Precipitation pulses and interpulse dry periods are major drivers of dryland ecosystem function globally, yet how the patterning and timing of precipitation inputs and dry periods influence seedling recruitment in these systems is poorly understood. We conducted two experiments to understand how limited and variable patterns of precipitation inputs may influence recruitment of bluebunch wheatgrass (Pseudoroegneria spicata [Pursh] A. Löve). In the first experiment, we evaluated how precipitation magnitude and dry-d interval during spring influenced recruitment. Ambient precipitation was excluded during spring, and we experimentally applied 5 levels of water (25, 35, 45, 55, and 65 mm) and 5-dry-d durations (1, 2, 4, 6, or 8 dry d between waterings) to plots sown with P. spicata. In the second experiment, we evaluated how the seasonal timing and duration of dry d influenced recruitment. All ambient precipitation was excluded through late winter and spring, and we experimentally applied three levels of dry-d duration (10, 20, and 30 d) four times during the growing season (February, March, April, and May) to plots sown with P. spicata. We observed strong, nonlinear interactive effects of precipitation amount and dry-d interval on recruitment where the midpoint dry-d treatment (4 d) interacted with low water availability to drive a major decline in recruitment. We also found strong evidence that recruitment was limited by dry periods occurring in late winter as opposed to dry periods occurring through spring, with recruitment decreasing over 40% during February dry periods compared with dry periods in March, April, or May. By understanding how precipitation pulses and interpulse dry periods interact to drive recruitment, we can refine efforts to develop weather-centric restoration frameworks, as well as hone ongoing efforts to identify plant materials and seed enhancement technologies that may buffer effects of variable precipitation on recruitment.

降水脉冲和间断干旱时期是全球旱地生态系统功能的主要驱动力，然而，对这些系统中降水输入和干旱时期的模式和时间安排如何影响幼苗募集却知之甚少。我们进行了两个实验，以了解有限的和可变的降水输入模式如何影响蓝水麦草（Pseudoroegneria spicata [Pursh] A.Löve）的募集。在第一个实验中，我们评估了春季的降水量和干燥天数间隔如何影响募集。春季期间排除了环境降水，我们实验性地使用了5级水（25、35、45、55和65毫米）和5次干水持续时间（两次浇水之间分别为1、2、4、6或8干水） ）播种的种子。在第二个实验中，我们评估了干旱季节的季节性时机和持续时间如何影响招聘。在冬末和春季之前，所有的环境降水都被排除在外，我们在生长季节（二月，三月，四月和五月）对四次干旱水平持续时间（10、20和30 d）进行了四次试验与P. spicata。我们观察到降水量和旱田间隔对募集有强烈的非线性交互作用，其中中点旱田处理（4 d）与可用水量低相互作用，导致征募量大幅下降。我们还发现有力的证据表明，招聘受冬季后期干旱时期的限制，而不是春季干旱时期，与3月，4月或5月的干旱时期相比，2月干旱时期的招聘减少了40％以上。通过了解降水脉冲和间断干旱时段如何相互作用来驱动招聘，我们可以完善开发以天气为中心的恢复框架的工作，并继续进行不断的工作以识别可缓冲降水量变化对招聘的植物材料和种子增强技术。