Global seed dormancy patterns are driven by macroclimate but not fire regime

Seed dormancy maximizes plant recruitment in habitats with variation in environmental suitability for seedling establishment. Yet, we still lack a comprehensive synthesis of the macroecological drivers of nondormancy and the different classes of seed dormancy: physiological dormancy, morphophysiological dormancy and physical dormancy. We examined current geographic patterns and environmental correlates of global seed dormancy variation. Combining the most updated data set on seed dormancy classes for > 10 000 species with > 4 million georeferenced species occurrences covering all of the world's biomes, we test how this distribution is driven by climate and fire regime. Seed dormancy is prevalent in seasonally cold and dry climates. Physiological dormancy occurs in relatively dry climates with high temperature seasonality (e.g. temperate grasslands). Morphophysiological dormancy is more common in forest-dominated, cold biomes with comparatively high and evenly distributed precipitation. Physical dormancy is associated with dry climates with strong seasonal temperature and precipitation fluctuations (e.g. deserts and savannas). Nondormancy is associated with stable, warm and wetter climates (e.g. tropical rain forest). Pyroclimate had no significant effect on the distribution of seed dormancy. The environmental drivers considered in this study had a comparatively low predictive power, suggesting that macroclimate is just one of several global drivers of seed dormancy.种子休眠能够在幼苗建成所需环境适宜性存在变异的生境中，最大化植物种群的补充效果。然而，目前学界仍缺乏针对无休眠状态（nondormancy）以及各类种子休眠类型——即生理休眠（physiological dormancy）、形态生理休眠（morphophysiological dormancy）与物理休眠（physical dormancy）——的宏观生态驱动因子的综合梳理。 本研究针对全球种子休眠变异的现存地理格局及其环境关联因子展开了系统调查。本研究整合了针对逾1万种植物的最新种子休眠类型数据集，以及覆盖全球所有生物群区、超400万条带地理坐标的物种出现记录数据，以此检验气候与火制度对种子休眠分布格局的驱动作用。 种子休眠在季节性寒冷与干旱气候中普遍存在。生理休眠多见于温度季节性波动强烈的相对干旱气候区（例如温带草原）。形态生理休眠在以森林为主的寒冷生物群区中更为常见，该类区域降水相对充沛且分布均匀。物理休眠则与季节温度和降水波动剧烈的干旱气候相关（例如荒漠与稀树草原）。无休眠状态多存在于稳定、温暖且湿润的气候环境中（例如热带雨林）。火气候（pyroclimate）对种子休眠的分布无显著影响。 本研究纳入的环境驱动因子的预测能力相对有限，这表明宏观气候仅是调控全球种子休眠分布的多重驱动因子之一。