Stored carbon partly fuels fine‐root respiration but is not used for production of new fine roots. Issue 2 (7th May 2013)

• Record Type: Journal Article
• Authors: Lynch, Douglas J.; Matamala, Roser; Iversen, Colleen M.; Norby, Richard J.; Gonzalez‐Meler, Miquel A.
• Is Part Of: New phytologist. Volume 199:Issue 2(2013)
• Page Start: 420
• Page End: 430
• Publication Date: 2013-05-07
• Subjects: 13 C -- fine roots -- free‐air CO2 enrichment (FACE) -- post‐carboxylation fractionation -- root respiration -- root turnover -- stored carbon (C) -- Liquidambar styraciflua; Botany -- Periodicals; 580
• DOI: 10.1111/nph.12290
• Languages: English
• ISSNs: 0028-646X

Abstract

Summary: The relative use of new photosynthate compared to stored carbon (C) for the production and maintenance of fine roots, and the rate of C turnover in heterogeneous fine‐root populations, are poorly understood. We followed the relaxation of a 13 C tracer in fine roots in a Liquidambar styraciflua plantation at the conclusion of a free‐air CO2 enrichment experiment. Goals included quantifying the relative fractions of new photosynthate vs stored C used in root growth and root respiration, as well as the turnover rate of fine‐root C fixed during [CO2 ] fumigation. New fine‐root growth was largely from recent photosynthate, while nearly one‐quarter of respired C was from a storage pool. Changes in the isotopic composition of the fine‐root population over two full growing seasons indicated heterogeneous C pools; < 10% of root C had a residence time < 3 months, while a majority of root C had a residence time > 2 yr. Compared to a one‐pool model, a two‐pool model for C turnover in fine roots (with 5 and 0.37 yr −1 turnover times) doubles the fine‐root contribution to forest NPP (9–13%) and supports the 50% root‐to‐soil transfer rate often used in models.