Seasonality of soil respiration under gypsum and straw amendments in an arid saline-alkali soil
2021
Wang, Xiujun | Wang, Junyi | Wang, Jiaping
Soil respiration (or CO₂ production) is often determined by measuring CO₂ efflux; however, there are differences between them in saline-alkali soils of arid land. The purpose of this study is to test a hypothesis that CO₂ production exceeds efflux in arid saline-alkali soils under organic and gypsum amendments. We conducted a modeling study that was based on a two-year field experiment with four treatments: control, gypsum addition, wheat straw incorporation, and gypsum-straw combination. A diffusion model was forced by soil CO₂, temperature and moisture that were continuously recorded at 0, 8 and 15 cm, and calibrated by measured CO₂ efflux. We then applied the model to calculate CO₂ production and efflux over 2014–2015, and found a strong and similar seasonality in both CO₂ production and efflux under all treatments (i.e., highest in summer with one peak in 2014 and two peaks in 2015). Our results showed enhanced CO₂ production and efflux over short period following rainfall. There were significantly exponential relationships between CO₂ production/efflux and temperature. While straw incorporation significantly increased CO₂ production and efflux, straw incorporation combined with gypsum amendment caused a decrease in CO₂ production and efflux. CO₂ production exceeded CO₂ efflux mainly in the first half year, and annual difference was 33–130 g C m⁻², with larger differences under gypsum amendment. Our study implies that a portion of respired CO₂ is transformed into other forms and stored in saline-alkaline soils in arid land.
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