Abstract The main feed crops on dairy farms in the northeastern U.S. are alfalfa (Medicago sativa L.) and maize (Zea mays L.). Projected changes in climate along with increased atmospheric carbon dioxide (CO2) concentration will affect future production of these crops. We evaluated maize and alfalfa yield and evapotranspiration response to CO2 enrichment predicted by three process-based cropping system models, CropSyst, DSSAT and IFSM, in six counties of Pennsylvania and New York, using 25 years of daily weather and two concentrations of atmospheric CO2 (350 and 550 ppm). Positive effects of CO2 enrichment on crop growth have been documented using plants grown under controlled CO2 conditions; of particular relevance are results obtained in fields with free-air CO2 enrichment (FACE) technology. For evaluation, simulation results were compared among models and to FACE experimental data. The three models simulated similar maize response to increasing CO2 for grain yield, total biomass yield and harvest index, with predicted responses within the ranges reported in FACE experiments. The models may have slightly overestimated the yield response of maize during wet years compared with FACE experiments. The models also simulated increased productivity of alfalfa within the bounds observed in FACE experiments. While DSSAT and IFSM predicted yield increases of about 20%, Cropsyst predicted an increase of 32%, which is in the upper bound of FACE experimental data. For both crops, models simulated a lesser reduction in evapotranspiration under increasing CO2 than that measured in FACE experiments. The larger response of alfalfa may either shift rotations towards more alfalfa, or allow for a shorter alfalfa phase in a rotation depending on market and other production constraints. While there were overestimations in simulating maize productivity under no water stress and uncertainties in simulating evapotranspiration that are relevant for local and regional hydrology, these models adequately represented crop yield response to changes in atmospheric CO2 concentration.

中文翻译：

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大气二氧化碳升高对美国东北部玉米和苜蓿的影响：模型预测和观测数据的比较

摘要 美国东北部奶牛场的主要饲料作物是苜蓿 (Medicago sativa L.) 和玉米 (Zea mays L.)。预计的气候变化以及大气中二氧化碳 (CO2) 浓度的增加将影响这些作物的未来生产。我们在宾夕法尼亚州和纽约州的六个县使用 25 年的日常天气和两种大气 CO2 浓度，评估了玉米和苜蓿产量和蒸发蒸腾对 CO2 富集的响应，这些模型由三个基于过程的作物系统模型 CropSyst、DSSAT 和 IFSM 预测。 350 和 550 ppm）。已经使用在受控 CO2 条件下生长的植物记录了 CO2 富集对作物生长的积极影响；特别相关的是在使用自由空气二氧化碳富集 (FACE) 技术的领域中获得的结果。对于评估，模拟结果在模型之间进行比较，并与 FACE 实验数据进行比较。这三个模型模拟了类似的玉米对增加 CO2 的谷物产量、总生物量产量和收获指数的响应，预测响应在 FACE 实验报告的范围内。与 FACE 实验相比，这些模型可能略微高估了湿润年份玉米的产量响应。这些模型还模拟了在 FACE 实验中观察到的范围内苜蓿生产力的提高。DSSAT 和 IFSM 预测产量增加约 20%，而 Cropsyst 预测增加 32%，这是 FACE 实验数据的上限。对于这两种作物，模型模拟了在二氧化碳增加的情况下蒸发蒸腾量的减少比 FACE 实验中测量的要少。苜蓿的较大响应可能会将轮作转向更多的苜蓿，或者根据市场和其他生产限制允许轮作中的苜蓿阶段较短。虽然在没有水分胁迫的情况下模拟玉米生产力存在高估，并且在模拟与当地和区域水文相关的蒸发蒸腾方面存在不确定性，但这些模型充分代表了作物产量对大气 CO2 浓度变化的响应。