Environmental heterogeneity affects distributions of plant species, although the effects of fine‐scale heterogeneity on plant demographies are not widely studied. Diminutive winter annuals, especially rare taxa, can be sensitive to spatial variation in microenvironment as a consequence of their small stature above and belowground. To address whether spatial environmental heterogeneity affects demography, germination and fitness of Chorizanthe orcuttiana, an endangered winter annual distributed in distinct easterly and westerly microhabitats within an exceedingly narrow niche in California, we performed multiyear observational and empirical studies. We manipulated after‐ripening environment, soil moisture and ambient light at both aspects, and profiled microclimate, soil physicochemistry and soil microbiomes at all sites. We show that easterly aspects host larger plants in larger populations, and have lower air temperatures combined with higher soil moisture in comparison to the west‐facing sites. Yet, soil physicochemistry and microbiomes were similar across all sites. Manipulations of after‐ripening conditions showed that seeds exposed to low humidity (17%) during dormancy and sown at easterly aspects exhibited the highest germination percentages, whereas seeds incubated in situ and subsequently sown at westerly aspects yielded the lowest germination. Simultaneous manipulations of soil moisture and light showed that at both aspects higher moisture combined with shade led to higher germination, whereas ambient soil moisture combined with shade yielded the lowest germination. Altogether, our studies show that the diminutive, rare winter annual C. orcuttiana exhibits higher germination and plant fitness under cooler soil conditions with higher soil moisture while preferring drier environments during after‐ripening.

中文翻译：

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狭窄地方病，罕见冬季的种子萌发和植物适应性对微环境中空间异质性的响应

尽管未广泛研究精细异质性对植物种群的影响，但环境异质性影响植物物种的分布。微小的冬季年，尤其是稀有的分类单元，由于其在地上和地下的小身材，可能对微环境的空间变化敏感。解决空间环境异质性是否影响山楂的人口统计，萌发和适应性是一个濒临灭绝的冬季年，分布在加利福尼亚一个非常狭窄的生态位内，在不同的东风和西风微生境中，我们进行了多年的观察和实证研究。我们在两个方面都对成熟后的环境，土壤湿度和环境光进行了控制，并在所有地点进行了微气候，土壤理化和土壤微生物组的概况分析。我们显示，与朝西的地点相比，东风方面拥有较大的植物，人口更多，空气温度较低，土壤湿度较高。然而，所有地点的土壤物理化学和微生物组相似。熟后条件的处理表明，在休眠期间暴露于低湿度（17％）的种子并在向东播种时，种子表现出最高的发芽率，而孵育的种子原位并随后在西风下播种发芽率最低。对土壤水分和光线的同时处理表明，在两个方面，较高的水分和阴影会导致较高的发芽率，而周围的土壤水分和阴影会导致最低的发芽率。总的来说，我们的研究表明，在寒冷的土壤条件下，土壤水分较高的同时，较小的，稀有的冬季一年生桔小实蝇（C. orcuttiana）表现出较高的发芽和植物适应性，而在翻熟后更喜欢较干燥的环境。