Study On Soil Carbon Dioxide Transmission Process And Its Application In The Yellow River Delta Wetlands

The continuous increase in carbon dioxide emissions has led to global warming.As the largest carbon pool in the terrestrial ecosystem,soil is also one of the major sources of atmospheric carbon dioxide.Soil carbon dioxide transport is not only the key process of carbon cycle in terrestrial ecosystems,but also the second largest carbon flux between land and atmosphere.Its slight change will have a significant impact on atmospheric carbon dioxide concentration.Therefore,the study of soil carbon dioxide transport process will help to understand the global carbon cycle and respond to global climate change.Wetlands are one of the major components of terrestrial ecosystems.Although the total area is small,carbon reserves are huge.The Yellow River Delta is located in the interlaced area of rivers,seas and lands.The soil is heavily salinized and is a typical wetland in northern China.With the establishment and development of the Yellow River Delta region as a national strategy,studying the transport process of carbon dioxide in the wetland soil of the Yellow River Delta has important theoretical and guiding significance for the development of the region's green development,engineering construction and ecological civilization construction.This study was conducted using a combination of field experiments and theoretical analysis.The field experiment is divided into three parts:1)In order to explore the process of soil carbon dioxide transport,soil CO2 detectors(GMT221,Vaisala,Inc,Finland)and soil temperature sensors(The 109 Temperature Probe,Campbell Scientific,Inc)were installed in the test plots to continuously measure soil carbon dioxide concentrations and soil temperatures at different depths(15 cm,30 cm,45 cm).2)In order to explore the discharge rate of surface carbon dioxide flux and its daily variation,the LI-8100A soil carbon flux automatic measurement system(Li-Cor,Inc,Lincoln,NE,USA)was used to measure the surface carbon dioxide flux and surface temperature several times in succession.3)In order to understand the response mechanism of precipitation to the carbon dioxide transport process in soil,we conducted two artificial simulated precipitation tests,and measured the surface carbon dioxide flux of the experimental group(artificial precipitation)and the control group(without artificial precipitation)in real time.Processing and analysis of all the raw data obtained above,preliminary conclusions are as follows:(1)With the increase of soil depth,the soil carbon dioxide concentration increased significantly.At the same depth,the soil carbon dioxide concentration in autumn was significantly higher than that in winter,and this change was closely related to soil temperature.The surface carbon dioxide flux and atmospheric temperature have similar daily variations,showing a unimodal change curve.According to the regression equation,Q10 values for non-growth seasons in the region were 3.49 to 3.74.Q10 values decreased slightly with increasing temperatures.Due to the increase in surface temperature,the surface carbon dioxide flux in the summer(August)is significantly greater than the surface carbon dioxide flux in the spring(March).(2)Artificial simulation of precipitation control experiments found no "Birch effect" in the area.In contrast,artificial precipitation has a significant inhibitory effect on the transmission and diffusion of soil carbon dioxide to the earth's surface.Therefore,it is illustrated that precipitation is not only an absolute contribution to the release of surface carbon dioxide flux.When the soil moisture is too large or has reached saturation,precipitation will significantly inhibit the surface carbon dioxide flux.(3)Surface carbon dioxide flux has a highly significant linear or exponential correlation with soil carbon dioxide concentration gradient and soil temperature.We use an empirical model to estimate the surface carbon dioxide flux in the non-growth season of the Yellow River Delta wetland.By comparison,we found that all model fitting results are very similar in seasonal variation.The maximum value is 0.47 to 0.58?mol/m2/s,the minimum value is-0.15 to 0.01 ?mol/m2/s,and the average value is 0.1 to 0.13 ?mol/m/s.Due to the limited amount of data,further discussion and research are needed on the application of the established empirical model in the growing season and other ecosystems.