Time Space Variation Of Soil CO₂Flux In The Cultivated Sloping Land

Nowadays, people pay more and more attention to the global warming.CO₂is one of theimportant Green House Gases. Soil is an important terrestrial carbon pool. The soil erosion,transport and deposition driven by water and tillage have a large impact on the redistribution of soilorganic carbon in the landscape. Many researchers suggest that soil redistribution has an impact onthe rate of carbon input and decomposition, as a result of this, soil redistribution has a large impacton the carbon exchange between soil and atmosphere. Chinese loess plateau is the most seriousplace that affected by soil erosion in the world, so the study of the impact of soil erosion on soilCO₂flux in the sloping land in the loess plateau is very important. Our study conducted in acultivated sloping land in Chinese loess plateau, using¹³⁷Cs and²¹⁰Pbexas tracers to make sure theerosion and deposition site. The in-situ measurements of soil CO₂flux were conducted by Li-8100Automated Soil CO₂Flux System, soil temperature （5cm） and soil moisture （10cm） was measured at thesame time. The objectives of this study as follows:（1）researching the time space variation of soil CO₂flux in the erosion and deposition site;（2）explore the impact of soil erosion and deposition and soiltemperature and moisture on the soil CO₂flux. The results as follows:（1）the diurnal variation of soilmoisture is not significant, the diurnal variation pattern of soil CO₂flux is similar with the diurnalvariation pattern of soil temperature, with one peak every day, the highest value appears at the sametime or a little earlier than the highest value of soil temperature, soil temperature could explain41.70%-86.27%of the diurnal variation of soil CO₂flux in the erosion site and24.58%-78.95%in thedeposition site, the main control factor of the diurnal variation of soil CO₂flux is soil temperature whensoil moisture near the value of field water capacity;（2）the daily average of soil CO₂flux wascontrolled by both the soil temperature and soil moisture, R=aebTWccould explain75.6%of the timevariation of the daily average of soil CO₂flux in the erosion site and83.1%in the depositionsite;（3）the differences of soil temperature and soil moisture between the erosion and deposition siteis not consistency during the measurement time period, but the soil CO₂flux in the erosion sitealways lower than the deposition site, the total soil CO₂flux during the measurement time hassignificantly relationship with the area content of¹³⁷Cs and²¹⁰Pbex,the relationship between soilCO₂flux and the area content of¹³⁷Cs or²¹⁰Pbexis more significant when soil CO₂flux is relativehigher, the area content of²¹⁰Pbexis more suitable than¹³⁷Cs to explain the space variation of soilCO₂.In a word, the differences of soil CO₂flux between erosion and deposition site mainlycontrolled by the soil redistribution, neither soil temperature nor soil moisture is the main controlfactor.