Effects Of Soil Salinity On Soil CO₂ Flux In Tamarix“Shrub Islands”

The carbon cycle research in the context of global warming has attracted much attention.Carbon in wetland soils has become one of the hotspots in global change research.Tamarix chinensis Lour.as an important salt and alkali-tolerant plant in coastal wetlands,the issue of CO₂release from the shrub island formed by it needs to be clarified.This article uses the Yellow River Delta wetlands as the research area,based on field monitoring and indoor statistical analysis,habitat characteristics of Tamarix chinensis Lour.shrub island are analyzed.The effects of salinity on soil CO₂release in Tamarix chinensis Lour.shrub island in high-salinity and low-salinity environments were discussed.The results show:(1)There are two different habitat types in the study area:high-salt and low-salt.The soil SOM and AN contents of Tamarix chinensis Lour.shrub island under the two kinds of microscopes generally showed a trend of gradually decreasing from under the crown.Compared with high-salt habitats,Tamarix chinensis Lour.in low-salt habitats has higher ability to gather and raise.Tamarix chinensis Lour.shrub island in both habitats has the function of reducing the salinity of shrub soil.Make most of the sub-canopy salt ion content lower than the crown margin and bare ground.Compared to high-salt habitats,Tamarix chinensis Lour.in low-salt habitats has a higher salting ability,It shows that most of the salt ion content in low-salt habitats is lower than that in high-salt habitats.(2)The soil CO₂flux under Tamarix chinensis Lour.shrub island showed different changes.The CO₂flux in the soil under islands in low-salt habitats is generally higher than in high-salt habitats.Moreover,the average CO₂flux in the east direction is obviously higher than that in the south,west,and north directions.Affected by factors such as light and temperature,the daily dynamics of soil CO₂flux in"shrub island"basically showed a unimodal trend of first increase and then decrease.The maximum value appears around12:00-14:00.Soil CO₂flux was highest in summer,followed by autumn,and lowest in spring.In space,due to the influence of changes in soil salt content under shrub island,The CO₂flux showed a gradual decrease from under the crown to the periphery.(3)From shrub island to the crown edge to the bare land,the change of soil CO₂flux can be characterized by the rate of change.In the high salinity microscope,the CO₂emission from the canopy soil was reduced by 28.95%compared with that under the canopy.The CO₂emission from bare soil decreased by 54.89%.In the low-salt mirror,the CO₂emission from the canopy soil was reduced by 28.45%compared with that under the canopy.CO₂emission from bare soil decreased by 44.16%.From under the canopy to the bare land,the gradient of the CO₂release in the high-salt and low-salt habitats differed by10.73%.Regression analysis shows:Under the high salinity microscope,the one-degree quadratic polynomial model(y=0.0464x²-0.6556x+2.5428,R²=0.7981,P<0.05)can better express the relationship between soil SAL and soil CO₂flux.In addition to SAL,Cl^-and SO₄^2-also have a good fitting relationship with soil CO₂flux.Under low salinity microscope,the one-degree quadratic polynomial model(y=0.1753x²-1.5347x+3.8922,R²=0.6778,P<0.05)can better express the relationship between soil SAL and soil CO₂flux,In addition to SAL,Cl^-,Na⁺,Ca²⁺,and Mg²⁺also have a good fitting relationship with soil CO₂flux.The overall trend is that as the total salt content of the soil increases,the amount of soil CO₂release decreases.