The pratacultural ecosystem is a vital global food production system and the most extensive ecological barrier. Its responses to environmental and anthropogenic disturbances exhibit complex nonlinear dynamics. However, a unified framework to quantify these dynamics is still lacking. Hereby, we propose the life response curve (LRC) for pratacultural ecosystems. LRC describes the dynamic trajectory of the system along gradients of influencing factors as a three-stage process, including an adaptation stage, a response stage, and a stable stage. These stages are delineated by three key thresholds: the adaptation point (AP), optimum point (OP), and saturation point (SP). Based on the relationship between the initial and final states of the system, LRC defines four response patterns: over saturation (SP = OP > AP), surplus saturation (OP > SP > AP), equal saturation (OP > AP = SP), and deficit saturation (OP > AP > SP). The relationships among the three thresholds enable quantitative characterization of ecosystem resistance, resilience, and stability. The LRC is characterized by nonlinearity, a threshold group, irreversibility of the response process, and asymmetry around the optimum point. To validate the theoretical predictions of the LRC, we used the relationship between community aboveground biomass (AGB) and species richness (SR) as a response indicator. Field experiments were conducted along a precipitation gradient across four typical grassland types in China. The results showed that the relationship between AGB and SR changed regularly along the precipitation gradient. Positive correlation was observed in the desert steppe. A hump-shaped relationship appeared in the typical steppe. A negative correlation was found in the shrub grassland and subtropical grassland. These patterns correspond to the adaptation, response, and stable stages of the LRC, respectively. They are governed by the synergistic effects of resistance, resilience, and stability, and effectively validate the four response patterns proposed by the LRC. By proposing a dynamic model that includes initial stability, perturbation adaptation, threshold-driven transition, and a novel equilibrium state, the LRC overcomes the limitations of the classical three-threshold theory. This framework provides a theoretical foundation for adaptive grazing management, early warning of grassland degradation, and ecological restoration practices.