Understanding how semi-arid sandy grassland vegetation responds to precipitation change holds significance for predicting ecosystem resilience and succession. Using a seven-year field manipulation experiment in the Horqin Sandy Grassland, we examined vegetation structural/functional responses at population, functional-group, and community levels under contrasting precipitation patterns. Results showed that precipitation change amount primarily governed community composition responses, with species diversity increasing under low-amount changes but decreasing under high-amount changes, whereas precipitation change direction dominated productivity responses, with total biomass increasing under wetting but decreasing under drying. These communitylevel responses were modulated by two intrinsic pathways. A dominant pathway via key functional groups generally prevailed under extreme wetting, with the contrasting yet complementary expansions of annual forbs during drying and perennial grasses during wetting enhancing aboveground allocation of community productivity but suppressing belowground investment. A buffering pathway via community-level trade-offs, active under moderate precipitation changes and extreme drying, elevated the root-shoot ratio to coordinate aboveground-belowground productivity partitioning. Predicting vegetation succession and guiding restoration in semi-arid regions therefore requires attention to precipitation mode (beyond mean values), complementary functional groups, and belowground biomass allocation.