Temperature sensitivity of carbon dioxide production in aggregates and their responses to nitrogen addition in a freshwater marsh, Sanjiang Plain

Abstract

Nitrogen (N) availability may affect the decomposition of soil organic carbon (SOC) in a wetland experiencing global warming. The distribution of SOC within the soil matrix may be an important factor determining its turnover. However, the temperature sensitivity of SOC decomposition in aggregate and its response to N addition are crucial in the context of global warming but to date have been less obvious. Thus, an incubation experiment was conducted to investigate these problems in a freshwater marsh of Northeast China. The results showed that the rates of SOC decomposition in macro-aggregate were lower than that in micro-aggregate at high temperature (15°C), whereas macro-aggregate was the main source of carbon fluxes due to the largest mass contribution to bulk soil. Increasing temperature had a positive effect, while N addition produced neutral and negative effects on SOC decomposition. The micro-aggregate had the largest temperature sensitivity () within a temperature range from 5 to 15°C. A low level of N input had no effect on value in macro- and micro-aggregate as well as bulk soil, whereas a high level of N input significantly decreased the temperature sensitivity in 2–1 mm, < 0.25 mm aggregates and bulk soil. Our results suggest that SOC decomposition in micro-aggregate may be more sensitive to increasing temperatures, whereas this positive feedback to global warming may be weakened by enhanced N deposition in the near future.