Silicon (Si) accumulation is known to alleviate various biotic and abiotic stressors in plants with potential ecological consequences. However, for dicotyledonous plants our understanding of Si variation remains limited. We conducted a comparative experimental study to investigate (1) interspecific variation of foliar Si concentrations across 37 dicotyledonous forbs of temperate grasslands, (2) intraspecific variation in foliar Si concentration in response to soil Si availability, the influence of (3) phylogenetic relatedness, and (4) habitat association to moisture. Foliar Si differed markedly (approx. 70-fold) across the investigated forbs, with some species exhibiting Si accumulation similar to grasses. Foliar Si increased with soil Si availability, but the response varied across species: species with higher Si accumulation capacity showed a stronger response, indicating that they did not actively upregulate Si uptake under low soil Si availability. Foliar Si showed a pronounced phylogenetic signal, i.e., closely related species exhibited more similar foliar Si concentrations than distantly related species. Significant differences in foliar Si concentration within closely related species pairs nevertheless support that active Si uptake and associated high Si concentrations has evolved multiple times in forbs. Foliar Si was not higher in species associated with drier habitats, implying that in dicotyledonous forbs of temperate grasslands high foliar Si is not an adaptive trait to withstand drought. Our results demonstrated considerable inter- and intraspecific variation in foliar Si concentration in temperate forbs. This variation should have pervasive, but so far understudied, ecological consequences for community composition and functioning of temperate grasslands under land-use and climate change.

众所周知，硅 (Si) 的积累可以缓解植物中具有潜在生态后果的各种生物和非生物压力源。然而，对于双子叶植物，我们对 Si 变异的理解仍然有限。我们进行了一项比较实验研究，以调查（1）温带草原 37 种双子叶植物叶面硅浓度的种间变化，（2）叶面硅浓度响应土壤硅可用性的种内变化，（3）系统发育相关性的影响， (4) 栖息地与水分的关联。叶面硅在所研究的杂草中显着不同（约 70 倍），一些物种表现出与草相似的硅积累。叶面 Si 随着土壤 Si 可用性的增加而增加，但反应因物种而异：硅积累能力较高的物种表现出更强的反应，表明它们在土壤硅利用率低的情况下并没有主动上调硅的吸收。叶面硅表现出明显的系统发育信号，即密切相关的物种比远缘物种表现出更相似的叶面硅浓度。然而，密切相关的物种对中叶面硅浓度的显着差异支持活性硅吸收和相关的高硅浓度在杂草中已经进化了多次。在与较干燥栖息地相关的物种中，叶面硅含量并不高，这意味着在温带草原的双子叶植物中，叶面硅含量高并不是抵御干旱的适应性特征。我们的研究结果表明，温带杂草中叶面硅浓度存在相当大的种间和种内变化。