Effect of nitrogen addition on soil organic carbon in freshwater marsh of Northeast China
Increased nitrogen (N) input to ecosystems could alter soil organic carbon (C) dynamics, but the effect still remains uncertain. To better understand the effect of N addition on soil organic C in wetland ecosystems, a field experiment was conducted in a seasonally inundated freshwater marsh, the Sanjiang Plain, Northeast China. In this study, litter production, soil total organic C (TOC) concentration, microbial biomass C (MBC), organic C mineralization, metabolic quotient (qCO2) and mineralization quotient (qmC) in 0–15 cm depth were investigated after four consecutive years of N addition at four rates (CK, 0 g N m−2 year−1; low, 6 g N m−2 year−1; moderate, 12 g N m−2 year−1; high, 24 g N m−2 year−1). Four-year N addition increased litter production, and decreased soil organic C mineralization. In addition, soil TOC concentration and MBC generally increased at low and moderate N addition levels, but declined at high N addition level, whereas soil qCO2 and qmC showed a reverse trend. These results suggest that short-term N addition alters soil organic C dynamics in seasonally inundated freshwater marshes of Northeast China, and the effects vary with N fertilization rates.
KeywordsNitrogen enrichment The Sanjiang Plain Soil microbial biomass Soil organic C mineralization Wetlands
This work was supported by “Strategic Priority Research Program-Climate Change: Carbon Budget and Related Issues” of the Chinese Academy of Sciences (No. XDA05050508), National Natural Science Foundation of China (Nos. 40930527 and 41125001) and National Key Basic Research and Development projects of China (No. 2009CB421103). The authors thank James W. LaMoreaux and two anonymous reviewers for their suggestions.
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