Addition of External Organic Carbon and Native Soil Organic Carbon Decomposition: A Meta-Analysis

BACKGROUND: Extensive studies have been conducted to evaluate the effect of external organic Carbon on native soil organic carbon (SOC) decomposition. However, the direction and extent of this effect reported by different authors is inconsistent. OBJECTIVE: The objective was to provide a synthesis of existing data that comprehensively and quantitatively evaluates how the soil chemical properties and incubation conditions interact with additional external organic C to affect the native SOC decomposition. DATA SOURCE: A meta-analysis was conducted on previously published empirical studies that examined the effect of the addition of external organic carbon on the native SOC decomposition through isotopic techniques. RESULTS AND CONCLUSIONS: The addition of external organic C, when averaged across all studies, enhanced the native SOC decomposition by 26.5%. The soil with higher SOC content and fine texture showed significantly higher priming effects, whereas the soil with higher total nitrogen content showed an opposite trend. The soils with higher C:N ratios had significantly stronger priming effects than those with low C:N ratios. The decomposition of native SOC was significantly enhanced more at early stage of incubation (<15d) than at the later stages (>15d). In addition, the incubation temperature and the addition rate of organic matter significantly influenced the native SOC decomposition in response to the addition of external organic C.