Fine-root respiration in a loblolly pine (Pinus taeda L.) forest exposed to elevated CO₂ and N fertilization

• Published in: Plant, cell and environment Vol. 31; no. 11; pp. 1663 - 1672
• Main Authors: DRAKE, JOHN E, STOY, PAUL C, JACKSON, ROBERT B, DeLUCIA, EVAN H
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.11.2008; Blackwell Publishing Ltd; Blackwell
• Subjects: Analysis of Variance; Atmosphere; Biological and medical sciences; Carbon - metabolism; carbon cycle; Carbon Dioxide - metabolism; Cell Respiration; Duke FACE; Ecosystem; FACTS‐1; Fertilizers; Fundamental and applied biological sciences. Psychology; global climate change; Glucose - metabolism; Least-Squares Analysis; net ecosystem exchange; Nitrates - metabolism; Nitrogen - metabolism; North Carolina; Oxygen Consumption; Photosynthesis; Pinus taeda - metabolism; Plant Roots - metabolism; Seasons; soil respiration; Temperature; Trees - metabolism; North Carolina; Nitrogen fertilization; Forests; Root; Carbon dioxide; Plant ecology; Pinus taeda; soil respiration; Increase; Dynamical climatology; Carbon cycle; Climate change; Soils; net ecosystem exchange; Softwood forest tree; Gymnospermae; Global change; Coniferales; Spermatophyta; Ecosystem functioning; global climate change; Respiration; Duke FACE; FACTS-1
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/j.1365-3040.2008.01869.x

Forest ecosystems release large amounts of carbon to the atmosphere from fine-root respiration (Rr), but the control of this flux and its temperature sensitivity (Q₁₀) 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 Rr by directly measuring its Q₁₀in situ using temperature-controlled cuvettes buried around intact, attached roots. The proximal limits of Rr of loblolly pine (Pinus taeda L.) trees exposed to free-air CO₂ enrichment (FACE) and N fertilization were seasonally variable; enzyme capacity limited Rr in the winter, and a combination of substrate supply and adenylate availability limited Rr in summer months. The limiting factors of Rr were not affected by elevated CO₂ or N fertilization. Elevated CO₂ increased annual stand-level Rr by 34% whereas the combination of elevated CO₂ and N fertilization reduced Rr by 40%. Measurements of in situ Rr 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 Rr is coupled to daily canopy photosynthesis and increases with carbon allocation below ground.