Contrasting α- and β-Diversity Responses of Aboveground Vegetation and Soil Seed Banks to Experimental Warming over Two Consecutive Growing Seasons

Climate warming may alter both α and β diversity in alpine meadows, yet whether aboveground vegetation and soil seed banks respond synchronously remains unclear. Using a two-year open-top chamber (OTC) warming experiment, we investigated the responses of community composition, abundance, alpha diversity, and beta diversity in aboveground vegetation and the soil seed bank under experimental warming. Experimental warming significantly increased aboveground biomass to 1.73 times that of the CK treatment under the high-OTC treatment, while reducing species richness and the Shannon diversity index by 29.07% and 22.64%, respectively. Warming also promoted species turnover, increasing the beta diversity of aboveground vegetation by 24% and 37% under the low- and high-OTC treatments, respectively. In contrast, the soil seed bank mainly exhibited an increase in seed density, reaching 2.47 times that of the CK treatment under the high-OTC treatment, whereas species richness increased only slightly, and beta diversity remained relatively stable despite a significant, but comparatively smaller, shift in community composition. Overall, aboveground vegetation exhibited stronger responses to short-term warming, whereas the soil seed bank showed relatively stable diversity and community characteristics under the same warming treatments. These contrasting response patterns suggest that the greater stability of the soil seed bank may provide an important source of propagules for future vegetation regeneration and community restoration. Our findings reveal contrasting aboveground-belowground responses to warming and provide new insights into predicting the responses of alpine meadow plant communities to future climate warming.