公里至少 70 棵独立树木）可能会产生不成比例的积极影响关于鸟类丰富度。