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Dynamics of fine root carbon in Amazonian tropical ecosystems and the contribution of roots to soil respiration
Author(s) -
Trumbore Susan,
Da Costa Enir Salazar,
Nepstad Daniel C.,
Barbosa De Camargo Plínio,
Martinelli Luiz A.,
Ray David,
Restom Teresa,
Silver Whendee
Publication year - 2006
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1111/j.1365-2486.2005.001063.x
Subject(s) - radiocarbon dating , environmental science , ecosystem , soil respiration , carbon fibers , respiration , organic matter , carbon cycle , soil carbon , photosynthesis , atmosphere (unit) , root system , atmospheric sciences , botany , soil water , soil science , ecology , biology , geology , mathematics , physics , paleontology , algorithm , composite number , thermodynamics
Radiocarbon ( 14 C) 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 14 C 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 Δ 14 C 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 14 C) from the rate of C flow through the live root pool, and resolve these apparently disparate estimates of root C dynamics. Explaining the 14 C values in soil pore space CO 2 , in addition, requires that a portion of the decomposing roots be cycled through soil organic matter pools with decadal turnover time.