Plant–soil feedbacks of plants that are exposed to herbivory have been shown to differ from those of plants that are not exposed to herbivores. Likely, this process is mediated by jasmonic acid (JA) and salicylic acid (SA) defense pathways, which are induced by aboveground herbivory. Furthermore, exogenous application of these phytohormones to plants alters belowground communities, but whether this changes plant–soil feedbacks in natural systems is unknown. We applied exogenous sprays of JA and SA individually and in combination to field plots in a restored grassland. Control plots were sprayed with demineralized water. After three repeated application rounds, we transplanted seedlings of the plant–soil feedback model plant Jacobaea vulgaris as phytometer plants to test the effects of potential phytohormone-mediated changes in the soil, on plant performance during the response phase. We further measured how exogenous application of phytohormones altered plant-related ecosystem characteristics (plot-level); soil chemistry, plot productivity, insect communities and predation. Biomass of the phytometer plants only co-varied with plot productivity, but was not influenced by phytohormone applications. However, we did observe compound-specific effects of SA application on insect communities, most notably on parasitoid attraction, and of JA application on soil nitrogen levels. Although we did not find effects on plant–soil feedbacks, the effects of exogenous application of phytohormones did alter other ecosystem-level processes related to soil nutrient cycling, which may lead to legacy effects in the longer term. Furthermore, exogenous application of phytohormones led to altered attraction of specific insect groups.

中文翻译：

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外源施用植物激素可改变地上植物-昆虫的反应和地下养分的利用率，但不会导致植物-土壤反馈的差异

研究表明，暴露于草食动物的植物与植物的土壤反馈不同于未暴露于草食动物的植物。该过程可能由茉莉酸（JA）和水杨酸（SA）防御途径介导，这些途径是由地上食草动物诱导的。此外，这些植物激素在植物上的外源应用改变了地下群落，但是尚不清楚这是否会改变自然系统中植物-土壤的反馈。我们将JA和SA的外源喷雾剂单独或组合应用到恢复的草原上的田地中。对照地块用软化水喷雾。经过三轮重复的申请，我们移植了植物-土壤反馈模型植物寻常雅可比的幼苗作为植酸计的植物，以测试潜在的植物激素介导的土壤变化对响应阶段植物生长的影响。我们进一步测量了植物激素的外源应用如何改变了植物相关的生态系统特征（图水平）。土壤化学，地块生产力，昆虫群落和捕食。植酸计植物的生物量仅与样地生产力相关联，而不受植物激素应用的影响。但是，我们确实观察到SA施用对昆虫群落（尤其是对寄生虫的吸引力）和JA施用对土壤氮水平的化合物特异性作用。尽管我们没有发现对植物-土壤反馈的影响，但是外源施用植物激素的影响确实改变了其他与土壤养分循环相关的生态系统级过程，从长远来看，这可能会导致遗留效应。此外，外源应用植物激素导致特定昆虫群体的吸引力发生变化。