title: A global perspective on belowground carbon dynamics under nitrogen enrichment.
abstract: Nitrogen (N) effects on ecosystem carbon (C) budgets are critical to understand as C sequestration is considered as a mechanism to offset anthropogenic CO(2) 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.
authors.affiliation: Environmental Media Assessment Group-MD B243-01, National Center for Environmental Assessment, Office of Research and Development, U.S. EPA, Research Triangle Park, NC 27711, USA. lingliliu@hotmail.com
authors.forename: Lingli
authors.initials: L
authors.lastname: Liu
authors.forename: Tara L
authors.initials: TL
authors.lastname: Greaver
mesh_terms: D018533:Biomass; D002244:Carbon / Q000737:chemistry* / Q000378:metabolism; D009584:Nitrogen / Q000737:chemistry* / Q000378:metabolism; D012987:Soil; D012988:Soil Microbiology
chemical_list: D012987:Soil; D002244:Carbon; D009584:Nitrogen