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Keywords:

  • Carbon sequestration;
  • climate change;
  • DOC;
  • ecosystem C balance;
  • fine root;
  • litter;
  • microbial activity;
  • mineral soil;
  • organic soil;
  • soil respiration

Ecology Letters (2010) 13: 819–828

Abstract

Nitrogen (N) effects on ecosystem carbon (C) budgets are critical to understand as C sequestration is considered as a mechanism to offset anthropogenic CO2 emissions. Interactions between aboveground C and N cycling are more clearly characterized than belowground processes. Through synthesizing data from multiple terrestrial ecosystems, we quantified the responses of belowground C cycling under N addition. We found that N addition increased litter input from aboveground (+20%) but not from fine root. N addition inhibited microbial activity as indicated by a reduction in microbial respiration (−8%) and microbial biomass carbon (−20%). Although soil respiration was not altered by N addition, dissolved organic carbon concentration was increased by 18%, suggesting C leaching loss may increase. N addition increased the C content of the organic layer (+17%) but not the mineral soil layer. Overall, our meta-analysis indicates that N addition will increase short term belowground C storage by increasing C content of organic layer. However, it is difficult to predict the response of long term C sequestration since there is no significant change in mineral soil C content.