PROCESS AND MECHANISM OF SALINE-ALKALI SOIL CARBON UPTAKE POTENTIAL IN THE SONGNEN PLAIN OF CHINA
The monitoring of soil respiration in the saline-alkali soil of the Songnen Plain from 2019 to 2021 was used to investigate whether there exists a net carbon uptake process for the saline-alkali soil and clarify the role and function in the regional carbon cycle.Based on the 3-years continuous monitoring of in-situ soil respiration for the pure saline-alkali soil in the Songnen Plain during 2019-2021,the CO2 flux dynamics and environment response of saline-alkali soil was explored.The results were showed as follows.(1)Besides the carbon release,the periodic carbon uptake existed in the saline-alkali soil of the Songnen Plain,and the time and intensity of soil carbon uptake in different years were inconsistent.(2)In 2019 and 2021,the saline-alkali soil carbon uptake intermittently occurred at night at the beginning and/or end of the growing season respectively.The intensity was significantly correlated with soil temperature and moisture and the uptake was a chemical carbon absorption via NaHCO3-NaCO3 transformation dominated by soil water.(3)The saline-alkali soil had continuous carbon uptake during the flooding period induced by the heavy rainfalls.The inorganic carbon uptake was derived from the physical carbon absorption of atmospheric CO2 driven by temperature gradient to form hydrated carbon dioxide.The conclusion are listed as follows.(1)In different periods of growing season,inorganic carbon uptake in the saline-alkali soil of the Songnen Plain has the different pattern and intensity.(2)Soil moisture is the key factor affecting the intermittent carbon uptake of saline-alkali soil at night.Temperature difference is an important driving force affecting carbon uptake by flooding,with the increase of soil-atmosphere temperature difference,saline-alkali soil carbon uptake is enhanced.(3)The maximum nighttime soil carbon uptake in 2019 and 2021 was-0.312 μmol CO2 m-2 s-1 and-0.753 μmol CO2 m-2 s-1,respectively;the maximum intensity of carbon uptake during flooding in 2020 and 2021 was-1.507μmol CO2 m-2 s-1 and-1.27 μmol CO2 m-2 s-1,respectively.(4)The regular pattern of carbon uptake by saline-alkali soil in the Songnen Plain can contribute 15％to the annual net CO2ecosystem exchange(NEE).Regardless of the spatial heterogeneity of soil carbon uptake,the annual saline-alkali soil carbon uptake potential is estimated to be 0.37 TgCa-1.
万方数据
维普
