title: Fine-root respiration in a loblolly pine (Pinus taeda L.) forest exposed to elevated CO2 and N fertilization.
abstract: Forest ecosystems release large amounts of carbon to the atmosphere from fine-root respiration (R(r)), but the control of this flux and its temperature sensitivity (Q(10)) are poorly understood. We attempted to: (1) identify the factors limiting this flux using additions of glucose and an electron transport uncoupler (carbonyl cyanide m-chlorophenylhydrazone); and (2) improve yearly estimates of R(r) by directly measuring its Q(10)in situ using temperature-controlled cuvettes buried around intact, attached roots. The proximal limits of R(r) of loblolly pine (Pinus taeda L.) trees exposed to free-air CO(2) enrichment (FACE) and N fertilization were seasonally variable; enzyme capacity limited R(r) in the winter, and a combination of substrate supply and adenylate availability limited R(r) in summer months. The limiting factors of R(r) were not affected by elevated CO(2) or N fertilization. Elevated CO(2 )increased annual stand-level R(r) by 34% whereas the combination of elevated CO(2) and N fertilization reduced R(r) by 40%. Measurements of in situ R(r) with high temporal resolution detected diel patterns that were correlated with canopy photosynthesis with a lag of 1 d or less as measured by eddy covariance, indicating a dynamic link between canopy photosynthesis and root respiration. These results suggest that R(r) is coupled to daily canopy photosynthesis and increases with carbon allocation below ground.
authors.affiliation: Program in Ecology, Evolution, and Conservation Biology, University of Illinois at Urbana - Champaign, Urbana, IL 61801, USA.
authors.forename: John E
authors.initials: JE
authors.lastname: Drake
authors.forename: Paul C
authors.initials: PC
authors.lastname: Stoy
authors.forename: Robert B
authors.initials: RB
authors.lastname: Jackson
authors.forename: Evan H
authors.initials: EH
authors.lastname: DeLucia
mesh_terms: D000704:Analysis of Variance; D001272:Atmosphere; D002244:Carbon / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism*; D019069:Cell Respiration; D017753:Ecosystem; D005308:Fertilizers; D005947:Glucose / Q000378:metabolism; D016018:Least-Squares Analysis; D009566:Nitrates / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D009657:North Carolina; D010101:Oxygen Consumption; D010788:Photosynthesis; D041603:Pinus taeda / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism*; D012621:Seasons; D013696:Temperature; D014197:Trees / Q000378:metabolism
chemical_list: D005308:Fertilizers; D009566:Nitrates; D002245:Carbon Dioxide; D002244:Carbon; D005947:Glucose; D009584:Nitrogen; C006568:ammonium nitrate