Ground beetles are natural predators of insect pests and small seeds in agroecosystems. In semiarid cropping systems of the Northern Great Plains, there is a lack of knowledge to how ground beetles are affected by diversified cover crop rotations. In a 2-yr study (2018 and 2019), our experiment was a restricted-randomization strip-plot design, comprising summer fallow, an early-season cover crop mixture (five species), and a mid-season cover crop mixture (seven species), with three cover crop termination methods (i.e., herbicide, grazing, and haying). Using pitfall traps, we sampled ground beetles in five 48-h intervals throughout the growing season (n = 135 per year) using growing degree day (GDD) accumulations to better understand changes to ground beetle communities. Data analysis included the use of linear mixed-effects models, perMANOVA, and non-metric multidimensional scaling ordinations. We did not observe differences among cover crop termination methods; however, activity density in the early-season cover crop mixture decreased and in summer fallow increased throughout the growing season, whereas the mid-season cover crop mixture peaked in the middle of the summer. Ground beetle richness and evenness showed a nonlinear tendency, peaking in the middle of the growing season, with marginal differences between cover crops or fallow after the termination events. Also, differences in ground beetle composition were greatest in the early- and mid-season cover crop mixtures earlier in the growing season. Our study supports the use of cover crop mixtures to enhance ground beetle communities, with potential implications for pest management in dryland cropping systems.

中文翻译：

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旱地耕作系统对北部大平原地面甲虫群落（鞘翅目：步甲科）的影响


地面甲虫是农业生态系统中害虫和小种子的天然捕食者。在北部大平原的半干旱种植系统中，人们对多样化覆盖作物轮作如何影响地面甲虫缺乏了解。在一项为期 2 年的研究（2018 年和 2019 年）中，我们的实验采用限制随机化带状图设计，包括夏季休耕、早季覆盖作物混合物（五个物种）和中季覆盖作物混合物（七个物种）。种），采用三种覆盖作物终止方法（即除草剂、放牧和干草）。我们使用陷阱，在整个生长季节（n = 135 每年）中以 5 个 48 小时的间隔对地面甲虫进行了采样，并使用生长度日 (GDD) 积累来更好地了解地面甲虫群落的变化。数据分析包括使用线性混合效应模型、perMANOVA 和非度量多维尺度排序。我们没有观察到覆盖作物终止方法之间的差异；然而，在整个生长季，早季覆盖作物混合物的活动密度下降，夏季休耕增加，而中季覆盖作物混合物的活动密度在夏季中期达到峰值。地面甲虫的丰富度和均匀度表现出非线性趋势，在生长季节中期达到峰值，覆盖作物或终止事件后休耕之间存在边际差异。此外，在生长季节早期的早季和中季覆盖作物混合物中，地面甲虫组成的差异最大。我们的研究支持使用覆盖作物混合物来增强地面甲虫群落，这对旱地种植系统的害虫管理具有潜在影响。