Effect of Nitrogen Deposition on Soil CO2 Emission During Freezing-Thawing Incubation Period

Due to the traditional analysis method on the influence of soil nitrogen deposition on soil CO2 emissions during the freezing and thawing period, the initial impact of nitrogen deposition on soil CO2 emissions during the freezing and thawing incubation period was not analyzed, resulting in insufficient accuracy of the later analysis results. A new method was proposed to analyze the effect of nitrogen deposition on Soil CO2 emission during freeze-thaw cultivation. On this basis, the contents of soil temperature, moisture, inorganic nitrogen, and soluble carbon were determined. Three freeze-thaw models of nitrogen deposition levels were established. The influence of nitrogen deposition on Soil CO2 emission and the effect of nitrogen deposition on CO2 emission in alpine wetlands were studied by multivariate variance analysis. The effect of nitrogen deposition on CO2 emission of alpine wetlands was studied. The results showed that different soil temperatures and moisture content had a great influence on the seasonal variation of soil flux, which was generally consistent with the single peak of soil temperature, but highly consistent with the variation of soil moisture content in different growth periods. Nitrogen treatment changed the DOC content of soil organic matter. DOC content in the mineral layer and organic layer increased significantly in low and medium nitrogen treatments. The CO2 emission of soil in the freezing period is lower than that in a normal temperature period, and that in multiple freezing periods is less than that in one freezing period. The CO2 emission rate of soil under freeze-thaw conditions is the smallest, and the CO2 emission rate of soil after thaw is the largest. Appropriate nitrogen deposition can promote soil CO2 emission, while high nitrogen deposition can inhibit CO2 emission.