CO2 enrichment increases carbon and nitrogen input from fine roots in a deciduous forest.
* Greater fine-root production under elevated [CO2] may increase the input of carbon (C) and nitrogen (N) to the soil profile because fine root populations turn over quickly in forested ecosystems. * Here, the effect of elevated [CO)] was assessed on root biomass and N inputs at several soil depths by combining a long-term minirhizotron dataset with continuous, root-specific measurements of root mass and [N]. The experiment was conducted in a CO(2)-enriched sweetgum (Liquidambar styraciflua) plantation. * CO2) enrichment had no effect on root tissue density or [N] within a given diameter class. Root biomass production and standing crop were doubled under elevated [CO2]. Though fine-root turnover declined under elevated [CO2], fine-root mortality was also nearly doubled under CO2 enrichment. Over 9 yr, root mortality resulted in 681 g m(-2) of extra C and 9 g m(-2) of extra N input to the soil system under elevated [CO2]. At least half of these inputs were below 30 cm soil depth. * Increased C and N input to the soil under CO2 enrichment, especially below 30 cm depth, might alter soil C storage and N mineralization. Future research should focus on quantifying root decomposition dynamics and C and N mineralization deeper in the soil.
Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN, USA.
Colleen M
CM
Iversen
Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
Joanne
J
Ledford
Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
Richard J
RJ
Norby
D018533:Biomass; D002244:Carbon / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism*; D031317:Liquidambar / Q000033:anatomy & histology / Q000254:growth & development / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism*; D009656:North America; D018517:Plant Roots / Q000033:anatomy & histology / Q000254:growth & development / Q000378:metabolism; D012987:Soil; D014197:Trees / Q000254:growth & development / Q000378:metabolism*
D012987:Soil; D002245:Carbon Dioxide; D002244:Carbon; D009584:Nitrogen