Effect of temperature and moisture on O₂ evolution rate of cultivated Phaeozem: analyses of a long-term field experiment

Soil temperature and moisture are the main ecological factors regulating the processes of production and emission of CO₂ from soil surface. The CO₂ evolution rate from cultivated clay Phaeozem (Russia, Moscow region; 54°50’N, 37°35’E) were studied under field conditions from November 1997 to October 2002. The daily mean CO₂ evolution rate varied widely – from 0.9 to 246 mg C/m²/h. The total annual CO₂ flux from cultivated Phaeozem averaged 352 ± 148 g C/m²/yr, the interannual variability amounted to 42%. We found significant linear trends (R = 0.46–0.55, P < 0.001) reflecting the relationship between CO₂ emission and soil temperature through the whole observation period and during spring and autumn seasons as well. The exponential equations described these relationships for the same periods more adequately than the simple linear equations (R = 0.62–0.68, P < 0.01). The temperature coefficient Q₁₀ comprised 2.3 (for the whole data set) and was essentially higher 3.2–3.6 during the spring and autumn. The correlation between CO₂ evolution rate and soil moisture was insignificant for the whole period, winter, spring and autumn seasons as well. During the summer, correlation between CO₂ evolution rate and soil moisture was positive and very close (R = 0.74, P < 0.001), indicating that the soil moisture content was a main factor limitative the rate of CO₂ emission from soil for this period.