Data from: Unraveling conflicting density- and distance-dependent effects on plant reproduction using a spatially-explicit approach

1. Density- and distance-dependent (DDD) mechanisms are important determinants of plant reproductive success (PRS). Different components of sequential PRS can operate either in the same or in different directions and thus reinforce or neutralize each other, and they may also operate at different spatial scales. Thus, spatially-explicit approaches are needed to detect such complex DDD effects across multiple PRS components and spatial scales. 2. To reveal DDD effects of different components of early PRS of the Iberian pear (Pyrus bourgaeana) sampled over three consecutive years, we used marked point pattern analysis. Our special interest is to identify conflicting processes that regulate populations at different spatial scales, e.g. whether DDD on fruit initiation and on fruit development acted in opposite directions. To evaluate the significance of observed mark correlation functions based on empirical data (e.g. fruiting success) we compared them to expectations given by spatially-explicit null models. 3. Diverse DDD processes affected several aspects of PRS in a variable extent over the three seasons. First, early fruit set was higher for individuals with more neighbors at small distances (i.e. up to 40m). However, late P. bourgaeana fruit set decreased with increasing number of nearby neighbors, but these effects canceled for overall fruit set that did not show DDD effects. Second, the absolute number of fruits produced (crop sizes) by trees showed positive density dependence in 2011 and 2012 but not in 2013. Finally, the total number of seeds produced did not show DDD effects, indicating that conflicting demographic processes can disrupt the initial spatial pattern of tree investment in reproduction. 4. Synthesis: Understanding complex spatial effects of density- and distance-dependent (DDD) processes requires dissection of component processes to attain the complete picture since contrasting DDD processes may be hidden behind a single cumulative measure of reproductive success. The combination of novel and classic mark correlation functions used here constitute a powerful spatially-explicit tool that can be broadly applied to unravel conflicting mechanisms of DDD regulating the persistence of sessile organisms at a range of spatial scales. Our findings help to explain why some authors failed to find expected DDD of PRS and highlight the importance of detailed multi-year field studies on plant reproductive success.

1. 密度距离依赖（Density- and distance-dependent, DDD）机制是影响植物繁殖成功（plant reproductive success, PRS）的重要决定因素。序列式PRS的不同组分既可以同向发挥作用，也可反向调控，由此彼此增强或抵消效应，且这些组分的作用尺度也可能存在差异。因此，需要采用空间显式方法，才能在多个PRS组分与空间尺度上检测到这类复杂的DDD效应。
2. 为揭示连续三年采样的伊比利亚梨（Pyrus bourgaeana）早期PRS不同组分的DDD效应，本研究采用了标记点格局分析（marked point pattern analysis）方法。我们的核心研究目标是识别在不同空间尺度上调控种群的冲突性过程，例如调控坐果起始与果实发育的DDD效应是否呈反向作用。为评估基于实测数据（如坐果成功率）得到的观测标记相关函数（mark correlation functions）的显著性，我们将其与空间显式零模型给出的预期值进行了对比。
3. 在三年的研究周期中，多样的DDD过程以不同强度影响了PRS的多个维度。首先，在小尺度（即40米以内）邻株数量更多的个体，其早期坐果率更高。但伊比利亚梨的晚期坐果率则随邻株数量增加而降低，不过这类效应在整体坐果率中被抵消，整体坐果率未表现出DDD效应。其次，树木的绝对结实量（单株果实总数）在2011年与2012年呈现正密度依赖效应，但2013年未出现该效应。最后，单株种子总产出未表现出DDD效应，这表明冲突性种群统计过程可破坏植物繁殖投入的初始空间格局。
4. 研究总结：要理解密度距离依赖过程的复杂空间效应，需要拆解其组分过程以获取完整认知，因为反向的DDD过程可能隐藏在单一的繁殖成功累积指标之后。本研究结合使用的新型与经典标记相关函数，构成了一套强大的空间显式分析工具，可被广泛用于解析在多种空间尺度上调控固着生物（sessile organisms）存续的DDD冲突机制。本研究结果有助于解释为何部分学者未能观测到预期的PRS DDD效应，同时也凸显了针对植物繁殖成功开展长期多年度野外实地研究的重要性。