Plant–plant interactions regulate plant community structure and function. Shifts in these interactions due to global climate change, mediated through disproportional increases of certain species or functional groups, may strongly affect plant community properties. Still, we lack knowledge of community‐level effects of climate‐driven changes in biotic interactions. We examined plant community interactions by experimentally removing a dominant functional group, graminoids, in semi‐natural grasslands in Southern Norway. To test whether the effect of graminoid removal varied with climate, the experiment was replicated across broad‐scale temperature and precipitation gradients. To quantify community‐level interactions across sites, we tested for changes in the remaining vascular community (i.e. forbs) cover, richness, evenness, and functional traits reflecting leaf‐economic investment and plant size over five years. The effect of graminoid removal on forb community structure and functioning varied over time, and along the climate gradients. Forb cover increased in response to graminoid removal, especially at warmer sites. Species richness increased following removal irrespective of climate, whilst evenness increased under warmer and wetter conditions irrespective of removal. No climate or removal effect was found for species turnover. Functional trait responses varied along the precipitation gradient – compared to controls, forb mean SLA decreased in drier conditions after graminoid removal. Leaf thickness increased under cooler and drier conditions irrespective of removal. These community structure alterations demonstrate stronger competitive interactions between forbs and graminoids under warmer conditions, whilst functional trait responses indicate a facilitative effect of graminoids under drier conditions. This indicates that both competition and facilitation regulate plant communities, suggesting complexity when scaling from populations to communities. Finally, both temperature and precipitation determine the direction and intensity of biotic interactions, with ecosystem‐wide implications for forb persistence and ecosystem functioning under future climates. Further work is needed to generalise the role of changing interactions in mediating community responses to climate change.

中文翻译：

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高山草原植物功能群相互作用随着变暖而加剧


植物与植物之间的相互作用调节植物群落的结构和功能。全球气候变化导致这些相互作用的变化，通过某些物种或功能群的不成比例的增加来介导，可能会强烈影响植物群落的特性。尽管如此，我们仍然缺乏对气候驱动的生物相互作用变化对社区层面影响的了解。我们通过实验去除挪威南部半天然草原中的主要功能群禾本科植物来研究植物群落的相互作用。为了测试禾本科植物去除的效果是否随气候变化而变化，在大范围的温度和降水梯度上重复了该实验。为了量化跨地点的群落水平相互作用，我们测试了剩余维管群落（即杂草）覆盖度、丰富度、均匀度和功能性状的变化，反映了五年内叶片经济投资和植物大小。禾本科植物的去除对杂草群落结构和功能的影响随着时间和气候梯度而变化。由于禾本科植物的去除，杂草覆盖率增加，特别是在温暖的地方。无论气候如何，移除后物种丰富度都会增加，而无论是否移除，在温暖和潮湿的条件下均匀度都会增加。没有发现气候或清除对物种更替有影响。功能性状响应随降水梯度而变化——与对照相比，在去除禾本科植物后，在干燥条件下，福布平均 SLA 降低。无论是否去除，在较冷和干燥的条件下叶片厚度都会增加。 这些群落结构的改变表明，在温暖的条件下，非禾本科植物和禾本科植物之间存在更强的竞争性相互作用，而功能性状反应表明，在干燥的条件下，禾本科植物具有促进作用。这表明竞争和促进都调节着植物群落，表明从种群到群落的扩展是复杂的。最后，温度和降水决定了生物相互作用的方向和强度，对未来气候下的福林持久性和生态系统功能具有整个生态系统的影响。需要进一步开展工作来概括不断变化的互动在调解社区应对气候变化方面的作用。