The relationship between species richness and productivity (SRPR) has been a long-studied and hotly debated topic in ecology. Different studies have reported different results with variable shapes (i.e. unimodal, linear) and directions (i.e. positive, negative) of SRPRs depending on spatial grain (i.e. size of sampling unit for species richness), productivity estimates and study extent. In this study, we quantified the effect of multiple estimates of productivity (aboveground, belowground and total biomass, and various measures of soil fertility) on species richness across three spatial grains (0.04, 1 and 25 m²) across temperate grasslands from two regions in central Europe. We analyzed SRPR in each of the two regional datasets separately, as well as the two datasets pooled together. Our results have revealed that differences caused by spatial grain were unexpectedly small, and the direction of the SRPR was consistent within each productivity estimate, but differed between regions. Productivity estimates (across all spatial scales) had different, sometimes contrasting effects on SRPR (together with predictive power) within a region, and this pattern was more pronounced when compared between regions. The combination of different datasets led to very different results than when these were analyzed separately. We did not find any evidence for a unimodal response. This study points to the necessity of careful assessing when combining datasets from different regions, even if the plant communities belong to the same vegetation type. The dataset combination may blur the role of different drivers, which likely determine the shape and strength of SRPR. We suggest that data and study comparability may be enhanced by consistently using the same productivity estimates, which would allow for more robust interpretation of possible ecological drivers underlying the SRPR.

中文翻译：

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物种丰富度-生产力关系因区域和生产力估计而异，但与空间分辨率无关

物种丰富度和生产力（SRPR）之间的关系一直是生态学中一个长期研究和激烈争论的话题。不同的研究报告了不同的结果，SRPR 的可变形状（即单峰、线性）和方向（即正、负）取决于空间粒度（即物种丰富度的抽样单位大小）、生产力估计和研究范围。在本研究中，我们量化了生产力的多重估计（地上、地下和总生物量，以及土壤肥力的各种测量）对三种空间谷物（0.04、1 和 25 m ²）物种丰富度的影响) 横跨中欧两个地区的温带草原。我们分别分析了两个区域数据集中的 SRPR，以及汇集在一起​​的两个数据集。我们的结果表明，空间粒度引起的差异出乎意料地小，SRPR 的方向在每个生产力估计中是一致的，但在地区之间有所不同。生产力估计（跨所有空间尺度）对一个区域内的 SRPR（连同预测能力）有不同的、有时是相反的影响，并且在区域之间进行比较时，这种模式更为明显。与单独分析相比，不同数据集的组合导致了非常不同的结果。我们没有发现任何单峰反应的证据。本研究指出，即使植物群落属于同一植被类型，在组合来自不同地区的数据集时也必须仔细评估。数据集组合可能会模糊不同驱动因素的作用，这可能决定了 SRPR 的形状和强度。我们建议通过一致使用相同的生产力估计可以增强数据和研究的可比性，这将允许对 SRPR 潜在的生态驱动因素进行更可靠的解释。