|其他摘要||Soil CO2 flux is the second largest flux of carbon cycle in terrestrial ecosystems, and can result in a significant change to the atmospheric CO2 concentration with slight modification in its rate. Thus, soil CO2 flux is a critical ecological process for future atmospheric CO2 concentration, and is considered as an important regulator of regional and global carbon cycle. The abiotic absorption of atmospheric CO2 in saline/alkaline soil is a unique and brand-new phenomenon, which break the assumption that soil CO2 fluxes are purely biological in origin, leading arid and semi-arid lands as a large sink for CO2 beside the oceans. However, due to lacking differentiation standard and quantification data, the significance of abiotic CO2 flux to soil CO2 flux and global carbon cycle is still uncertainty. The experiment was carried out from 2009 to 2012 at Fukang Station of Desert Ecology. The cause of negative CO2 flux was analyzed by monitor In situ soil CO2 flux in field. To determine the potential contribution of abiotic CO2 flux to soil CO2 flux, the abiotic CO2 flux was differentiated by sterilization treatment with pressure steam chamber. The controlling factors were identified by comparing abiotic CO2 flux among various sterilized saline/alkaline soils. Based on the theory of CO2 dissolution chemistry, the saline/alkaline soil abiotic CO2 flux model was established to simulate the movement and transformation of CO2 in the soil, and validated by measurement. The main results are as follows:
(1) Along with weakened soil biotic CO2 flux during night time, the negative soil CO2 flux in the saline/alkaline soil were attributed to the atmospheric CO2 concentration fluctuation and an abiotic chemical processes in the soil.
(2) As a significant components of soil CO2 flux in saline/alkaline soil, soil abiotic CO2 flux accounted for 60%-90% variation of soil CO2 flux. The strength of abiotic CO2 flux was 1.3-1.6 multiple than soil biotic CO2 flux. Thus, the soil biotic CO2 flux was significantly underestimated by neglecting soil abiotic CO2 flux.
(3) For certain saline/alkaline soil, temperature is the main factor which dominated the soil abiotic CO2 flux. Saline/alkaline soil tends to absorb CO2 at low temperature, and release CO2 at high temperature. Soil pH was a good indicator for the potential abiotic soluble carbon pool. The pH had different impact on soil abiotic CO2 flux while the temperature was low or high. Although potential abiotic soluble carbon pool was also increased with soil salinity, it required considerable soil salinity difference to change the abiotic CO2 flux.
(4) By the validation of abiotic CO2 flux model, the soil abiotic chemical process was confirmed to be the dissolution of CO2 in soil. CO2 was existed as different kinds of carbonate species in soil solution and transformed from one to another.
(5) At the diel scale, the variation of atmospheric CO2 concentration rather than temperature dominated soil CO2 flux at night. The consequence of ignoring the effects of atmospheric CO2 concentration is overestimated the effects of temperature on soil CO2 flux and overestimated the temperature sensitivity of soil CO2 flux, which would cause large errors in climate model for prediction global climate change.
Therefore, the non-negligible role of soil abiotic CO2 flux as potential contribution to the ecosystem carbon cycle requires further investigation towards a better understanding of soil CO2 flux and global carbon cycle. Our study highlights the need to include atmospheric CO2 concentration than temperature to characterize the diel variation of soil CO2 flux. Recruiting the atmospheric CO2 concentration module into global change model will dramatically improve our ability to predict future patterns of ecosystem carbon cycling.|
王忠媛. 盐碱土无机CO2通量的分离和量化[D]. 北京. 中国科学院大学,2016.