Although ecological disturbances can have a strong influence on pollinators through changes in habitat, virtually no studies have quantified how characteristics of wildfire influence the demography of essential pollinators. Nevertheless, evaluating this topic is critical for understanding how wildfire is linked to pollinator population dynamics, particularly given recent changes in wildfire frequency and severity in many regions of the world. In this study, we measured the demographic response of the blue orchard bee (Osmia lignaria) across a natural gradient of wildfire severity to assess how variation in wildfire characteristics influenced reproductive output, offspring sex ratio, and offspring mass. We placed nest blocks with a standardized number and sex ratio of pre-emergent adult bees across the wildfire gradient, finding some evidence for a positive but highly variable relationship between reproductive output and fire severity surrounding the nest site at both local (100 m) and landscape (750 m) scales. In addition, the production of female offspring was > 10% greater at nest sites experiencing the greatest landscape-scale fire severity relative to the lowest-severity areas. The finding that blue orchard bees biased offspring production towards the more expensive offspring sex with increasing fire severity shows a functional response to changes in habitat quality through increased density of flowering plants. Our findings indicate that burned mixed-conifer forest provides forage for the blue orchard bee across a severity gradient, and that the increase in floral resources that follows high-severity fire leads females to shift resource allocation to the more costly sex when nesting.

尽管生态干扰可以通过栖息地的变化对传粉媒介产生强烈影响，但实际上，尚无任何研究量化野火特征如何影响基本传粉媒介的人口统计。但是，评估该主题对于了解野火与传粉媒介种群动态之间的联系至关重要，特别是考虑到世界上许多地区最近的野火发生频率和严重性发生了变化。在这项研究中，我们测量了蓝色果园蜂（Osmia lignaria）的人口统计学响应），在野火严重程度的自然梯度上评估野火特征的变化如何影响繁殖能力，后代性别比和后代质量。我们在野火梯度上放置了具有标准化数量和出苗前成年蜜蜂性别比的鸟巢块，发现了一些证据表明，在当地（100 m）和100 m处，鸟巢周围的繁殖力与火势之间存在正但高度可变的关系景观（750 m）规模。此外，相对于严重程度最低的地区，经历最大火势的巢穴地区的雌性后代的产量要高出10％以上。蓝果园蜜蜂将后代的生产偏向更昂贵的后代，火势越来越严重，这一发现表明通过增加开花植物的密度，对栖息地质量变化的功能性反应。我们的研究结果表明，燃烧的针叶树混交林在严重度梯度上为蓝色果园蜂提供了觅食，而高强度火种后花卉资源的增加导致雌性在筑巢时将资源分配转移到成本更高的性上。