How climate change will modify belowground tritrophic interactions is poorly understood, despite their importance for agricultural productivity. Here, we manipulated the three major abiotic factors associated with climate change (atmospheric CO₂, temperature, and soil moisture) and investigated their individual and joint effects on the interaction between maize, the banded cucumber beetle (Diabrotica balteata), and the entomopathogenic nematode (EPN) Heterorhabditis bacteriophora. Changes in individual abiotic parameters had a strong influence on plant biomass, leaf wilting, sugar concentrations, protein levels, and benzoxazinoid contents. Yet, when combined to simulate a predicted climate scenario (Representative Concentration Pathway 8.5, RCP 8.5), their effects mostly counter-balanced each other. Only the sharp negative impact of drought on leaf wilting was not fully compensated. In both current and predicted scenarios, root damage resulted in increased leaf wilting, reduced root biomass, and reconfigured the plant sugar metabolism. Single climatic variables modulated the herbivore performance and survival in an additive manner, although slight interactions were also observed. Increased temperature and CO₂ levels both enhanced the performance of the insect, but elevated temperature also decreased its survival. Elevated temperatures and CO₂ further directly impeded the EPN infectivity potential, while lower moisture levels improved it through plant- and/or herbivore-mediated changes. In the RCP 8.5 scenario, temperature and CO₂ showed interactive effects on EPN infectivity, which was overall decreased by 40%. We conclude that root pest problems may worsen with climate change due to increased herbivore performance and reduced top-down control by biological control agents.

尽管气候变化对农业生产力很重要，但人们对气候变化如何改变地下三营养相互作用却知之甚少。在这里，我们操纵了与气候变化相关的三个主要非生物因素（大气 CO _{2 、温度和土壤水分），并研究了它们对玉米、带状黄瓜甲虫 (} Diabrotica balteata ) 和昆虫病原线虫之间相互作用的个体和联合影响(EPN)细菌异柄杆菌. 个体非生物参数的变化对植物生物量、叶片萎蔫、糖浓度、蛋白质水平和苯并恶嗪类含量有很大影响。然而，当结合模拟预测的气候情景（代表性浓度路径 8.5，RCP 8.5）时，它们的影响大多相互抵消。只有干旱对叶片萎蔫的严重负面影响没有得到充分补偿。在当前和预测的情况下，根系损伤导致叶片萎蔫增加，根系生物量减少，并重新配置植物糖代谢。单一气候变量以累加的方式调节了食草动物的表现和生存，尽管也观察到了轻微的相互作用。温度升高和 CO ₂水平都提高了昆虫的表现，但升高的温度也降低了它的生存。升高的温度和 CO ₂进一步直接阻碍了 EPN 的感染潜力，而较低的水分含量通过植物和/或食草动物介导的变化改善了它。在 RCP 8.5 情景中，温度和 CO ₂对 EPN 感染性有交互影响，总体下降了 40%。我们得出结论，由于草食动物性能的提高和生物控制剂自上而下的控制减少，根系害虫问题可能会随着气候变化而恶化。