Study On Soil CO₂ Flux Monitoring System Based On Concentration Gradient Method

Soil respiration is an important way for terrestrial carbon pools to enter into atmospheric carbon pools.It is also a key ecological process affecting the change of atmospheric CO2 concentration.As one of the main components of terrestrial ecosystem carbon cycle,soil respiration is an important circulation way of global carbon cycle and has a direct impact on global carbon balance.Only by studying the changes of CO2 flux in different layers of soil vertical profile,can we have a better understanding of the generation of CO2 gas in soil.Therefore,a monitoring system of soil CO2 flux(soil respiration)based on concentration gradient method is proposed and designed,which can simultaneously measure CO2 concentration,temperature and moisture at three different depths of soil vertical profile,and calculate CO2 flux by Fick’s first law.Firstly,this paper introduces the related research of soil CO2 flux monitoring system.Based on the principle of measurement,the software and hardware functions of the monitoring system are designed,and a monitoring system based on STM32 single chip computer is built.The concentration gradient method is used to measure soil CO2 flux.Then,the experiment verifies that the monitoring system of soil CO2 flux has good stability and accuracy.Finally,through the soil CO2 flux measurement experiment,five kinds of gas diffusion coefficient models were used to calculate the CO2 flux under different soil moisture content,bulk density and fertilization conditions,and compared with the alkali absorption method to evaluate and analyze the applicability of the five diffusion coefficient models.The results show that Moldrup model has the best applicability,followed by MQ model,Penman model,Marshall model and PMQ model have poor applicability.