Livestock grazing can have a strong impact on herbivore abundance, distribution and community. However, not all species of herbivores respond the same way to livestock grazing, and we still have a poor understanding of the underlying mechanisms driving these differential responses. Here, we investigate the effect of light intensity cattle grazing on the abundance of two grasshoppers (Euchorthippus cheui and E. unicolor) that co‐occur in the same grasslands and feed on the same food plant (the dominant grass Leymus chinensis). The two grasshopper species differ in phenology so that their peak abundances are separated into early‐ and late‐growing seasons. We used an exclosure experiment to monitor grasshopper abundance and food quality in the field under grazed and ungrazed conditions, and performed feeding trials to examine grasshopper preference for grazed or ungrazed food plants in the laboratory. We found that the nitrogen content of L. chinensis leaves continuously declined in the ungrazed areas, but was significantly enhanced by cattle grazing over the growing season. Cattle grazing facilitated the early‐season grasshopper E. cheui, whereas it suppressed the late‐season grasshopper E. unicolor. Moreover, feeding trials showed that E. cheui preferred L. chinensis from grazed plots, while E. unicolor preferred the leaves from ungrazed plots. We conclude that livestock grazing has opposite effects on the two grasshopper species, and that these effects may be driven by grazing‐induced changes in plant nutrient content and the unique nutritional niches of the grasshoppers. These results suggest that insects that belong to the same guild can have opposite nutrient requirements, related to their distinct phenologies, and that this can ultimately affect their response to cattle grazing. Our results show that phenology may link insect physiological needs to local resource availabilities, and should be given more attention in future work on interactions between large herbivores and insects.

中文翻译：

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草食动物物候学可以预测牲畜放牧对植物质量变化的反应

放牧对食草动物的丰度，分布和群落有很大影响。但是，并非所有的草食动物物种对家畜放牧的反应方式都相同，我们对驱动这些差异反应的潜在机制仍然知之甚少。在这里，我们调查的光强度放牧对丰2只蝗虫（效果Euchorthippus cheui和E.单色）是（占主导地位的草共同出现在同一草地和饲料在同一个食品厂羊草）。两种蚱hopper的物候特征不同，因此它们的高峰丰度被分为早期和晚期生长季节。我们使用了一项放牧实验来监测草食和未草食条件下田间的蚱grass丰度和食物质量，并在实验室中进行了饲喂试验，以检查草食或未草食的植物对蚱hopper的偏好。我们发现，氮含量羊草叶子在ungrazed地区持续下降，但放牧牛在生长季节显著增强。牛吃草促进了赛季初的蚂蚱E. cheui，而这抑制了赛季末蚂蚱E.单色。此外，饲养试验表明，E. cheui从放牧地块中优先选择中华L. chinensis，而从裸草地块中选择单色E.uni.e。我们得出的结论是，放牧对两种蚱species有相反的影响，而这些影响可能是由放牧引起的植物养分含量变化和蚱hopper独特的营养生态位驱动的。这些结果表明，属于同一行会的昆虫可能具有相反的养分需求，这与它们不同的物候有关，并且这最终会影响它们对牛放牧的反应。我们的结果表明，物候学可能会将昆虫的生理需求与当地资源的可利用性联系起来，在今后有关大型草食动物与昆虫之间相互作用的研究中应给予更多关注。