Variations and controlling factors of carbon dioxide and methane fluxes in a meadow-rice ecosystem in a semi-arid region.

• The meadow-rice mixed ecosystem acted as CO 2 sink and CH 4 source. • CH 4 emissions were regulated by soil moisture during the dry period. • The seasonal dynamics of GPP, R eco , and CH 4 throughout the growing season were mainly regulated by T s and T a. Although previous studies have illustrated the variations in carbon dioxide (CO 2) and methane (CH 4) fluxes for different types of wetlands, there have been few reports on those of meadow-rice mixed ecosystems in semi-arid regions. In this study, eddy covariance (EC) technique was utilized to measure CO 2 and CH 4 fluxes for a meadow-rice mixed ecosystem during the growing season in 2020 in the Horqin Sandy Land, North China. The results indicated obvious diurnal and seasonal variations in gross primary productivity (GPP), ecosystem respiration (R eco), net CO 2 exchange (NEE), and CH 4 flux, with high levels during the vigorous growing stage and low levels during the early and late growing stages. The mean daily GPP, R eco , NEE, and CH 4 were 11.33 g CO 2 m−2 d−1, 6.37 g CO 2 m−2 d−1, −4.96 g CO 2 m−2 d−1, and 81.97 mg CH 4 m−2 d−1, respectively. The accumulated values of GPP, R eco , NEE, and CH 4 during the growing season were 1,756.54 g CO 2 m−2 (478.62 g C m−2), 987.30 g CO 2 m−2 (269.02 g C m−2), −769.24 g CO 2 m−2 (−209.60 g C m−2), and 12.7 g CH 4 m−2 (9.55 g C m−2), respectively, showing that the meadow-rice mixed ecosystem acted as CO 2 sink and CH 4 source. Low intensity CH 4 emissions were maintained during the dry period and were controlled by soil moisture (SM). The seasonal dynamics of GPP, R eco , and CH 4 throughout the growing season were mainly controlled by soil temperature (T s) and air temperature (T a). [ABSTRACT FROM AUTHOR]