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Accelerated belowground C cycling in a managed agriforest ecosystem exposed to elevated carbon dioxide concentrations
Author(s) -
Trueman Rebecca J.,
GonzalezMeler Miquel A.
Publication year - 2005
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.1365-2486.2005.00984.x
Subject(s) - soil respiration , carbon dioxide , cycling , carbon cycle , soil carbon , carbon dioxide in earth's atmosphere , environmental science , decomposition , carbon fibers , soil organic matter , respiration , ecosystem , environmental chemistry , heterotroph , chemistry , agronomy , soil water , ecology , botany , soil science , biology , forestry , materials science , genetics , composite number , bacteria , composite material , geography
We investigated the effects of three elevated atmospheric CO 2 levels on a Populus deltoides plantation at Biosphere 2 Laboratory in Oracle Arizona. Stable isotopes of carbon have been used as tracers to separate the carbon present before the CO 2 treatments started (old C), from that fixed after CO 2 treatments began (new C). Tree growth at elevated [CO 2 ] increased inputs to soil organic matter (SOM) by increasing the production of fine roots and accelerating the rate of root C turnover. However, soil carbon content decreased as [CO 2 ] in the atmosphere increased and inputs of new C were not found in SOM. Consequently, the rates of soil respiration increased by 141% and 176% in the 800 and 1200 μL L −1 plantations, respectively, when compared with ambient [CO 2 ] after 4 years of exposure. However, the increase in decomposition of old SOM (i.e. already present when CO 2 treatments began) accounted for 72% and 69% of the increase in soil respiration seen under elevated [CO 2 ]. This resulted in a net loss of soil C at a rate that was between 10 and 20 times faster at elevated [CO 2 ] than at ambient conditions. The inability to retain new and old C in the soil may stem from the lack of stabilization of SOM, allowing for its rapid decomposition by soil heterotrophs.