Species traits may determine plant interactions along with soil microbiome, further shaping plant–soil feedbacks (PSFs). However, how plant traits modulate PSFs and, consequently, the dominance of plant functional groups remains unclear. We used a combination of field surveys and a two‐phase PSF experiment to investigate whether forbs and graminoids differed in PSFs and in their trait–PSF associations. When grown in forb‐conditioned soils, forbs experienced stronger negative feedbacks, while graminoids experienced positive feedbacks. Graminoid‐conditioned soil resulted in neutral PSFs for both functional types. Forbs with thin roots and small seeds showed more‐negative PSFs than those with thick roots and large seeds. Conversely, graminoids with acquisitive root and leaf traits (i.e., thin roots and thin leaves) demonstrated greater positive PSFs than graminoids with thick roots and tough leaves. By distinguishing overall and soil biota‐mediated PSFs, we found that the associations between plant traits and PSFs within both functional groups were mainly mediated by soil biota. A simulation model demonstrated that such differences in PSFs could lead to a dominance of graminoids over forbs in natural plant communities, which might explain why graminoids dominate in grasslands. Our study provides new insights into the differentiation and adaptation of plant life‐history strategies under selection pressures imposed by soil biota.

中文翻译：

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为什么禾本科物种占优势？性状介导的植物-土壤反馈塑造群落组成

物种性状可能决定植物与土壤微生物组的相互作用，进一步塑造植物-土壤反馈（PSF）。然而，植物性状如何调节 PSF 以及植物功能群的主导地位仍不清楚。我们结合实地调查和两阶段 PSF 实验来研究非禾本科植物和禾本科植物在 PSF 及其性状与 PSF 关联方面是否存在差异。当在非禾本科植物生长的土壤中生长时，禾本科植物经历了更强的负反馈，而禾本科植物则经历了正反馈。禾本科植物调理的土壤导致两种功能类型的 PSF 呈中性。根细、种子小的杂草比根粗、种子大的杂草表现出更负的 PSF。相反，具有获得性根和叶性状（即细根和薄叶）的禾本科植物比具有厚根和坚韧叶子的禾本科植物表现出更大的正PSF。通过区分总体 PSF 和土壤生物群介导的 PSF，我们发现两个功能组内植物性状和 PSF 之间的关联主要由土壤生物群介导。模拟模型表明，PSF 的这种差异可能导致天然植物群落中禾本科植物相对于非草本植物占主导地位，这可能解释了为什么禾本科植物在草原中占主导地位。我们的研究为植物生活史策略在土壤生物群施加的选择压力下的分化和适应提供了新的见解。