Plant reproduction is highly sensitive to stress from severe weather. While facilitation has been shown to buffer negative impacts along stress gradients, less is known about facilitating plant reproduction in drought periods. Because intensity and frequency of drought are predicted to increase, plant reproductive facilitation has important implications for a species ability to adapt to changes in climate. Our primary study objective is to test if nurse shrubs act as reproductive micro-refugia across soil types, by improving reproductive potential of perennial bunchgrass neighbors subjected to severe drought. To investigate this objective, we designed a fully factored study testing direct interaction between shrub and bunchgrasses in eastern Oregon sagebrush steppe, at two sites with different soil types. The study consisted of six simple effect treatments combining three moisture regimes (moist, ambient, and drought) with two shrub conditions (shrub intact or shrub removed). Our results indicate when facilitation of reproductive potential occurs, it occurs strongly and particularly in drought, consistent with the stress gradient hypothesis (SGH), where several species produced at least 54% more inflorescences in the presence of shrub neighbors. In addition, we found facilitation to be consistent with the SGH at the species level likely reflecting differences in plant strategy and perception of strain, but to follow alternative SGH models more closely at the site level where facilitation declined on the drier soil. Ultimately, our findings highlight the importance of facilitation in improving plant reproductive potential in drought, and support the role of nurse shrubs as micro-refugia in a changing climate.

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干旱条件下灌木会提高邻居跨土壤类型的繁殖机会吗？

植物繁殖对恶劣天气的胁迫高度敏感。尽管便利化已显示出可以缓解沿应力梯度的负面影响，但人们对于在干旱时期促进植物繁殖的了解却很少。由于干旱的强度和频率预计会增加，因此植物繁殖的便利化对物种适应气候变化的能力具有重要意义。我们的主要研究目标是通过提高常年发生于严重干旱中的束草邻居的繁殖潜力，来测试护士灌木是否在整个土壤类型中都充当着微繁殖的避难所。为了研究这一目标，我们设计了一个全因子研究，测试了俄勒冈东部鼠尾草草原中灌木和束草在两个土壤类型不同的地方之间的直接相互作用。该研究由六种简单的效果处理组成，将三种湿度模式（潮湿，环境和干旱）与两种灌木条件（完整的灌木或去除的灌木）结合在一起。我们的结果表明，当促进繁殖潜力发生时，它会强烈发生，尤其是在干旱中，这与应力梯度假设（SGH）一致，在灌木邻域中，几种物种的花序至少多出54％。此外，我们发现在物种层面上促进与SGH一致，可能反映了植物策略和品系差异，但在干燥土壤上促进减弱的地点层面上，更紧密地遵循替代性SGH模型。最终，我们的发现凸显了促进干旱对提高植物繁殖潜力的重要性，