Exploring the response of net ecosystem CO2 exchange to precipitation events in a wet meadow ecosystem by using an improved semi-empirical physical model

• The proposed model showed better performance by introducing parameters with physical significance. • NEE generally shows an exponential-form response to precipitation within the threshold interval of 5–40 mm. • NEE is highly sensitive to post-drought precipitation with a positive intraday value. Wet meadows are crucial natural carbon sinks in arid and semi-arid grasslands, playing a pivotal role in terrestrial carbon cycling. Maintaining these ecosystems has emerged as a critical strategy for climate change mitigation, but the impacts of altered precipitation regimes under global warming on their carbon sequestration capacity still remain poorly quantified. This study developed a semi-empirical physical model with enhanced parameterization methods to evaluate the dynamic responses of net ecosystem CO 2 exchange (NEE) to precipitation disturbances. A wet meadow ecosystem in a typical steppe was taken as the study case , with precipitation events of different intensities systematically considered. Three key advances were achieved. First, the model incorporates interpretable parameters with explicit calculation methods, overcoming previous reliance on empirical values and enhancing predictive accuracy. Second, a characteristic NEE response pattern was identified, with carbon absorption peaking immediately post-precipitation before gradually returning to baseline levels. Our results established 5 mm as the precipitation threshold for triggering detectable NEE anomalies, and demonstrated ecosystem resilience even under extreme 40 mm events. The resistance and resilience times were quantified as 0.23–2.90 days and 6–33 days respectively, exhibiting positive correlations with precipitation intensity . Third, mechanistic analysis reveals that precipitation variability modulates carbon sequestration through coordinated controls on vegetation photosynthesis and multi-interface ecological respiration processes. These findings provide theoretical references for optimizing carbon sink management and predicting ecosystem stability under climate change.