中国松嫩平原盐碱土固碳潜力过程及机理研究

PROCESS AND MECHANISM OF SALINE-ALKALI SOIL CARBON UPTAKE POTENTIAL IN THE SONGNEN PLAIN OF CHINA

关键词:  盐碱土  土壤呼吸  夜间吸碳  水淹  松嫩平原

Key words:  saline-alkali soil  soil respiration  nocturnal carbon uptake  waterlogging  Songnen Plain

摘要:

目的 通过2019—2021年对松嫩平原盐碱地土壤呼吸的监测，探究盐碱土是否存在净碳吸收过程，明确盐碱土碳吸收在区域碳循环中的作用和地位。方法 文章基于纯盐碱地原位土壤呼吸的3年连续监测，探究盐碱地土壤CO₂通量动态变化及其环境响应。结果 （1）松嫩平原盐碱地除碳释放外存在阶段性碳吸收，不同年份盐碱土发生碳吸收的时间和强度不一致。（2）2019年和2021年土壤碳吸收主要发生在夜间，两次间歇性碳吸收分别发生于生长季初期和末期，其强度与土壤温、湿度显著相关，是由水分参与下的NaCO₃转化为NaHCO₃的化学性吸碳。（3）松嫩平原盐碱土在水淹期间存在连续性碳吸收，水淹状态下的吸碳来源于温度梯度驱动的大气CO₂形成水合二氧化碳的物理性吸碳。结论 （1）生长季的不同时期，松嫩平原盐碱土有着不同的碳吸收模式和强度。（2）土壤水分是影响盐碱土夜间间歇性吸碳的关键因素，温差是影响水淹吸碳的重要驱动力，随着温差加大，土壤碳吸收加强。（3）2019年和2021年夜间土壤碳吸收的最大值分别为-0.31 μmol CO₂ m^-2 s^-1和-0.75 μmol CO₂ m^-2 s^-1；2020年和2021年淹水期间碳吸收最大强度为-1.51 μmol CO₂ m^-2 s^-1和-1.27 μmol CO₂ m^-2 s^-1。（4）松嫩平原盐碱土的规律性固碳可为生态系统年净碳吸收贡献15%。不考虑土壤碳吸收的空间异质性，其每年的碳吸收潜力预计可达0.37 Tg C a^-1。

Abstract:

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 -1.507 μmol 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 CO₂ ecosystem 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 Tg C a^-1.