Pollinator declines have been documented globally, but little information is available about native bee ecology in Midwestern U.S. agriculture. This project seeks to optimize pollinator support and weed suppression in a 3-yr crop rotation with a fallow growing season. During fallow, one of five cover crop treatments (T1: crimson, red, and ladino clover and Bob oats [Fabales: Fabaceae - Trifolium incarnatum L., Trifolium pratense L., Trifolium repens L., and Cyperales: Poaceae - Avena sativa]; T2: crimson clover and oats; T3: red clover and oats; T4: ladino clover and oats; T5: no cover crop; T6/control: winter wheat [Cyperales: Poaceae - Triticum aestivum] L.) was seeded in one-half of 25 agricultural fields, whereas wheat was left unharvested in the other half as a comparison. Treatments that provide season-long floral resources support the greatest bee diversity and abundance (T1), and treatments with red clover support declining (Hymenoptera: Apidae) Bombus species (T1 and T3). Late-season floral resources may be important, yet limited (T1 and T4), and some species of agricultural weeds provide floral resources. Floral diversity may be less important than flower abundance or timing for pollinator diversity (T1–T4). Weed diversity was greatest in the no cover crop treatment (T5), least in winter wheat (T6), and intermediate in cover crop treatments (T1–T4) with no differences in weeds of economic concern. Wheat suppresses weeds but does not provide floral resources for pollinators. These results may also be applicable to marginal lands taken out of cultivation or field margin pollinator plantings in a typical corn–soybean rotation. Floral resource availability across the landscape is critical to maintain pollinator diversity.

中文翻译：

---

覆盖作物对传粉媒介栖息地提供和杂草抑制的功效

传粉媒介的减少已在全球范围内得到记录，但有关美国中西部农业本地蜜蜂生态学的信息很少。该项目旨在在休耕季节的 3 年轮作中优化传粉媒介支持和杂草抑制。在休耕期间，五种覆盖作物处理中的一种（T1：深红色、红色和拉丁三叶草和 Bob oats [Fabales：豆科 - Trifolium incarnatum L.、Trifolium pratense L.、Trifolium repens L. 和 Cyperales：禾本科 - Avena sativa] ；T2：深红三叶草和燕麦；T3：红三叶草和燕麦；T4：拉丁三叶草和燕麦；T5：无覆盖作物；T6/对照：冬小麦 [Cyperales: Poaceae - Triticum aestivum] L.) 25 个农田的一半，而另一半没有收获小麦作为比较。提供全季花卉资源的处理支持最大的蜜蜂多样性和丰度（T1），而红三叶草处理支持下降（膜翅目：蜜蜂科）熊蜂物种（T1 和 T3）。晚季花卉资源可能很重要，但也很有限（T1 和 T4），一些农业杂草提供了花卉资源。对于传粉媒介多样性（T1-T4），花卉多样性可能不如花卉丰度或时间重要。杂草多样性在无覆盖作物处理 (T5) 中最大，在冬小麦 (T6) 中最少，在覆盖作物处理 (T1-T4) 中的杂草多样性居中，经济问题杂草没有差异。小麦抑制杂草，但不为传粉媒介提供花卉资源。这些结果也可能适用于典型的玉米-大豆轮作中从耕作中取出的边缘土地或田间边缘传粉媒介种植。整个景观的花卉资源可用性对于维持传粉媒介的多样性至关重要。