Greater Soil Carbon Sequestration under Nitrogen-fixing Trees Compared with <Emphasis Type="Italic">Eucalyptus</Emphasis> Species |
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Authors: | Sigrid C Resh Dan Binkley John A Parrotta |
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Institution: | (1) Department of Forest Sciences, Colorado State University, Fort Collins, Colorado 80523, USA , US;(2) Graduate Degree Program in Ecology and Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, Colorado 80523, USA; and , US;(3) United States Department of Agriculture–Forest Service, International Institute of Tropical Forestry, P.O. Box 25,000, Rio Piedras,, Puerto Rico 00928, USA , US |
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Abstract: | Forests with nitrogen-fixing trees (N–fixers) typically accumulate more carbon (C) in soils than similar forests without N–fixing
trees. This difference may develop from fundamentally different processes, with either greater accumulation of recently fixed
C or reduced decomposition of older soil C. We compared the soil C pools under N–fixers with Eucalyptus (non–N–fixers) at four tropical sites: two sites on Andisol soils in Hawaii and two sites on Vertisol and Entisol soils in
Puerto Rico. Using stable carbon isotope techniques, we tracked the loss of the old soil organic C from the previous C4 land use (SOC4) and the gain of new soil organic C from the C3, N–fixer, and non–N–fixer plantations (SOC3). Soils beneath N–fixing trees sequestered 0.11 ± 0.07 kg m−2 y−1 (mean ± one standard error) of total soil organic carbon (SOCT) compared with no change under Eucalyptus (0.00 ± 0.07 kg m−2 y−1; P = 0.02). About 55% of the greater SOCT sequestration under the N–fixers resulted from greater retention of old SOC4, and 45% resulted from greater accretion of new SOC3. Soil N accretion under the N–fixers explained 62% of the variability of the greater retention of old SOC4 under the N–fixers. The greater retention of older soil C under N–fixing trees is a novel finding and may be important for
strategies that use reforestation or afforestation to offset C emissions.
Received 12 March 2001; accepted 5 October 2001. |
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Keywords: | : carbon accretion carbon retention carbon sequestration Eucalyptus Hawaii isotopes nitrogen-fixing trees Puerto Rico soil organic carbon |
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