Dynamics of fine root carbon in Amazonian tropical ecosystems and the contribution of roots to soil respiration

Radiocarbon (¹⁴C) provides a measure of the mean age of carbon (C) in roots, or the time elapsed since the C making up root tissues was fixed from the atmosphere. Radiocarbon signatures of live and dead fine (<2 mm diameter) roots in two mature Amazon tropical forests are consistent with average...

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Veröffentlicht in:Global change biology Jg. 12; H. 2; S. 217 - 229
Hauptverfasser: Trumbore, Susan, Costa, Enir Salazar Da, Nepstad, Daniel C, Barbosa De Camargo, Plínio, Martinelli, Luiz A, Ray, David, Restom, Teresa, Silver, Whendee
Format: Journal Article
Sprache:Englisch
Veröffentlicht: Oxford, UK Oxford, UK : Blackwell Science Ltd 01.02.2006
Blackwell Science Ltd
Blackwell Publishing Ltd
Schlagworte:
Amazonia
belowground
biodegradation
biogeochemical cycles
biological activity in soil
Brazil
carbon
carbon cycle
Carbon dioxide
decomposition
Ecosystems
fine root
forest litter
forest soils
gas emissions
Organic matter
Plant tissues
radiocarbon
radiolabeling
radionuclides
Rainforests
rhizosphere
root respiration
Roots
soil microorganisms
Soil organic matter
soil respiration
Soils
tropical forest
Tropical forests
tropical soils
turnover
Turnover time
Brazil
Amazonia
ISSN:1354-1013, 1365-2486
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Zusammenfassung:Radiocarbon (¹⁴C) provides a measure of the mean age of carbon (C) in roots, or the time elapsed since the C making up root tissues was fixed from the atmosphere. Radiocarbon signatures of live and dead fine (<2 mm diameter) roots in two mature Amazon tropical forests are consistent with average ages of 4-11 years (ranging from <1 to >40 years). Measurements of ¹⁴C in the structural tissues of roots known to have grown during 2002 demonstrate that new roots are constructed from recent (<2-year-old) photosynthetic products. High [Delta]¹⁴C values in live roots most likely indicate the mean lifetime of the root rather than the isotopic signature of inherited C or C taken up from the soil. Estimates of the mean residence time of C in forest fine roots (inventory divided by loss rate) are substantially shorter (1-3 years) than the age of standing fine root C stocks obtained from radiocarbon (4-11 years). By assuming positively skewed distributions for root ages, we can effectively decouple the mean age of C in live fine roots (measured using ¹⁴C) from the rate of C flow through the live root pool, and resolve these apparently disparate estimates of root C dynamics. Explaining the ¹⁴C values in soil pore space CO₂, in addition, requires that a portion of the decomposing roots be cycled through soil organic matter pools with decadal turnover time.
Bibliographie:http://dx.doi.org/10.1111/j.1365-2486.2005.001063.x
ArticleID:GCB1063
istex:A0EEDD9D596EC0FF8AA0307B23C51AEB99329695
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ISSN:1354-1013
1365-2486
DOI:10.1111/j.1365-2486.2005.001063.x