Mulching practices improve soil hydrothermal conditions, which cause changes in soil respiration. Conventional straw mulching has low productivity in areas with relatively low temperatures. Meanwhile, the responses of soil respiration to mulching practices and the relationship between changes in environmental factors caused by mulching and carbon (C) components are not clear in dryland agroecosystem. In this study, we monitored seasonal changes in soil respiration flux and heterotrophic respiration flux of winter wheat fields under different mulching practices in a semiarid rainfed agroecosystem of northern China. The fields were designed for the following three treatments: straw strip mulching (SSM), plastic film mulching (PFM), and non-mulching (CK). Compared to CK, SSM decreased cumulative soil respiration and heterotrophic respiration by 11.6% and 13.3%, whereas PFM increased these values by 12.8% and 8.5%, respectively. SSM significantly decreased soil temperature but increased soil water-filled pore space (WFPS), while PFM significantly increased soil WFPS without affecting soil temperature. Respiration flux was more highly correlated with soil temperature and air temperature than with WFPS and rainfall. SSM and PFM respectively increased by 5.7–9.1% and 10.8–35.5% for grain yield, by 8.1–45.6% and 16.2–69.5% for straw yield, by 8.6–28.6% and 15.1–36.4% for net primary production, and by 23.1–80.6% and 20.3–95.2% for net ecosystem production. Furthermore, mulching practices had a great potential of soil C sequestration and SSM significantly increased soil organic carbon. Changes in ecosystem C components were primarily driven by biomass, followed by soil temperature and air temperature rather than WFPS and rainfall. Based on the sustainability of agroecosystems, SSM increased grain yield of winter wheat while reduced carbon emissions, which showed great potential for C sequestration and may create an environmentally friendly C sink system in a semiarid rainfed agroecosystem of northern China.