The temporal variations of soil CO₂ efflux (Rs) under sown alfalfa pasture and rangeland in the Loess Plateau was studied. Results showed t㏊t diurnal changes of soil CO₂ efflux were highly associated with changes of soil temperature, with tendency t㏊t the minimum values occurred between 0100 to 0600 (Beijing Standard Time, BST), maximum value between 1200 and 1600. Soil temperature at 5㎝ depth gave the highest correlation coefficient and account for 72.2% and 89.5% of diurnal variation in soil CO₂ effluxes at rangeland and alfalfa pasture, respectively. Annual CO₂ emissions from alfalfa pasture were 488.5 g C/㎡/yr, which was higher t㏊n t㏊t from rangeland.

• X. J. Chen
• F. J. Hou