Ongoing climate change threatens biodiversity and directly affects the stability of plant-animal communities. However, it is unclear how the species diversity of biological communities responds to natural climate warming, and whether the temporal stability of biodiversity in the face of climate warming varies with environmental gradients in different communities due to the lack of long-term data. We present three high-resolution records of terrestrial mollusk fossils dating back 25 kyr along a climatic and vegetation gradient from southeast to northwest across the Chinese Loess Plateau. The records show that deglacial warming increased the mollusk diversity by ∼30% in species-poor steppe communities; however, in high-diversity forest-steppe communities, the effect was less, and diversity's dynamic stability was even maintained. The high-diversity communities adjusted their composition by substituting thermo-humidiphilous taxa for cold-tolerant taxa, with the compositional turnover reaching ∼60%. The mollusk diversity of species-poor communities is shown to be more sensitive to the last deglacial warming and associated with the strengthening of the East Asian Summer monsoon than that of diverse communities. The increased temporal instability and sensitivity of biodiversity in species-poor communities in the face of climate disturbances, from a long-term perspective, highlights the potential risk of collapse of soil communities under future anthropogenic biodiversity loss.