Respiration Characteristics of Different Sized Soil Aggregates and Their Contribution to Carbon Emissions

The respiration characteristics of different sized yellow brown soil aggregates and their contribution to carbon emissions were assessed by soil pot experiment. Results showed that the respiration rates of aggregates and homogenized soil were highest at the beginning of the incubation, and then showed a descending tendency during the period of incubation. During the incubation time, the homogenized soil had the highest respiration rate. The respiration rates varied with aggregate size: (>5 mm)>(<1 mm)≈(1~5 mm). This indicated that the largest macroaggregates (>5 mm) had the highest contribution to carbon emissions. Correlation analysis showed that the respiration rates of different sized soil aggregates were significantly and exponentially correlated with soil temperature. The Q₁₀ values ranged from 2.53 to 5.11 and had the same variation tendency in different aggregates with soil organic carbon (SOC) and total nitrogen (TN). The <1 mm aggregates had the highest Q₁₀ value and SOC and TN contents, while>5mm and 1~5 mm aggregates had lower Q₁₀ values and SOC and TN contents. Our results suggested that both the contents of SOC and TN and the soil structure affected temperature sensitivity of soil respiration.