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Open Access Publications from the University of California

Investigating short-term response of soil moisture-temperature-CO2 interactions to weather anomalies

  • Author(s): Anjileli, Hassan
  • Advisor(s): AghaKouchak, Amir
  • et al.

Global warming, caused by the increase of CO2 emissions, has increased frequency and intensity of climate extremes. Extreme events have large impacts on the terrestrial ecosystem carbon. Therefore, it is fundamental to investigate the subterrestrial processes of producing carbon dioxide. Carbon dioxide flux is affiliated with heterotroph and autotroph and they are influenced by abiotic and biotic factors. In this study we investigated the soil moisture-soil temperature-soil respiration relationships on bare soil and the impact of hot days and warm spells on soil respiration. Measurements were taken from February to June 2016 in Southern California (33° 39ʹ32.7ʺ N, 117° 50ʹ55.9ʺ W) where several hot spells occurred. Bias corrected maximum air temperature was used to calculate the warm spell threshold. Land and atmospheric parameters respond with dealt to soil respiration. Association metrics were employed to explore the relationship between soil respiration and both collected and time-lagged data. Soil moisture and soil temperature were the two most important factors affecting soil respiration whereas soil temperature was the ascendant factor. The results show that soil with temperatures ranging from 20 to 25 °C displays the highest average CO2 flux value (~ 1.12 μmol CO2 m-2 s-1). By deviating from the soil temperature range of 20 to 25 °C the average CO2 flux decreases. Soil respiration increases by around 50% when soil temperature increases from 15 to 20 °C to 20 to 25 °C and decreases by 48% by deviating from the soil temperature range of 20 to 25 °C to 25 to 30 °C. Soil respiration decreased when both soil moisture and soil temperature were out of the optimum range (0.225 to 0.250 m3/m3 and 20 to 25 °C, respectively) of microorganism. In other words, soil respiration decreased when soil moisture and or soil temperature were too low or too high. Hot days or warm spells intensified soil temperature, leading to low soil respiration compared to non-hot days or warm spells. A net flux of 0.60 grams of CO2 per m-2 was released during the study period.

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