The relationship between species richness and productivity changes with spatial scale, but the way in which it changes and the underlying mechanisms remain unclear. We address this critical knowledge gap using a new mechanistic model of the spatial scaling of species richness–productivity (SP) relationships for a local community. Our model is neutral and hence assumes that species dynamics are driven by dispersal limitation and demographic stochasticity. We showed analytically that SP relationships predicted by our model are typically unimodal. Consistent with previous simulation-based studies, the positive phase of our unimodal SP relationship was driven by a sampling effect (“more-individuals effect”) whereas the negative phase was driven by relatively more propagules being of local as opposed to external origin (“dilution effect”). Our main novel finding related to the spatial scaling of the unimodal SP relationship: the peak shifted to the left with increasing spatial scale, such that the decreasing phase covered a greater range of productivity. This was driven by an increase in the strength of the dilution effect relative to the more-individuals effect, reflecting higher area/perimeter ratios at larger spatial scales. Our theoretical predictions are qualitatively consistent with the spatial scaling of SP relationships documented for trees in localized forest communities across the world.

中文翻译：

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物种丰富度与当地社区生产力关系的空间尺度：中性模型的分析结果

物种丰富度与生产力之间的关系随空间规模而变化，但其变化方式和潜在机制仍不清楚。我们使用一种新的力学模型来解决这一关键的知识鸿沟，该模型对当地社区的物种丰富度与生产力（SP）关系具有空间比例。我们的模型是中性的，因此假设物种动态是由扩散限制和人口统计随机性驱动的。我们通过分析表明，我们的模型预测的SP关系通常是单峰的。与以前的基于模拟的研究一致，我们的单峰SP关系的正相是由采样效应（“更多个体效应”）驱动的，而负相则是由相对于外部起源的相对较多的繁殖体驱动的（“稀释效应”）。我们的主要新发现与单峰SP关系的空间尺度有关：随着空间尺度的增大，峰向左移动，从而减小的相位覆盖了更大的生产率范围。这是由于稀释效应的强度相对于个体效应的增强所致，反映了更大的空间尺度下更高的面积/周长比。我们的理论预测在质量上与世界各地局部森林群落中树木记录的SP关系的空间尺度一致。这是由于稀释效应的强度相对于个体效应的增强所致，反映了更大的空间尺度下更高的面积/周长比。我们的理论预测在质量上与世界各地局部森林群落中树木记录的SP关系的空间尺度一致。这是由于稀释效应的强度相对于个体效应的增强所致，反映了更大的空间尺度下更高的面积/周长比。我们的理论预测在质量上与世界各地局部森林群落中树木记录的SP关系的空间尺度一致。