Winter soil CO2 efflux and its contribution to annual soil respiration in different ecosystems of Ebinur Lake Area

Arid and semiarid areas account for about one-third of the total land surface, and which play an important role in the global carbon cycle and climate system. However, up to now, compare with plenty knowledge information on winter soil efflux of forest ecosystems in mid-latitude ecosystems, winter soil efflux of arid areas at mid-latitude ecosystems is scare, Ebinur Lake Area, which is the study area of the present study, is located in arid regions of Northern China, with a vulnerable ecological environment suffering from extreme weather and climate. The objectives of this study were: (1) measure the winter soil respiration rate in our study area and determine its major environmental factors; (2) determine the winter soil CO2 efflux and its contribution to annual soil CO2 efflux in different ecosystems; and (3) discuss the estimated method of soil respiration that is most suitable to arid areas. We measured winter soil CO2 efflux and the associated environment factors in a farmland ecosystem (50a and 9a cotton fields), an abandoned land ecosystem (7a and 3a abandoned lands) and desert ecosystem (Populus euphratica, Phragmites australis communities and sandy desert) in Ebinur Lake Area, China. The average winter soil respiration rate in the arid areas in the mid-latitude was 0.063 μmol m−2 s−1 to 0.730 μmol m−2 s−1. Specifically, the average winter soil respiration rate in the farmland ecosystems, abandoned land ecosystems and desert ecosystems were 0.686 μmol m−2 s−1, 0.443 μmol m−2 s−1 and 0.276 μmol m−2 s−1, respectively. Range of annual Q 10 (known as the increase in soil respiration rate per 10°C increase in temperature) in the three ecosystems were 0.989 to 4.962, 1.971 to 2.096 and 0.947 to 5.173, respectively. The relatively higher Q 10 values in the different ecosystems were all obtained in winter. We found that water (in the form of soil moisture or atmospheric humidity) was the primary factor that affected the change of soil respiration rate in the winter. Winter soil CO2 efflux were 9 g C m−2 to 132 g C m−2 and 19 g C m−2 to 130 g C m−2 by the observed and modelled method for soil respiration, respectively. The average winter soil CO2 efflux were 79.4 and 78.7 g C m−2, reLspectively. The contributions of winter soil CO2 efflux to annual one were 4% to 31% and 4% to 30%. In the study area, the model using the observed ecosystem-specific response equations between soil respiration and water-temperature simulated the soil respiration rate was the most suitable ones.