Contribution of winter soil respiration to annual soil CO _2 emission in a Mollisol under different tillage practices in northeast China

摘要

Winter soil CO _2 emission is a very important component of the annual carbon budgets, however, almost no information on winter CO _2 emission is available from the cropland soil in northeast China. In this study, soil CO _2 flux was measured for a 2-year period from an ongoing tillage trial on Black soil in northeast China to quantify seasonal patterns in soil CO _2 flux rate and wintertime contribution to annual soil respiration. Average soil CO _2 flux rates in the winter (November to March) were between 0.64 to 1.22 g CO _2 m -2 d ~(-1), in the non-growing season (October and April) were 2.09-3.56 g CO _2 m -2 d ~(-1), whereas in the growing season (May to September) they were between 10.9 to 12.7 g CO _2 m ~(-2) d ~(-1), with no significant differences among tillage treatments. Total winter, non-growing and growing season soil CO _2 emissions were 0.28-0.45 Mg C ha ~(-1), 0.36-0.53 Mg C ha ~(-1), and 4.52-5.55 Mg C ha ~(-1), respectively, among tillage treatments. The contributions of winter soil respiration to annual soil CO _2 emission ranged from 5.1 to 7.1%, and the non-growing season emission ranged from 11.4 to 15.2% among tillage treatments. Our results indicate that in northeast China, cropland Black soil continuously emits CO _2 throughout the non-growing season, and the wintertime soil respiration plays a significant role in annual soil carbon budgets. Hence winter soil CO _2 emission must be taken into consideration when the role of the soil ecosystem is assessed as either a sink or source of CO _2 to the atmosphere.