The vulnerability of rangeland beef cattle production to increasing climate variability in the US Great Plains has received minimal attention in spite of potentially adverse socioeconomic and ecological consequences. Vulnerability was assessed as the frequency and magnitude of years in which net primary production (NPP) deviated >±25% from mean values, to represent major forage surplus and deficit years, for a historic reference period (1981–2010), mid‐century (2041–2065), and late‐century (2075–2099) periods. NPP was simulated by MC2, a dynamic global vegetation model, driven by five climate projections for representative concentration pathway (RCP) 4.5 and 8.5. Historically, 4–4.7 years per decade showed either NPP surpluses or deficits. The future number of extreme years increased to 5.4–6.4 and 5.9–6.9 per decade for RCP 4.5 and 8.5, respectively, which represents an increase of 33%–56% and 38%–73%, respectively. Future simulations exhibited increases in surplus years to between 3 and 5 years in the Northern Plains and 3–3.5 in the Southern Plains. The number of deficit years remained near historic values of 2 in the Northern Plains, but increased in the Southern Plains from 2.5 to 3.3 per decade. Historically, NPP in extreme surplus and deficit years both deviated 40% from mean NPP in all three regions. The magnitude of deficit years increased by 6%–17% in future simulations for all three regions, while the magnitude of surplus years decreased 16% in the Northern Plains and increased 16% in the Southern Plains. The Southern Plains was the only region to exhibit an increase in the magnitude of both surplus and deficit years. Unprecedented future variability of NPP may surpass the existing adaptive capacity of beef producers and adversely impact the economic viability of rangeland cattle production and ecological sustainability of rangeland resources.

中文翻译：

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在美国大平原，牧场肉牛生产对气候引起的NPP波动的脆弱性。

尽管美国大平原地区的牧场肉牛生产容易受到气候变化的影响，但其潜在的社会经济和生态后果却受到了最小的关注。脆弱性被评估为本世纪中叶的历史参考期间（1981-2010年）的净初级生产（NPP）偏离均值>±25％的年份和幅度，代表主要的牧草盈余和赤字年份。 （2041–2065）和本世纪后期（2075–2099）。NPP是由MC2（一种动态的全球植被模型）模拟的，该模型由代表浓度路径（RCP）4.5和8.5的五个气候预测驱动。从历史上看，每十年4-4.7年显示出NPP盈余或赤字。对于RCP 4.5和8.5，未来的极端年份数增加到每十年5.4-6.4和5.9-6.9，分别增长了33％–56％和38％–73％。未来的模拟显示，盈余年数增加到北部平原的3至5年和南部平原的3至3.5年。在北部平原，赤字年份的数量保持在接近历史价值2的水平，但是在南部平原，赤字年份的数量从每十年的2.5增至3.3。从历史上看，极端盈余和赤字年份的NPP都偏离了所有三个地区的平均NPP。在所有三个地区的未来模拟中，赤字年份的数量增加了6％–17％，而北部平原的盈余年份的数量减少了16％，而南部平原的盈余年份的数量则增加了16％。南部平原是唯一一个盈余年限和赤字年均增加的地区。