The underlying mechanisms by which different levels of warming affect respiration are likely to vary. Identifying the drivers of respiration across varying levels of warming is essential for more accurately predicting changes in carbon processes under future warming scenarios. 

This study conducted a long-term warming experiment in an alpine meadow ecosystem to investigate diurnal respiration dynamics. We analyzed diurnal and nocturnal ecosystem respiration changes under five warming gradients and investigated the mechanisms behind these changes. 

Our results show that warming significantly decreased diurnal respiration. Moreover, with increasing warming intensity, the limiting factor for respiration transitioned from nutrient to water scarcity. Low-level warming decreases soil respiration, mainly by reducing soil nutrient pools. High-level warming mainly reduces soil respiration by decreasing soil moisture. Warming significantly reduces aboveground biomass, leading to a corresponding decrease in respiration. We also observed that nocturnal respiration exhibited a pronounced and more complicated response compared to daytime respiration under warming conditions.

Our results emphasize the critical roles of nutrients and water in modulating CO2 emission flux under climate warming. Therefore, soil resource management is crucial for enhancing carbon sequestration in alpine grasslands.