Aboveground net primary productivity (ANPP) in grasslands is an important integrator of terrestrial ecosystem function, a key driver of global biogeochemical cycles, and a critical source of food for wild and domesticated herbivores. ANPP exhibits high spatial and temporal variability, driven by a suite of factors including precipitation amount and pattern, biotic and abiotic legacies, and topographic heterogeneity. Global climate models forecast an altered hydrological cycle due to climate change, including higher precipitation variability and more extreme events, which may further increase spatiotemporal variability in ANPP. Therefore, it is essential to understand the sensitivity of this central ecosystem function to various precipitation metrics, legacies, and topographic positions to better inform sustainable grassland management. In this study, we analyzed long‐term (36‐yr) ANPP data collected across a topographic sequence in the semiarid shortgrass steppe of North America to examine patterns and drivers of spatiotemporal variability in ANPP. We observed that (1) ANPP varied substantially by topographic position, with greater divergence during years with high production, (2) ANPP variability was higher temporally (16‐fold maximum difference across years) than spatially (4‐fold maximum difference across topographic positions), (3) warm‐season perennial grasses were the dominant plant functional type across all topographic positions and strongly influenced total ANPP dynamics, and (4) ANPP had strong sensitivities to current year precipitation amount and pattern that varied by plant functional type, as well as weaker sensitivities to precipitation and productivity legacies. Overall, the lowest topographic position had the highest sensitivity to precipitation, likely due to higher resource availability via the downhill movement of water and nutrients during years with high precipitation and large rainfall events. These results suggest that temporal and spatial ANPP variability in shortgrass steppe is primarily driven by the combined effects of precipitation amount and pattern during the current year, with the dominant warm‐season perennial grasses governing these responses.

中文翻译：

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在半干旱草地上，生产力对降水量和模式的敏感性随地形位置而变化

草原地上净初级生产力（ANPP）是陆地生态系统功能的重要整合者，是全球生物地球化学循环的主要驱动力，并且是野生和驯化草食动物的重要食物来源。在一系列因素的驱动下，ANPP表现出高度的时空变异性，包括降水量和模式，生物和非生物遗产以及地形异质性。全球气候模型预测，由于气候变化，水文周期将发生变化，包括更高的降水变化和更多的极端事件，这可能会进一步增加ANPP的时空变化。因此，必须了解该中央生态系统功能对各种降水量指标，遗产和地形位置的敏感性，以便更好地为可持续草地管理提供依据。在这项研究中，我们分析了北美半干旱短草草原跨地形序列收集的长期（36年）ANPP数据，以检验ANPP时空变异的模式和驱动因素。我们观察到（1）ANPP随地形位置而变化很大，高产量年份间差异更大;（2）ANPP的时间变化性（年度最大差异为16倍）高于空间上的差异（年度最大差异为4倍） ），（3）暖季多年生禾草是所有地形位置上的主要植物功能类型，并强烈影响总的ANPP动态，（4）ANPP对当年降水量和随植物功能类型而变化的模式有很强的敏感性。以及对降水和生产力遗留的敏感性较弱。总体而言，最低的地形位置对降水具有最高的敏感性，这可能是由于在降水量高和降雨事件多的年份中，由于水和养分的下坡运动而获得了更多的资源。这些结果表明，短草草原的时空ANPP变异主要是由当年降水量和格局的综合影响所驱动，而主要的暖季多年生禾草支配这些响应。