A better understanding of thermal acclimation of leaf dark respiration in response to nocturnal and diurnal warming could help accurately predict the changes in carbon exchange of terrestrial ecosystems under global warming, especially under the asymmetric warming. A field manipulative experiment was established with control, nocturnal warming (1800-0600hours), diurnal warming (0600-1800hours), and diel warming (24h) under naturally fluctuating conditions in a semiarid temperate steppe in northern China in April 2006. Temperature response curves of in situ leaf dark respiration for Stipa krylovii Roshev. were measured at night (R-n) and after 30min of darkness imposed in the daytime (R-d). Leaf nonstructural carbohydrates were determined before sunrise and at sunset. Results showed that R-n could acclimate to nocturnal warming and diurnal warming, but R-d could not. The decreases in Q(10) (temperature sensitivity) of R-n under nocturnal-warming and diurnal warming regimes might be attributed to greater depletion of total nonstructural carbohydrates (TNC). The real-time and intertwined metabolic interactions between chloroplastic and mitochondrial metabolism in the daytime could affect the impacts of warming on metabolite pools and the distinct response of R-n and R-d to warming. Projection on climate change-carbon feedback under climate warming must account for thermal acclimation of leaf dark respiration separately by R-n and R-d.