Above-ground and below-ground interactions are essential for the assembly of forest communities and the maintenance of multiple ecosystem functions. However, there is limited understanding of how above-ground plant and below-ground soil microbial communities are associated across different climatic zones and along environmental gradients. Using comprehensive inventory data from 186 permanent plots along elevation gradients across three climate zones (subtropical, temperate-subtropical and temperate mountain forests), we examined the diversity associations between different groups of plants (woody and herbaceous) and soil microbes (fungi and bacteria). Associations between soil fungi and plants were stronger than those between soil bacteria and plants, particularly at the beta diversity level. Moreover, we observed that associations between soil microbes and plants were more pronounced in forests at low latitudes and intermediate elevations, and were sensitive to local abiotic conditions, including climatic and edaphic variables. Synthesis: These findings suggest that variation in climatic and edaphic conditions along environmental gradients is associated with differences in the strength of above-ground–below-ground associations. In addition to direct effects of climate change, plant and soil microbial communities could thus be indirectly affected via their biotic interactions under changing environmental conditions. This could have far-reaching consequences for community assembly and ecosystem functioning.