Research focus on the phenology of plants has accompanied current trends in climate warming, because the two are inextricably linked. Warmer temperatures have led to advanced plant phenology in a range of systems, although some responses are species specific. However, other stressors, such as herbivory, can delay or advance plant phenology, and few studies have addressed the combined impact of these drivers. We experimentally warmed plots with open top chambers (OTCs) and simulated herbivory resistance to insect outbreaks with methyl jasmonate (MeJA), along an elevational climatic gradient. We then recorded vegetative and reproductive phenology in two functionally important dwarf shrubs, the deciduous Vaccinium myrtillus (bilberry) and the evergreen V. vitis‐idaea (lingonberry), to test the responses to the combined treatments. Based on earlier findings, we expected larger phenological responses at higher elevations and for bilberry. We found that in the year after MeJA application, both bilberry and lingonberry delayed vegetative and reproductive phenology, although responses were stronger in bilberry. Warming with OTCs weakly advanced phenology in both species, but combined effects were not consistent. We further examined the consequences of this altered phenology on reproductive output with multigroup piecewise structural equation modelling and found that herbivory resistance driven changes to phenology had a strong mediating effect on berry numbers, particularly under warmed conditions and mainly in the year after MeJA application. Synthesis. These results demonstrate the need to consider combined pressures in understanding the impacts of global change on plants and highlight that multiple drivers may have unidentified synergetic effects on species phenology and reproduction.

中文翻译：

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矮灌木的食草抗性与模拟变暖相结合，以改变物候并减少繁殖


对植物物候学的研究重点伴随着当前气候变暖的趋势，因为这两者有着千丝万缕的联系。温暖的温度导致一系列系统中的植物物候学发展，尽管有些反应是特定于物种的。然而，其他压力因素，如食草性，可以延迟或促进植物物候学，很少有研究解决这些驱动因素的综合影响。我们用开顶室 （OTC） 对地块进行实验加热，并沿海拔气候梯度用茉莉酸甲酯 （MeJA） 模拟食草动物对昆虫爆发的抵抗力。然后，我们记录了两种功能重要的矮小灌木，即落叶越桔（越桔）和常绿 V. vitis‐idaea （越橘）的营养和生殖物候，以测试对联合处理的反应。根据早期的发现，我们预计在高海拔地区和越橘的物候反应会更大。我们发现，在应用 MeJA 后的一年中，越橘和越橘都延迟了营养和生殖物候，尽管越橘的反应更强。OTCs 的变暖对两个物种的物候学进展较弱，但综合效应并不一致。我们通过多组分段结构方程模型进一步研究了这种改变的物候对繁殖输出的影响，发现食草抗性驱动的物候变化对浆果数量有很强的中介作用，特别是在温暖的条件下，主要是在施用 MeJA 后的一年。合成。 这些结果表明，在理解全球变化对植物的影响时，需要考虑综合压力，并强调多个驱动因素可能对物种物候和繁殖产生未确定的协同效应。