One of the ultimate goals of Ecology is to understand factors explaining biodiversity patterns, which is fundamental to minimizing anthropogenic impacts and establishing better conservation policies. Silicon (Si) is a functional micronutrient associated with plant traits and processes such as vegetative growth, respiration, and decomposition rates. Here, we investigated the role of plant Si content across 16 plant communities in Israel. We built and compared three distinct structural equation models to measure the role and relative importance of plant Si content. Between 2020 and 2021, we established plots in each community and estimated plant Si content, soil Si content, species richness, functional diversity, green biomass, plant coverage, and annual rainfall. In contrast to a null model, the best model including plant Si content explained an additional variation of 42% in green biomass, 14% in species richness, and 9% in functional diversity. Plant Si content can, thus, improve the understanding of community structure and an ecosystem process (green biomass). This knowledge may improve the predictive power of plant community models under distinct climate change scenarios.