Soil CO2 emissions from five different types of land use on the semiarid Loess Plateau of China, with emphasis on the contribution of winter soil respiration

Many studies have investigated the response of soil respiration to environmental factors. However, there are few studies estimating soil CO2 emissions in the land use of the Loess Plateau, China. Five different types of land use including a natural oak (Quercus liaotungensis) forest, a natural oriental arborvitae (Platycladus orientalis) forest, a black locust (Robinia pseudoacacia) plantation, a natural shrubland, and bare land were investigated from April 2010 to April 2012 in the semiarid Loess Plateau region. Total and winter season soil CO2 emissions were estimated using integration and interpolation methods based on periodic measurements of soil respiration and environmental factors. The integrated average annual and winter soil CO2 emissions (555.73-937.53 g C m−2 and 96.57-146.70 g C m−2) were higher than the interpolated values (480.52-805.83 g C m−2 and 82.83-102.31 g C m−2). The mean soil CO2 efflux and mean winter soil CO2 efflux during the 2 years ranged from 2.03 to 3.23 μmol m−2 s−1 and 0.52-0.80 μmol m−2 s−1 among different types of land use. The mean winter soil CO2 efflux was 11-25% of that of the mean growing season. Q10 values for the five types were negatively correlated with average soil temperature and moisture. Soil organic carbon content, soil total nitrogen content and C/N ratio were not correlated with the amount of winter soil CO2 emission, but correlated with annual total CO2 emission and the contribution rate from winter period in positive and negative trends, respectively. Model improvement may improve the estimation accuracy of soil CO2 emissions using the integration method, and increasing the frequency of soil respiration measurements is important for the interpolation method. It is inferred that the annual carbon sequestration, CO2 emission, and the economical conditions of carbon budget follow a descending sequence as oak forest > shrubland > oriental arborvitae forest > black locust plantation > bare land.